NVIDIA Cumulus Linux

Cumulus Linux 4.0 User Guide

What is Cumulus Linux?

NVIDIA® Cumulus Linux is the first full-featured Linux operating system for the networking industry. The Debian Buster-based, networking-focused distribution runs on hardware produced by a broad partner ecosystem, ensuring unmatched customer choice regarding silicon, optics, cables, and systems.

This user guide provides in-depth documentation on the Cumulus Linux installation process, system configuration and management, network solutions, and monitoring and troubleshooting recommendations. In addition, the quick start guide provides an end-to-end setup process to get you started.

Cumulus Linux 4.0 includes the latest NetQ agent and CLI, which is installed by default on the Cumulus Linux switch. Use NetQ to monitor and manage your data center network infrastructure and operational health. Refer to the NetQ documentation for details.

For a list of the new features in this release, see What's New. For bug fixes and known issues present in this release, refer to the Cumulus Linux 4.0 Release Notes.

Open Source Contributions

To implement various Cumulus Linux features, Cumulus Networks has forked various software projects, like CFEngine Netdev and some Puppet Labs packages. Some of the forked code resides in the Cumulus Networks GitHub repository and some is available as part of the Cumulus Linux repository as Debian source packages.

PDF Documents

You can view the complete Cumulus Linux 4.0 user guide as a single page to print to PDF here.

What's New

This document supports the Cumulus Linux 4.0 release, and lists new platforms and features.

What’s New in Cumulus Linux 4.0

Cumulus Linux 4.0 supports new platforms, provides bug fixes, and contains several new features and improvements:

New Platforms

New Features and Enhancements

Unsupported Features

Unsupported Platforms

These platforms are not supported in Cumulus Linux 4.0. They are supported in Cumulus Linux 3.7 until that release reaches its end of life.

The following platforms are supported in Cumulus Linux 3.7 but are not yet supported in Cumulus Linux 4.0. These platforms will be supported in a future Cumulus Linux release.

Dell Platforms

Delta Platforms

Edgecore Platforms

Mellanox Platforms

Penguin Platforms

Quanta Platforms

Supermicro Platforms

Quick Start Guide

This quick start guide provides an end-to-end setup process for installing and running Cumulus Linux, as well as a collection of example commands for getting started after installation is complete.

Prerequisites

Intermediate-level Linux knowledge is assumed for this guide. You need to be familiar with basic text editing, Unix file permissions, and process monitoring. A variety of text editors are pre-installed, including vi and nano.

You must have access to a Linux or UNIX shell. If you are running Windows, use a Linux environment like Cygwin as your command line tool for interacting with Cumulus Linux.

If you are a networking engineer but are unfamiliar with Linux concepts, refer to this reference guide to compare the Cumulus Linux CLI and configuration options, and their equivalent Cisco Nexus 3000 NX-OS commands and settings. You can also watch a series of short videos introducing you to Linux and Cumulus Linux-specific concepts.

Install Cumulus Linux

To install Cumulus Linux, you use ONIE (Open Network Install Environment), an extension to the traditional U-Boot software that allows for automatic discovery of a network installer image. This facilitates the ecosystem model of procuring switches with an operating system choice, such as Cumulus Linux. The easiest way to install Cumulus Linux with ONIE is with local HTTP discovery:

  1. If your host (laptop or server) is IPv6-enabled, make sure it is running a web server. If the host is IPv4-enabled, make sure it is running DHCP in addition to a web server.

  2. Download the Cumulus Linux installation file to the root directory of the web server. Rename this file onie-installer.

  3. Connect your host using an Ethernet cable to the management Ethernet port of the switch.

  4. Power on the switch. The switch downloads the ONIE image installer and boots. You can watch the progress of the install in your terminal. After the installation completes, the Cumulus Linux login prompt appears in the terminal window.

These steps describe a flexible unattended installation method. You do not need a console cable. A fresh install with ONIE using a local web server typically completes in less than ten minutes.

You have more options for installing Cumulus Linux with ONIE. Read Installing a New Cumulus Linux Image to install Cumulus Linux using ONIE in the following ways:

  • DHCP/web server with and without DHCP options
  • Web server without DHCP
  • FTP without a web server
  • Local file
  • USB

After installing Cumulus Linux, you are ready to:

Getting Started

When starting Cumulus Linux for the first time, the management port makes a DHCPv4 request. To determine the IP address of the switch, you can cross reference the MAC address of the switch with your DHCP server. The MAC address is typically located on the side of the switch or on the box in which the unit ships.

Login Credentials

The default installation includes the system account (root), with full system privileges and the user account (cumulus), with sudo privileges. The root account password is locked by default (which prohibits login). The cumulus account is configured with this default password:

CumulusLinux!

In this quick start guide, you use the cumulus account to configure Cumulus Linux.

For optimum security, change the default password with the passwd command before you configure Cumulus Linux on the switch.

All accounts except root are permitted remote SSH login; you can use sudo to grant a non-root account root-level access. Commands that change the system configuration require this elevated level of access.

For more information about sudo, read Using sudo to Delegate Privileges.

Serial Console Management

You are encouraged to perform management and configuration over the network, either in band or out of band. A serial console is fully supported; however, you might prefer the convenience of network-based management.

Typically, switches ship from the manufacturer with a mating DB9 serial cable. Switches with ONIE are always set to a 115200 baud rate.

Wired Ethernet Management

Switches supported in Cumulus Linux always contain at least one dedicated Ethernet management port, which is named eth0. This interface is geared specifically for out-of-band management use. The management interface uses DHCPv4 for addressing by default. You can set a static IP address with the Network Command Line Utility (NCLU) or by editing the /etc/network/interfaces file (Linux).

Set the static IP address with the interface address and interface gateway NCLU commands:

cumulus@switch:~$ net add interface eth0 ip address 192.0.2.42/24
cumulus@switch:~$ net add interface eth0 ip gateway 192.0.2.1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Set a static IP address by editing the /etc/network/interfaces file:

cumulus@switch:~$ sudo nano /etc/network/interfaces
# Management interface
auto eth0
iface eth0
    address 192.0.2.42/24
    gateway 192.0.2.1

Configure the Hostname and Timezone

Configure the hostname and timezone for your switch. The hostname identifies the switch; make sure you configure the hostname to be unique and descriptive.

  • Do not use an underscore (_) in the hostname; underscores are not permitted.
  • Avoid using apostrophes or non-ASCII characters in the hostname. Cumulus Linux does not parse these characters.
  • The command prompt in the terminal does not reflect the new hostname until you either log out of the switch or start a new shell.
  • When you use the NCLU command to set the hostname, DHCP does not override the hostname when you reboot the switch. However, if you disable the hostname setting with NCLU, DHCP does override the hostname the next time you reboot the switch.

To change the hostname:

Run the net add hostname command, which modifies both the /etc/hostname and /etc/hosts files with the desired hostname.

cumulus@switch:~$ net add hostname <hostname>
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
  1. Change the hostname with the hostnamectl command; for example:

    cumulus@switch:~$ sudo hostnamectl set-hostname leaf01
    
  2. In the /etc/hosts file, replace the host for IP address 127.0.1.1 with the new hostname:

    cumulus@switch:~$ sudo nano /etc/hosts
    ...
    127.0.1.1       leaf01
    

The default timezone on the switch is (Coordinated Universal Time) UTC. Change the timezone on your switch to be the timezone for your location.

To update the timezone, use NTP interactive mode:

  1. Run the following command in a terminal.

    cumulus@switch:~$ sudo dpkg-reconfigure tzdata
    
  2. Follow the on screen menu options to select the geographic area and region.

    Programs that are already running (including log files) and users currently logged in, do not see timezone changes made with interactive mode. To set the timezone for all services and daemons, reboot the switch.

Verify the System Time

Before you install the license, verify that the date and time on the switch are correct, and correct the date and time if necessary. If the date and time is incorrect, the switch might not be able to synchronize with Puppet or might return errors after you restart switchd:

Warning: Unit file of switchd.service changed on disk, 'systemctl daemon-reload' recommended.

Install the License

Cumulus Linux is licensed on a per-instance basis. Each network system is fully operational, enabling any capability to be utilized on the switch with the exception of forwarding on switch panel ports. Only eth0 and console ports are activated on an unlicensed instance of Cumulus Linux. Enabling front panel ports requires a license.

NVIDIA provides a generic license for Cumulus Linux. Download the license from the NVIDIA Enterprise support portal and apply it.

There are three ways to install the license onto the switch:

Check that your license is installed with the cl-license command.

cumulus@switch:~$ cl-license 
user@example.com|$ampleL1cen$et3xt

It is not necessary to reboot the switch to activate the switch ports. After you install the license, restart the switchd service. All front panel ports become active and show up as swp1, swp2, and so on.

cumulus@switch:~$ sudo systemctl restart switchd.service

If a license is not installed on a Cumulus Linux switch, the switchd service does not start. After you install the license, start switchd as described above.

Configure Breakout Ports with Splitter Cables

If you are using 4x10G DAC or AOC cables, or want to break out 100G or 40G switch ports, configure the breakout ports. For more details, see Switch Port Attributes.

Test Cable Connectivity

By default, all data plane ports (every Ethernet port except the management interface, eth0) are disabled.

To test cable connectivity:

To administratively enable a port:

cumulus@switch:~$ net add interface swp1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To administratively enable all physical ports, run the following command, where swp1-52 represents a switch with switch ports numbered from swp1 to swp52:

cumulus@switch:~$ net add interface swp1-52
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To view link status, use the net show interface all command. The following examples show the output of ports in admin down, down, and up modes:

cumulus@switch:~$ net show interface all
State  Name           Spd  MTU    Mode           LLDP                    Summary
-----  -------------  ---  -----  -------------  ----------------------  -------------------------
UP     lo             N/A  65536  Loopback                               IP: 127.0.0.1/8
       lo                                                                IP: 10.0.0.11/32
       lo                                                                IP: 10.0.0.112/32
       lo                                                                IP: ::1/128
UP     eth0           1G   1500   Mgmt           oob-mgmt-switch (swp6)  Master: mgmt(UP)
       eth0                                                              IP: 192.168.0.11/24(DHCP)
UP     swp1           1G   9000   BondMember     server01 (eth1)         Master: bond01(UP)
UP     swp2           1G   9000   BondMember     server02 (eth1)         Master: bond02(UP)
ADMDN  swp45          N/A  1500   NotConfigured
ADMDN  swp46          N/A  1500   NotConfigured
ADMDN  swp47          N/A  1500   NotConfigured
ADMDN  swp48          N/A  1500   NotConfigured
UP     swp49          1G   9000   BondMember     leaf02 (swp49)          Master: peerlink(UP)
UP     swp50          1G   9000   BondMember     leaf02 (swp50)          Master: peerlink(UP)
UP     swp51          1G   9216   NotConfigured  spine01 (swp1)
UP     swp52          1G   9216   NotConfigured  spine02 (swp1)
UP     bond01         1G   9000   802.3ad                                Master: bridge(UP)
       bond01                                                            Bond Members: swp1(UP)
UP     bond02         1G   9000   802.3ad                                Master: bridge(UP)
       bond02                                                            Bond Members: swp2(UP)
UP     bridge         N/A  1500   Bridge/L2
UP     mgmt           N/A  65536  Interface/L3                           IP: 127.0.0.1/8
UP     peerlink       2G   9000   802.3ad                                Master: bridge(UP)
       peerlink                                                          Bond Members: swp49(UP)
       peerlink                                                          Bond Members: swp50(UP)
DN     peerlink.4094  2G   9000   SubInt/L3                              IP: 169.254.1.1/30
ADMDN  vagrant        N/A  1500   NotConfigured
UP     vlan13         N/A  1500   Interface/L3                           Master: vrf1(UP)
       vlan13                                                            IP: 10.1.3.11/24
UP     vlan13-v0      N/A  1500   Interface/L3                           Master: vrf1(UP)
       vlan13-v0                                                         IP: 10.1.3.1/24
UP     vlan24         N/A  1500   Interface/L3                           Master: vrf1(UP)
       vlan24                                                            IP: 10.2.4.11/24
UP     vlan24-v0      N/A  1500   Interface/L3                           Master: vrf1(UP)
       vlan24-v0                                                         IP: 10.2.4.1/24
UP     vlan4001       N/A  1500   NotConfigured                          Master: vrf1(UP)
UP     vni13          N/A  9000   Access/L2                              Master: bridge(UP)
UP     vni24          N/A  9000   Access/L2                              Master: bridge(UP)
UP     vrf1           N/A  65536  NotConfigured
UP     vxlan4001      N/A  1500   Access/L2                              Master: bridge(UP)

To enable a port, run the ip link set <interface> up command. For example:

cumulus@switch:~$ sudo ip link set swp1 up

As root, run the following bash script to administratively enable all physical ports:

cumulus@switch:~$ sudo su -
cumulus@switch:~$ for i in /sys/class/net/*; do iface=`basename $i`; if [[ $iface == swp* ]]; then ip link set $iface up fi done

To view link status, use the ip link show command. The following examples show the output of a port in down and up mode:

# Administratively Down
swp1: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT qlen 1000

# Administratively Up but Layer 1 protocol is Down
swp1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT qlen 500

# Administratively Up, Layer 1 protocol is Up
swp1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 500

Configure Switch Ports

Layer 2 Port Configuration

Cumulus Linux does not put all ports into a bridge by default. To create a bridge and configure one or more front panel ports as members of the bridge, use the following examples as a guide.

In the following configuration example, the front panel port swp1 is placed into a bridge called bridge.

cumulus@switch:~$ net add bridge bridge ports swp1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

You can add a range of ports in one command. For example, to add swp1 through swp10, swp12, and swp14 through swp20 to bridge:

cumulus@switch:~$ net add bridge bridge ports swp1-10,12,14-20
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

In the following configuration example, the front panel port swp1 is placed into a bridge called br0:

    ...
    auto br0
    iface br0
      bridge-ports swp1
      bridge-stp on

To put a range of ports into a bridge, use the glob keyword. For example, to add swp1 through swp10, swp12, and swp14 through swp20 to br0:

    ...
    auto br0
    iface br0
      bridge-ports glob swp1-10 swp12 glob swp14-20
      bridge-stp on

To activate or apply the configuration to the kernel:

# First, check for typos:
cumulus@switch:~$ sudo ifquery -a

# Then activate the change if no errors are found:
cumulus@switch:~$ sudo ifup -a

To view the changes in the kernel, use the brctl command:

cumulus@switch:~$ brctl show
bridge name     bridge id              STP enabled     interfaces
br0             8000.089e01cedcc2       yes              swp1

Layer 3 Port Configuration

You can also configure a front panel port or bridge interface as a layer 3 port.

In the following configuration example, the front panel port swp1 is configured as a layer 3 access port:

cumulus@switch:~$ net add interface swp1 ip address 10.1.1.1/30
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To add an IP address to a bridge interface, you must put it into a VLAN interface. If you want to use a VLAN other than the native one, set the bridge PVID:

cumulus@switch:~$ net add vlan 100 ip address 10.2.2.1/24
cumulus@switch:~$ net add bridge bridge pvid 100
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

In the following configuration example, the front panel port swp1 is configured as a layer 3 access port:

auto swp1
iface swp1
  address 10.1.1.1/30

To add an IP address to a bridge interface, include the address under the iface stanza in the /etc/network/interfaces file. If you want to use a VLAN other than the native one, set the bridge PVID:

auto br0
iface br0
    address 10.2.2.1/24
    bridge-ports glob swp1-10 swp12 glob swp14-20
    bridge-pvid 100
    bridge-stp on

To activate or apply the configuration to the kernel:

# First check for typos:
cumulus@switch:~$ sudo ifquery -a

# Then activate the change if no errors are found:
cumulus@switch:~$ sudo ifup -a

To view the changes in the kernel, use the ip addr show command:

cumulus@switch:~$ ip addr show
...
4. swp1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bridge state UP group default qlen 1000
        link/ether 44:38:39:00:6e:fe brd ff:ff:ff:ff:ff:ff
...
14: bridge: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    link/ether 44:38:39:00:00:04 brd ff:ff:ff:ff:ff:ff
    inet6 fe80::4638:39ff:fe00:4/64 scope link 
        valid_lft forever preferred_lft forever
...

Configure a Loopback Interface

Cumulus Linux has a loopback preconfigured in the /etc/network/interfaces file. When the switch boots up, it has a loopback interface, called lo, which is up and assigned an IP address of 127.0.0.1.

The loopback interface lo must always be specified in the /etc/network/interfaces file and must always be up.

To see the status of the loopback interface (lo):

Use the net show interface lo command.

cumulus@switch:~$ net show interface lo
    Name    MAC                Speed    MTU    Mode
--  ------  -----------------  -------  -----  --------
UP  lo      00:00:00:00:00:00  N/A      65536  Loopback

Alias
-----
loopback interface
IP Details
-------------------------  --------------------
IP:                        127.0.0.1/8, ::1/128
IP Neighbor(ARP) Entries:  0

The loopback is up and is assigned an IP address of 127.0.0.1.

To add an IP address to a loopback interface, configure the lo interface:

cumulus@switch:~$ net add loopback lo ip address 10.1.1.1/32
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

You can configure multiple loopback addresses by adding additional address lines:

cumulus@switch:~$ net add loopback lo ip address 172.16.2.1/24
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Use the ip addr show lo command.

cumulus@switch:~$ ip addr show lo
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host
        valid_lft forever preferred_lft forever

The loopback is up and is assigned an IP address of 127.0.0.1.

To add an IP address to a loopback interface, add it directly under the iface lo inet loopback definition in the /etc network/interfaces file:

auto lo
iface lo inet loopback
    address 10.1.1.1

If an IP address is configured without a mask (as shown above), the IP address becomes a /32. So, in the above case, 10.1.1.1 is actually 10.1.1.1/32.

You can add multiple loopback addresses by adding additional address lines in the /etc/network/interfaces file:

auto lo
iface lo inet loopback
    address 10.1.1.1
    address 172.16.2.1/24

Installation Management

This section describes how to manage, install, and upgrade Cumulus Linux on your switch.

Managing Cumulus Linux Disk Images

The Cumulus Linux operating system resides on a switch as a disk image. This section discusses how to manage the disk image.

To install a new Cumulus Linux disk image, refer to Installing a New Cumulus Linux Image. To upgrade Cumulus Linux, refer to Upgrading Cumulus Linux.

Determine the Switch Platform

To determine if your switch is on an x86 or ARM platform, run the uname -m command.

For example, on an x86 platform, uname -m outputs x86_64:

cumulus@switch:~$ uname -m
 x86_64

On an ARM platform, uname -m outputs armv7l:

cumulus@switch:~$ uname -m
 armv7l

Reprovision the System (Restart the Installer)

Reprovisioning the system deletes all system data from the switch.

To stage an ONIE installer from the network (where ONIE automatically locates the installer), run the onie-select -i command. A reboot is required for the reinstall to begin.

cumulus@switch:~$ sudo onie-select -i
WARNING:
WARNING: Operating System install requested.
WARNING: This will wipe out all system data.
WARNING:
Are you sure (y/N)? y
Enabling install at next reboot...done.
Reboot required to take effect.

To cancel a pending reinstall operation, run the onie-select -c command:

cumulus@switch:~$ sudo onie-select -c
Cancelling pending install at next reboot...done.

To stage an installer located in a specific location, run the onie-install -i command. You can specify a local, absolute or relative path, an HTTP or HTTPS server, SCP or FTP server. You can also stage a Zero Touch Provisioning (ZTP) script along with the installer. The onie-install command is typically used with the -a option to activate installation. If you do not specify the -a option, a reboot is required for the reinstall to begin.

The following example stages the installer located at http://203.0.113.10/image-installer together with the ZTP script located at http://203.0.113.10/ztp-script and activates installation and ZTP:

cumulus@switch:~$ sudo onie-install -i http://203.0.113.10/image-installer
cumulus@switch:~$ sudo onie-install -z http://203.0.113.10/ztp-script
cumulus@switch:~$ sudo onie-install -a

You can also specify these options together in the same command. For example:

cumulus@switch:~$ sudo onie-install -i http://203.0.113.10/image-installer -z http://203.0.113.10/ztp-script -a

To see more onie-install options, run man onie-install.

Migrate from Cumulus Linux to ONIE (Uninstall All Images and Remove the Configuration)

To remove all installed images and configurations, and return the switch to its factory defaults, run the onie-select -k command.

The onie-select -k command takes a long time to run as it overwrites the entire NOS section of the flash. Only use this command if you want to erase all NOS data and take the switch out of service.

cumulus@switch:~$ sudo onie-select -k
WARNING:
WARNING: Operating System uninstall requested.
WARNING: This will wipe out all system data.
WARNING:
Are you sure (y/N)? y
Enabling uninstall at next reboot...done.
Reboot required to take effect.

A reboot is required for the uninstallation process to begin.

To cancel a pending uninstall operation, run the onie-select -c command:

cumulus@switch:~$ sudo onie-select -c
Cancelling pending uninstall at next reboot...done.

Boot into Rescue Mode

If your system becomes unresponsive is some way, you can correct certain issues by booting into ONIE rescue mode. In rescue mode, the file systems are unmounted and you can use various Cumulus Linux utilities to try and resolve a problem.

To reboot the system into ONIE rescue mode, run the onie-select -r command:

cumulus@switch:~$ sudo onie-select -r
WARNING:
WARNING: Rescue boot requested.
WARNING:
Are you sure (y/N)? y
Enabling rescue at next reboot...done.
Reboot required to take effect.

A reboot is required to boot into rescue mode.

To cancel a pending rescue boot operation, run the onie-select -c command:

cumulus@switch:~$ sudo onie-select -c
Cancelling pending rescue at next reboot...done.

Inspect the Image File

The Cumulus Linux installation disk image file is executable. From a running switch, you can display, extract, and verify the contents of the image file.

To display the contents of the Cumulus Linux image file, pass the info option to the image file. For example, to display the contents of an image file called onie-installer located in the /var/lib/cumulus/installer directory:

cumulus@switch:~$ sudo /var/lib/cumulus/installer/onie-installer info
Verifying image checksum ...OK.
Preparing image archive ... OK.
Control File Contents
=====================
Description: Cumulus Linux 4.0.0
Release: 4.0.0
Architecture: amd64
Switch-Architecture: bcm-amd64
Build-Id: dirtyz224615f
Build-Date: 2019-05-17T16:34:22+00:00
Build-User: clbuilder
Homepage: http://www.cumulusnetworks.com/
Min-Disk-Size: 1073741824
Min-Ram-Size: 536870912
mkimage-version: 0.11.111_gbcf0

To extract the contents of the image file, use with the extract <path> option. For example, to extract an image file called onie-installer located in the /var/lib/cumulus/installer directory to the mypath directory:

cumulus@switch:~$ sudo /var/lib/cumulus/installer/onie-installer extract mypath
total 181860
-rw-r--r-- 1 4000 4000       308 May 16 19:04 control
drwxr-xr-x 5 4000 4000      4096 Apr 26 21:28 embedded-installer
-rw-r--r-- 1 4000 4000  13273936 May 16 19:04 initrd
-rw-r--r-- 1 4000 4000   4239088 May 16 19:04 kernel
-rw-r--r-- 1 4000 4000 168701528 May 16 19:04 sysroot.tar

To verify the contents of the image file, use with the verify option. For example, to verify the contents of an image file called onie-installer located in the /var/lib/cumulus/installer directory:

cumulus@switch:~$ sudo /var/lib/cumulus/installer/onie-installer verify
Verifying image checksum ...OK.
Preparing image archive ... OK.
./cumulus-linux-bcm-amd64.bin.1: 161: ./cumulus-linux-bcm-amd64.bin.1: onie-sysinfo: not found
Verifying image compatibility ...OK.
Verifying system ram ...OK.
Open Network Install Environment (ONIE) Home Page

Installing a New Cumulus Linux Image

You can install a new Cumulus Linux disk image using ONIE, an open source project (equivalent to PXE on servers) that enables the installation of network operating systems (NOS) on bare metal switches.

Before you install Cumulus Linux, the switch can be in two different states:

The sections below describe some of the different ways you can install the Cumulus Linux disk image, such as using a DHCP/web server, FTP, TFTP, a local file, or a USB drive. Steps are provided for both installing directly from ONIE (if no image is installed on the switch) and from Cumulus Linux (if the image is already installed on the switch), where applicable. For additional methods to find and install the Cumulus Linux image, see the ONIE Design Specification.

You can download a Cumulus Linux image from the NVIDIA Enterprise support portal.

Installing the Cumulus Linux disk image is destructive; configuration files on the switch are not saved; copy them to a different server before installing.

In the following procedures:

Install Using a DHCP/Web Server with DHCP Options

To install Cumulus Linux using a DHCP/web server with DHCP options, set up a DHCP/web server on your laptop and connect the eth0 management port of the switch to your laptop. After you connect the cable, the installation proceeds as follows:

  1. The bare metal switch boots up and requests an IP address (DHCP request).
  2. The DHCP server acknowledges and responds with DHCP option 114 and the location of the installation image.
  3. ONIE downloads the Cumulus Linux disk image, installs, and reboots.
  4. Success! You are now running Cumulus Linux.

The most common method is to send DHCP option 114 with the entire URL to the web server (this can be the same system). However, there are many other ways to use DHCP even if you do not have full control over DHCP. See the ONIE user guide for help with partial installer URLs and advanced DHCP options; both articles list more supported DHCP options.

Here is an example DHCP configuration with an ISC DHCP server:

subnet 172.0.24.0 netmask 255.255.255.0 {
  range 172.0.24.20 172.0.24.200;
  option default-url = "http://172.0.24.14/onie-installer-[PLATFORM]";
}

Here is an example DHCP configuration with dnsmasq (static address assignment):

dhcp-host=sw4,192.168.100.14,6c:64:1a:00:03:ba,set:sw4
dhcp-option=tag:sw4,114,"http://roz.rtplab.test/onie-installer-[PLATFORM]"

If you do not have a web server, you can use this free Apache example.

Install Using a DHCP/Web Server without DHCP Options

Follow the steps below if you can log into the switch on a serial console (ONIE), or log in on the console or with ssh (Install from Cumulus Linux).

  1. Place the Cumulus Linux disk image in a directory on the web server.

  2. Run the onie-nos-install command:

    ONIE:/ #onie-nos-install http://10.0.1.251/path/to/cumulus-install-[PLATFORM].bin
    
  1. Place the Cumulus Linux disk image in a directory on the web server.

  2. From the Cumulus Linux command prompt, run the onie-install command, then reboot the switch.

    cumulus@switch:~$ sudo onie-install -a -i http://10.0.1.251/path/to/cumulus-install-[PLATFORM].bin
    

Install Using a Web Server with no DHCP

Follow the steps below if you can log into the switch on a serial console (ONIE), or log in on the console or with ssh (Install from Cumulus Linux) but no DHCP server is available.

You need a console connection to access the switch; you cannot perform this procedure remotely.

  1. ONIE is in discovery mode. You must disable discovery mode with the following command:

    onie# onie-discovery-stop
    

    On older ONIE versions, if the onie-discovery-stop command is not supported, run:

    onie# /etc/init.d/discover.sh stop
    
  2. Assign a static address to eth0 with the ip addr add command:

    ONIE:/ #ip addr add 10.0.1.252/24 dev eth0
    
  3. Place the Cumulus Linux disk image in a directory on your web server.

  4. Run the installer manually (because there are no DHCP options):

    ONIE:/ #onie-nos-install http://10.0.1.251/path/to/cumulus-install-[PLATFORM].bin
    
  1. Place the Cumulus Linux disk image in a directory on your web server.

  2. From the Cumulus Linux command prompt, run the onie-install command, then reboot the switch.

    cumulus@switch:~$ sudo onie-install -a -i http://10.0.1.251/path/to/cumulus-install-[PLATFORM].bin
    

Install Using FTP Without a Web Server

Follow the steps below if your laptop is on the same network as the switch eth0 interface but no DHCP server is available.

  1. Set up DHCP or static addressing for eth0. The following example assigns a static address to eth0:

    ONIE:/ #ip addr add 10.0.1.252/24 dev eth0
    
  2. If you are using static addressing, disable ONIE discovery mode:

    onie# onie-discovery-stop
    

    On older ONIE versions, if the onie-discovery-stop command is not supported, run:

    onie# /etc/init.d/discover.sh stop
    
  3. Place the Cumulus Linux disk image into a TFTP or FTP directory.

  4. If you are not using DHCP options, run one of the following commands (tftp for TFTP or ftp for FTP):

    ONIE# onie-nos-install ftp://local-ftp-server/cumulus-install-[PLATFORM].bin
    
    ONIE# onie-nos-install tftp://local-tftp-server/cumulus-install-[PLATFORM].bin
    
  1. Place the Cumulus Linux disk image into an FTP directory (TFTP is not supported in Cumulus Linux).

  2. From the Cumulus Linux command prompt, run the following command:

    cumulus@switch:~$ sudo onie-install -a -i ftp://local-ftp-server/cumulus-install-[PLATFORM].bin
    

Install Using a Local File

Follow the steps below to install the disk image referencing a local file.

  1. Set up DHCP or static addressing for eth0. The following example assigns a static address to eth0:

    ONIE:/ #ip addr add 10.0.1.252/24 dev eth0
    
  2. If you are using static addressing, disable ONIE discovery mode.

    onie# onie-discovery-stop
    

    On older ONIE versions, if the onie-discovery-stop command is not supported, run:

    onie# /etc/init.d/discover.sh stop
    
  3. Use scp to copy the Cumulus Linux disk image to the switch.

  4. Run the installer manually from ONIE:

    ONIE:/ #onie-nos-install /path/to/local/file/cumulus-install-[PLATFORM].bin
    
  1. Copy the Cumulus Linux disk image to the switch.

  2. From the Cumulus Linux command prompt, run the onie-install command, then reboot the switch.

    cumulus@switch:~$ sudo onie-install -a -i /path/to/local/file/cumulus-install-[PLATFORM].bin
    

Install Using a USB Drive

Follow the steps below to install the Cumulus Linux disk image using a USB drive. Instructions are provided for x86 and ARM platforms.

Installing Cumulus Linux using a USB drive is fine for a single switch here and there but is not scalable. DHCP can scale to hundreds of switch installs with zero manual input unlike USB installs.

Prepare for USB Installation

  1. From the NVIDIA Enterprise support portal, download the appropriate Cumulus Linux image for your x86 or ARM platform.

  2. From a computer, prepare your USB drive by formatting it using one of the supported formats: FAT32, vFAT or EXT2.

    Optional: Prepare a USB Drive inside Cumulus Linux

    Use caution when performing these actions; it is possible to severely damage your system with the following utilities.

    1. Insert your USB drive into the USB port on the switch running Cumulus Linux and log in to the switch. Examine output from cat /proc/partitions and sudo fdisk -l [device] to determine on which device your USB drive can be found. For example, sudo fdisk -l /dev/sdb.

      These instructions assume your USB drive is the /dev/sdb device, which is typical if you insert the USB drive after the machine is already booted. However, if you insert the USB drive during the boot process, it is possible that your USB drive is the /dev/sda device. Make sure to modify the commands below to use the proper device for your USB drive.

    2. Create a new partition table on the USB drive. (The parted utility should already be installed. However, if it is not, install it with sudo -E apt-get install parted.)

      sudo parted /dev/sdb mklabel msdos
      
    3. Create a new partition on the USB drive:

      sudo parted /dev/sdb -a optimal mkpart primary 0% 100%
      
    4. Format the partition to your filesystem of choice using one of the examples below:

      sudo mkfs.ext2 /dev/sdb1
      sudo mkfs.msdos -F 32 /dev/sdb1
      sudo mkfs.vfat /dev/sdb1
      

      To use mkfs.msdos or mkfs.vfat, you need to install the dosfstools package from the Debian software repositories, as they are not included by default.

    5. To continue installing Cumulus Linux, mount the USB drive to move files

      sudo mkdir /mnt/usb
      sudo mount /dev/sdb1 /mnt/usb
      
  3. Copy the Cumulus Linux disk image to the USB drive, then rename the image file to:

    • onie-installer-x86_64, if installing on an x86 platform
    • onie-installer-arm, if installing on an ARM platform

    When using a Mac or Windows computer to rename the installation file, the file extension might still be present. Make sure to remove the file extension otherwise ONIE is not able to detect the file.

  4. Insert the USB drive into the switch, then continue with the appropriate instructions below for your x86 or ARM platform.

  1. Prepare the switch for installation:

    • If the switch is offline, connect to the console and power on the switch.
    • If the switch is already online in ONIE, use the reboot command.

    SSH sessions to the switch get dropped after this step. To complete the remaining instructions, connect to the console of the switch. Cumulus Linux switches display their boot process to the console; you need to monitor the console specifically to complete the next step.

  2. Monitor the console and select the ONIE option from the first GRUB screen shown below.

  1. Cumulus Linux on x86 uses GRUB chainloading to present a second GRUB menu specific to the ONIE partition. No action is necessary in this menu to select the default option ONIE: Install OS.
  1. The USB drive is recognized and mounted automatically. The image file is located and automatic installation of Cumulus Linux begins. Here is some sample output:

    ONIE: OS Install Mode  ...
    
    Version : quanta_common_rangeley-2014.05.05-6919d98-201410171013
    Build  Date: 2014-10-17T10:13+0800
    Info: Mounting kernel filesystems...  done.
    Info: Mounting LABEL=ONIE-BOOT on /mnt/onie-boot  ...
    initializing eth0...
    scsi 6:0:0:0: Direct-Access  SanDisk Cruzer Facet 1.26 PQ: 0 ANSI: 6
    sd 6:0:0:0: [sdb] 31266816 512-byte logical blocks: (16.0 GB/14.9 GiB)
    sd 6:0:0:0: [sdb] Write Protect is off
    sd 6:0:0:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
    sd 6:0:0:0: [sdb] Attached SCSI disk
    
    ...
    
    ONIE:  Executing installer: file://dev/sdb1/onie-installer-x86_64
    Verifying image checksum ... OK.
    Preparing image archive ... OK.
    Dumping image info...
    Control File Contents
    =====================
    Description: Cumulus Linux
    OS-Release:  4.0.0~1571178373.763fd151
    Architecture: amd64
    Date:  Fri, 22 November 2019 17:10:30 -0700
    Installer-Version:  1.2
    Platforms: accton_as5712_54x accton_as6712_32x  mlx_sx1400_i73612 dell_s4000_c2338 dell_s3000_c2338  cel_redstone_xp cel_smallstone_xp cel_pebble quanta_panther  quanta_ly8_rangeley quanta_ly6_rangeley quanta_ly9_rangeley
    
    Homepage: http://www.cumulusnetworks.com/
    
  2. After installation completes, the switch automatically reboots into the newly installed instance of Cumulus Linux.

  1. Prepare the switch for installation:

    • If the switch is offline, connect to the console and power on the switch.
    • If the switch is already online in ONIE, use the reboot command.

    SSH sessions to the switch get dropped after this step. To complete the remaining instructions, connect to the console of the switch. Cumulus Linux switches display their boot process to the console; you need to monitor the console specifically to complete the next step.

  2. Interrupt the normal boot process before the countdown (shown below) completes. Press any key to stop the autoboot.

    U-Boot 2013.01-00016-gddbf4a9-dirty (Feb 14 2014 - 16:30:46) Accton: 1.4.0.5
    
    CPU0: P2020, Version: 2.1, (0x80e20021)
    Core: E500, Version: 5.1, (0x80211051)
    Clock Configuration:
        CPU0:1200 MHz, CPU1:1200 MHz,
        CCB:600 MHz,
        DDR:400 MHz (800 MT/s data rate) (Asynchronous), LBC:37.500 MHz
    L1: D-cache 32 kB enabled
    I-cache 32 kB enabled
    ...
    
    USB: USB2513 hub OK
    Hit any key to stop autoboot: 0
    
  3. A command prompt appears so that you can run commands. Execute the following command:

    run onie_bootcmd
    
  4. The USB drive is recognized and mounted automatically. The image file is located and automatic installation of Cumulus Linux begins. Here is some sample output:

    Loading Open Network Install Environment  ...
    Platform: arm-as4610_54p-r0
    Version : 1.6.1.3
    WARNING: adjusting available memory to 30000000
    ## Booting kernel from Legacy Image at ec040000  ...
        Image Name:   as6701_32x.1.6.1.3
        Image Type:   ARM Linux Multi-File Image (gzip compressed)
        Data Size:    4456555 Bytes = 4.3 MiB
        Load Address: 00000000
        Entry Point:  00000000
        Contents:
            Image 0: 3738543 Bytes = 3.6 MiB
            Image 1: 706440 Bytes = 689.9 KiB
            Image 2: 11555 Bytes = 11.3 KiB
        Verifying Checksum ... OK
    ## Loading init Ramdisk from multi component Legacy Image at ec040000  ...
    ## Flattened Device Tree from multi component Image at EC040000
        Booting using the fdt at 0xec47d388
        Uncompressing Multi-File Image ... OK
        Loading Ramdisk to 2ff53000, end 2ffff788 ... OK
        Loading Device Tree to 03ffa000, end 03fffd22 ... OK
    ...
    
    ONIE: Starting ONIE Service Discovery
    ONIE: Executing installer: file://dev/sdb1/onie-installer-arm
    Verifying image checksum ... OK.
    Preparing image archive ... OK.
    Dumping image info ...
    Control File Contents
    =====================
    Description: Cumulus Linux
    OS-Release: 3.0.0-3b46bef-201509041633-build
    Architecture: arm
    Date: Fri, 27 May 2016 17:08:35 -0700
    Installer-Version: 1.2
    Platforms: accton_as4600_54t, accton_as6701_32x, accton_5652, accton_as5610_52x, dni_6448, dni_7448, dni_c7448n, cel_kennisis, cel_redstone, cel_smallstone, cumulus_p2020, quanta_lb9, quanta_ly2, quanta_ly2r, quanta_ly6_p2020
    Homepage: http://www.cumulusnetworks.com/
    
  5. After installation completes, the switch automatically reboots into the newly installed instance of Cumulus Linux.

Upgrading Cumulus Linux

This topic describes how to upgrade Cumulus Linux on your switch.

Consider deploying, provisioning, configuring, and upgrading switches using automation, even with small networks or test labs. During the upgrade process, you can quickly upgrade dozens of devices in a repeatable manner. Using tools like Ansible, Chef, or Puppet for configuration management greatly increases the speed and accuracy of the next major upgrade; these tools also enable the quick swap of failed switch hardware.

Before You Upgrade

Be sure to read the knowledge base article Upgrades: Network Device Worldview and Linux Host Worldview Comparison, which provides a detailed comparison between the network device and Linux host worldview of upgrade and installation.

Back up Configuration Files

Understanding the location of configuration data is required for successful upgrades, migrations, and backup. As with other Linux distributions, the /etc directory is the primary location for all configuration data in Cumulus Linux. The following list is a likely set of files that you need to back up and migrate to a new release. Make sure you examine any file that has been changed. Consider making the following files and directories part of a backup strategy.

File Name and Location Explanation Cumulus Linux Documentation Debian Documentation
/etc/network/ Network configuration files, most notably /etc/network/interfaces and /etc/network/interfaces.d/ Switch Port Attributes N/A
/etc/resolv.conf DNS resolution Not unique to Cumulus Linux: wiki.debian.org/NetworkConfiguration https://www.debian.org/doc/manuals/debian-reference/ch05.en.html
/etc/frr/ Routing application (responsible for BGP and OSPF) FRRouting Overview N/A
/etc/hostname Configuration file for the hostname of the switch Quick Start Guide https://wiki.debian.org/HowTo/ChangeHostname
/etc/hosts Configuration file for the hostname of the switch Quick Start Guide https://wiki.debian.org/HowTo/ChangeHostname
/etc/cumulus/acl/* Netfilter configuration Netfilter - ACLs N/A
/etc/cumulus/ports.conf Breakout cable configuration file Switch Port Attributes N/A; read the guide on breakout cables
/etc/cumulus/switchd.conf switchd configuration Configuring switchd N/A; read the guide on switchd configuration
File Name and Location Explanation Cumulus Linux Documentation Debian Documentation
/etc/motd Message of the day Not unique to Cumulus Linux wiki.debian.org/motd
/etc/passwd User account information Not unique to Cumulus Linux https://www.debian.org/doc/manuals/debian-reference/ch04.en.html
/etc/shadow Secure user account information Not unique to Cumulus Linux https://www.debian.org/doc/manuals/debian-reference/ch04.en.html
/etc/group Defines user groups on the switch Not unique to Cumulus Linux https://www.debian.org/doc/manuals/debian-reference/ch04.en.html
/etc/lldpd.conf Link Layer Discover Protocol (LLDP) daemon configuration Link Layer Discovery Protocol https://packages.debian.org/buster/lldpd
/etc/lldpd.d/ Configuration directory for lldpd Link Layer Discovery Protocol https://packages.debian.org/buster/lldpd
/etc/nsswitch.conf Name Service Switch (NSS) configuration file TACACS N/A
/etc/ssh/ SSH configuration files SSH for Remote Access https://wiki.debian.org/SSH
/etc/sudoers, /etc/sudoers.d Best practice is to place changes in /etc/sudoers.d/ instead of /etc/sudoers; changes in the /etc/sudoers.d/ directory are not lost during upgrade. Using sudo to Delegate Privileges
File Name and Location Explanation
/etc/bcm.d/ Per-platform hardware configuration directory, created on first boot. Do not copy.
/etc/mlx/ Per-platform hardware configuration directory, created on first boot. Do not copy.
/etc/default/clagd Created and managed by ifupdown2. Do not copy.
/etc/default/grub Grub init table. Do not modify manually.
/etc/default/hwclock Platform hardware-specific file. Created during first boot. Do not copy.
/etc/init Platform initialization files. Do not copy.
/etc/init.d/ Platform initialization files. Do not copy.
/etc/fstab Static information on filesystem. Do not copy.
/etc/image-release System version data. Do not copy.
/etc/os-release System version data. Do not copy.
/etc/lsb-release System version data. Do not copy.
/etc/lvm/archive Filesystem files. Do not copy.
/etc/lvm/backup Filesystem files. Do not copy.
/etc/modules Created during first boot. Do not copy.
/etc/modules-load.d/ Created during first boot. Do not copy.
/etc/sensors.d Platform-specific sensor data. Created during first boot. Do not copy.
/root/.ansible Ansible tmp files. Do not copy.
/home/cumulus/.ansible Ansible tmp files. Do not copy.

You can check which files have changed since the last binary install with the following commands. Be sure to back up any changed files:

  • Run the sudo dpkg --verify command to show a list of changed files.
  • Run the egrep -v '^$|^#|=""$' /etc/default/isc-dhcp-* command to see if any of the generated /etc/default/isc-* files have changed.
  • If you are using the root user account, consider including /root/.
  • If you have custom user accounts, consider including /home/<username>/.
  • Run the net show configuration files | grep -B 1 "===" command and back up the files listed in the command output.

Create a cl-support File

Before and after you upgrade the switch, run the cl-support script to create a cl-support archive file. The file is a compressed archive of useful information for troubleshooting. If you experience any issues during upgrade, you can send this archive file to the Cumulus Linux support team to investigate.

  1. Create the cl-support archive file with the cl-support command:

    cumulus@switch:~$ sudo cl-support
    
  2. Copy the cl-support file off the switch to a different location.

  3. After upgrade is complete, run the cl-support command again to create a new archive file:

    cumulus@switch:~$ sudo cl-support
    

Upgrade Cumulus Linux

To upgrade to Cumulus Linux 4.0 from Cumulus Linux 3.7, you must install a disk image of the new release using ONIE. You cannot upgrade packages with the apt-get upgrade command.

ONIE is an open source project (equivalent to PXE on servers) that enables the installation of network operating systems (NOS) on a bare metal switch.

Upgrading an MLAG pair requires additional steps. If you are using MLAG to dual connect two Cumulus Linux switches in your environment, follow the steps in Upgrading Cumulus Linux below to ensure a smooth upgrade.

Lightweight network virtualization (LNV) is deprecated in Cumulus Linux 4.0 in favor of Ethernet virtual private networks (EVPN. If your network is configured for LNV, you need to migrate your network configuration to a BGP EVPN configuration that is functionally equivalent before you upgrade to Cumulus Linux 4.0. Refer to Migrating from LNV to EVPN..

Be aware of the following when installing the disk image:

To upgrade the switch:

  1. Back up the configurations off the switch.

  2. Download the Cumulus Linux image.

  3. Install the disk image with the onie-install -a -i <image-location> command, which boots the switch into ONIE. The following example command installs the image from a web server, then reboots the switch. There are additional ways to install the disk image, such as using FTP, TFTP, a local file, or a USB drive. For more information, see Installing a New Cumulus Linux Image.

    cumulus@switch:~$ sudo onie-install -a -i http://10.0.1.251/cumulus-linux-4.0.0-mlx-amd64.bin && sudo reboot
    
  4. Restore the configuration files to the new release - ideally with automation.

  5. Verify correct operation with the old configurations on the new release.

  6. Reinstall third party applications and associated configurations.

Upgrade Switches in an MLAG Pair

If you are using MLAG to dual connect two switches in your environment, follow the steps below to upgrade the switches.

You must upgrade both switches in the MLAG pair to the same release of Cumulus Linux.

Only during the upgrade process does Cumulus Linux supports different software versions between MLAG peer switches. After you upgrade the first MLAG switch in the pair, run the clagctl showtimers command to monitor the init-delay timer. When the timer expires, make the upgraded MLAG switch the primary, then upgrade the peer to the same version of Cumulus Linux.

Running different versions of Cumulus Linux on MLAG peer switches outside of the upgrade time period is untested and might have unexpected results.

For networks with MLAG deployments, only upgrade to Cumulus Linux 4.0 from version 3.7.10 or later. If you are using a version of Cumulus Linux earlier than 3.7.10, you must upgrade to version 3.7.10 first, then upgrade to version 4.0. Version 3.7.10 is available on the NVIDIA Enterprise support portal.

During upgrade, MLAG bonds stay single-connected while the switches are running different major releases; for example, while leaf01 is running 3.7.12 and leaf02 is running 4.1.1.

This is due to a change in the bonding driver regarding how the actor port key is derived, which causes the port key to have a different value for links with the same speed/duplex settings across different major releases. The port key received from the LACP partner must remain consistent between all bond members in order for all bonds to be synchronized. When each MLAG switch sends LACPDUs with different port keys, only links to one MLAG switch are in sync.

  1. Verify the switch is in the secondary role:

    cumulus@switch:~$ clagctl status
    
  2. Shut down the core uplink layer 3 interfaces:

    cumulus@switch:~$ sudo ip link set swpX down
    
  3. Shut down the peer link:

    cumulus@switch:~$ sudo ip link set peerlink down
    
  4. To boot the switch into ONIE, run the onie-install -a -i <image-location> command. The following example command installs the image from a web server. There are additional ways to install the Cumulus Linux image, such as using FTP, a local file, or a USB drive. For more information, see Installing a New Cumulus Linux Image.

    cumulus@switch:~$ sudo onie-install -a -i http://10.0.1.251/downloads/cumulus-linux-4.1.0-mlx-amd64.bin
    

    To upgrade the switch with package upgrade instead of booting into ONIE, run the sudo -E apt-get update and sudo -E apt-get upgrade commands; see Package Upgrade.

  5. Reboot the switch:

    cumulus@switch:~$ sudo reboot
    
  6. If you installed a new image on the switch, restore the configuration files to the new release.

  7. Verify STP convergence across both switches:

    cumulus@switch:~$ mstpctl showall
    
  8. Verify core uplinks and peer links are UP:

    cumulus@switch:~$ net show interface
    
  9. Verify MLAG convergence:

    cumulus@switch:~$ clagctl status
    
  10. Make this secondary switch the primary:

cumulus@switch:~$ clagctl priority 2048
  1. Verify the other switch is now in the secondary role.

  2. Repeat steps 2-9 on the new secondary switch.

  3. Remove the priority 2048 and restore the priority back to 32768 on the current primary switch:

    cumulus@switch:~$ clagctl priority 32768
    

Roll Back a Cumulus Linux Installation

Even the most well planned and tested upgrades can result in unforeseen problems; sometimes the best solution is to roll back to the previous state. There are three main strategies; all require detailed planning and execution:

The method you employ is specific to your deployment strategy, so providing detailed steps for each scenario is outside the scope of this document.

Third Party Packages

Third party packages in the Linux host world often use the same package system as the distribution into which it is to be installed (for example, Debian uses apt-get). Or, the package might be compiled and installed by the system administrator. Configuration and executable files generally follow the same filesystem hierarchy standards as other applications.

If you install any third party applications on a Cumulus Linux switch, configuration data is typically installed into the /etc directory, but it is not guaranteed. It is your responsibility to understand the behavior and configuration file information of any third party packages installed on the switch.

After you upgrade using a full disk image install, you need to reinstall any third party packages or any Cumulus Linux add-on packages.

Migrating from LNV to EVPN

Lightweight network virtualization (LNV) is deprecated in Cumulus Linux 4.0 in favor of Ethernet virtual private networks (EVPN) to enable interoperability with switches from other manufacturers, to commit to industry standards, and because the benefits of EVPN outweigh those of LNV.

If your network is configured for LNV, you need to migrate your network configuration to a BGP EVPN configuration that is functionally equivalent before you upgrade to Cumulus Linux 4.0 or later.

Migration Considerations

You cannot run LNV and EVPN at the same time for the following reasons:

Upgrade to EVPN

When upgrading to EVPN, automation, such as Ansible, is highly recommended. Automation ensures minimal downtime, reduces human error, and is useful at almost any scale.

Consider using NCLU to update the configuration. NCLU has the following benefits:

The upgrade steps described here are based on the following example topology (based on the Cumulus Linux Reference Topology):

This topology:

The BGP EVPN configuration for a centralized routing topology is slightly different on the exit/routing leafs compared to the other ToR leaf switches.

  1. Run the following NCLU commands on each type of device shown (leaf, exit, spine):

    Leaf node NCLU commands

    # BGP changes
    cumulus@switch:~$ net add bgp l2vpn evpn neighbor swp51-52 activate
    cumulus@switch:~$ net add bgp l2vpn evpn advertise-all-vni
    
    # Disable MAC learning on VNI
    cumulus@switch:~$ net add vxlan vni-13 bridge learning off
    cumulus@switch:~$ net add vxlan vni-24 bridge learning off
    
    # Remove LNV (vxrd) configuration
    cumulus@switch:~$ net del loopback lo vxrd-src-ip
    cumulus@switch:~$ net del loopback lo vxrd-svcnode-ip
    

    Exit node NCLU commands

    # BGP changes
    cumulus@switch:~$ net add bgp l2vpn evpn neighbor swp51-52 activate
    cumulus@switch:~$ net add bgp l2vpn evpn advertise-all-vni
    cumulus@switch:~$ net add bgp l2vpn evpn advertise-default-gw
    
    # Disable MAC learning on VNI
    cumulus@switch:~$ net add vxlan vni-13 bridge learning off
    cumulus@switch:~$ net add vxlan vni-24 bridge learning off
    
    # Remove LNV (vxrd) configuration
    cumulus@switch:~$ net del loopback lo vxrd-src-ip
    cumulus@switch:~$ net del loopback lo vxrd-svcnode-ip
    

    Spine node NCLU commands

    # BGP changes
    cumulus@switch:~$ net add bgp l2vpn evpn neighbor swp1-4 activate
    
    Remove LNV service node (vxsnd) configuration
    cumulus@switch:~$ net del lnv service-node anycast-ip 10.0.0.200
    cumulus@switch:~$ net del lnv service-node peers 10.0.0.21 10.0.0.22
    cumulus@switch:~$ net del lnv service-node source [primary-loopback-ip]
    
    # Remove unused LNV anycast address 10.0.0.200
    cumulus@switch:~$ net del loopback lo ip address 10.0.0.200/32
    cumulus@switch:~$ net del bgp ipv4 unicast network 10.0.0.200/32
    
  2. Manually disable and stop the LNV daemons. NCLU can remove the LNV configuration from the configuration files, but you must manually stop and disable these daemons before you commit the NCLU changes. After you commit the NCLU changes, NCLU restarts the BGP daemon, which enables the EVPN address family.

    Traffic loss can start to occur at this point.

  3. To disable and stop the LNV registration daemon, run the following commands on the leaf and exit nodes:

    cumulus@switch:~$ sudo systemctl disable vxrd
    cumulus@switch:~$ sudo systemctl stop vxrd
    
  4. To disable and stop the LNV service node daemon, run the following commands on the spine nodes:

    cumulus@switch:~$ sudo systemctl disable vxsnd
    cumulus@switch:~$ sudo systemctl stop vxsnd
    
  5. To commit and apply the pending NCLU changes, run the following command on all the nodes:

    cumulus@switch:~$ net commit
    

Verify the Upgrade

To check that LNV is disabled, run the net show lnv command on any node. This command returns no output when LNV is disabled.

This command is for verification on Cumulus Linux 3.x only. This command has been removed in Cumulus Linux 4.0 and does not work after you upgrade.

cumulus@switch:~$ net show lnv

To ensure that EVPN BGP neighbors are up, run the net show bgp l2vpn summary command:

cumulus@switch:~$ net show bgp l2vpn evpn summary
BGP router identifier 10.0.0.11, local AS number 65011 vrf-id 0
BGP table version 0
RIB entries 23, using 3496 bytes of memory
Peers 2, using 39 KiB of memory
Neighbor        V         AS MsgRcvd MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd
spine01(swp51)  4      65020   10932   11064        0    0    0 00:14:28           48
spine02(swp52)  4      65020   10938   11068        0    0    0 00:14:27           48
Total number of neighbors 2

To examine the EVPN routes, run the net show bgp l2vpn evpn route command. Because a MAC address only appears as a type-2 route if the host has generated traffic and its MAC is learned by the local EVPN-enabled switch, a host that does not send any traffic does not create a type-2 EVPN route until it sends a frame that ingresses the EVPN-enabled local switch.

cumulus@switch:~$ net show bgp l2vpn evpn route  
BGP table version is 45, local router ID is 10.0.0.11
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
EVPN type-2 prefix: [2]:[ESI]:[EthTag]:[MAClen]:[MAC]:[IPlen]:[IP]
EVPN type-3 prefix: [3]:[EthTag]:[IPlen]:[OrigIP]
EVPN type-5 prefix: [5]:[ESI]:[EthTag]:[IPlen]:[IP]
    Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 10.0.0.11:2
*> [2]:[0]:[0]:[48]:[00:03:00:11:11:01]
                    10.0.0.100                         32768 i
*> [2]:[0]:[0]:[48]:[02:03:00:11:11:01]
                    10.0.0.100                         32768 i
*> [2]:[0]:[0]:[48]:[02:03:00:11:11:02]
                    10.0.0.100                         32768 i
*> [3]:[0]:[32]:[10.0.0.100]
                    10.0.0.100                         32768 i
Route Distinguisher: 10.0.0.11:3
*> [2]:[0]:[0]:[48]:[00:03:00:22:22:02]
                    10.0.0.100                         32768 i
*> [2]:[0]:[0]:[48]:[02:03:00:22:22:01]
                    10.0.0.100                         32768 i
*> [2]:[0]:[0]:[48]:[02:03:00:22:22:02]
                    10.0.0.100                         32768 i
*> [3]:[0]:[32]:[10.0.0.100]
                    10.0.0.100                         32768 i
Route Distinguisher: 10.0.0.13:2
*  [2]:[0]:[0]:[48]:[00:03:00:33:33:01]
                    10.0.0.101                             0 65020 65013 i
*> [2]:[0]:[0]:[48]:[00:03:00:33:33:01]
                    10.0.0.101                             0 65020 65013 i
*  [2]:[0]:[0]:[48]:[02:03:00:33:33:01]
                    10.0.0.101                             0 65020 65013 i
*> [2]:[0]:[0]:[48]:[02:03:00:33:33:01]
                    10.0.0.101                             0 65020 65013 i
*  [2]:[0]:[0]:[48]:[02:03:00:33:33:02]
                    10.0.0.101                             0 65020 65013 i
*> [2]:[0]:[0]:[48]:[02:03:00:33:33:02]
                    10.0.0.101                             0 65020 65013 i
*  [3]:[0]:[32]:[10.0.0.101]
                    10.0.0.101                             0 65020 65013 i
*> [3]:[0]:[32]:[10.0.0.101]
                    10.0.0.101                             0 65020 65013 i
...

You can filter the EVPN route output by route type. The multicast route type corresponds to type-3. The prefix route type is type-5 (but is not used here).

cumulus@switch:~$ net show bgp l2vpn evpn route type
   macip      : MAC-IP (Type-2) route
   multicast  : Multicast
   prefix     : An IPv4 or IPv6 prefix

In the EVPN route output below, Cumulus Linux learned 00:03:00:33:33:01 with a next-hop (VTEP IP address) of 10.0.0.101. The MAC address of server03 is 00:03:00:33:33:01.

cumulus@leaf01:~$ net show bgp l2vpn evpn route
...

Route Distinguisher: 10.0.0.13:2
*  [2]:[0]:[0]:[48]:[00:03:00:33:33:01]
                     10.0.0.101                             0 65020 65013 i
...

To ensure the type-2 route is installed in the bridge table, run the net show bridge macs <mac-address> command on leaf01:

cumulus@leaf01:~$ net show bridge macs 00:03:00:33:33:01
VLAN      Master  Interface  MAC                TunnelDest  State  Flags          LastSeen
--------  ------  ---------  -----------------  ----------  -----  -------------  --------
13        bridge  vni-13     00:03:00:33:33:01                     offload        00:01:49
untagged          vni-13     00:03:00:33:33:01  10.0.0.101         self, offload  00:01:49

Back up and Restore

You can back up the current configuration on a switch and restore the configuration on the same switch or on another Cumulus Linux switch of the same type and release. The backup is a compressed tar file that includes all configuration files installed by Debian packages and marked as configuration files. In addition, the backup contains files in the /etc directory that are not installed by a Debian package but are modified when you install a new image or enable/disable certain services (such as the Cumulus license file).

Cumulus Linux automatically creates a backup of the configuration files on the switch after you install the Cumulus Linux image, in case you want to return to the initial switch configuration. NCLU automatically creates a backup of the configuration files when you run the net commit command and restores a previous configuration when you run the net rollback command.

Back up Configuration Files

To back up the current configuration files on the switch, run the config-backup command:

cumulus@switch:~$ sudo config-backup

If you run this command without any options, Cumulus Linux creates a backup of the current configuration and stores the backup file in the /var/lib/config-backup/backups directory. The filename includes the date and time you run the backup, and the switch name; for example, config_backup-2019-04-23-21.30.47_leaf01. You can restore the backup with the config-restore command, described below.

The switch can store up to 30 non-permanent backup files (or can allocate a maximum of 25 MB of disc space) in addition to the permanent backup files (see the -p option below). When this limit is reached, Cumulus Linux keeps the oldest and the newest backup files, then starts removing the second oldest file up to the second newest file.

Cumulus Linux recommends you copy the backup file off the switch after backup is complete.

The config-backup command includes the following options:

Option Description
-h Displays this list of command options.
-d Enables debugging output, which shows status messages during the backup process.
-D <description> Adds a description, which is shown in the archive file list when you run the config-restore -l command.
-p Adds -perm to the end of the backup filename to mark it as permanent. For example, config_backup-2019-04-23-21.30.47_leaf01-perm. Be careful when using this option. Permanent backup files are not removed.
-q Runs the command in quiet mode. No status messages are shown, only errors.
-t <type> Specifies the type of configuration, which is shown in the archive file list when you run the config-restore -l command. You can provide any short text. For example, you can specify pre, post, or pre-restore.
-v Enables verbose mode to show messages during the backup process.
-X <pattern> Excludes certain files that match a specified pattern. For example, to exclude all backup files ending with a tilde (~), use the -X .*~$ option.

config-backup Command Examples

The following command example creates a backup file in debugging mode and provides the description myconfig, which shows in the backup archive list.

cumulus@switch:~$ sudo config-backup -d -D myconfig 

The following command example creates a backup file in quiet mode and excludes files that end in a tilde (~).

cumulus@switch:~$ sudo config-backup -q -X .*~$

The following command example creates a backup file in verbose mode and marks the file as permanent.

cumulus@switch:~$ sudo config-backup -pv

Restore Backup Files

You can restore a backup to the same switch or to a different switch. When restoring to a different switch, the switch must be of the same type and release. For example, you can restore a backup from a Broadcom Trident3 switch to a Broadcom Trident3 switch; however, you cannot restore a backup from a Broadcom Trident3 switch to a Mellanox Spectrum or to a Broadcom Tomahawk2 switch.

To restore a backup file, run the config-restore command with a specific filename (-b <filename>), file number (-n <number>), or the -N option, which restores the most recent backup file.

You can run the config-restore -l command to list the archived backup files by filename and number (see config-restore Command Examples below).

cumulus@switch:~$ sudo config-restore -b config_backup-2019-04-23-21.30.47_leaf01
cumulus@switch:~$ sudo config-restore -n 10
cumulus@switch:~$ sudo config-restore -N

After the backup file is restored successfully, you are prompted to restart any affected services or reboot the switch if necessary.

Cumulus Linux reports any issues encountered during restore and prompts you to continue or stop.

  • The config-restore command requires a filename, file number, or the most recent file option (-N).
  • You can only run one config-backup or config-restore command instance at the same time.

The config-restore command includes the following options:

Option Description
-h Displays this list of command options.
-a <directory> Restores the backup to the directory specified.
-B Runs no backup before restoring the configuration. If you do not specify this option, Cumulus Linux runs a backup to save the current configuration before the restore so that you can do a rollback if needed.
-b <filename> Specifies the name of the backup file you want to restore (shown by -l).
-D Shows the differences between the current configuration and the configuration in the backup file.
-d Displays debugging output, which provides status messages during the restore process.
-f Forces the restore; does not prompt for confirmations.
-F <filename> Shows differences for only this file (used with -D).
-i Displays information about the current backup file.
-L Lists the configuration files in the backup file.
-l Lists all backup files archived on the switch and includes the file number, type, and description.
-N Restores the newest (most recent) backup file.
-n <number> Specifies the backup file by number (shown by -l).
-q Runs the command in quiet mode. No status messages are displayed, only errors.
-T Runs the command in test mode; does not restore the configuration but shows what would be restored.
-v Enables verbose mode to display status messages during restore.

config-restore Command Examples

The following command example lists the backup files available on the switch. The list includes the file number (#), type, description, and filename. Type is the text specified with the config-backup -t option.

cumulus@switch:~$ sudo config-restore -l
# Type       Description               Name
1 Initial    First system boot         config_backup-2019-04-23-00.42.11_cumulus-perm
2 Initial    First system boot         config_backup-2019-04-23-00.47.43_cumulus-perm
3 Initial    First system boot         config_backup-2019-04-23-18.12.26_cumulus-perm
4 pre nclu "net commit" (user cumulus) config_backup-2019-04-23-19.55.13_leaf01
5 post-4     nclu "net commit" (user cumulus)   config_backup-2019-04-23-19.55.26_leaf01
6            config_backup-2019-04-23-21.20.41_leaf01
7            config_backup-2019-04-23-21.30.47_leaf01-perm
...

The following command example runs in verbose mode to restore the backup file config_backup-2019-04-23-21.30.47_leaf01.

cumulus@switch:~$ sudo config-restore -v -b config_backup-2019-04-23-21.30.47_leaf01

The following command example runs test mode to restore the most recent backup file (no configuration is actually restored).

cumulus@switch:~$ sudo config-restore -T -N

The following command example lists the files in the most recent backup file.

cumulus@switch:~$ sudo config-restore -L -N

Adding and Updating Packages

You use the Advanced Packaging Tool (apt) to manage additional applications (in the form of packages) and to install the latest updates.

Updating, upgrading, and installing packages with apt causes disruptions to network services:

  • Upgrading a package might result in services being restarted or stopped as part of the upgrade process.
  • Installing a package might disrupt core services by changing core service dependency packages. In some cases, installing new packages might also upgrade additional existing packages due to dependencies.

If services are stopped, you might need to reboot the switch for those services to restart.

Update the Package Cache

To work properly, apt relies on a local cache listing of the available packages. You must populate the cache initially, then periodically update it with sudo -E apt-get update:

cumulus@switch:~$ sudo -E apt-get update
Get:1 http://apt.cumulusnetworks.com CumulusLinux-4-latest InRelease [7,624 B]
Get:2 http://apt.cumulusnetworks.com CumulusLinux-4-security-updates-latest InRelease [7,555 B]
Get:3 http://apt.cumulusnetworks.com CumulusLinux-4-latest-updates InRelease [7,660 B]
Get:4 http://apt.cumulusnetworks.com CumulusLinux-4-latest/cumulus Sources [20 B]
Get:5 http://apt.cumulusnetworks.com CumulusLinux-4-latest/upstream Sources [20 B]
Get:6 http://apt.cumulusnetworks.com CumulusLinux-4-latest/cumulus amd64 Packages [38.4 kB]
Get:7 http://apt.cumulusnetworks.com CumulusLinux-4--latest/upstream amd64 Packages [445 kB]
Get:8 http://apt.cumulusnetworks.com CumulusLinux-4-security-updates-latest/cumulus Sources [20 B]
Get:9 http://apt.cumulusnetworks.com CumulusLinux-4-security-updates-latest/upstream Sources [11.8 kB]
Get:10 http://apt.cumulusnetworks.com CumulusLinux-4-security-updates-latest/cumulus amd64 Packages [20 B]
Get:11 http://apt.cumulusnetworks.com CumulusLinux-4-security-updates-latest/upstream amd64 Packages [8,941 B]
Get:12 http://apt.cumulusnetworks.com CumulusLinux-4-updates-latest/cumulus Sources [20 B]
Get:13 http://apt.cumulusnetworks.com CumulusLinux-4-updates-latest/upstream Sources [776 B]
Get:14 http://apt.cumulusnetworks.com CumulusLinux-4-updates-latest/cumulus amd64 Packages [38.4 kB]
Get:15 http://apt.cumulusnetworks.com CumulusLinux-4-updates-latest/upstream amd64 Packages [444 kB]
Ign http://apt.cumulusnetworks.com CumulusLinux-4-latest/cumulus Translation-en_US
Ign http://apt.cumulusnetworks.com CumulusLinux-4-latest/cumulus Translation-en
Ign http://apt.cumulusnetworks.com CumulusLinux-4-latest/upstream Translation-en_US
Ign http://apt.cumulusnetworks.com CumulusLinux-4-latest/upstream Translation-en
Ign http://apt.cumulusnetworks.com CumulusLinux-4-security-updates-latest/cumulus Translation-en_US
Ign http://apt.cumulusnetworks.com CumulusLinux-4-security-updates-latest/cumulus Translation-en
Ign http://apt.cumulusnetworks.com CumulusLinux-4-security-updates-latest/upstream Translation-en_US
Ign http://apt.cumulusnetworks.com CumulusLinux-4-security-updates-latest/upstream Translation-en
Ign http://apt.cumulusnetworks.com CumulusLinux-4-updates-latest/cumulus Translation-en_US
Ign http://apt.cumulusnetworks.com CumulusLinux-4-updates-latest/cumulus Translation-en
Ign http://apt.cumulusnetworks.com CumulusLinux-4-updates-latest/upstream Translation-en_US
Ign http://apt.cumulusnetworks.com CumulusLinux-4-updates-latest/upstream Translation-en
Fetched 1,011 kB in 1s (797 kB/s)
Reading package lists... Done

Use the -E option with sudo whenever you run any apt-get command. This option preserves your environment variables (such as HTTP proxies) before you install new packages or upgrade your distribution.

List Available Packages

After the cache is populated, use the apt-cache command to search the cache and find the packages in which you are interested or to get information about an available package.

Here are examples of the search and show sub-commands:

cumulus@switch:~$ apt-cache search tcp
collectd-core - statistics collection and monitoring daemon (core system)
fakeroot - tool for simulating superuser privileges
iperf - Internet Protocol bandwidth measuring tool
iptraf-ng - Next Generation Interactive Colorful IP LAN Monitor
libfakeroot - tool for simulating superuser privileges - shared libraries
libfstrm0 - Frame Streams (fstrm) library
libibverbs1 - Library for direct userspace use of RDMA (InfiniBand/iWARP)
libnginx-mod-stream - Stream module for Nginx
libqt4-network - Qt 4 network module
librtr-dev - Small extensible RPKI-RTR-Client C library - development files
librtr0 - Small extensible RPKI-RTR-Client C library
libwiretap8 - network packet capture library -- shared library
libwrap0 - Wietse Venema's TCP wrappers library
libwrap0-dev - Wietse Venema's TCP wrappers library, development files
netbase - Basic TCP/IP networking system
nmap-common - Architecture independent files for nmap
nuttcp - network performance measurement tool
openssh-client - secure shell (SSH) client, for secure access to remote machines
openssh-server - secure shell (SSH) server, for secure access from remote machines
openssh-sftp-server - secure shell (SSH) sftp server module, for SFTP access from remote machines
python-dpkt - Python 2 packet creation / parsing module for basic TCP/IP protocols
rsyslog - reliable system and kernel logging daemon
socat - multipurpose relay for bidirectional data transfer
tcpdump - command-line network traffic analyzer
cumulus@switch:~$ apt-cache show tcpdump
Package: tcpdump
Version: 4.9.3-1~deb10u1
Installed-Size: 1109
Maintainer: Romain Francoise <rfrancoise@debian.org>
Architecture: amd64
Replaces: apparmor-profiles-extra (<< 1.12~)
Depends: libc6 (>= 2.14), libpcap0.8 (>= 1.5.1), libssl1.1 (>= 1.1.0)
Suggests: apparmor (>= 2.3)
Breaks: apparmor-profiles-extra (<< 1.12~)
Size: 400060
SHA256: 3a63be16f96004bdf8848056f2621fbd863fadc0baf44bdcbc5d75dd98331fd3
SHA1: 2ab9f0d2673f49da466f5164ecec8836350aed42
MD5sum: 603baaf914de63f62a9f8055709257f3
Description: command-line network traffic analyzer
 This program allows you to dump the traffic on a network. tcpdump
 is able to examine IPv4, ICMPv4, IPv6, ICMPv6, UDP, TCP, SNMP, AFS
 BGP, RIP, PIM, DVMRP, IGMP, SMB, OSPF, NFS and many other packet
 types.
 .
 It can be used to print out the headers of packets on a network
 interface, filter packets that match a certain expression. You can
 use this tool to track down network problems, to detect attacks
 or to monitor network activities.
Description-md5: f01841bfda357d116d7ff7b7a47e8782
Homepage: http://www.tcpdump.org/
Multi-Arch: foreign
Section: net
Priority: optional
Filename: pool/upstream/t/tcpdump/tcpdump_4.9.3-1~deb10u1_amd64.deb

The search commands look for the search terms not only in the package name but in other parts of the package information; the search matches on more packages than you might expect.

List Packages Installed on the System

apt-cache command shows information about all the packages available in the repository. To see which packages are actually installed on your system with their versions, run the following commands.

Run the net show package version command:

cumulus@switch:~$ net show package version
Package                            Installed Version(s)
---------------------------------  -----------------------------------------------------------------------
acpi                               1.7-1.1
acpi-support-base                  0.142-8
acpid                              1:2.0.31-1
adduser                            3.118
apt                                1.8.2
arping                             2.19-6
arptables                          0.0.4+snapshot20181021-4

Run the dpkg -l command:

cumulus@switch:~$ dpkg -l
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                Version                   Architecture Description
+++-===================-=========================-============-=================================
ii  acpi                1.7-1.1                   amd64        displays information on ACPI devices
ii  acpi-support-base   0.142-8                   all          scripts for handling base ACPI events such as th
ii  acpid               1:2.0.31-1                amd64        Advanced Configuration and Power Interface event
ii  adduser             3.118                     all          add and remove users and groups
ii  apt                 1.8.2                     amd64        commandline package manager
ii  arping              2.19-6                    amd64        sends IP and/or ARP pings (to the MAC address)
ii  arptables           0.0.4+snapshot20181021-4  amd64        ARP table administration
...

The apps repository was removed in Cumulus Linux 4.0.0.

Show the Version of a Package

To show the version of a specific package installed on the system:

Run the net show package version <package> command. For example, the following command shows which version of the vrf package is installed on the system:

cumulus@switch:~$ net show package version vrf
1.0-cl4u1

Run the Linux dpkg -l <package_name> command. For example, the following command shows which version of the vrf package is installed on the system:

cumulus@switch:~$ dpkg -l vrf
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name       Version      Architecture Description
+++-==========-============-============-=================================
ii  vrf        1.0-cl4u1    amd64        Linux tools for VRF

Upgrade Packages

You cannot upgrade to Cumulus Linux 4.0 from Cumulus 3.7 by upgrading packages. You must install a disk image using ONIE. Refer to Upgrading Cumulus Linux.

To upgrade all the packages installed on the system to their latest versions, run the following commands:

cumulus@switch:~$ sudo -E apt-get update
cumulus@switch:~$ sudo -E apt-get upgrade

A list of packages that will be upgraded is displayed and you are prompted to continue.

The above commands upgrade all installed versions with their latest versions but do not install any new packages.

Add Packages from Another Repository

As shipped, Cumulus Linux searches the Cumulus Linux repository for available packages. You can add additional repositories to search by adding them to the list of sources that apt-get consults. See man sources.list for more information.

NVIDIA has added features or made bug fixes to certain packages; you must not replace these packages with versions from other repositories. Cumulus Linux is configured to ensure that the packages from the Cumulus Linux repository are always preferred over packages from other repositories.

If you want to install packages that are not in the Cumulus Linux repository, the procedure is the same as above, but with one additional step.

Packages that are not part of the Cumulus Linux Repository are not typically tested and might not be supported by Cumulus Linux Technical Support.

Installing packages outside of the Cumulus Linux repository requires the use of sudo -E apt-get; however, depending on the package, you can use easy-install and other commands.

To install a new package, complete the following steps:

  1. Run the dpkg command to ensure that the package is not already installed on the system:

    cumulus@switch:~$ dpkg -l | grep {name of package}
    
  2. If the package is installed already, ensure it is the version you need. If it is an older version, update the package from the Cumulus Linux repository:

    cumulus@switch:~$ sudo -E apt-get update
    cumulus@switch:~$ sudo -E apt-get install {name of package}
    cumulus@switch:~$ sudo -E apt-get upgrade
    
  3. If the package is not on the system, the package source location is most likely not in the /etc/apt/sources.list file. If the source for the new package is not in sources.list, edit and add the appropriate source to the file. For example, add the following if you want a package from the Debian repository that is not in the Cumulus Linux repository:

    deb http://http.us.debian.org/debian buster main
    deb http://security.debian.org/ buster/updates main
    

    Otherwise, the repository might be listed in /etc/apt/sources.list but is commented out, as can be the case with the early-access repository:

    #deb http://apt.cumulusnetworks.com/repo CumulusLinux-4-early-access cumulus
    

    To uncomment the repository, remove the # at the start of the line, then save the file:

    deb http://apt.cumulusnetworks.com/repo CumulusLinux-4-early-access cumulus
    
  4. Run sudo -E apt-get update, then install the package and upgrade:

    cumulus@switch:~$ sudo -E apt-get update
    cumulus@switch:~$ sudo -E apt-get install {name of package}
    cumulus@switch:~$ sudo -E apt-get upgrade
    

Add Packages from the Cumulus Linux Local Archive

Cumulus Linux contains a local archive embedded in the Cumulus Linux disk image. This archive contains the packages needed to install ifplugd, LDAP, RADIUS or TACACS+ without needing a network connection.

The archive is called cumulus-local-apt-archive and is referenced in the /etc/apt/cumulus-local-apt-archive-sources.list file. It contains the following packages:

You add these packages normally with apt-get update && apt-get install, as described above.

Caveats and Errata

At this time, you cannot directly browse the contents of the apt.cumulusnetworks.com repository using HTTP.

Zero Touch Provisioning - ZTP

Zero touch provisioning (ZTP) enables you to deploy network devices quickly in large-scale environments. On first boot, Cumulus Linux invokes ZTP, which executes the provisioning automation used to deploy the device for its intended role in the network.

The provisioning framework allows for a one-time, user-provided script to be executed. You can develop this script using a variety of automation tools and scripting languages, providing ample flexibility for you to design the provisioning scheme to meet your needs. You can also use it to add the switch to a configuration management (CM) platform such as Puppet, Chef, CFEngine or possibly a custom, proprietary tool.

While developing and testing the provisioning logic, you can use the ztp command in Cumulus Linux to manually invoke your provisioning script on a device.

ZTP in Cumulus Linux can occur automatically in one of the following ways, in this order:

Each method is discussed in greater detail below.

Use a Local File

ZTP only looks once for a ZTP script on the local file system when the switch boots. ZTP searches for an install script that matches an ONIE-style waterfall in /var/lib/cumulus/ztp, looking for the most specific name first, and ending at the most generic:

For example:

cumulus-ztp-amd64-cel_pebble-rUNKNOWN
cumulus-ztp-amd64-cel_pebble
cumulus-ztp-cel_pebble
cumulus-ztp-amd64
cumulus-ztp

You can also trigger the ZTP process manually by running the ztp --run <URL> command, where the URL is the path to the ZTP script.

Use a USB Drive

This feature has been tested only with thumb drives, not an actual external large USB hard drive.

If the ztp process does not discover a local script, it tries once to locate an inserted but unmounted USB drive. If it discovers one, it begins the ZTP process.

Cumulus Linux supports the use of a FAT32, FAT16, or VFAT-formatted USB drive as an installation source for ZTP scripts. You must plug in the USB drive before you power up the switch.

At minimum, the script must:

Follow these steps to perform ZTP using a USB drive:

  1. Copy the Cumulus Linux license and installation image to the USB drive.
  2. The ztp process searches the root filesystem of the newly mounted drive for filenames matching an ONIE-style waterfall (see the patterns and examples above), looking for the most specific name first, and ending at the most generic.
  3. The contents of the script are parsed to ensure it contains the CUMULUS-AUTOPROVISIONING flag (see example scripts).

The USB drive is mounted to a temporary directory under /tmp (for example, /tmp/tmpigGgjf/). To reference files on the USB drive, use the environment variable ZTP_USB_MOUNTPOINT to refer to the USB root partition.

ZTP over DHCP

If the ztp process does not discover a local/ONIE script or applicable USB drive, it checks DHCP every ten seconds for up to five minutes for the presence of a ZTP URL specified in /var/run/ztp.dhcp. The URL can be any of HTTP, HTTPS, FTP, or TFTP.

For ZTP using DHCP, provisioning initially takes place over the management network and is initiated through a DHCP hook. A DHCP option is used to specify a configuration script. This script is then requested from the Web server and executed locally on the switch.

The ZTP process over DHCP follows these steps:

  1. The first time you boot Cumulus Linux, eth0 is configured for DHCP and makes a DHCP request.
  2. The DHCP server offers a lease to the switch.
  3. If option 239 is present in the response, the ZTP process starts.
  4. The ZTP process requests the contents of the script from the URL, sending additional HTTP headers containing details about the switch.
  5. The contents of the script are parsed to ensure it contains the CUMULUS-AUTOPROVISIONING flag (see example scripts).
  6. If provisioning is necessary, the script executes locally on the switch with root privileges.
  7. The return code of the script is examined. If it is 0, the provisioning state is marked as complete in the autoprovisioning configuration file.

Trigger ZTP over DHCP

If provisioning has not already occurred, it is possible to trigger the ZTP process over DHCP when eth0 is set to use DHCP and one of the following events occur:

You can also run the ztp --run <URL> command, where the URL is the path to the ZTP script.

Configure the DHCP Server

During the DHCP process over eth0, Cumulus Linux requests DHCP option 239. This option is used to specify the custom provisioning script.

For example, the /etc/dhcp/dhcpd.conf file for an ISC DHCP server looks like:

option cumulus-provision-url code 239 = text;

  subnet 192.0.2.0 netmask 255.255.255.0 {
  range 192.0.2.100 192.168.0.200;
  option cumulus-provision-url "http://192.0.2.1/demo.sh";
}

Additionally, you can specify the hostname of the switch with the host-name option:

subnet 192.168.0.0 netmask 255.255.255.0 {
  range 192.168.0.100 192.168.0.200;
  option cumulus-provision-url "http://192.0.2.1/demo.sh";
  host dc1-tor-sw1 { hardware ethernet 44:38:39:00:1a:6b; fixed-address 192.168.0.101; option host-name "dc1-tor-sw1"; }
}

Do not use an underscore (_) in the hostname; underscores are not permitted in hostnames.

Inspect HTTP Headers

The following HTTP headers are sent in the request to the webserver to retrieve the provisioning script:

Header                        Value                 Example
------                        -----                 -------
User-Agent                                          CumulusLinux-AutoProvision/0.4
CUMULUS-ARCH                  CPU architecture      x86_64
CUMULUS-BUILD                                       4.0.0-5c6829a-201309251712-final
CUMULUS-LICENSE-INSTALLED     Either 0 or 1         1
CUMULUS-MANUFACTURER                                odm
CUMULUS-PRODUCTNAME                                 switch_model
CUMULUS-SERIAL                                      XYZ123004
CUMULUS-BASE-MAC                                    44:38:39:FF:40:94
CUMULUS-MGMT-MAC                                    44:38:39:FF:00:00
CUMULUS-VERSION                                     4.0.0
CUMULUS-PROV-COUNT                                  0
CUMULUS-PROV-MAX                                    32

Write ZTP Scripts

Remember to include the following line in any of the supported scripts that you expect to run using the autoprovisioning framework.

# CUMULUS-AUTOPROVISIONING

This line is required somewhere in the script file for execution to occur.

The script must contain the CUMULUS-AUTOPROVISIONING flag. You can include this flag in a comment or remark; the flag does not need to be echoed or written to stdout.

You can write the script in any language currently supported by Cumulus Linux, such as:

The script must return an exit code of 0 upon success, as this triggers the autoprovisioning process to be marked as complete in the autoprovisioning configuration file.

The following script installs Cumulus Linux and its license from a USB drive and applies a configuration:

#!/bin/bash
function error() {
  echo -e "\e[0;33mERROR: The ZTP script failed while running the command $BASH_COMMAND at line $BASH_LINENO.\e[0m" >&2
  exit 1
}

# Log all output from this script
exec >> /var/log/autoprovision 2>&1
date "+%FT%T ztp starting script $0"

trap error ERR

#Add Debian Repositories
echo "deb http://http.us.debian.org/debian buster main" >> /etc/apt/sources.list
echo "deb http://security.debian.org/ buster/updates main" >> /etc/apt/sources.list

#Update Package Cache
apt-get update -y

#Load interface config from usb
cp ${ZTP_USB_MOUNTPOINT}/interfaces /etc/network/interfaces

#Load port config from usb
#   (if breakout cables are used for certain interfaces)
cp ${ZTP_USB_MOUNTPOINT}/ports.conf /etc/cumulus/ports.conf

#Install a License from usb and restart switchd
/usr/cumulus/bin/cl-license -i ${ZTP_USB_MOUNTPOINT}/license.txt && systemctl restart switchd.service

#Reload interfaces to apply loaded config
ifreload -a

#Output state of interfaces
net show interface

# CUMULUS-AUTOPROVISIONING
exit 0

Best Practices

ZTP scripts come in different forms and frequently perform many of the same tasks. As BASH is the most common language used for ZTP scripts, the following BASH snippets are provided to accelerate your ability to perform common tasks with robust error checking.

Install a License

Use the following function to include error checking for license file installation.

function install_license(){
     # Install license
     echo "$(date) INFO: Installing License..."
     echo $1 | /usr/cumulus/bin/cl-license -i
     return_code=$?
     if [ "$return_code" == "0" ]; then
         echo "$(date) INFO: License Installed."
     else
         echo "$(date) ERROR: License not installed. Return code was: $return_code"
         /usr/cumulus/bin/cl-license
         exit 1
     fi
}

Test DNS Name Resolution

DNS names are frequently used in ZTP scripts. The ping_until_reachable function tests that each DNS name resolves into a reachable IP address. Call this function with each DNS target used in your script before you use the DNS name elsewhere in your script.

The following example shows how to call the ping_until_reachable function in the context of a larger task.

function ping_until_reachable(){
    last_code=1
    max_tries=30
    tries=0
    while [ "0" != "$last_code" ] && [ "$tries" -lt "$max_tries" ]; do
        tries=$((tries+1))
        echo "$(date) INFO: ( Attempt $tries of $max_tries ) Pinging $1 Target Until Reachable."
        ping $1 -c2 &> /dev/null
        last_code=$?
            sleep 1
    done
    if [ "$tries" -eq "$max_tries" ] && [ "$last_code" -ne "0" ]; then
        echo "$(date) ERROR: Reached maximum number of attempts to ping the target $1 ."
        exit 1
    fi
}

Check the Cumulus Linux Release

The following script segment demonstrates how to check which Cumulus Linux release is running currently and upgrades the node if the release is not the target release. If the release is the target release, normal ZTP tasks execute. This script calls the ping_until_reachable script (described above) to make sure the server holding the image server and the ZTP script is reachable.

function init_ztp(){
    #do normal ZTP tasks
}

CUMULUS_TARGET_RELEASE=3.5.3
CUMULUS_CURRENT_RELEASE=$(cat /etc/lsb-release  | grep RELEASE | cut -d "=" -f2)
IMAGE_SERVER_HOSTNAME=webserver.example.com
IMAGE_SERVER= "http:// "$IMAGE_SERVER_HOSTNAME "/ "$CUMULUS_TARGET_RELEASE ".bin "
ZTP_URL= "http:// "$IMAGE_SERVER_HOSTNAME "/ztp.sh "

if [ "$CUMULUS_TARGET_RELEASE" != "$CUMULUS_CURRENT_RELEASE" ]; then
    ping_until_reachable $IMAGE_SERVER_HOSTNAME
    /usr/cumulus/bin/onie-install -fa -i $IMAGE_SERVER -z $ZTP_URL && reboot
else
    init_ztp && reboot
fi
exit 0

Apply Management VRF Configuration

If you apply a management VRF in your script, either apply it last or reboot instead. If you do not apply a management VRF last, you need to prepend any commands that require eth0 to communicate out with /usr/bin/ip vrf exec mgmt; for example, /usr/bin/ip vrf exec mgmt apt-get update -y.

Perform Ansible Provisioning Callbacks

After initially configuring a node with ZTP, use Provisioning Callbacks to inform Ansible Tower or AWX that the node is ready for more detailed provisioning. The following example demonstrates how to use a provisioning callback:

/usr/bin/curl -H "Content-Type:application/json" -k -X POST --data '{"host_config_key":"'somekey'"}' -u username:password http://ansible.example.com/api/v2/job_templates/1111/callback/

Disable the DHCP Hostname Override Setting

Make sure to disable the DHCP hostname override setting in your script (NCLU does this automatically).

function set_hostname(){
    # Remove DHCP Setting of Hostname
    sed s/'SETHOSTNAME="yes"'/'SETHOSTNAME="no"'/g -i /etc/dhcp/dhclient-exit-hooks.d/dhcp-sethostname
    hostnamectl set-hostname $1
}

NCLU in ZTP Scripts

Not all aspects of NCLU are supported when running during ZTP. Use traditional Linux methods of providing configuration to the switch during ZTP.

When you use NCLU in ZTP scripts, add the following loop to make sure NCLU has time to start up before being called.

# Waiting for NCLU to finish starting up
last_code=1
while [ "1" == "$last_code" ]; do
    net show interface &> /dev/null
    last_code=$?
done

net add vrf mgmt
net add time zone Etc/UTC
net add time ntp server 192.168.0.254 iburst
net commit

Test ZTP Scripts

There are a few commands you can use to test and debug your ZTP scripts.

You can use verbose mode to debug your script and see where your script failed. Include the -v option when you run ZTP:

cumulus@switch:~$ sudo ztp -v -r http://192.0.2.1/demo.sh
Attempting to provision via ZTP Manual from http://192.0.2.1/demo.sh

Broadcast message from root@dell-s6010-01 (ttyS0) (Tue May 10 22:44:17 2016):  

ZTP: Attempting to provision via ZTP Manual from http://192.0.2.1/demo.sh
ZTP Manual: URL response code 200
ZTP Manual: Found Marker CUMULUS-AUTOPROVISIONING
ZTP Manual: Executing http://192.0.2.1/demo.sh
error: ZTP Manual: Payload returned code 1
error: Script returned failure

To see if ZTP is enabled and to see results of the most recent execution, you can run the ztp -s command.

cumulus@switch:~$ ztp -s
ZTP INFO:

State              enabled
Version            1.0
Result             Script Failure
Date               Mon 20 May 2019 09:31:27 PM UTC
Method             ZTP DHCP
URL                http://192.0.2.1/demo.sh

If ZTP runs when the switch boots and not manually, you can run the systemctl -l status ztp.service then journalctl -l -u ztp.service to see if any failures occur:

cumulus@switch:~$ sudo systemctl -l status ztp.service
● ztp.service - Cumulus Linux ZTP
    Loaded: loaded (/lib/systemd/system/ztp.service; enabled)
    Active: failed (Result: exit-code) since Wed 2016-05-11 16:38:45 UTC; 1min 47s ago
        Docs: man:ztp(8)
    Process: 400 ExecStart=/usr/sbin/ztp -b (code=exited, status=1/FAILURE)
    Main PID: 400 (code=exited, status=1/FAILURE)

May 11 16:37:45 cumulus ztp[400]: ztp [400]: ZTP USB: Device not found
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: ZTP DHCP: Looking for ZTP Script provided by DHCP
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: Attempting to provision via ZTP DHCP from http://192.0.2.1/demo.sh
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: ZTP DHCP: URL response code 200
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: ZTP DHCP: Found Marker CUMULUS-AUTOPROVISIONING
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: ZTP DHCP: Executing http://192.0.2.1/demo.sh
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: ZTP DHCP: Payload returned code 1
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: Script returned failure
May 11 16:38:45 dell-s6010-01 systemd[1]: ztp.service: main process exited, code=exited, status=1/FAILURE
May 11 16:38:45 dell-s6010-01 systemd[1]: Unit ztp.service entered failed state.
cumulus@switch:~$
cumulus@switch:~$ sudo journalctl -l -u ztp.service --no-pager
-- Logs begin at Wed 2016-05-11 16:37:42 UTC, end at Wed 2016-05-11 16:40:39 UTC. --
May 11 16:37:45 cumulus ztp[400]: ztp [400]: /var/lib/cumulus/ztp: Sate Directory does not exist. Creating it...
May 11 16:37:45 cumulus ztp[400]: ztp [400]: /var/run/ztp.lock: Lock File does not exist. Creating it...
May 11 16:37:45 cumulus ztp[400]: ztp [400]: /var/lib/cumulus/ztp/ztp_state.log: State File does not exist. Creating it...
May 11 16:37:45 cumulus ztp[400]: ztp [400]: ZTP LOCAL: Looking for ZTP local Script
May 11 16:37:45 cumulus ztp[400]: ztp [400]: ZTP LOCAL: Waterfall search for /var/lib/cumulus/ztp/cumulus-ztp-x86_64-dell_s6010_s1220-rUNKNOWN
May 11 16:37:45 cumulus ztp[400]: ztp [400]: ZTP LOCAL: Waterfall search for /var/lib/cumulus/ztp/cumulus-ztp-x86_64-dell_s6010_s1220
May 11 16:37:45 cumulus ztp[400]: ztp [400]: ZTP LOCAL: Waterfall search for /var/lib/cumulus/ztp/cumulus-ztp-x86_64-dell
May 11 16:37:45 cumulus ztp[400]: ztp [400]: ZTP LOCAL: Waterfall search for /var/lib/cumulus/ztp/cumulus-ztp-x86_64
May 11 16:37:45 cumulus ztp[400]: ztp [400]: ZTP LOCAL: Waterfall search for /var/lib/cumulus/ztp/cumulus-ztp
May 11 16:37:45 cumulus ztp[400]: ztp [400]: ZTP USB: Looking for unmounted USB devices
May 11 16:37:45 cumulus ztp[400]: ztp [400]: ZTP USB: Parsing partitions
May 11 16:37:45 cumulus ztp[400]: ztp [400]: ZTP USB: Device not found
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: ZTP DHCP: Looking for ZTP Script provided by DHCP
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: Attempting to provision via ZTP DHCP from http://192.0.2.1/demo.sh
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: ZTP DHCP: URL response code 200
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: ZTP DHCP: Found Marker CUMULUS-AUTOPROVISIONING
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: ZTP DHCP: Executing http://192.0.2.1/demo.sh
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: ZTP DHCP: Payload returned code 1
May 11 16:38:45 dell-s6010-01 ztp[400]: ztp [400]: Script returned failure
May 11 16:38:45 dell-s6010-01 systemd[1]: ztp.service: main process exited, code=exited, status=1/FAILURE
May 11 16:38:45 dell-s6010-01 systemd[1]: Unit ztp.service entered failed state.

Instead of running journalctl, you can see the log history by running:

cumulus@switch:~$ cat /var/log/syslog | grep ztp
2016-05-11T16:37:45.132583+00:00 cumulus ztp [400]: /var/lib/cumulus/ztp: State Directory does not exist. Creating it...
2016-05-11T16:37:45.134081+00:00 cumulus ztp [400]: /var/run/ztp.lock: Lock File does not exist. Creating it...
2016-05-11T16:37:45.135360+00:00 cumulus ztp [400]: /var/lib/cumulus/ztp/ztp_state.log: State File does not exist. Creating it...
2016-05-11T16:37:45.185598+00:00 cumulus ztp [400]: ZTP LOCAL: Looking for ZTP local Script
2016-05-11T16:37:45.485084+00:00 cumulus ztp [400]: ZTP LOCAL: Waterfall search for /var/lib/cumulus/ztp/cumulus-ztp-x86_64-dell_s6010_s1220-rUNKNOWN
2016-05-11T16:37:45.486394+00:00 cumulus ztp [400]: ZTP LOCAL: Waterfall search for /var/lib/cumulus/ztp/cumulus-ztp-x86_64-dell_s6010_s1220
2016-05-11T16:37:45.488385+00:00 cumulus ztp [400]: ZTP LOCAL: Waterfall search for /var/lib/cumulus/ztp/cumulus-ztp-x86_64-dell
2016-05-11T16:37:45.489665+00:00 cumulus ztp [400]: ZTP LOCAL: Waterfall search for /var/lib/cumulus/ztp/cumulus-ztp-x86_64
2016-05-11T16:37:45.490854+00:00 cumulus ztp [400]: ZTP LOCAL: Waterfall search for /var/lib/cumulus/ztp/cumulus-ztp
2016-05-11T16:37:45.492296+00:00 cumulus ztp [400]: ZTP USB: Looking for unmounted USB devices
2016-05-11T16:37:45.493525+00:00 cumulus ztp [400]: ZTP USB: Parsing partitions
2016-05-11T16:37:45.636422+00:00 cumulus ztp [400]: ZTP USB: Device not found
2016-05-11T16:38:43.372857+00:00 cumulus ztp [1805]: Found ZTP DHCP Request
2016-05-11T16:38:45.696562+00:00 cumulus ztp [400]: ZTP DHCP: Looking for ZTP Script provided by DHCP
2016-05-11T16:38:45.698598+00:00 cumulus ztp [400]: Attempting to provision via ZTP DHCP from http://192.0.2.1/demo.sh
2016-05-11T16:38:45.816275+00:00 cumulus ztp [400]: ZTP DHCP: URL response code 200
2016-05-11T16:38:45.817446+00:00 cumulus ztp [400]: ZTP DHCP: Found Marker CUMULUS-AUTOPROVISIONING
2016-05-11T16:38:45.818402+00:00 cumulus ztp [400]: ZTP DHCP: Executing http://192.0.2.1/demo.sh
2016-05-11T16:38:45.834240+00:00 cumulus ztp [400]: ZTP DHCP: Payload returned code 1
2016-05-11T16:38:45.835488+00:00 cumulus ztp [400]: Script returned failure
2016-05-11T16:38:45.876334+00:00 cumulus systemd[1]: ztp.service: main process exited, code=exited, status=1/FAILURE
2016-05-11T16:38:45.879410+00:00 cumulus systemd[1]: Unit ztp.service entered failed state.

If you see that the issue is a script failure, you can modify the script and then run ZTP manually using ztp -v -r <URL/path to that script>, as above.

cumulus@switch:~$ sudo ztp -v -r http://192.0.2.1/demo.sh
Attempting to provision via ZTP Manual from http://192.0.2.1/demo.sh

Broadcast message from root@dell-s6010-01 (ttyS0) (Tue May 10 22:44:17 2019):  

ZTP: Attempting to provision via ZTP Manual from http://192.0.2.1/demo.sh
ZTP Manual: URL response code 200
ZTP Manual: Found Marker CUMULUS-AUTOPROVISIONING
ZTP Manual: Executing http://192.0.2.1/demo.sh
error: ZTP Manual: Payload returned code 1
error: Script returned failure
cumulus@switch:~$ sudo ztp -s
State         enabled
Version       1.0
Result        Script Failure
Date          Mon 20 May 2019 09:31:27 PM UTC
Method        ZTP Manual
URL           http://192.0.2.1/demo.sh

Use the following command to check syslog for information about ZTP:

cumulus@switch:~$ sudo grep -i ztp /var/log/syslog

Common ZTP Script Errors

Could not find referenced script/interpreter in downloaded payload

cumulus@leaf01:~$ sudo cat /var/log/syslog | grep ztp
2018-04-24T15:06:08.887041+00:00 leaf01 ztp [13404]: Attempting to provision via ZTP Manual from http://192.168.0.254/ztp_oob_windows.sh
2018-04-24T15:06:09.106633+00:00 leaf01 ztp [13404]: ZTP Manual: URL response code 200
2018-04-24T15:06:09.107327+00:00 leaf01 ztp [13404]: ZTP Manual: Found Marker CUMULUS-AUTOPROVISIONING
2018-04-24T15:06:09.107635+00:00 leaf01 ztp [13404]: ZTP Manual: Executing http://192.168.0.254/ztp_oob_windows.sh
2018-04-24T15:06:09.132651+00:00 leaf01 ztp [13404]: ZTP Manual: Could not find referenced script/interpreter in downloaded payload.
2018-04-24T15:06:14.135521+00:00 leaf01 ztp [13404]: ZTP Manual: Retrying
2018-04-24T15:06:14.138915+00:00 leaf01 ztp [13404]: ZTP Manual: URL response code 200
2018-04-24T15:06:14.139162+00:00 leaf01 ztp [13404]: ZTP Manual: Found Marker CUMULUS-AUTOPROVISIONING
2018-04-24T15:06:14.139448+00:00 leaf01 ztp [13404]: ZTP Manual: Executing http://192.168.0.254/ztp_oob_windows.sh
2018-04-24T15:06:14.143261+00:00 leaf01 ztp [13404]: ZTP Manual: Could not find referenced script/interpreter in downloaded payload.
2018-04-24T15:06:24.147580+00:00 leaf01 ztp [13404]: ZTP Manual: Retrying
2018-04-24T15:06:24.150945+00:00 leaf01 ztp [13404]: ZTP Manual: URL response code 200
2018-04-24T15:06:24.151177+00:00 leaf01 ztp [13404]: ZTP Manual: Found Marker CUMULUS-AUTOPROVISIONING
2018-04-24T15:06:24.151374+00:00 leaf01 ztp [13404]: ZTP Manual: Executing http://192.168.0.254/ztp_oob_windows.sh
2018-04-24T15:06:24.155026+00:00 leaf01 ztp [13404]: ZTP Manual: Could not find referenced script/interpreter in downloaded payload.
2018-04-24T15:06:39.164957+00:00 leaf01 ztp [13404]: ZTP Manual: Retrying
2018-04-24T15:06:39.165425+00:00 leaf01 ztp [13404]: Script returned failure
2018-04-24T15:06:39.175959+00:00 leaf01 ztp [13404]: ZTP script failed. Exiting...

Errors in syslog for ZTP like those shown above often occur if the script is created (or edited as some point) on a Windows machine. Check to make sure that the \r\n characters are not present in the end-of-line encodings.

Use the cat -v ztp.sh command to view the contents of the script and search for any hidden characters.

root@oob-mgmt-server:/var/www/html# cat -v ./ztp_oob_windows.sh 
#!/bin/bash^M
^M
###################^M
#   ZTP Script^M
###################^M
^M
/usr/cumulus/bin/cl-license -i http://192.168.0.254/license.txt^M
^M
# Clean method of performing a Reboot^M
nohup bash -c 'sleep 2; shutdown now -r "Rebooting to Complete ZTP"' &^M
^M
exit 0^M
^M
# The line below is required to be a valid ZTP script^M
#CUMULUS-AUTOPROVISIONING^M
root@oob-mgmt-server:/var/www/html#

The ^M characters in the output of your ZTP script, as shown above, indicate the presence of Windows end-of-line encodings that you need to remove.

Use the translate (tr) command on any Linux system to remove the '\r' characters from the file.

root@oob-mgmt-server:/var/www/html# tr -d '\r' < ztp_oob_windows.sh > ztp_oob_unix.sh
root@oob-mgmt-server:/var/www/html# cat -v ./ztp_oob_unix.sh 
#!/bin/bash
###################
#   ZTP Script
###################
/usr/cumulus/bin/cl-license -i http://192.168.0.254/license.txt
# Clean method of performing a Reboot
nohup bash -c 'sleep 2; shutdown now -r "Rebooting to Complete ZTP"' &
exit 0
# The line below is required to be a valid ZTP script
#CUMULUS-AUTOPROVISIONING
root@oob-mgmt-server:/var/www/html#

Manually Use the ztp Command

To enable ZTP, use the -e option:

cumulus@switch:~$ sudo ztp -e

Enabling ZTP means that ZTP tries to run the next time the switch boots. However, if ZTP already ran on a previous boot up or if a manual configuration has been found, ZTP will just exit without trying to look for any script.

ZTP checks for these manual configurations during bootup:

  • Password changes
  • Users and groups changes
  • Packages changes
  • Interfaces changes
  • The presence of an installed license

When the switch is booted for the very first time, ZTP records the state of important files that are most likely going to be modified after that the switch is configured. If ZTP is still enabled after a reboot, ZTP compares the recorded state to the current state of these files. If they do not match, ZTP considers that the switch has already been provisioned and exits. These files are only erased after a reset.

To reset ZTP to its original state, use the -R option. This removes the ztp directory and ZTP runs the next time the switch reboots.

cumulus@switch:~$ sudo ztp -R

To disable ZTP, use the -d option:

cumulus@switch:~$ sudo ztp -d

To force provisioning to occur and ignore the status listed in the configuration file, use the -r option:

cumulus@switch:~$ sudo ztp -r cumulus-ztp.sh

To see the current ZTP state, use the -s option:

cumulus@switch:~$ sudo ztp -s
ZTP INFO:
State          disabled
Version        1.0
Result         success
Date           Mon May 20 21:51:04 2019 UTC
Method         Switch manually configured  
URL            None

Notes

System Configuration

This section describes how to configure your Cumulus Linux switch. You can set the date and time, configure authentication, authorization, and accounting and configure access control lists (ACLs), which control the traffic entering your network.

This section also describes the services and daemons that Cumulus Linux uses, and describes how to configure switchd, the daemon at the heart of Cumulus Linux.

An overview of the Network Command Line Utility (NCLU) is also provided.

Network Command Line Utility - NCLU

The Network Command Line Utility (NCLU) is a command line interface for that simplifies the networking configuration process.

NCLU resides in the Linux user space and provides consistent access to networking commands directly through bash, making configuration and troubleshooting simple and easy; no need to edit files or enter modes and sub-modes. NCLU provides these benefits:

The NCLU wrapper utility called net is capable of configuring layer 2 and layer 3 features of the networking stack, installing ACLs and VXLANs, restoring configuration files, as well as providing monitoring and troubleshooting functionality for these features. You can configure both the /etc/network/interfaces and /etc/frr/frr.conf files with net, in addition to running show and clear commands related to ifupdown2 and FRRouting.

If you use automation to configure your switches, NVIDIA recommends that you do not use NCLU. Edit configuration files directly.

NCLU Basics

Use the following workflow to stage and commit changes to Cumulus Linux with NCLU:

  1. Use the net add and net del commands to stage and remove configuration changes.
  2. Use the net pending command to review staged changes.
  3. Use net commit and net abort to commit and delete staged changes.

net commit applies the changes to the relevant configuration files, such as /etc/network/interfaces, then runs necessary follow on commands to enable the configuration, such as ifreload -a.

If two different users try to commit a change at the same time, NCLU displays a warning but implements the change according to the first commit received. The second user will need to abort the commit.

When you have a running configuration, you can review and update the configuration with the following commands:

Tab Completion, Verification, and Inline Help

In addition to tab completion and partial keyword command identification, NCLU includes verification checks to ensure you use the correct syntax. The examples below show the output for incorrect commands:

cumulus@switch:~$ net add bgp router-id 1.1.1.1/32
ERROR: Command not found

Did you mean one of the following?
    net add bgp router-id <ipv4>
        This command is looking for an IP address, not an IP/prefixlen

cumulus@switch:~$ net add bgp router-id 1.1.1.1
cumulus@switch:~$ net add int swp10 mtu <TAB>
    <552-9216> :
cumulus@switch:~$ net add int swp10 mtu 9300
ERROR: Command not found

Did you mean one of the following?
    net add interface <interface> mtu <552-9216>

NCLU has a comprehensive built in help system. In addition to the net man page, you can use ?and help to display available commands:

cumulus@switch:~$ net help

Usage:
    # net <COMMAND> [<ARGS>] [help]
    #
    # net is a command line utility for networking on Cumulus Linux switches.
    #
    # COMMANDS are listed below and have context specific arguments which can
    # be explored by typing "<TAB>" or "help" anytime while using net.
    #
    # Use 'man net' for a more comprehensive overview.

    net abort
    net commit [verbose] [confirm [<number-seconds>]] [description <wildcard>]
    net commit permanent <wildcard>
    net del all
    net help [verbose]
    net pending [json]
    net rollback (<number>|last)
    net rollback description <wildcard-snapshot>
    net show commit (history|<number>|last)
    net show rollback (<number>|last)
    net show rollback description <wildcard-snapshot>
    net show configuration [commands|files|acl|bgp|multicast|ospf|ospf6]
    net show configuration interface [<interface>] [json]

Options:

    # Help commands
    help     : context sensitive information; see section below
    example  : detailed examples of common workflows

    # Configuration commands
    add      : add/modify configuration
    del      : remove configuration


    # Commit buffer commands
    abort    : abandon changes in the commit buffer
    commit   : apply the commit buffer to the system
    pending  : show changes staged in the commit buffer
    rollback : revert to a previous configuration state

    # Status commands
    show     : show command output
    clear    : clear counters, BGP neighbors, etc

cumulus@switch:~$ net help bestpath
The following commands contain keyword(s) 'bestpath'

    net (add|del) bgp bestpath as-path multipath-relax [as-set|no-as-set]
    net (add|del) bgp bestpath compare-routerid
    net (add|del) bgp bestpath med missing-as-worst
    net (add|del) bgp ipv4 labeled-unicast neighbor <bgppeer> addpath-tx-bestpath-per-AS
    net (add|del) bgp ipv4 unicast neighbor <bgppeer> addpath-tx-bestpath-per-AS
    net (add|del) bgp ipv6 labeled-unicast neighbor <bgppeer> addpath-tx-bestpath-per-AS
    net (add|del) bgp ipv6 unicast neighbor <bgppeer> addpath-tx-bestpath-per-AS
    net (add|del) bgp neighbor <bgppeer> addpath-tx-bestpath-per-AS
    net (add|del) bgp vrf <text> bestpath as-path multipath-relax [as-set|no-as-set]
    net (add|del) bgp vrf <text> bestpath compare-routerid
    net (add|del) bgp vrf <text> bestpath med missing-as-worst
    net (add|del) bgp vrf <text> ipv4 labeled-unicast neighbor <bgppeer> addpath-tx-bestpath-per-AS
    net (add|del) bgp vrf <text> ipv4 unicast neighbor <bgppeer> addpath-tx-bestpath-per-AS
    net (add|del) bgp vrf <text> ipv6 labeled-unicast neighbor <bgppeer> addpath-tx-bestpath-per-AS
    net (add|del) bgp vrf <text> ipv6 unicast neighbor <bgppeer> addpath-tx-bestpath-per-AS
    net (add|del) bgp vrf <text> neighbor <bgppeer> addpath-tx-bestpath-per-AS
    net add bgp debug bestpath <ip/prefixlen>
    net del bgp debug bestpath [<ip/prefixlen>]
    net show bgp (<ipv4>|<ipv4/prefixlen>|<ipv6>|<ipv6/prefixlen>) [bestpath|multipath] [json]
    net show bgp vrf <text> (<ipv4>|<ipv4/prefixlen>|<ipv6>|<ipv6/prefixlen>) [bestpath|multipath] [json]

You can configure multiple interfaces at once:

cumulus@switch:~$ net add int swp7-9,12,15-17,22 mtu 9216

Search for Specific Commands

To search for specific NCLU commands so that you can identify the correct syntax to use, run the net help verbose | <term> command. For example, to show only commands that include clag (for MLAG):

cumulus@leaf01:mgmt:~$ net help verbose | grep clag
    net example clag basic-clag
    net example clag l2-with-server-vlan-trunks
    net example clag l3-uplinks-virtual-address
    net add clag peer sys-mac <mac-clag> interface <interface> (primary|secondary) [backup-ip <ipv4>]
    net add clag peer sys-mac <mac-clag> interface <interface> (primary|secondary) [backup-ip <ipv4> vrf <text>]
    net del clag peer
    net add clag port bond <interface> interface <interface> clag-id <0-65535>
    net del clag port bond <interface>
    net show clag [our-macs|our-multicast-entries|our-multicast-route|our-multicast-router-ports|peer-macs|peer-multicast-entries|peer-multicast-route|peer-multicast-router-ports|params|backup-ip|id] [verbose] [json]
    net show clag macs [<mac>] [json]
    net show clag neighbors [verbose]
    net show clag peer-lacp-rate
    net show clag verify-vlans [verbose]
    net show clag status [verbose] [json]
    net add bond <interface> clag id <0-65535>
    net add interface <interface> clag args <wildcard>
    net add interface <interface> clag backup-ip (<ipv4>|<ipv4> vrf <text>)
    net add interface <interface> clag enable (yes|no)
    net add interface <interface> clag peer-ip (<ipv4>|<ipv6>|linklocal)
    net add interface <interface> clag priority <0-65535>
    net add interface <interface> clag sys-mac <mac>
    net add loopback lo clag vxlan-anycast-ip <ipv4>
    net del bond <interface> clag id [<0-65535>]
    net del interface <interface> clag args [<wildcard>]
    ...

Add ? (Question Mark) Ability to NCLU

While tab completion is enabled by default, you can also configure NCLU to use the ? (question mark character) to look at available commands. To enable this feature for the cumulus user, open the following file:

cumulus@switch:~$ sudo nano ~/.inputrc

Uncomment the very last line in the .inputrc file so that the file changes from this:

# Uncomment to use ? as an alternative to
# ?: complete

to this:

# Uncomment to use ? as an alternative to
?: complete

Save the file and reconnect to the switch. The ? (question mark) abilitywill work on all subsequent sessions on the switch.

cumulus@switch:~$ net
    abort     :  abandon changes in the commit buffer
    add       :  add/modify configuration
    clear     :  clear counters, BGP neighbors, etc
    commit    :  apply the commit buffer to the system
    del       :  remove configuration
    example   :  detailed examples of common workflows
    help      :  Show this screen and exit
    pending   :  show changes staged in the commit buffer
    rollback  :  revert to a previous configuration state
    show      :  show command output

When the question mark is typed, NCLU autocompletes and shows all available options, but the question mark does not actually appear on the terminal. This is normal, expected behavior.

Built-In Examples

NCLU has a number of built in examples to guide you through basic configuration setup:

cumulus@switch:~$ net example
    acl              :  access-list
    bgp              :  Border Gateway Protocol
    bond             :  bond, port-channel, etc
    bridge           :  a layer2 bridge
    clag             :  Multi-Chassis Link Aggregation
    dhcp             :  Dynamic Host Configuration Protocol
    dot1x            :  Configure, Enable, Delete or Show IEEE 802.1X EAPOL
    evpn             :  Ethernet VPN
    link-settings    :  Physical link parameters
    management-vrf   :  Management VRF
    mlag             :  Multi-Chassis Link Aggregation
    ospf             :  Open Shortest Path First (OSPFv2)
    snmp-server      :  Configure the SNMP server
    syslog           :  Set syslog logging
    vlan-interfaces  :  IP interfaces for VLANs
    voice-vlan       :  VLAN used for IP Phones
    vrr              :  add help text
cumulus@switch:~$ net example bridge

Scenario
========
We are configuring switch1 and would like to configure the following
- configure switch1 as an L2 switch for host-11 and host-12
- enable vlans 10-20
- place host-11 in vlan 10
- place host-12 in vlan 20
- create an SVI interface for vlan 10
- create an SVI interface for vlan 20
- assign IP 10.0.0.1/24 to the SVI for vlan 10
- assign IP 20.0.0.1/24 to the SVI for vlan 20
- configure swp3 as a trunk for vlans 10, 11, 12 and 20
                  swp3
         *switch1 --------- switch2
            /\
      swp1 /  \ swp2
          /    \
         /      \
     host-11   host-12

switch1 net commands
====================
- enable vlans 10-20
switch1# net add vlan 10-20
- place host-11 in vlan 10
- place host-12 in vlan 20
switch1# net add int swp1 bridge access 10
switch1# net add int swp2 bridge access 20
- create an SVI interface for vlan 10
- create an SVI interface for vlan 20
- assign IP 10.0.0.1/24 to the SVI for vlan 10
- assign IP 20.0.0.1/24 to the SVI for vlan 20
switch1# net add vlan 10 ip address 10.0.0.1/24
switch1# net add vlan 20 ip address 20.0.0.1/24
- configure swp3 as a trunk for vlans 10, 11, 12 and 20
switch1# net add int swp3 bridge trunk vlans 10-12,20
switch1# net pending
switch1# net commit

Verification
============
switch1# net show interface
switch1# net show bridge macs

Configure User Accounts

You can configure user accounts in Cumulus Linux with read-only or edit permissions for NCLU:

The examples below demonstrate how to add a new user account or modify an existing user account called myuser.

To add a new user account with NCLU show permissions:

cumulus@switch:~$ sudo adduser --ingroup netshow myuser
Adding user `myuser' ...
Adding new user `myuser' (1001) with group `netshow'...
...

To add NCLU show permissions to a user account that already exists:

cumulus@switch:~$ sudo addgroup myuser netshow
Adding user `myuser' to group `netshow' ...
Adding user myuser to group netshow
Done

To add a new user account with NCLU edit permissions:

cumulus@switch:~$ sudo adduser --ingroup netedit myuser
Adding user `myuser' ...
Adding new user `myuser' (1001) with group `netedit'
...

To add NCLU edit permissions to a user account that already exists:

cumulus@switch:~$ sudo addgroup myuser netedit
Adding user `myuser' to group `netedit' ...
Adding user myuser to group netedit
Done

You can use the adduser command for local user accounts only. You can use the addgroup command for both local and remote user accounts. For a remote user account, you must use the mapping username, such as tacacs3 or radius_user, not the TACACS or RADIUS account name.

If the user tries to run commands that are not allowed, the following error displays:

myuser@switch:~$ net add hostname host01
ERROR: User username does not have permission to make networking changes.

Edit the netd.conf File

Instead of using the NCLU commands described above, you can manually configure users and groups to be able to run NCLU commands.

Edit the /etc/netd.conf file to add users to the users_with_edit and users_with_show lines in the file, then save the file.

For example, if you want the user netoperator to be able to run both edit and show commands, add the user to the users_with_edit and users_with_show lines in the /etc/netd.conf file:

cumulus@switch:~$ sudo nano /etc/netd.conf

# Control which users/groups are allowed to run 'add', 'del',
# 'clear', 'net abort', 'net commit' and restart services
# to apply those changes
users_with_edit = root, cumulus, netoperator
groups_with_edit = netedit

# Control which users/groups are allowed to run 'show' commands
users_with_show = root, cumulus, netoperator
groups_with_show = netshow, netedit

To configure a new user group to use NCLU, add that group to the groups_with_edit and groups_with_show lines in the file.

Use caution giving edit permissions to groups. For example, do not give edit permissions to the tacacs group.

Restart the netd Service

Whenever you modify netd.conf or when NSS services change, you must restart the netd service for the changes to take effect:

cumulus@switch:~$ sudo systemctl restart netd.service

Back Up the Configuration to a Single File

You can easily back up your NCLU configuration to a file by outputting the results of net show configuration commands to a file, then retrieving the contents of the file using the source command. You can then view the configuration at any time or copy it to other switches and use the source command to apply that configuration to those switches.

For example, to copy the configuration of a leaf switch called leaf01, run the following command:

cumulus@leaf01:~$ net show configuration commands >> leaf01.txt

With the commands all stored in a single file, you can now copy this file to another ToR switch in your network called leaf01 and apply the configuration by running:

cumulus@leaf01:~$ source leaf01.txt

Advanced Configuration

NCLU needs no initial configuration; however, if you need to modify certain configuration, you must manually update the /etc/netd.conf file. You can configure this file to allow different permission levels for users to edit configurations and run show commands. The file also contains a blacklist that hides less frequently used terms from the tabbed autocomplete.

After you edit the netd.conf file, restart the netd service for the changes to take effect.

cumulus@switch:~$ sudo nano /etc/netd.conf
cumulus@switch:~$ sudo systemctl restart netd.service
Configuration Variable Default Setting Description
show_linux_command False When true, displays the Linux command running in the background.
color_diffs True When true, the diffs shown in net pending and net commit use colors.
enable_<component> True When true, enables you to configure the component with NCLU. For example, when enable_frr is true, you can use NCLU to configure FRR.
users_with_edit root, cumulus Sets the Linux users with root edit privileges.
groups_with_edit root, cumulus Sets the Linux groups with root edit privileges.
users_with_show root, cumulus Controls which users are allowed to run show commands.
groups_with_show root, cumulus Controls which groups are allowed to run show commands.
ifupdown_blacklist address-purge, bond-ad-actor-sys-prio, bond-ad-actor-system, bond-num-grat-arp,bond-num-unsol-na, bond-use-carrier, bond-xmit-hash-policy, bridge-bridgeprio, bridge-fd, bridge-hashel, bridge-hashmax, bridge-hello, bridge-igmp-querier-src, bridge-maxage, bridge-maxwait, bridge-mclmc, bridge-mclmi bridge-mcmi, bridge-mcqi, bridge-mcqpi, bridge-mcqri, bridge-mcrouter, bridge-mcsqc, bridge-mcsqi, bridge-pathcosts, bridge-port-pvids, bridge-port-vids, bridge-portprios, bridge-waitport, broadcast, link-type, mstpctl-ageing, mstpctl-fdelay, mstpctl-forcevers, mstpctl-hello, mstpctl-maxage, mstpctl-maxhops, mstpctl-portp2p, mstpctl-portpathcost, mstpctl-portrestrtcn, mstpctl-treeportcost, mstpctl-treeportprio, mstpctl-txholdcount, netmask, preferred-lifetime, scope, vxlan-ageing, vxlan-learning, vxlan-port, up, down, bridge-gcint, bridge-mcqifaddr, bridge-mcqv4src Hides corner case command options from tab complete, to simplify and streamline output.

net provides an environment variable to set where the net output is directed. To only use stdout, set the NCLU_TAB_STDOUT environment variable to true. The value is not case sensitive.

Caveats and Errata

Unsupported Interface Names

NCLU does not support interfaces named dev.

Bonds With No Configured Members

If a bond interface is configured and it contains no members NCLU will report the interace does not exist.

Large NCLU Inputs

Each NCLU command must be parsed by the system. Large inputs, for example a large paste of NCLU commands can take some time, sometimes minutes, to process.

Setting Date and Time

Setting the time zone, date and time requires root privileges; use sudo.

Set the Time Zone

You can use one of two methods to set the time zone on the switch:

Edit the /etc/timezone File

To see the current time zone, list the contents of /etc/timezone:

cumulus@switch:~$ cat /etc/timezone
US/Eastern

Edit the file to add your desired time zone. A list of valid time zones can be found here.

Use the following command to apply the new time zone immediately.

cumulus@switch:~$ sudo dpkg-reconfigure --frontend noninteractive tzdata

Use the following command to change the /etc/localtime to reflect your current timezone. Use the same value as the previous step.

sudo ln -sf /usr/share/zoneinfo/US/Eastern /etc/localtime

Use the Guided Wizard

To set the time zone using the guided wizard, run dpkg-reconfigure tzdata as root:

cumulus@switch:~$ sudo dpkg-reconfigure tzdata

For more information, see the Debian System Administrator's Manual - Time.

Set the Date and Time

The switch contains a battery backed hardware clock that maintains the time while the switch is powered off and in between reboots. When the switch is running, the Cumulus Linux operating system maintains its own software clock.

During boot up, the time from the hardware clock is copied into the operating system’s software clock. The software clock is then used for all timekeeping responsibilities. During system shutdown, the software clock is copied back to the battery backed hardware clock.

You can set the date and time on the software clock using the date command. First, determine your current time zone:

cumulus@switch:~$ date +%Z

If you need to reconfigure the current time zone, refer to the instructions above.

Then, to set the system clock according to the time zone configured:

cumulus@switch:~$ sudo date -s "Tue Jan 12 00:37:13 2016"

See man date(1) for more information.

You can write the current value of the system (software) clock to the hardware clock using the hwclock command:

cumulus@switch:~$ sudo hwclock -w

See man hwclock(8) for more information.

Use NTP

The ntpd daemon running on the switch implements the NTP protocol. It synchronizes the system time with time servers listed in the /etc/ntp.conf file. The ntpd daemon is started at boot by default. See man ntpd(8) for details.

If you intend to run this service within a VRF, including the management VRF, follow these steps for configuring the service.

Configure NTP Servers

The default NTP configuration comprises the following servers, which are listed in the /etc/ntpd.conf file:

To add the NTP server or servers you want to use:

Run the following commands. Include the iburst option to increase the sync speed.

cumulus@switch:~$ net add time ntp server 4.cumulusnetworks.pool.ntp.org iburst
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands add the NTP server to the list of servers in the /etc/ntp.conf file:

# pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
# pick a different set every time it starts up.  Please consider joining the
# pool: <http://www.pool.ntp.org/join.html>
server 0.cumulusnetworks.pool.ntp.org iburst
server 1.cumulusnetworks.pool.ntp.org iburst
server 2.cumulusnetworks.pool.ntp.org iburst
server 3.cumulusnetworks.pool.ntp.org iburst
server 4.cumulusnetworks.pool.ntp.org iburst

Edit the /etc/ntp.conf file to add or update NTP server information:

cumulus@switch:~$ sudo nano /etc/ntp.conf
# pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
# pick a different set every time it starts up.  Please consider joining the
# pool: <http://www.pool.ntp.org/join.html>
server 0.cumulusnetworks.pool.ntp.org iburst
server 1.cumulusnetworks.pool.ntp.org iburst
server 2.cumulusnetworks.pool.ntp.org iburst
server 3.cumulusnetworks.pool.ntp.org iburst
server 4.cumulusnetworks.pool.ntp.org iburst

To set the initial date and time with NTP before starting the ntpd daemon, run the ntpd -q command. This command is the same as ntpdate, which is to be retired and no longer available.

Be aware that ntpd -q can hang if the time servers are not reachable.

To verify that ntpd is running on the system:

cumulus@switch:~$ ps -ef | grep ntp
ntp       4074     1  0 Jun20 ?        00:00:33 /usr/sbin/ntpd -p /var/run/ntpd.pid -g -u 101:102

To check the NTP peer status:

Run the net show time ntp servers command:

cumulus@switch:~$ net show time ntp servers 
      remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+minime.fdf.net  58.180.158.150   3 u  140 1024  377   55.659    0.339   1.464
+69.195.159.158  128.138.140.44   2 u  259 1024  377   41.587    1.011   1.677
*chl.la          216.218.192.202  2 u  210 1024  377    4.008    1.277   1.628
+vps3.drown.org  17.253.2.125     2 u  743 1024  377   39.319   -0.316   1.384

Run the ntpq -p command:

cumulus@switch:~$ ntpq -p
      remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+ec2-34-225-6-20 129.6.15.30      2 u   73 1024  377   70.414   -2.414   4.110
+lax1.m-d.net    132.163.96.1     2 u   69 1024  377   11.676    0.155   2.736
*69.195.159.158  199.102.46.72    2 u  133 1024  377   48.047   -0.457   1.856
-2.time.dbsinet. 198.60.22.240    2 u 1057 1024  377   63.973    2.182   2.692

To remove one or more NTP servers:

Run the net del time ntp <server> command. The following example commands remove some of the default NTP servers.

cumulus@switch:~$ net del time ntp server 0.cumulusnetworks.pool.ntp.org
cumulus@switch:~$ net del time ntp server 1.cumulusnetworks.pool.ntp.org
cumulus@switch:~$ net del time ntp server 2.cumulusnetworks.pool.ntp.org
cumulus@switch:~$ net del time ntp server 3.cumulusnetworks.pool.ntp.org
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/ntp.conf file to delete the NTP servers.

cumulus@switch:~$ sudo nano /etc/ntp.conf
...
# pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
# pick a different set every time it starts up.  Please consider joining the
# pool: <http://www.pool.ntp.org/join.html>
server 4.cumulusnetworks.pool.ntp.org iburst
...

Specify the NTP Source Interface

By default, the source interface that NTP uses is eth0. To change the source interface:

Run the net add time ntp source <interface> command. The following command example changes the NTP source interface to swp10.

cumulus@switch:~$ net add time ntp source swp10
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following configuration snippet in the ntp.conf file:

...
# Specify interfaces
interface listen swp10
...

Edit the /etc/ntp.conf file and modify the entry under the # Specify interfaces comment. The following example shows that the NTP source interface is swp10.

cumulus@switch:~$ sudo nano /etc/ntp.conf
...
# Specify interfaces
interface listen swp10
...

Use NTP in a DHCP Environment

You can use DHCP to specify your NTP servers. Ensure that the DHCP-generated configuration file named /run/ntp.conf.dhcp exists. This file is generated by the /etc/dhcp/dhclient-exit-hooks.d/ntp script and is a copy of the default /etc/ntp.conf with a modified server list from the DHCP server. If this file does not exist and you plan on using DHCP in the future, you can copy your current /etc/ntp.conf file to the location of the DHCP file.

To use DHCP to specify your NTP servers, run the sudo -E systemctl edit ntp.service command and add the ExecStart= line:

cumulus@switch:~$ sudo -E systemctl edit ntp.service
[Service]
ExecStart=
ExecStart=/usr/sbin/ntpd -n -u ntp:ntp -g -c /run/ntp.conf.dhcp

The sudo -E systemctl edit ntp.service command always updates the base ntp.service even if ntp@mgmt.service is used. The ntp@mgmt.service is re-generated automatically.

To validate that your configuration, run these commands:

cumulus@switch:~$ sudo systemctl restart ntp
cumulus@switch:~$ sudo systemctl status -n0 ntp.service

If the state is not Active, or the alternate configuration file does not appear in the ntp command line, it is likely that a mistake was made. In this case, correct the mistake and rerun the three commands above to verify.

When you use the above procedure to specify your NTP servers, the NCLU commands for changing NTP settings do not take effect.

Configure NTP with Authorization Keys

For added security, you can configure NTP to use authorization keys.

Configure the NTP server:

  1. Create a .keys file, such as /etc/ntp.keys. Specify a key identifier (a number from 1-65535), an encryption method (M for MD5), and the password. The following provides an example:

    #
    # PLEASE DO NOT USE THE DEFAULT VALUES HERE.
    #
    #65535  M  akey
    #1      M  pass
    
    1  M  CumulusLinux!
    
  2. In the /etc/ntp/ntp.conf file, add a pointer to the /etc/ntp.keys file you created above and specify the key identifier. For example:

    keys /etc/ntp/ntp.keys
    trustedkey 1
    controlkey 1
    requestkey 1
    
  3. Restart NTP with the sudo systemctl restart ntp command.

Configure the NTP client (the Cumulus Linux switch):

  1. Create the same .keys file you created on the NTP server (/etc/ntp.keys). For example:

    cumulus@switch:~$  sudo nano /etc/ntp.keys
    #
    # PLEASE DO NOT USE THE DEFAULT VALUES HERE.
    #
    #65535  M  akey
    #1      M  pass
    
      1  M  CumulusLinux!
    
  2. Edit the /etc/ntp.conf file to specify the server you want to use, the key identifier, and a pointer to the /etc/ntp.keys file you created in step 1. For example:

    cumulus@switch:~$ sudo nano /etc/ntp.conf
    ...
    # You do need to talk to an NTP server or two (or three).
    #pool ntp.your-provider.example
    # OR
    #server ntp.your-provider.example
    
    # pool.ntp.org maps to about 1000 low-stratum NTP servers.  Your server will
    # pick a different set every time it starts up.  Please consider joining the
    # pool: <http://www.pool.ntp.org/join.html>
    #server 0.cumulusnetworks.pool.ntp.org iburst
    #server 1.cumulusnetworks.pool.ntp.org iburst
    #server 2.cumulusnetworks.pool.ntp.org iburst
    #server 3.cumulusnetworks.pool.ntp.org iburst
    server 10.50.23.121 key 1
    
    #keys
    keys /etc/ntp.keys
    trustedkey 1
    controlkey 1
    requestkey 1
    ...
    
  3. Restart NTP in the active VRF (default or management). For example:

    cumulus@switch:~$ systemctl restart ntp@mgmt.service
    
  4. Wait a few minutes, then run the ntpq -c as command to verify the configuration:

    cumulus@switch:~$ ntpq -c as
    
    ind assid status  conf reach auth condition  last_event cnt
    ===========================================================
      1 40828  f014   yes   yes   ok     reject   reachable  1
    

After authorization is accepted, you see the following command output:

cumulus@switch:~$ ntpq -c as

ind assid status  conf reach auth condition  last_event cnt
===========================================================
  1 40828  f61a   yes   yes   ok   sys.peer    sys_peer  1

Precision Time Protocol (PTP) Boundary Clock

With the growth of low latency and high performance applications, precision timing has become increasingly important. Precision Time Protocol (PTP) is used to synchronize clocks in a network and is capable of sub-microsecond accuracy. The clocks are organized in a master-slave hierarchy. The slaves are synchronized to their masters, which can be slaves to their own masters. The hierarchy is created and updated automatically by the best master clock (BMC) algorithm, which runs on every clock. The grandmaster clock is the top-level master and is typically synchronized by using a Global Positioning System (GPS) time source to provide a high-degree of accuracy.

A boundary clock has multiple ports; one or more master ports and one or more slave ports. The master ports provide time (the time can originate from other masters further up the hierarchy) and the slave ports receive time. The boundary clock absorbs sync messages in the slave port, uses that port to set its clock, then generates new sync messages from this clock out of all of its master ports.

Cumulus Linux includes the linuxptp package for PTP, which uses the phc2sys daemon to synchronize the PTP clock with the system clock.

  • Cumulus Linux currently supports PTP on the Mellanox Spectrum ASIC only.
  • PTP is supported in boundary clock mode only (the switch provides timing to downstream servers; it is a slave to a higher-level clock and a master to downstream clocks).
  • The switch uses hardware time stamping to capture timestamps from an Ethernet frame at the physical layer. This allows PTP to account for delays in message transfer and greatly improves the accuracy of time synchronization.
  • Only IPv4/UDP PTP packets are supported.
  • Only a single PTP domain per network is supported. A PTP domain is a network or a portion of a network within which all the clocks are synchronized.

In the following example, boundary clock 2 receives time from Master 1 (the grandmaster) on a PTP slave port, sets its clock and passes the time down from the PTP master port to boundary clock 1. Boundary clock 1 receives the time on a PTP slave port, sets its clock and passes the time down the hierarchy through the PTP master ports to the hosts that receive the time.

Enable the PTP Boundary Clock on the Switch

To enable the PTP boundary clock on the switch:

  1. Open the /etc/cumulus/switchd.conf file in a text editor and add the following line:

    ptp.timestamping = TRUE
    
  2. Restart switchd:

    cumulus@switch:~$ sudo systemctl restart switchd.service
    

Configure the PTP Boundary Clock

To configure a boundary clock:

  1. Configure the interfaces on the switch that you want to use for PTP. Each interface must be configured as a layer 3 routed interface with an IP address.

    • PTP is supported on BGP unnumbered interfaces.
    • PTP is not supported on switched virtual interfaces (SVIs).

    cumulus@switch:~$ net add interface swp13s0 ip address 10.0.0.9/32
    cumulus@switch:~$ net add interface swp13s1 ip address 10.0.0.10/32
    
  2. Configure PTP options on the switch:

    • Set the gm-capable option to no to configure the switch to be a boundary clock.
    • Set the priority, which selects the best master clock. You can set priority 1 or 2. For each priority, you can use a number between 0 and 255. The default priority is 255. For the boundary clock, use a number above 128. The lower priority is applied first.
    • Add the time-stamping parameter. The switch automatically enables hardware time-stamping to capture timestamps from an Ethernet frame at the physical layer. If you are testing PTP in a virtual environment, hardware time-stamping is not available; however the time-stamping parameter is still required.
    • Add the PTP master and slave interfaces. You do not specify which is a master interface and which is a slave interface; this is determined by the PTP packet received. The following commands provide an example configuration:
    cumulus@switch:~$ net add ptp global gm-capable no
    cumulus@switch:~$ net add ptp global priority2 254
    cumulus@switch:~$ net add ptp global priority1 254
    cumulus@switch:~$ net add ptp global time-stamping
    cumulus@switch:~$ net add ptp interface swp13s0
    cumulus@switch:~$ net add ptp interface swp13s1
    cumulus@switch:~$ net pending
    cumulus@switch:~$ net commit
    

    The ptp4l man page describes all the configuration parameters.

  3. Restart the ptp4l and phc2sys daemons:

    cumulus@switch:~$ sudo systemctl restart ptp4l.service phc2sys.service
    

    The configuration is saved in the /etc/ptp4l.conf file.

  4. Enable the services to start at boot time:

    cumulus@switch:~$ sudo systemctl enable ptp4l.service phc2sys.service
    

Example Configuration

In the following example, the boundary clock on the switch receives time from Master 1 (the grandmaster) on PTP slave port swp3s0, sets its clock and passes the time down through PTP master ports swp3s1, swp3s2, and swp3s3 to the hosts that receive the time.

The configuration for the above example is shown below. The example assumes that you have already configured the layer 3 routed interfaces (swp3s0, swp3s1, swp3s2, and swp3s3) you want to use for PTP.

cumulus@switch:~$ net add ptp global gm-capable no
cumulus@switch:~$ net add ptp global priority2 254
cumulus@switch:~$ net add ptp global priority1 254
cumulus@switch:~$ net add ptp global time-stamping
cumulus@switch:~$ net add ptp interface swp3s0
cumulus@switch:~$ net add ptp interface swp3s1
cumulus@switch:~$ net add ptp interface swp3s2
cumulus@switch:~$ net add ptp interface swp3s3
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Verify PTP Boundary Clock Configuration

To view a summary of the PTP configuration on the switch, run the net show configuration ptp command:

cumulus@switch:~$ net show configuration ptp
ptp
  global

    slaveOnly
      0

    priority1
      255

    priority2
      255

    domainNumber
      0

    logging_level
      5

    path_trace_enabled
      0

    use_syslog
      1

    verbose
      0

    summary_interval
      0

    time_stamping
      hardware

    gmCapable
      0
  swp15s0
  swp15s1
...

View PTP Status Information

To view PTP status information, run the net show ptp parent_data_set command:

cumulus@switch:~$ net show ptp parent_data_set
parent_data_set
===============
parentPortIdentity                    000200.fffe.000001-1
parentStats                           0
observedParentOffsetScaledLogVariance 0xffff
observedParentClockPhaseChangeRate    0x7fffffff
grandmasterPriority1                  127
gm.ClockClass                         248
gm.ClockAccuracy                      0xfe
gm.OffsetScaledLogVariance            0xffff
grandmasterPriority2                  127
grandmasterIdentity                   000200.fffe.000001

To view the additional PTP status information, including the delta in nanoseconds from the master clock, run the sudo pmc -u -b 0 'GET TIME_STATUS_NP' command:

cumulus@switch:~$ sudo pmc -u -b 0 'GET TIME_STATUS_NP'
sending: GET TIME_STATUS_NP
    7cfe90.fffe.f56dfc-0 seq 0 RESPONSE MANAGEMENT TIME_STATUS_NP
        master_offset              12610
        ingress_time               1525717806521177336
        cumulativeScaledRateOffset +0.000000000
        scaledLastGmPhaseChange    0
        gmTimeBaseIndicator        0
        lastGmPhaseChange          0x0000'0000000000000000.0000
        gmPresent                  true
        gmIdentity                 000200.fffe.000005
    000200.fffe.000005-1 seq 0 RESPONSE MANAGEMENT TIME_STATUS_NP
        master_offset              0
        ingress_time               0
        cumulativeScaledRateOffset +0.000000000
        scaledLastGmPhaseChange    0
        gmTimeBaseIndicator        0
        lastGmPhaseChange          0x0000'0000000000000000.0000
        gmPresent                  false
        gmIdentity                 000200.fffe.000005
    000200.fffe.000006-1 seq 0 RESPONSE MANAGEMENT TIME_STATUS_NP
        master_offset              5544033534
        ingress_time               1525717812106811842
        cumulativeScaledRateOffset +0.000000000
        scaledLastGmPhaseChange    0
        gmTimeBaseIndicator        0
        lastGmPhaseChange          0x0000'0000000000000000.0000
        gmPresent                  true
        gmIdentity                 000200.fffe.000005

Delete PTP Boundary Clock Configuration

To delete PTP configuration, delete the PTP master and slave interfaces. The following example commands delete the PTP interfaces swp3s0, swp3s1, and swp3s2.

cumulus@switch:~$ net del ptp interface swp3s0
cumulus@switch:~$ net del ptp interface swp3s1
cumulus@switch:~$ net del ptp interface swp3s2
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Considerations

Spanning Tree and PTP

PTP frames are affected by STP filtering; events, such as an STP topology change (where ports temporarily go into the blocking state), can cause interruptions to PTP communications.

If you configure PTP on bridge ports, NVIDIA recommends that the bridge ports are spanning tree edge ports or in a bridge domain where spanning tree is disabled.

Authentication, Authorization and Accounting

This section descibes how to set up user accounts, ssh for remote access, LDAP authentication, TACACS Plus, and RADIUS AAA.

SSH for Remote Access

You can generate authentication keys to access a Cumulus Linux switch securely with the ssh-keygen component of the Secure Shell (SSH) protocol. Cumulus Linux uses the OpenSSH package to provide this functionality. This section describes how to generate an SSH key pair.

Generate an SSH Key Pair

  1. To generate the SSH key pair, run the ssh-keygen command and follow the prompts:

    To configure a completely passwordless system, do not enter a passphrase when prompted in the following step.

    cumulus@leaf01:~$ ssh-keygen
    Generating public/private rsa key pair.
    Enter file in which to save the key (/home/cumulus/.ssh/id_rsa):
    Enter passphrase (empty for no passphrase):
    Enter same passphrase again:
    Your identification has been saved in /home/cumulus/.ssh/id_rsa.
    Your public key has been saved in /home/cumulus/.ssh/id_rsa.pub.
    The key fingerprint is:
    5a:b4:16:a0:f9:14:6b:51:f6:f6:c0:76:1a:35:2b:bb cumulus@leaf04
    The key's randomart image is:
    +---[RSA 2048]----+
    |      +.o   o    |
    |     o * o . o   |
    |    o + o O o    |
    |     + . = O     |
    |      . S o .    |
    |       +   .     |
    |      .   E      |
    |                 |
    |                 |
    +-----------------+
    
  2. To copy the generated public key to the desired location, run the ssh-copy-id command and follow the prompts:

    cumulus@leaf01:~$ ssh-copy-id -i /home/cumulus/.ssh/id_rsa.pub cumulus@leaf02
    The authenticity of host 'leaf02 (192.168.0.11)' can't be established.
    ECDSA key fingerprint is b1:ce:b7:6a:20:f4:06:3a:09:3c:d9:42:de:99:66:6e.
    Are you sure you want to continue connecting (yes/no)? yes
    /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
    /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
    cumulus@leaf01's password:
    
    Number of key(s) added: 1
    

    ssh-copy-id does not work if the username on the remote switch is different from the username on the local switch. To work around this issue, use the scp command instead:

    cumulus@leaf01:~$ scp .ssh/id_rsa.pub cumulus@leaf02:.ssh/authorized_keys
    Enter passphrase for key '/home/cumulus/.ssh/id_rsa':
    id_rsa.pub
    
  3. Connect to the remote switch to confirm that the authentication keys are in place:

    cumulus@leaf01:~$ ssh cumulus@leaf02
    
    Welcome to Cumulus VX (TM)
    
    Cumulus VX (TM) is a community supported virtual appliance designed for
    experiencing, testing and prototyping the latest technology.
    For any questions or technical support, visit our community site at:
    http://community.cumulusnetworks.com
    
    The registered trademark Linux (R) is used pursuant to a sublicense from LMI,
    the exclusive licensee of Linus Torvalds, owner of the mark on a world-wide basis.
    Last login: Thu Sep 29 16:56:54 2016
    

User Accounts

By default, Cumulus Linux has two user accounts: cumulus and root.

The cumulus account:

The root account:

For optimal security, change the default password with the passwd command before you configure Cumulus Linux on the switch.

You can add additional user accounts as needed. Like the cumulus account, these accounts must use sudo to execute privileged commands; be sure to include them in the sudo group. For example:

cumulus@switch:~$ sudo adduser NEWUSERNAME sudo

To access the switch without a password, you need to boot into a single shell/user mode.

You can add and configure user accounts in Cumulus Linux with read-only or edit permissions for NCLU. For more information, see Configure User Accounts.

Enable Remote Access for the root User

The root user does not have a password and cannot log into a switch using SSH. This default account behavior is consistent with Debian. To connect to a switch using the root account, you can do one of the following:

Generate an SSH Key for the root Account

  1. In a terminal on your host system (not the switch), check to see if a key already exists:

    root@host:~# ls -al ~/.ssh/
    

    The name of the key is similar to id_dsa.pub, id_rsa.pub, or id_ecdsa.pub.

  2. If a key does not exist, generate a new one by first creating the RSA key pair:

    root@host:~# ssh-keygen -t rsa
    
  3. You are prompted to enter a file in which to save the key (/root/.ssh/id_rsa). Press Enter to use the home directory of the root user or provide a different destination.

  4. You are prompted to enter a passphrase (empty for no passphrase). This is optional but it does provide an extra layer of security.

  5. The public key is now located in /root/.ssh/id_rsa.pub. The private key (identification) is now located in /root/.ssh/id_rsa.

  6. Copy the public key to the switch. SSH to the switch as the cumulus user, then run:

    cumulus@switch:~$ sudo mkdir -p /root/.ssh
    cumulus@switch:~$ echo <SSH public key string> | sudo tee -a /root/.ssh/authorized_keys
    

Set the root User Password

  1. Run the following command:

    cumulus@switch:~$ sudo passwd root
    
  2. Change the PermitRootLogin setting in the /etc/ssh/sshd_config file from without-password to yes.

    cumulus@switch:~$ sudo nano /etc/ssh/sshd_config
    ...
    # Authentication:
    LoginGraceTime 120
    PermitRootLogin yes
    StrictModes yes
    ...  
    
  3. Restart the ssh service:

    cumulus@switch:~$ sudo systemctl reload ssh.service
    

Using sudo to Delegate Privileges

By default, Cumulus Linux has two user accounts: root and cumulus. The cumulus account is a normal user and is in the group sudo.

You can add more user accounts as needed. Like the cumulus account, these accounts must use sudo to execute privileged commands.

sudo Basics

sudo allows you to execute a command as superuser or another user as specified by the security policy. See man sudo(8) for details.

The default security policy is sudoers, which is configured using /etc/sudoers. Use /etc/sudoers.d/ to add to the default sudoers policy. See man sudoers(5) for details.

Use visudo only to edit the sudoers file; do not use another editor like vi or emacs. See man visudo(8) for details.

When creating a new file in /etc/sudoers.d, use visudo -f. This option performs sanity checks before writing the file to avoid errors that prevent sudo from working.

Errors in the sudoers file can result in losing the ability to elevate privileges to root. You can fix this issue only by power cycling the switch and booting into single user mode. Before modifying sudoers, enable the root user by setting a password for the root user.

By default, users in the sudo group can use sudo to execute privileged commands. To add users to the sudo group, use the useradd(8) or usermod(8) command. To see which users belong to the sudo group, see /etc/group (man group(5)).

You can run any command as sudo, including su. A password is required.

The example below shows how to use sudo as a non-privileged user cumulus to bring up an interface:

cumulus@switch:~$ ip link show dev swp1
3: swp1: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master br0 state DOWN mode DEFAULT qlen 500
link/ether 44:38:39:00:27:9f brd ff:ff:ff:ff:ff:ff

cumulus@switch:~$ ip link set dev swp1 up
RTNETLINK answers: Operation not permitted

cumulus@switch:~$ sudo ip link set dev swp1 up
Password:

umulus@switch:~$ ip link show dev swp1
3: swp1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br0 state UP mode DEFAULT qlen 500
link/ether 44:38:39:00:27:9f brd ff:ff:ff:ff:ff:ff

sudoers Examples

The following examples show how you grant as few privileges as necessary to a user or group of users to allow them to perform the required task. For each example, the system group noc is used; groups are prefixed with an %.

When executed by an unprivileged user, the example commands below must be prefixed with sudo.

Category Privilege Example Command sudoers Entry
Monitoring Switch port information ethtool -m swp1 %noc ALL=(ALL) NOPASSWD:/sbin/ethtool
Monitoring System diagnostics cl-support %noc ALL=(ALL) NOPASSWD:/usr/cumulus/bin/cl-support
Monitoring Routing diagnostics cl-resource-query %noc ALL=(ALL) NOPASSWD:/usr/cumulus/bin/cl-resource-query
Image management Install images onie-select http://lab/install.bin %noc ALL=(ALL) NOPASSWD:/usr/cumulus/bin/onie-select
Package management Any apt-get command apt-get update or apt-get install %noc ALL=(ALL) NOPASSWD:/usr/bin/apt-get
Package management Just apt-get update apt-get update %noc ALL=(ALL) NOPASSWD:/usr/bin/apt-get update
Package management Install packages apt-get install vim %noc ALL=(ALL) NOPASSWD:/usr/bin/apt-get install *
Package management Upgrading apt-get upgrade %noc ALL=(ALL) NOPASSWD:/usr/bin/apt-get upgrade
Netfilter Install ACL policies cl-acltool -i %noc ALL=(ALL) NOPASSWD:/usr/cumulus/bin/cl-acltool
Netfilter List iptables rules iptables -L %noc ALL=(ALL) NOPASSWD:/sbin/iptables
L1 + 2 features Any LLDP command lldpcli show neighbors / configure %noc ALL=(ALL) NOPASSWD:/usr/sbin/lldpcli
L1 + 2 features Just show neighbors lldpcli show neighbors %noc ALL=(ALL) NOPASSWD:/usr/sbin/lldpcli show neighbors*
Interfaces Modify any interface ip link set dev swp1 {up|down} %noc ALL=(ALL) NOPASSWD:/sbin/ip link set *
Interfaces Up any interface ifup swp1 %noc ALL=(ALL) NOPASSWD:/sbin/ifup
Interfaces Down any interface ifdown swp1 %noc ALL=(ALL) NOPASSWD:/sbin/ifdown
Interfaces Up/down only swp2 ifup swp2 / ifdown swp2 %noc ALL=(ALL) NOPASSWD:/sbin/ifup swp2,/sbin/ifdown swp2
Interfaces Any IP address change ip addr {add|del} 192.0.2.1/30 dev swp1 %noc ALL=(ALL) NOPASSWD:/sbin/ip addr *
Interfaces Only set IP address ip addr add 192.0.2.1/30 dev swp1 %noc ALL=(ALL) NOPASSWD:/sbin/ip addr add *
Ethernet bridging Any bridge command brctl addbr br0 / brctl delif br0 swp1 %noc ALL=(ALL) NOPASSWD:/sbin/brctl
Ethernet bridging Add bridges and interfaces brctl addbr br0 / brctl addif br0 swp1 %noc ALL=(ALL) NOPASSWD:/sbin/brctl addbr *,/sbin/brctl addif *
Spanning tree Set STP properties mstpctl setmaxage br2 20 %noc ALL=(ALL) NOPASSWD:/sbin/mstpctl
Troubleshooting Restart switchd systemctl restart switchd.service %noc ALL=(ALL) NOPASSWD:/usr/sbin/service switchd *
Troubleshooting Restart any service systemctl cron switchd.service %noc ALL=(ALL) NOPASSWD:/usr/sbin/service
Troubleshooting Packet capture tcpdump %noc ALL=(ALL) NOPASSWD:/usr/sbin/tcpdump
L3 Add static routes ip route add 10.2.0.0/16 via 10.0.0.1 %noc ALL=(ALL) NOPASSWD:/bin/ip route add *
L3 Delete static routes ip route del 10.2.0.0/16 via 10.0.0.1 %noc ALL=(ALL) NOPASSWD:/bin/ip route del *
L3 Any static route change ip route * %noc ALL=(ALL) NOPASSWD:/bin/ip route *
L3 Any iproute command ip * %noc ALL=(ALL) NOPASSWD:/bin/ip
L3 Non-modal OSPF cl-ospf area 0.0.0.1 range 10.0.0.0/24 %noc ALL=(ALL) NOPASSWD:/usr/bin/cl-ospf

LDAP Authentication and Authorization

Cumulus Linux uses Pluggable Authentication Modules (PAM) and Name Service Switch (NSS) for user authentication. NSS enables PAM to use LDAP to provide user authentication, group mapping, and information for other services on the system.

There are three common ways to configure LDAP authentication on Linux: you can use libnss-ldap, libnss-ldapd, or libnss-sss. This chapter describes libnss-ldapd only. From internal testing, this library worked best with Cumulus Linux and is the easiest to configure, automate, and troubleshoot.

Install libnss-ldapd

The libldap-2.4-2 and libldap-common LDAP packages are already installed on the Cumulus Linux image; however you need to install these additional packages to use LDAP authentication:

To install the additional packages, run the following command:

cumulus@switch:~$ sudo apt-get install libnss-ldapd libpam-ldapd ldap-utils nslcd

You can also install these packages even if the switch is not connected to the internet, as they are contained in the cumulus-local-apt-archive repository that is embedded in the Cumulus Linux disk image.

Follow the interactive prompts to specify the LDAP URI, search base distinguished name (DN), and services that must have LDAP lookups enabled. You need to select at least the passwd, group, and shadow services (press space to select a service). When done, click OK. This creates a very basic LDAP configuration using anonymous bind and initiates user search under the base DN specified.

After the dialog closes, the install process prints information similar to the following:

/etc/nsswitch.conf: enable LDAP lookups for group
/etc/nsswitch.conf: enable LDAP lookups for passwd
/etc/nsswitch.conf: enable LDAP lookups for shadow

After the installation is complete, the name service caching daemon (nslcd) runs. This service handles all the LDAP protocol interactions and caches information returned from the LDAP server. ldap is appended in the /etc/nsswitch.conf file, as is the secondary information source for passwd, group, and shadow. The local files (/etc/passwd, /etc/groups and /etc/shadow) are used first, as specified by the compat source.

passwd: compat ldap
group: compat ldap
shadow: compat ldap

Keep compat as the first source in NSS for passwd, group, and shadow. This prevents you from getting locked out of the system.

Entering incorrect information during the installation process might produce configuration errors. You can correct the information after installation by editing certain configuration files.

Be sure to restart netd after editing the files.

Alternative Installation Method Using debconf-utils

Instead of running the installer and following the interactive prompts, as described above, you can pre-seed the installer parameters using debconf-utils.

  1. Run apt-get install debconf-utils and create the pre-seeded parameters using debconf-set-selections. Provide the appropriate answers.

  2. Run debconf-show <pkg> to check the settings. Here is an example of how to pre-seed answers to the installer questions using debconf-set-selections:

    root# debconf-set-selections <<'zzzEndOfFilezzz'
    
    # LDAP database user. Leave blank will be populated later!
    
    nslcd nslcd/ldap-binddn  string
    
    # LDAP user password. Leave blank!
    nslcd nslcd/ldap-bindpw   password
    
    # LDAP server search base:
    nslcd nslcd/ldap-base string  ou=support,dc=rtp,dc=example,dc=test
    
    # LDAP server URI. Using ldap over ssl.
    nslcd nslcd/ldap-uris string  ldaps://myadserver.rtp.example.test
    
    # New to 0.9. restart cron, exim and others libraries without asking
    nslcd libraries/restart-without-asking: boolean true
    
    # LDAP authentication to use:
    # Choices: none, simple, SASL
    # Using simple because its easy to configure. Security comes by using LDAP over SSL
    # keep /etc/nslcd.conf 'rw' to root for basic security of bindDN password
    nslcd nslcd/ldap-auth-type    select  simple
    
    # Don't set starttls to true
    nslcd nslcd/ldap-starttls     boolean false
    
    # Check server's SSL certificate:
    # Choices: never, allow, try, demand
    nslcd nslcd/ldap-reqcert      select  never
    
    # Choices: Ccreds credential caching - password saving, Unix authentication, LDAP Authentication , Create home directory on first time login, Ccreds credential caching - password checking
    # This is where "mkhomedir" pam config is activated that allows automatic creation of home directory
    libpam-runtime        libpam-runtime/profiles multiselect     ccreds-save, unix, ldap, mkhomedir , ccreds-check
    
    # for internal use; can be preseeded
    man-db        man-db/auto-update      boolean true
    
    # Name services to configure:
    # Choices: aliases, ethers, group, hosts, netgroup, networks, passwd, protocols, rpc, services,  shadow
    libnss-ldapd  libnss-ldapd/nsswitch   multiselect     group, passwd, shadow
    libnss-ldapd  libnss-ldapd/clean_nsswitch     boolean false
    
    ## define platform specific libnss-ldapd debconf questions/answers. 
    ## For demo used amd64.
    libnss-ldapd:amd64    libnss-ldapd/nsswitch   multiselect     group, passwd, shadow
    libnss-ldapd:amd64    libnss-ldapd/clean_nsswitch     boolean false
    # libnss-ldapd:powerpc   libnss-ldapd/nsswitch   multiselect     group, passwd, shadow
    # libnss-ldapd:powerpc    libnss-ldapd/clean_nsswitch     boolean false
    
    zzzEndOfFilezzz
    

Update the nslcd.conf File

After installation, update the main configuration file (/etc/nslcd.conf) to accommodate the expected LDAP server settings.

This section documents some of the more important options that relate to security and how queries are handled. For details on all the available configuration options, read the nslcd.conf man page.

After first editing the /etc/nslcd.conf file and/or enabling LDAP in the /etc/nsswitch.conf file, you must restart netd with the sudo systemctl restart netd command. If you disable LDAP, you need to restart the netd service.

Connection

The LDAP client starts a session by connecting to the LDAP server on TCP and UDP port 389 or on port 636 for LDAPS. Depending on the configuration, this connection might be unauthenticated (anonymous bind); otherwise, the client must provide a bind user and password. The variables used to define the connection to the LDAP server are the URI and bind credentials.

The URI is mandatory and specifies the LDAP server location using the FQDN or IP address. The URI also designates whether to use ldap:// for clear text transport, or ldaps:// for SSL/TLS encrypted transport. You can also specify an alternate port in the URI. In production environments, the LDAPS protocol is recommended so that all communications are secure.

After the connection to the server is complete, the BIND operation authenticates the session. The BIND credentials are optional, and if not specified, an anonymous bind is assumed. This is typically not allowed in most production environments. Configure authenticated (Simple) BIND by specifying the user (binddn) and password (bindpw) in the configuration. Another option is to use SASL (Simple Authentication and Security Layer) BIND, which provides authentication services using other mechanisms, like Kerberos. Contact your LDAP server administrator for this information as it depends on the configuration of the LDAP server and the credentials that are created for the client device.

# The location at which the LDAP server(s) should be reachable.
uri ldaps://ldap.example.com
# The DN to bind with for normal lookups.
binddn cn=CLswitch,ou=infra,dc=example,dc=com
bindpw CuMuLuS

Search Function

When an LDAP client requests information about a resource, it must connect and bind to the server. Then, it performs one or more resource queries depending on the lookup. All search queries sent to the LDAP server are created using the configured search base, filter, and the desired entry (uid=myuser) being searched. If the LDAP directory is large, this search might take a significant amount of time. It is a good idea to define a more specific search base for the common maps (passwd and group).

# The search base that will be used for all queries.
base dc=example,dc=com
# Mapped search bases to speed up common queries.
base passwd ou=people,dc=example,dc=com
base group ou=groups,dc=example,dc=com

Search Filters

It is also common to use search filters to specify criteria used when searching for objects within the directory. This is used to limit the search scope when authenticating users. The default filters applied are:

filter passwd (objectClass=posixAccount)
filter group (objectClass=posixGroup)

Attribute Mapping

The map configuration allows you to override the attributes pushed from LDAP. To override an attribute for a given map, specify the attribute name and the new value. This is useful to ensure that the shell is bash and the home directory is /home/cumulus:

map    passwd homeDirectory "/home/cumulus"
map    passwd shell "/bin/bash"

In LDAP, the map refers to one of the supported maps specified in the manpage for nslcd.conf (such as passwd or group).

Create Home Directory on Login

If you want to use unique home directories, run the sudo pam-auth-update command and select Create home directory on login in the PAM configuration dialog (press the space bar to select the option). Select OK, then press Enter to save the update and close the dialog.

cumulus@switch:~$ sudo pam-auth-update

The home directory for any user that logs in (using LDAP or not) is created and populated with the standard dotfiles from /etc/skel if it does not already exist.

When nslcd starts, you might see an error message similar to the following (where 5816 is the nslcd PID):

nslcd[5816]: unable to dlopen /usr/lib/x86_64-linux-gnu/sasl2/libsasldb.so: libdb-5.3.so: cannot open
shared object file: No such file or directory

You can safely ignore this message. The libdb package and resulting log messages from nslcd do not cause any issues when you use LDAP as a client for login and authentication.

Example Configuration

Here is an example configuration using Cumulus Linux.

# /etc/nslcd.conf
# nslcd configuration file. See nslcd.conf(5)
# for details.

# The user and group nslcd should run as.
uid nslcd
gid nslcd

# The location at which the LDAP server(s) should be reachable.
uri ldaps://myadserver.rtp.example.test

# The search base that will be used for all queries.
base ou=support,dc=rtp,dc=example,dc=test

# The LDAP protocol version to use.
#ldap_version 3

# The DN to bind with for normal lookups.
# defconf-set-selections doesn't seem to set this. so have to manually set this.
binddn CN=cumulus admin,CN=Users,DC=rtp,DC=example,DC=test
bindpw 1Q2w3e4r!

# The DN used for password modifications by root.
#rootpwmoddn cn=admin,dc=example,dc=com

# SSL options
#ssl off (default)
# Not good does not prevent man in the middle attacks
#tls_reqcert demand(default)
tls_cacertfile /etc/ssl/certs/rtp-example-ca.crt

# The search scope.
#scope sub

# Add nested group support
# Supported in nslcd 0.9 and higher.
# default wheezy install of nslcd supports on 0.8. wheezy-backports has 0.9
nss_nested_groups yes

# Mappings for Active Directory
# (replace the SIDs in the objectSid mappings with the value for your domain)
# "dsquery * -filter (samaccountname=testuser1) -attr ObjectSID" where cn == 'testuser1'
pagesize 1000
referrals off
idle_timelimit 1000

# Do not allow uids lower than 100 to login (aka Administrator)
# not needed as pam already has this support
# nss_min_uid 1000

# This filter says to get all users who are part of the cumuluslnxadm group. Supports nested groups.
# Example, mary is part of the snrnetworkadm group which is part of cumuluslnxadm group
# Ref: http://msdn.microsoft.com/en-us/library/aa746475%28VS.85%29.aspx (LDAP_MATCHING_RULE_IN_CHAIN)
filter passwd (&(Objectclass=user)(!(objectClass=computer))(memberOf:1.2.840.113556.1.4.1941:=cn=cumuluslnxadm,ou=groups,ou=support,dc=rtp,dc=example,dc=test))
map    passwd uid           sAMAccountName
map    passwd uidNumber     objectSid:S-1-5-21-1391733952-3059161487-1245441232
map    passwd gidNumber     objectSid:S-1-5-21-1391733952-3059161487-1245441232
map    passwd homeDirectory "/home/$sAMAccountName"
map    passwd gecos         displayName
map    passwd loginShell    "/bin/bash"

# Filter for any AD group or user in the baseDN. the reason for filtering for the
# user to make sure group listing for user files don't say '<user> <gid>'. instead will say '<user> <user>'
# So for cosmetic reasons..nothing more.
filter group (&(|(objectClass=group)(Objectclass=user))(!(objectClass=computer)))
map    group gidNumber     objectSid:S-1-5-21-1391733952-3059161487-1245441232
map    group cn            sAMAccountName

Troubleshooting

nslcd Debug Mode

When setting up LDAP authentication for the first time, turn off the nslcd service using the systemctl stop nslcd.service command (or the systemctl stop nslcd@mgmt.service if you are running the service in a management VRF) and run it in debug mode. Debug mode works whether you are using LDAP over SSL (port 636) or an unencrypted LDAP connection (port 389).

cumulus@switch:~$ sudo systemctl stop nslcd.service
cumulus@switch:~$ sudo nslcd -d

After you enable debug mode, run the following command to test LDAP queries:

cumulus@switch:~$ getent passwd

If LDAP is configured correctly, the following messages appear after you run the getent command:

nslcd: DEBUG: accept() failed (ignored): Resource temporarily unavailable
nslcd: [8e1f29] DEBUG: connection from pid=11766 uid=0 gid=0
nslcd: [8e1f29] <passwd(all)> DEBUG: myldap_search(base="dc=example,dc=com", filter="(objectClass=posixAccount)")
nslcd: [8e1f29] <passwd(all)> DEBUG: ldap_result(): uid=myuser,ou=people,dc=example,dc=com
nslcd: [8e1f29] <passwd(all)> DEBUG: ldap_result(): ... 152 more results
nslcd: [8e1f29] <passwd(all)> DEBUG: ldap_result(): end of results (162 total)

In the output above, <passwd(all)> indicates that the entire directory structure is queried.

You can query a specific user with the following command:

cumulus@switch:~$ getent passwd myuser

You can replace myuser with any username on the switch. The following debug output indicates that user myuser exists:

nslcd: DEBUG: add_uri(ldap://10.50.21.101)
nslcd: version 0.8.10 starting
nslcd: DEBUG: unlink() of /var/run/nslcd/socket failed (ignored): No such file or directory
nslcd: DEBUG: setgroups(0,NULL) done
nslcd: DEBUG: setgid(110) done
nslcd: DEBUG: setuid(107) done
nslcd: accepting connections
nslcd: DEBUG: accept() failed (ignored): Resource temporarily unavailable
nslcd: [8b4567] DEBUG: connection from pid=11369 uid=0 gid=0
nslcd: [8b4567] <passwd="myuser"> DEBUG: myldap_search(base="dc=cumulusnetworks,dc=com", filter="(&(objectClass=posixAccount)(uid=myuser))")
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_initialize(ldap://<ip_address>)
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_set_rebind_proc()
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_set_option(LDAP_OPT_PROTOCOL_VERSION,3)
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_set_option(LDAP_OPT_DEREF,0)
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_set_option(LDAP_OPT_TIMELIMIT,0)
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_set_option(LDAP_OPT_TIMEOUT,0)
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_set_option(LDAP_OPT_NETWORK_TIMEOUT,0)
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_set_option(LDAP_OPT_REFERRALS,LDAP_OPT_ON)
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_set_option(LDAP_OPT_RESTART,LDAP_OPT_ON)
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_simple_bind_s(NULL,NULL) (uri="ldap://<ip_address>")
nslcd: [8b4567] <passwd="myuser"> DEBUG: ldap_result(): end of results (0 total)

Common Problems

SSL/TLS

NSCD

nscd --invalidate = passwd
nscd --invalidate = group
cumulus@switch:~$ sudo nscd -K
cumulus@switch:~$ sudo systemctl restart nslcd.service

If you are running the nslcd service in a management VRF, you need to run the systemctl restart nslcd@mgmt.service command instead of the systemctl restart nslcd.service command. For example:

cumulus@switch:~$ sudo nscd -K
cumulus@switch:~$ sudo systemctl restart nslcd@mgmt.service

LDAP

Configure LDAP Authorization

Linux uses the sudo command to allow non-administrator users (such as the default cumulus user account) to perform privileged operations. To control the users authorized to use sudo, the /etc/sudoers file and files located in the /etc/sudoers.d/ directory define a series of rules. Typically, the rules are based on groups, but can also be defined for specific users. You can add sudo rules using the group names from LDAP. For example, if a group of users are associated with the group netadmin, you can add a rule to give those users sudo privileges. Refer to the sudoers manual (man sudoers) for a complete usage description. The following shows an example in the /etc/sudoers file:

# The basic structure of a user specification is "who where = (as_whom) what ".
%sudo ALL=(ALL:ALL) ALL
%netadmin ALL=(ALL:ALL) ALL

Active Directory Configuration

Active Directory (AD) is a fully featured LDAP-based NIS server create by Microsoft. It offers unique features that classic OpenLDAP servers do not have. AD can be more complicated to configure on the client and each version works a little differently with Linux-based LDAP clients. Some more advanced configuration examples, from testing LDAP clients on Cumulus Linux with Active Directory (AD/LDAP), are available in our knowledge base.

LDAP Verification Tools

Typically, password and group information is retrieved from LDAP and cached by the LDAP client daemon. To test the LDAP interaction, you can use these command-line tools to trigger an LDAP query from the device. This helps to create the best filters and verify the information sent back from the LDAP server.

Identify a User with the id Command

The id command performs a username lookup by following the lookup information sources in NSS for the passwd service. This simply returns the user ID, group ID and the group list retrieved from the information source. In the following example, the user cumulus is locally defined in /etc/passwd, and myuser is on LDAP. The NSS configuration has the passwd map configured with the sources compat ldap:

cumulus@switch:~$ id cumulus
uid=1000(cumulus) gid=1000(cumulus) groups=1000(cumulus),24(cdrom),25(floppy),27(sudo),29(audio),30(dip),44(video),46(plugdev)
cumulus@switch:~$ id myuser
uid=1230(myuser) gid=3000(Development) groups=3000(Development),500(Employees),27(sudo)

getent

The getent command retrieves all records found with NSS for a given map. It can also retrieve a specific entry under that map. You can perform tests with the passwd, group, shadow, or any other map configured in the /etc/nsswitch.conf file. The output from this command is formatted according to the map requested. For the passwd service, the structure of the output is the same as the entries in /etc/passwd. The group map outputs the same structure as /etc/group.

In this example, looking up a specific user in the passwd map, the user cumulus is locally defined in /etc/passwd, and myuser is only in LDAP.

cumulus@switch:~$ getent passwd cumulus
cumulus:x:1000:1000::/home/cumulus:/bin/bash
cumulus@switch:~$ getent passwd myuser
myuser:x:1230:3000:My Test User:/home/myuser:/bin/bash

In the next example, looking up a specific group in the group service, the group cumulus is locally defined in /etc/groups, and netadmin is on LDAP.

cumulus@switch:~$ getent group cumulus
cumulus:x:1000:
cumulus@switch:~$ getent group netadmin
netadmin:*:502:larry,moe,curly,shemp

Running the command getent passwd or getent group without a specific request returns all local and LDAP entries for the passwd and group maps.

The ldapsearch command performs LDAP operations directly on the LDAP server. This does not interact with NSS. This command helps display what the LDAP daemon process is receiving back from the server. The command has many options. The simplest option uses anonymous bind to the host and specifies the search DN and the attribute to look up.

cumulus@switch:~$ ldapsearch -H ldap://ldap.example.com -b dc=example,dc=com -x uid=myuser
Click to expand the command output ...
# extended LDIF
#
# LDAPv3
# base <dc=example,dc=com> with scope subtree
# filter: uid=myuser
# requesting: ALL
#
# myuser, people, example.com
dn: uid=myuser,ou=people,dc=example,dc=com
cn: My User
displayName: My User
gecos: myuser
gidNumber: 3000
givenName: My
homeDirectory: /home/myuser
initials: MU
loginShell: /bin/bash
mail: myuser@example.com
objectClass: inetOrgPerson
objectClass: posixAccount
objectClass: shadowAccount
objectClass: top
shadowExpire: -1
shadowFlag: 0
shadowMax: 999999
shadowMin: 8
shadowWarning: 7
sn: User
uid: myuser
uidNumber: 1234

# search result
search: 2
result: 0 Success

# numResponses: 2
# numEntries: 1

NCLU

To use NCLU, a user must be in either the netshow or netedit NCLU group in the LDAP database. You can either:

In the following example, a user that is not in the netshow or netedit NCLU group in the LDAP database runs the NCLU net show version command, which produces an error:

hsolo@switch:~$ net show version
ERROR: 'getpwuid(): uid not found: 0922'
See /var/log/netd.log for more details

To add user to the netshow or netedit NCLU group in the LDAP database, either edit the /etc/group file manually or use the sudo adduser USERNAME netshow command, then restart netd. For example, to add the user bill to the netshow group:

cumulus@switch:~$ sudo adduser hsolo netshow
Adding user `hsolo' to group `netshow' ...
Adding user hsolo to group netshow
Done.

cumulus@switch:~$ sudo systemctl restart netd

Now, the user can run the NCLU net show commands successfully:

hsolo@switch:~$ net show version
NCLU_VERSION=1.0-cl4u1~1555625956.7cfe305
DISTRIB_ID="Cumulus Linux"
DISTRIB_RELEASE=4.0.0~1555370771.772c26b6
DISTRIB_DESCRIPTION="Cumulus Linux 4.0.0~1555370771.772c26b6"

LDAP Browsers

There are several GUI LDAP clients available that help you work with LDAP servers. These are free tools that show the structure of the LDAP database graphically.

TACACS

Cumulus Linux implements TACACS+ client AAA (Accounting, Authentication, and Authorization) in a transparent way with minimal configuration. The client implements the TACACS+ protocol as described in this IETF document. There is no need to create accounts or directories on the switch. Accounting records are sent to all configured TACACS+ servers by default. Use of per-command authorization requires additional setup on the switch.

Supported Features

Install the TACACS+ Client Packages

You can install the TACACS+ packages even if the switch is not connected to the internet, as they are contained in the cumulus-local-apt-archive repository that is embedded in the Cumulus Linux disk image.

To install all required packages, run these commands:

cumulus@switch:~$ sudo -E apt-get update
cumulus@switch:~$ sudo -E apt-get install tacplus-client

Configure the TACACS+ Client

After installing TACACS+, edit the /etc/tacplus_servers file to add at least one server and one shared secret (key). You can specify the server and secret parameters in any order anywhere in the file. Whitespace (spaces or tabs) are not allowed. For example, if your TACACS+ server IP address is 192.168.0.30 and your shared secret is tacacskey, add these parameters to the /etc/tacplus_servers file:

secret=tacacskey
server=192.168.0.30

Cumulus Linux supports a maximum of seven TACACS+ servers. To specify multiple servers, add one per line to the /etc/tacplus_servers file.

Connections are made in the order in which they are listed in this file. In most cases, you do not need to change any other parameters. You can add parameters used by any of the packages to this file, which affects all the TACACS+ client software. For example, the timeout value for NSS lookups (see description below) is set to 5 seconds by default in the /etc/tacplus_nss.conf file, whereas the timeout value for other packages is 10 seconds and is set in the /etc/tacplus_servers file. The timeout value is per connection to the TACACS+ servers. (If authorization is configured per command, the timeout occurs for each command.) There are several (typically four) connections to the server per login attempt from PAM, as well as two or more through NSS. Therefore, with the default timeout values, a TACACS+ server that is not reachable can delay logins by a minute or more per unreachable server. If you must list unreachable TACACS+ servers, place them at the end of the server list and consider reducing the timeout values.

When you add or remove TACACS+ servers, you must restart auditd (with the systemctl restart auditd command) or you must send a signal (with killall -HUP audisp-tacplus) before audisp-tacplus rereads the configuration to see the changed server list.

You can also configure the IP address used as the source IP address when communicating with the TACACS+ server. See TACACS Configuration Parameters below for the full list of TACACS+ parameters.

Following is the complete list of the TACACS+ client configuration files, and their use.

Filename
Description
/etc/tacplus_servers This is the primary file that requires configuration after installation. The file is used by all packages with include=/etc/tacplus_servers parameters in the other configuration files that are installed. Typically, this file contains the shared secrets; make sure that the Linux file mode is 600.
/etc/nsswitch.conf When the libnss_tacplus package is installed, this file is configured to enable tacplus lookups via libnss_tacplus. If you replace this file by automation or other means, you need to add tacplus as the first lookup method for the passwd database line.
/etc/tacplus_nss.conf This file sets the basic parameters for libnss_tacplus. It includes a debug variable for debugging NSS lookups separately from other client packages.
/usr/share/pam-configs/tacplus This is the configuration file for pam-auth-update to generate the files in the next row. These configurations are used at login, by su, and by ssh.
/etc/pam.d/common-* The /etc/pam.d/common-* files are updated for tacplus authentication. The files are updated with pam-auth-update, when libpam-tacplus is installed or removed.
/etc/sudoers.d/tacplus This file allows TACACS+ privilege level 15 users to run commands with sudo. The file includes an example (commented out) of how to enable privilege level 15 TACACS users to use sudo without having to enter a password and provides an example of how to enable all TACACS users to run specific commands with sudo. Only edit this file with the visudo -f /etc/sudoers.d/tacplus command.
/etc/audisp/plugins.d/audisp-tacplus.conf This is the audisp plugin configuration file. Typically, no modifications are required.
/etc/audisp/audisp-tac_plus.conf This is the TACACS+ server configuration file for accounting. Typically, no modifications are required. You can use this configuration file when you only want to debug TACACS+ accounting issues, not all TACACS+ users.
/etc/audit/rules.d/audisp-tacplus.rules The auditd rules for TACACS+ accounting. The augenrules command uses all rule files to generate the rules file (described below).
/etc/audit/audit.rules This is the audit rules file generated when auditd is installed.

You can edit the /etc/pam.d/common-* files manually. However, if you run pam-auth-update again after making the changes, the update fails. Only perform configuration in /usr/share/pam-configs/tacplus, then run pam-auth-update.

TACACS+ Authentication (login)

The initial authentication configuration is done through the PAM modules and an updated version of the libpam-tacplus package. When the package is installed, the PAM configuration is updated in /etc/pam.d with the pam-auth-update command. If you have made changes to your PAM configuration, you need to integrate these changes yourself. If you are also using LDAP with the libpam-ldap package, you might need to edit the PAM configuration to ensure the LDAP and TACACS ordering that you prefer. The libpam-tacplus are configured to skip over rules and the values in the success=2 might require adjustments to skip over LDAP rules.

A user privilege level is determined by the TACACS+ privilege attribute priv_lvl for the user that is returned by the TACACS+ server during the user authorization exchange. The client accepts the attribute in either the mandatory or optional forms and also accepts priv-lvl as the attribute name. The attribute value must be a numeric string in the range 0 to 15, with 15 the most privileged level.

By default, TACACS+ users at privilege levels other than 15 are not allowed to run sudo commands and are limited to commands that can be run with standard Linux user permissions.

TACACS+ Client Sequencing

Due to SSH and login processing mechanisms, Cumulus Linux needs to know the following very early in the AAA sequence:

The only way to do this for non-local users — that is, users not present in the local password file — is to send a TACACS+ authorization request as the first communication with the TACACS+ server, prior to the authentication and before a password is requested from the user logging in.

Some TACACS+ servers need special configuration to allow authorization requests prior to authentication. Contact your TACACS+ server vendor for the proper configuration if your TACACS+ server does not allow the initial authorization request.

Local Fallback Authentication

You can configure the switch to allow local fallback authentication for a user when the TACACS servers are unreachable, do not include the user for authentication, or have the user in the exclude user list.

To allow local fallback authentication for a user, add a local privileged user account on the switch with the same username as a TACACS user. A local user is always active even when the TACACS service is not running.

To configure local fallback authentication:

  1. Edit the /etc/nsswitch.conf file to remove the keyword tacplus from the line starting with passwd. (You need to add the keyword back in step 3.)

    An example of the /etc/nsswitch.conf file with the keyword tacplus removed from the line starting with passwd is shown below.

    cumulus@switch:~$ sudo nano /etc/nsswitch.conf
    #
    # Example configuration of GNU Name Service Switch functionality.
    # If you have the `glibc-doc-reference' and `info' packages installed, try:
    # `info libc "Name Service Switch"' for information about this file.
    
    passwd:         files
    group:          tacplus files
    shadow:         files
    gshadow:        files
    ...
    
  2. To enable the local privileged user to run sudo and NCLU commands, run the adduser commands shown below. In the example commands, the TACACS account name is tacadmin.

    The first adduser command prompts for information and a password. You can skip most of the requested information by pressing ENTER.

    cumulus@switch:~$ sudo adduser --ingroup tacacs tacadmin
    cumulus@switch:~$ sudo adduser tacadmin netedit
    cumulus@switch:~$ sudo adduser tacadmin sudo
    
  3. Edit the /etc/nsswitch.conf file to add the keyword tacplus back to the line starting with passwd (the keyword you removed in the first step).

    cumulus@switch:~$ sudo nano /etc/nsswitch.conf
    #
    # Example configuration of GNU Name Service Switch functionality.
    # If you have the `glibc-doc-reference' and `info' packages installed, try:
    # `info libc "Name Service Switch"' for information about this file.
    passwd:         tacplus files
    group:          tacplus files
    shadow:         files
    gshadow:        files
    ...
    
  4. Restart the netd service with the following command:

    cumulus@switch:~$ sudo systemctl restart netd
    

TACACS+ Accounting

TACACS+ accounting is implemented with the audisp module, with an additional plugin for auditd/audisp. The plugin maps the auid in the accounting record to a TACACS login, based on the auid and sessionid. The audisp module requires libnss_tacplus and uses the libtacplus_map.so library interfaces as part of the modified libpam_tacplus package.

Communication with the TACACS+ servers is done with the libsimple-tacact1 library, through dlopen(). A maximum of 240 bytes of command name and arguments are sent in the accounting record, due to the TACACS+ field length limitation of 255 bytes.

All Linux commands result in an accounting record, including commands run as part of the login process or as sub-processes of other commands. This can sometimes generate a large number of accounting records.

Configure the IP address and encryption key of the server in the /etc/tacplus_servers file. Minimal configuration to auditd and audisp is necessary to enable the audit records necessary for accounting. These records are installed as part of the package.

audisp-tacplus installs the audit rules for command accounting. Modifying the configuration files is not usually necessary. However, when a management VRF is configured, the accounting configuration does need special modification because the auditd service starts prior to networking. It is necessary to add the vrf parameter and to signal the audisp-tacplus process to reread the configuration. The example below shows that the management VRF is named mgmt. You can place the vrf parameter in either the /etc/tacplus_servers file or in the /etc/audisp/audisp-tac_plus.conf file.

vrf=mgmt

After editing the configuration file, send the HUP signal killall -HUP audisp-tacplus to notify the accounting process to reread the file.

All sudo commands run by TACACS+ users generate accounting records against the original TACACS+ login name.

For more information, refer to the audisp.8 and auditd.8 man pages.

Configure NCLU for TACACS+ Users

When you install or upgrade TACACS+ packages, mapped user accounts are created automatically. All tacacs0 through tacacs15 users are added to the netshow group.

For any TACACS+ users to execute net add, net del, and net commit commands and to restart services with NCLU, you need to add those users to the users_with_edit variable in the /etc/netd.conf file. Add the tacacs15 user and, depending upon your policies, other users (tacacs1 through tacacs14) to this variable.

To give a TACACS+ user access to the show commands, add the tacacs group to the groups_with_show variable.

Do not add the tacacs group to the groups_with_edit variable; this is dangerous and can potentially enable any user to log into the switch as the root user.

To add the users, edit the /etc/netd.conf file:

cumulus@switch:~$ sudo nano /etc/netd.conf
...
# Control which users/groups are allowed to run "add", "del",
# "clear", "abort", and "commit" commands.
users_with_edit = root, cumulus, tacacs15
groups_with_edit = netedit

# Control which users/groups are allowed to run "show" commands
users_with_show = root, cumulus
groups_with_show = netshow, netedit, tacacs
...

After you save and exit the netd.conf file, restart the netd service. Run:

cumulus@switch:~$ sudo systemctl restart netd

TACACS+ Per-command Authorization

The tacplus-auth command handles the per-command authorization. To make this an enforced authorization, you must change the TACACS+ login to use a restricted shell, with a very limited executable search path. Otherwise, the user can bypass the authorization. The tacplus-restrict utility simplifies the setup of the restricted environment. The example below initializes the environment for the tacacs0 user account. This is the account used for TACACS+ users at privilege level 0.

tacuser0@switch:~$ sudo tacplus-restrict -i -u tacacs0 -a command1 command2 ... commandN

If the user/command combination is not authorized by the TACACS+ server, a message similar to the following displays:

tacuser0@switch:~$ net show version
net not authorized by TACACS+ with given arguments, not executing

The following table provides the command options:

Option Description
-i Initializes the environment. You only need to issue this option once per username.
-a You can invoke the utility with the -a option as many times as desired. For each command in the -a list, a symbolic link is created from tacplus-auth to the relative portion of the command name in the local bin subdirectory. You also need to enable these commands on the TACACS+ server (refer to the TACACS+ server documentation). It is common to have the server allow some options to a command, but not others.
-f Re-initializes the environment. If you need to restart, issue the -f option with -i to force the re-initialization; otherwise, repeated use of -i is ignored.
As part of the initialization:
- The user’s shell is changed to /bin/rbash.
- Any existing dot files are saved.
- A limited environment is set up that does not allow general command execution, but instead allows only commands from the user’s local bin subdirectory.

For example, if you want to allow the user to be able to run the net and ip commands (if authorized by the TACACS+ server), use the command:

cumulus@switch:~$ sudo tacplus-restrict -i -u tacacs0 -a ip net

After running this command, examine the tacacs0 directory::

cumulus@switch:~$ sudo ls -lR ~tacacs0
total 12
lrwxrwxrwx 1 root root 22 Nov 21 22:07 ip -> /usr/sbin/tacplus-auth
lrwxrwxrwx 1 root root 22 Nov 21 22:07 net -> /usr/sbin/tacplus-auth

Other than shell built-ins, the only two commands the privilege level 0 TACACS users can run are the ip and net commands.

If you mistakenly add potential commands with the -a option, you can remove them. The example below shows how to remove the net command:

cumulus@switch:~$ sudo rm ~tacacs0/bin/net

You can remove all commands as follows:

cumulus@switch:~$ sudo rm ~tacacs0/bin/*

Use the man command on the switch for more information on tacplus-auth and tacplus-restrict.

cumulus@switch:~$ man tacplus-auth tacplus-restrict

NSS Plugin

When used with pam_tacplus, TACACS+ authenticated users can log in without a local account on the system using the NSS plugin that comes with the tacplus_nss package. The plugin uses the mapped tacplus information if the user is not found in the local password file, provides the getpwnam() and getpwuid()entry point,s and uses the TACACS+ authentication functions.

The plugin asks the TACACS+ server if the user is known, and then for relevant attributes to determine the privilege level of the user. When the libnss_tacplus package is installed, nsswitch.conf is modified to set tacplus as the first lookup method for passwd. If the order is changed, lookups return the local accounts, such as tacacs0

If the user is not found, a mapped lookup is performed using the libtacplus.so exported functions. The privilege level is appended to tacacs and the lookup searches for the name in the local password file. For example, privilege level 15 searches for the tacacs15 user. If the user is found, the password structure is filled in with information for the user.

If the user is not found, the privilege level is decremented and checked again until privilege level 0 (user tacacs0) is reached. This allows use of only the two local users tacacs0 and tacacs15, if minimal configuration is desired.

TACACS Configuration Parameters

The recognized configuration options are the same as the libpam_tacplus command line arguments; however, not all pam_tacplus options are supported. These configuration parameters are documented in the tacplus_servers.5 man page, which is part of the libpam-tacplus package.

The table below describes the configuration options available:

Configuration Option Description
debug The output debugging information through syslog(3).
Note: Debugging is heavy, including passwords. Do not leave debugging enabled on a production switch after you have completed troubleshooting.
secret=STRING The secret key used to encrypt and decrypt packets sent to and received from the server.
You can specify the secret key more than once in any order with respect to the server= parameter. When fewer secret= parameters are specified, the last secret given is used for the remaining servers.
Only use this parameter in files such as /etc/tacplus_servers that are not world readable.
server=hostname
server=ip-address
Adds a TACACS+ server to the servers list. Servers are queried in turn until a match is found, or no servers remain in the list. Can be specified up to 7 times. An IP address can be optionally followed by a port number, preceded by a “:”. The default port is 49.
Note: When sending accounting records, the record is sent to all servers in the list if acct_all=1, which is the default.
source_ip=ipv4-address Sets the IP address used as the source IP address when communicating with the TACACS+ server. You must specify an IPv4 address. IPv6 addresses and hostnames are not supported. The address must must be valid for the interface being used.
timeout=seconds TACACS+ server(s) communication timeout.
This parameter defaults to 10 seconds in the /etc/tacplus_servers file, but defaults to 5 seconds in the /etc/tacplus_nss.conf file.
include=/file/name A supplemental configuration file to avoid duplicating configuration information. You can include up to 8 more configuration files.
min_uid=value The minimum user ID that the NSS plugin looks up. Setting it to 0 means uid 0 (root) is never looked up, which is desirable for performance reasons. The value should not be greater than the local TACACS+ user IDs (0 through 15), to ensure they can be looked up.
exclude_users=user1,user2,… A comma-separated list of usernames that are never looked up by the NSS plugin, set in the tacplus_nss.conf file. You cannot use * (asterisk) as a wild card in the list. While it’s not a legal username, bash may lookup this as a user name during pathname completion, so it is included in this list as a username string.
Note: Do not remove the cumulus user from the exclude_users list, because doing so can make it impossible to log in as the cumulus user, which is the primary administrative account in Cumulus Linux. If you do remove the cumulus user, add some other local fallback user that does not rely on TACACS but is a member of sudo and netedit groups, so that these accounts can run sudo and NCLU commands.
login=string TACACS+ authentication service (pap, chap, or login).
The default value is pap.
user_homedir=1 This is not enabled by default. When enabled, a separate home directory for each TACACS+ user is created when the TACACS+ user first logs in. By default, the home directory in the mapping accounts in /etc/passwd (/home/tacacs0 … /home/tacacs15) is used. If the home directory does not exist, it is created with the mkhomedir_helper program, in the same way as pam_mkhomedir.
This option is not honored for accounts with restricted shells when per-command authorization is enabled.
acct_all=1 Configuration option for audisp_tacplus and pam_tacplus sending accounting records to all supplied servers (1), or the first server to respond (0).
The default value is 1.
timeout=seconds Sets the timeout in seconds for connections to each TACACS+ server.
The default is 10 seconds for all lookups except that NSS lookups use a 5 second timeout.
vrf=vrf-name If the management network is in a VRF, set this variable to the VRF name. This is typically mgmt. When this variable is set, the connection to the TACACS+ accounting servers is made through the named VRF.
service TACACS+ accounting and authorization service. Examples include shell, pap, raccess, ppp, and slip.
The default value is shell.
protocol TACACS+ protocol field. This option is use dependent. PAM uses the SSH protocol.

Remove the TACACS+ Client Packages

To remove all of the TACACS+ client packages, use the following commands:

cumulus@switch:~$ sudo -E apt-get remove tacplus-client
cumulus@switch:~$ sudo -E apt-get autoremove

To remove the TACACS+ client configuration files as well as the packages (recommended), use this command:

cumulus@switch:~$ sudo -E apt-get autoremove --purge

Troubleshooting

Basic Server Connectivity or NSS Issues

You can use the getent command to determine if TACACS+ is configured correctly and if the local password is stored in the configuration files. In the example commands below, the cumulus user represents the local user, while cumulusTAC represents the TACACS user.

To look up the username within all NSS methods:

cumulus@switch:~$ sudo getent passwd cumulusTAC
cumulusTAC:x:1016:1001:TACACS+ mapped user at privilege level 15,,,:/home/tacacs15:/bin/bash

To look up the user within the local database only:

cumulus@switch:~$ sudo getent -s compat passwd cumulus
cumulus:x:1000:1000:cumulus,,,:/home/cumulus:/bin/bash

To look up the user within the TACACS+ database only:

cumulus@switch:~$ sudo getent -s tacplus passwd cumulusTAC
cumulusTAC:x:1016:1001:TACACS+ mapped user at privilege level 15,,,:/home/tacacs15:/bin/bash

If TACACS does not appear to be working correctly, debug the following configuration files by adding the debug=1 parameter to one or more of these files:

You can also add debug=1 to individual pam_tacplus lines in /etc/pam.d/common*.

All log messages are stored in /var/log/syslog.

Incorrect Shared Key

The TACACS client on the switch and the TACACS server should have the same shared secret key. If this key is incorrect, the following message is printed to syslog:

2017-09-05T19:57:00.356520+00:00 leaf01 sshd[3176]: nss_tacplus: TACACS+ server 192.168.0.254:49 read failed with protocol error (incorrect shared secret?) user cumulus

Issues with Per-command Authorization

To debug TACACS user command authorization, have the TACACS+ user enter the following command at a shell prompt, then try the command again:

tacuser0@switch:~$ export TACACSAUTHDEBUG=1

When this debugging is enabled, additional information is shown for the command authorization conversation with the TACACS+ server:

tacuser0@switch:~$ net pending
tacplus-auth: found matching command (/usr/bin/net) request authorization
tacplus-auth: error connecting to 10.0.3.195:49 to request authorization for net: Transport endpoint is not connected
tacplus-auth: cmd not authorized (16)
tacplus-auth: net not authorized from 192.168.3.189:49
net not authorized by TACACS+ with given arguments, not executing
tacuser0@switch:~$ net show version
tacplus-auth: found matching command (/usr/bin/net) request authorization
tacplus-auth: error connecting to 10.0.3.195:49 to request authorization for net: Transport endpoint is not connected
tacplus-auth: 192.168.3.189:49 authorized command net
tacplus-auth: net authorized, executing
DISTRIB_ID="Cumulus Linux"
DISTRIB_RELEASE=4.0.0
DISTRIB_DESCRIPTION="Cumulus Linux 4.0.0"

To disable debugging:

tacuser0@switch:~$ export -n TACACSAUTHDEBUG

Debug Issues with Accounting Records

If you have added or deleted TACACS+ servers from the configuration files, make sure you notify the audisp plugin with this command:

cumulus@switch:~$ sudo killall -HUP audisp-tacplus

If accounting records are still not being sent, add debug=1 to the /etc/audisp/audisp-tac_plus.conf file, then issue the command above to notify the plugin. Ask the TACACS+ user to run a command and examine the end of /var/log/syslog for messages from the plugin. You can also check the auditing log file /var/log/audit audit.log to be sure the auditing records are being written. If they are not, restart the audit daemon with:

cumulus@switch:~$ sudo systemctl restart auditd.service

TACACS Component Software Descriptions

The following table describes the different pieces of software involved with delivering TACACS.

Package Name Description
audisp-tacplus_1.0.0-1-cl3u3 This package uses auditing data from auditd to send accounting records to the TACACS+ server and is started as part of auditd.
libtac2_1.4.0-cl3u2 Basic TACACS+ server utility and communications routines.
libnss-tacplus_1.0.1-cl3u3 Provides an interface between libc username lookups, the mapping functions, and the TACACS+ server.
tacplus-auth-1.0.0-cl3u1 This package includes the tacplus-restrict setup utility, which enables you to perform per-command TACACS+ authorization. Per-command authorization is not done by default.
libpam-tacplus_1.4.0-1-cl3u2 A modified version of the standard Debian package.
libtacplus-map1_1.0.0-cl3u2 The mapping functionality between local and TACACS+ users on the server. Sets the immutable sessionid and auditing UID to ensure the original user can be tracked through multiple processes and privilege changes. Sets the auditing loginuid as immutable if supported. Creates and maintains a status database in /run/tacacs_client_map to manage and lookup mappings.
libsimple-tacacct1_1.0.0-cl3u2 Provides an interface for programs to send accounting records to the TACACS+ server. Used by audisp-tacplus.
libtac2-bin_1.4.0-cl3u2 Provides the tacc testing program and TACACS+ man page.

Limitations

TACACS+ Client Is only Supported through the Management Interface

The TACACS+ client is only supported through the management interface on the switch: eth0, eth1, or the VRF management interface. The TACACS+ client is not supported through bonds, switch virtual interfaces (SVIs), or switch port interfaces (swp).

Multiple TACACS+ Users

If two or more TACACS+ users are logged in simultaneously with the same privilege level, while the accounting records are maintained correctly, a lookup on either name will match both users, while a UID lookup will only return the user that logged in first.

This means that any processes run by either user will be attributed to both, and all files created by either user will be attributed to the first name matched. This is similar to adding two local users to the password file with the same UID and GID, and is an inherent limitation of using the UID for the base user from the password file.

The current algorithm returns the first name matching the UID from the mapping file; this can be the first or the second user that logged in.

To work around this issue, you can use the switch audit log or the TACACS server accounting logs to determine which processes and files are created by each user.

The Linux auditd system does not always generate audit events for processes when terminated with a signal (with the kill system call or internal errors such as SIGSEGV). As a result, processes that exit on a signal that is not caught and handled, might not generate a STOP accounting record.

Issues with deluser Command

TACACS+ and other non-local users that run the deluser command with the --remove-home option will see an error about not finding the user in /etc/passwd:

tacuser0@switch: deluser --remove-home USERNAME
userdel: cannot remove entry 'USERNAME' from /etc/passwd
/usr/sbin/deluser: `/usr/sbin/userdel USERNAME' returned error code 1. Exiting

However, the command does remove the home directory. The user can still log in on that account, but will not have a valid home directory. This is a known upstream issue with the deluser command for all non-local users.

Only use the --remove-home option when the user_homedir=1 configuration command is in use.

When Both TACACS+ and RADIUS AAA Clients are Installed

When you have both the TACACS+ and the RADIUS AAA client installed, RADIUS login is not attempted. As a workaround, do not install both the TACACS+ and the RADIUS AAA client on the same switch.

RADIUS AAA

Various add-on packages enable RADIUS users to log in to Cumulus Linux switches in a transparent way with minimal configuration. There is no need to create accounts or directories on the switch. Authentication is handled with PAM and includes login, ssh, sudo and su.

Install the RADIUS Packages

You can install the RADIUS packages even if the switch is not connected to the internet, as they are contained in the cumulus-local-apt-archive repository that is embedded in the Cumulus Linux disk image.

To install the RADIUS packages:

cumulus@switch:~$ sudo apt-get update
cumulus@switch:~$ sudo apt-get install libnss-mapuser libpam-radius-auth

After installation is complete, either reboot the switch or run the sudo systemctl restart netd command.

The libpam-radius-auth package supplied with the Cumulus Linux RADIUS client is a newer version than the one in Debian Buster. This package contains support for IPv6, the src_ip option described below, as well as a number of bug fixes and minor features. The package also includes VRF support, provides man pages describing the PAM and RADIUS configuration, and sets the SUDO_PROMPT environment variable to the login name for RADIUS mapping support.

The libnss-mapuser package is specific to Cumulus Linux and supports the getgrent, getgrnam and getgrgid library interfaces. These interfaces add logged in RADIUS users to the group member list for groups that contain the mapped_user (radius_user) if the RADIUS account is unprivileged, and add privileged RADIUS users to the group member list for groups that contain the mapped_priv_user (radius_priv_user) during the group lookups.

During package installation:

Configure the RADIUS Client

To configure the RADIUS client, edit the /etc/pam_radius_auth.conf file:

  1. Add the hostname or IP address of at least one RADIUS server (such as a freeradius server on Linux), and the shared secret used to authenticate and encrypt communication with each server.

    The hostname of the switch must be resolvable to an IP address, which, in general, is fixed in DNS. If for some reason you cannot find the hostname in DNS, you can add the hostname to the /etc/hosts file manually. However, this can cause problems since the IP address is usually assigned by DHCP, which can change at any time.

    Multiple server configuration lines are verified in the order listed. Other than memory, there is no limit to the number of RADIUS servers you can use.

    The server port number or name is optional. The system looks up the port in the /etc/services file. However, you can override the ports in the /etc/pam_radius_auth.conf file.

  2. If the server is slow or latencies are high, change the timeout setting. The setting defaults to 3 seconds.

  3. If you want to use a specific interface to reach the RADIUS server, specify the src_ip option. You can specify the hostname of the interface, an IPv4, or an IPv6 address. If you specify the src_ip option, you must also specify the timeout option.

  4. Set the vrf-name field. This is typically set to mgmt if you are using a management VRF. You cannot specify more than one VRF.

The configuration file includes the mapped_priv_user field that sets the account used for privileged RADIUS users and the priv-lvl field that sets the minimum value for the privilege level to be considered a privileged login (the default value is 15). If you edit these fields, make sure the values match those set in the /etc/nss_mapuser.conf file.

The following example provides a sample /etc/pam_radius_auth.conf file configuration:

mapped_priv_user   radius_priv_user
# server[:port]    shared_secret   timeout (secs)  src_ip
192.168.0.254      secretkey
other-server       othersecret     3               192.168.1.10
# when mgmt vrf is in use
vrf-name mgmt

If this is the first time you are configuring the RADIUS client, uncomment the debug line to help with troubleshooting. The debugging messages are written to /var/log/syslog. When the RADIUS client is working correctly, comment out the debug line.

As an optional step, you can set PAM configuration keywords by editing the /usr/share/pam-configs/radius file. After you edit the file, you must run the pam-auth-update --package command. PAM configuration keywords are described in the pam_radius_auth (8) man page.

The privilege level for the user on the switch is determined by the value of the VSA (Vendor Specific Attribute) shell:priv-lvl. If the attribute is not returned, the user is unprivileged. The following shows an example using the freeradius server for a fully-privileged user.

Service-Type = Administrative-User,
Cisco-AVPair = "shell:roles=network-administrator",
Cisco-AVPair += "shell:priv-lvl=15"

The VSA vendor name (Cisco-AVPair in the example above) can have any content. The RADIUS client only checks for the string shell:priv-lvl.

Enable Login without Local Accounts

Because LDAP is not commonly used with switches and adding accounts locally is cumbersome, Cumulus Linux includes a mapping capability with the libnss-mapuser package.

Mapping is done using two NSS (Name Service Switch) plugins, one for account name, and one for UID lookup. These accounts are configured automatically in /etc/nsswitch.conf during installation and are removed when the package is removed. See the nss_mapuser (8) man page for the full description of this plugin.

A username is mapped at login to a fixed account specified in the configuration file, with the fields of the fixed account used as a template for the user that is logging in.

For example, if the name being looked up is dave and the fixed account in the configuration file is radius_user, and that entry in /etc/passwd is:

radius_user:x:1017:1002:radius user:/home/radius_user:/bin/bash

then the matching line returned by running getent passwd dave is:

cumulus@switch:~$ getent passwd dave
dave:x:1017:1002:dave mapped user:/home/dave:/bin/bash

The home directory /home/dave is created during the login process if it does not already exist and is populated with the standard skeleton files by the mkhomedir_helper command.

The configuration file /etc/nss_mapuser.conf is used to configure the plugins. The file includes the mapped account name, which is radius_user by default. You can change the mapped account name by editing the file. The nss_mapuser (5) man page describes the configuration file.

A flat file mapping is done based on the session number assigned during login, which persists across su and sudo. The mapping is removed at logout.

Local Fallback Authentication

If a site wants to allow local fallback authentication for a user when none of the RADIUS servers can be reached you can add a privileged user account as a local account on the switch. The local account must have the same unique identifier as the privileged user and the shell must be the same.

To configure local fallback authentication:

  1. dd a local privileged user account. For example, if the radius_priv_user account in the /etc/passwd file is radius_priv_user:x:1002:1001::/home/radius_priv_user:/sbin/radius_shell, run the following command to add a local privileged user account named johnadmin:

    cumulus@switch:~$ sudo useradd -u 1002 -g 1001 -o -s /sbin/radius_shell johnadmin
    
  2. To enable the local privileged user to run sudo and NCLU commands, run the following commands:

    cumulus@switch:~$ sudo adduser johnadmin netedit
    cumulus@switch:~$ sudo adduser johnadmin sudo
    cumulus@switch:~$ sudo systemctl restart netd
    
  3. Edit the /etc/passwd file to move the local user line before to the radius_priv_user line:

    cumulus@switch:~$ sudo vi /etc/passwd
    ...
    johnadmin:x:1002:1001::/home/johnadmin:/sbin/radius_shell
    radius_priv_user:x:1002:1001::/home/radius_priv_user:/sbin/radius_shell
    
  4. To set the local password for the local user, run the following command:

    cumulus@switch:~$ sudo passwd johnadmin
    

Verify RADIUS Client Configuration

To verify that the RADIUS client is configured correctly, log in as a non-privileged user and run a net add interface command.

In this example, the ops user is not a privileged RADIUS user so they cannot add an interface.

ops@leaf01:~$ net add interface swp1
ERROR: User ops does not have permission to make networking changes.

In this example, the admin user is a privileged RADIUS user (with privilege level 15) so is able to add interface swp1.

admin@leaf01:~$ net add interface swp1
admin@leaf01:~$ net pending
--- /etc/network/interfaces    2018-04-06 14:49:33.099331830 +0000
+++ /var/run/nclu/iface/interfaces.tmp    2018-04-06 16:01:16.057639999 +0000
@@ -3,10 +3,13 @@

  source /etc/network/interfaces.d/*.intf

  # The loopback network interface
  auto lo
  iface lo inet loopback

  # The primary network interface
  auto eth0
  iface eth0 inet dhcp
+
+auto swp1
iface swp1
...

Remove RADIUS Client Packages

Remove the RADIUS packages with the following command:

cumulus@switch:~$ sudo apt-get remove libnss-mapuser libpam-radius-auth

When you remove the packages, the plugins are removed from the /etc/nsswitch.conf file and from the PAM files.

To remove all configuration files for these packages, run:

cumulus@switch:~$ sudo apt-get purge libnss-mapuser libpam-radius-auth

The RADIUS fixed account is not removed from the /etc/passwd or /etc/group file and the home directories are not removed. They remain in case there are modifications to the account or files in the home directories.

To remove the home directories of the RADIUS users, first get the list by running:

cumulus@switch:~$ sudo ls -l /home | grep radius

For all users listed, except the radius_user, run this command to remove the home directories:

cumulus@switch:~$ sudo deluser --remove-home USERNAME

where USERNAME is the account name (the home directory relative portion). This command gives the following warning because the user is not listed in the /etc/passwd file.

userdel: cannot remove entry 'USERNAME' from /etc/passwd
/usr/sbin/deluser: `/usr/sbin/userdel USERNAME' returned error code 1. Exiting.

After removing all the RADIUS users, run the command to remove the fixed account. If the account has been changed in the /etc/nss_mapuser.conf file, use that account name instead of radius_user.

cumulus@switch:~$ sudo deluser --remove-home radius_user
cumulus@switch:~$ sudo deluser --remove-home radius_priv_user
cumulus@switch:~$ sudo delgroup radius_users

Limitations

Netfilter - ACLs

Netfilter is the packet filtering framework in Cumulus Linux as well as most other Linux distributions. There are a number of tools available for configuring ACLs in Cumulus Linux:

NCLU and cl-acltool operate on various configuration files and use iptables, ip6tables, and ebtables to install rules into the kernel. In addition, NCLU and cl-acltool program rules in hardware for interfaces involving switch port interfaces, which iptables, ip6tables and ebtables cannot do on their own.

In many instances, you can use NCLU to configure ACLs; however, in some cases, you must use cl-acltool. The examples below specify when to use which tool.

If you need help to configure ACLs, run net example acl to see a basic configuration:

Example
cumulus@leaf01:~$ net example acl

Scenario
========
We would like to use access-lists on 'switch' to
- Restrict inbound traffic on swp1 to traffic from 10.1.1.0/24 destined for 10.1.2.0/24
- Restrict outbound traffic on swp2 to http, https, or ssh

         *switch
            /\
      swp1 /  \ swp2
          /    \
         /      \
     host-11   host-12

switch net commands
====================

Create an ACL that accepts traffic from 10.1.1.0/24 destined for 10.1.2.0/24 and drops all other traffic

switch# net add acl ipv4 MYACL accept source-ip 10.1.1.0/24 dest-ip 10.1.2.0/24
switch# net add acl ipv4 MYACL drop source-ip any dest-ip any

Apply MYACL inbound on swp1

switch# net add interface swp1 acl ipv4 MYACL inbound

Create an ACL that accepts http, https, or ssh traffic and drops all other traffic.

switch# net add acl ipv4 WEB_OR_SSH accept tcp source-ip any source-port any dest-ip any dest-port http
switch# net add acl ipv4 WEB_OR_SSH accept tcp source-ip any source-port http dest-ip any dest-port any
switch# net add acl ipv4 WEB_OR_SSH accept tcp source-ip any source-port any dest-ip any dest-port https
switch# net add acl ipv4 WEB_OR_SSH accept tcp source-ip any source-port https dest-ip any dest-port any
switch# net add acl ipv4 WEB_OR_SSH accept tcp source-ip any source-port any dest-ip any dest-port ssh
switch# net add acl ipv4 WEB_OR_SSH accept tcp source-ip any source-port ssh dest-ip any dest-port any
switch# net add acl ipv4 WEB_OR_SSH drop source-ip any dest-ip any

Apply WEB_OR_SSH outbound on swp2
switch# net add interface swp2 acl ipv4 WEB_OR_SSH outbound

commit the staged changes
switch# net commit

Verification
============
switch# net show configuration acl

Traffic Rules In Cumulus Linux

Chains

Netfilter describes the mechanism for which packets are classified and controlled in the Linux kernel. Cumulus Linux uses the Netfilter framework to control the flow of traffic to, from, and across the switch. Netfilter does not require a separate software daemon to run; it is part of the Linux kernel itself. Netfilter asserts policies at layers 2, 3 and 4 of the OSI model by inspecting packet and frame headers based on a list of rules. Rules are defined using syntax provided by the iptables, ip6tables and ebtables userspace applications.

The rules created by these programs inspect or operate on packets at several points in the life of the packet through the system. These five points are known as chains and are shown here:

The chains and their uses are:

Tables

When building rules to affect the flow of traffic, the individual chains can be accessed by tables. Linux provides three tables by default:

Each table has a set of default chains that can be used to modify or inspect packets at different points of the path through the switch. Chains contain the individual rules to influence traffic. Each table and the default chains they support are shown below. Tables and chains in green are supported by Cumulus Linux, those in red are not supported (that is, they are not hardware accelerated) at this time.

Rules

Rules are the items that actually classify traffic to be acted upon. Rules are applied to chains, which are attached to tables, similar to the graphic below.

Rules have several different components; the examples below highlight those different components.

How Rules Are Parsed and Applied

All the rules from each chain are read from iptables, ip6tables, and ebtables and entered in order into either the filter table or the mangle table. The rules are read from the kernel in the following order:

When rules are combined and put into one table, the order determines the relative priority of the rules; iptables and ip6tables have the highest precedence and ebtables has the lowest.

The Linux packet forwarding construct is an overlay for how the silicon underneath processes packets. Be aware of the following:

On Broadcom switches, the ingress INPUT chain rules match layer 2 and layer 3 multicast packets before multicast packet replication has occurred; therefore, a DROP rule affects all copies.

Rule Placement in Memory

INPUT and ingress (FORWARD -i) rules occupy the same memory space. A rule counts as ingress if the -i option is set. If both input and output options (-i and -o) are set, the rule is considered as ingress and occupies that memory space. For example:

-A FORWARD -i swp1 -o swp2 -s 10.0.14.2 -d 10.0.15.8 -p tcp -j ACCEPT

If you set an output flag with the INPUT chain, you see an error. For example, running cl-acltool -i on the following rule:

-A FORWARD,INPUT -i swp1 -o swp2 -s 10.0.14.2 -d 10.0.15.8 -p tcp -j ACCEPT

generates the following error:

error: line 2 : output interface specified with INPUT chain error processing rule '-A FORWARD,INPUT -i swp1 -o swp2 -s 10.0.14.2 -d 10.0.15.8 -p tcp -j ACCEPT'

However, removing the -o option and interface make it a valid rule.

Nonatomic Update Mode and Atomic Update Mode

In Cumulus Linux, atomic update mode is enabled by default. However, this mode limits the number of ACL rules that you can configure.

To increase the number of ACL rules that can be configured, configure the switch to operate in nonatomic mode.

How the Rules Get Installed

Instead of reserving 50% of your TCAM space for atomic updates, incremental update uses the available free space to write the new TCAM rules and swap over to the new rules after this is complete. Cumulus Linux then deletes the old rules and frees up the original TCAM space. If there is insufficient free space to complete this task, the original nonatomic update is performed, which interrupts traffic.

Enable Nonatomic Update Mode

You can enable nonatomic updates for switchd, which offer better scaling because all TCAM resources are used to actively impact traffic. With atomic updates, half of the hardware resources are on standby and do not actively impact traffic.

Incremental nonatomic updates are table based, so they do not interrupt network traffic when new rules are installed. The rules are mapped into the following tables and are updated in this order:

Only switches with the Broadcom ASIC support incremental nonataomic updates. Mellanox switches with the Spectrum-based ASIC only support standard nonatomic updates; using nonatomic mode on Spectrum-based ASICs impacts traffic on ACL updates.

The incremental nonatomic update operation follows this order:

  1. Updates are performed incrementally, one table at a time without stopping traffic.
  2. Cumulus Linux checks if the rules in a table have changed since the last time they were installed; if a table does not have any changes, it is not reinstalled.
  3. If there are changes in a table, the new rules are populated in new groups or slices in hardware, then that table is switched over to the new groups or slices.
  4. Finally, old resources for that table are freed. This process is repeated for each of the tables listed above.
  5. If sufficient resources do not exist to hold both the new rule set and old rule set, the regular nonatomic mode is attempted. This interrupts network traffic.
  6. If the regular nonatomic update fails, Cumulus Linux reverts back to the previous rules.

To always start switchd with nonatomic updates:

  1. Edit /etc/cumulus/switchd.conf.

  2. Add the following line to the file:

    acl.non_atomic_update_mode = TRUE
    
  3. Restart switchd:

    cumulus@switch:~$ sudo systemctl restart switchd.service
    

    During regular non-incremental nonatomic updates, traffic is stopped first, then enabled after the new configuration is written into the hardware completely.

Use iptables, ip6tables, and ebtables Directly

Using iptables, ip6tables, ebtables directly is not recommended because any rules installed in these cases only are applied to the Linux kernel and are not hardware accelerated using synchronization to the switch silicon. Running cl-acltool -i (the installation command) resets all rules and deletes anything that is not stored in /etc/cumulus/acl/policy.conf.

For example, performing:

cumulus@switch:~$ sudo iptables -A INPUT -p icmp --icmp-type echo-request -j DROP

Appears to work, and the rule appears when you run cl-acltool -L:

cumulus@switch:~$ sudo cl-acltool -L ip
-------------------------------
Listing rules of type iptables:
-------------------------------

TABLE filter :
Chain INPUT (policy ACCEPT 72 packets, 5236 bytes)
pkts bytes target prot opt in out source destination
0 0 DROP icmp -- any any anywhere anywhere icmp echo-request

However, the rule is not synced to hardware when applied in this way and running cl-acltool -i or reboot removes the rule without replacing it. To ensure all rules that can be in hardware are hardware accelerated, place them in /etc/cumulus/acl/policy.conf and install them by running cl-acltool -i.

Estimate the Number of Rules

To estimate the number of rules you can create from an ACL entry, first determine if that entry is an ingress or an egress. Then, determine if it is an IPv4-mac or IPv6 type rule. This determines the slice to which the rule belongs. Use the following to determine how many entries are used up for each type.

By default, each entry occupies one double wide entry, except if the entry is one of the following:

Match SVI and Bridged Interfaces in Rules

Cumulus Linux supports matching ACL rules for both ingress and egress interfaces on both VLAN-aware and traditional mode bridges, including bridge SVIs (switch VLAN interfaces) for input and output. However, keep the following in mind:

Example rules for a VLAN-aware bridge:

[ebtables]
-A FORWARD -i br0.100 -p IPv4 --ip-protocol icmp -j DROP
-A FORWARD -o br0.100 -p IPv4 --ip-protocol icmp -j ACCEPT

iptables]
-A FORWARD -i br0.100 -p icmp -j DROP
-A FORWARD --out-interface br0.100 -p icmp -j ACCEPT
-A FORWARD --in-interface br0.100 -j POLICE --set-mode  pkt  --set-rate  1 --set-burst 1 --set-class 0

Example rules for a traditional mode bridge:

[ebtables]
-A FORWARD -i br0 -p IPv4 --ip-protocol icmp -j DROP
-A FORWARD -o br0 -p IPv4 --ip-protocol icmp -j ACCEPT

[iptables]
-A FORWARD -i br0 -p icmp -j DROP
-A FORWARD --out-interface br0 -p icmp -j ACCEPT
-A FORWARD --in-interface br0 -j POLICE --set-mode  pkt  --set-rate  1 --set-burst 1 --set-class 0

Match on VLAN IDs on Layer 2 Interfaces

On switches with Spectrum ASICs, you can match on VLAN IDs on layer 2 interfaces for ingress rules.

The following example matches on a VLAN and DSCP class, and sets the internal class of the packet. This can be combined with ingress iptable rules to get extended matching on IP fields.

[ebtables]
-A FORWARD -p 802_1Q --vlan-id 100 -j mark --mark-set 102

[iptables]
-A FORWARD -i swp31 -m mark --mark 102 -m dscp --dscp-class CS1 -j SETCLASS --class 2

  • Cumulus Linux reserves mark values between 0 and 100; for example, if you use --mark-set 10, you see an error. Use mark values between 101 and 4196.
  • You cannot mark multiple VLANs with the same value.

Install and Manage ACL Rules with NCLU

NCLU provides an easy way to create custom ACLs in Cumulus Linux. The rules you create live in the /var/lib/cumulus/nclu/nclu_acl.conf file, which gets converted to a rules file, /etc/cumulus/acl/policy.d/50_nclu_acl.rules. This way, the rules you create with NCLU are independent of the two default files in /etc/cumulus/acl/policy.d/ 00control_plane.rules and 99control_plane_catch_all.rules, as the content in these files might get updated after you upgrade Cumulus Linux.

Instead of crafting a rule by hand then installing it using cl-acltool, NCLU handles many of the options automatically. For example, consider the following iptables rule:

-A FORWARD -i swp1 -o swp2 -s 10.0.14.2 -d 10.0.15.8 -p tcp -j ACCEPT

You create this rule, called EXAMPLE1, using NCLU like this:

cumulus@switch:~$ net add acl ipv4 EXAMPLE1 accept tcp source-ip 10.0.14.2/32 source-port any dest-ip 10.0.15.8/32 dest-port any
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

All options, such as the -j and -p, even FORWARD in the above rule, are added automatically when you apply the rule to the control plane; NCLU figures it all out for you.

You can also set a priority value, which specifies the order in which the rules get executed and the order in which they appear in the rules file. Lower numbers are executed first. To add a new rule in the middle, first run net show config acl, which displays the priority numbers. Otherwise, new rules get appended to the end of the list of rules in the nclu_acl.conf and 50_nclu_acl.rules files.

If you need to hand edit a rule, do not edit the 50_nclu_acl.rules file. Instead, edit the nclu_acl.conf file.

After you add the rule, you need to apply it to an inbound or outbound interface using net add int acl. The inbound interface in our example is swp1:

cumulus@switch:~$ net add int swp1 acl ipv4 EXAMPLE1 inbound
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

After you commit your changes, you can verify the rule you created with NCLU by running net show configuration acl:

cumulus@switch:~$ net show configuration acl
acl ipv4 EXAMPLEv4 priority 10 accept tcp source-ip 10.0.14.2/32 source-port any dest-ip 10.0.15.8/32 dest-port any

interface swp1
acl ipv4 EXAMPLE1 inbound

Or you can see all of the rules installed by running cat on the 50_nclu_acl.rules file:

cumulus@switch:~$ cat /etc/cumulus/acl/policy.d/50_nclu_acl.rules
[iptables]
# swp1: acl ipv4 EXAMPLE1 inbound
-A FORWARD --in-interface swp1 --out-interface swp2 -j ACCEPT -p tcp -s 10.0.14.2/32 -d 10.0.15.8/32 --dport 110

For INPUT and FORWARD rules, apply the rule to a control plane interface using net add control-plane:

cumulus@switch:~$ net add control-plane acl ipv4 EXAMPLE1 inbound
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To remove a rule, use net del acl ipv4|ipv6|mac RULENAME:

cumulus@switch:~$ net del acl ipv4 EXAMPLE1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

This deletes all rules from the 50_nclu_acl.rules file with that name. It also deletes the interfaces referenced in the nclu_acl.conf file.

Install and Manage ACL Rules with cl-acltool

You can manage Cumulus Linux ACLs with cl-acltool. Rules are first written to the iptables chains, as described above, and then synced to hardware via switchd.

Use iptables/ip6tables/ebtables and cl-acltool to manage rules in the default files, 00control_plane.rules and 99control_plane_catch_all.rules; they are not aware of rules created using NCLU.

To examine the current state of chains and list all installed rules, run:

cumulus@switch:~$ sudo cl-acltool -L all
 -------------------------------
Listing rules of type iptables:
-------------------------------

TABLE filter :
Chain INPUT (policy ACCEPT 90 packets, 14456 bytes)
pkts bytes target prot opt in out source destination
0 0 DROP all -- swp+ any 240.0.0.0/5 anywhere
0 0 DROP all -- swp+ any loopback/8 anywhere
0 0 DROP all -- swp+ any base-address.mcast.net/8 anywhere
0 0 DROP all -- swp+ any 255.255.255.255 anywhere ...

To list installed rules using native iptables, ip6tables and ebtables, use the -L option with the respective commands:

cumulus@switch:~$ sudo iptables -L
cumulus@switch:~$ sudo ip6tables -L
cumulus@switch:~$ sudo ebtables -L

To flush all installed rules, run:

cumulus@switch:~$ sudo cl-acltool -F all

To flush only the IPv4 iptables rules, run:

cumulus@switch:~$ sudo cl-acltool -F ip

If the install fails, ACL rules in the kernel and hardware are rolled back to the previous state. Errors from programming rules in the kernel or ASIC are reported appropriately.

Install Packet Filtering (ACL) Rules

cl-acltool takes access control list (ACL) rules input in files. Each ACL policy file contains iptables, ip6tables and ebtables categories under the tags [iptables], [ip6tables] and [ebtables].

Each rule in an ACL policy must be assigned to one of the rule categories above.

See man cl-acltool(5) for ACL rule details. For iptables rule syntax, see man iptables(8). For ip6tables rule syntax, see man ip6tables(8). For ebtables rule syntax, see man ebtables(8).

See man cl-acltool(5) and man cl-acltool(8) for further details on using cl-acltool. Some examples are listed here and more are listed later in this chapter.

By default:

  • ACL policy files are located in /etc/cumulus/acl/policy.d/.
  • All *.rules files in this directory are included in /etc/cumulus/acl/policy.conf.
  • All files included in this policy.conf file are installed when the switch boots up.
  • The policy.conf file expects rules files to have a .rules suffix as part of the file name.

Here is an example ACL policy file:

[iptables]
-A INPUT --in-interface swp1 -p tcp --dport 80 -j ACCEPT
-A FORWARD --in-interface swp1 -p tcp --dport 80 -j ACCEPT

[ip6tables]
-A INPUT --in-interface swp1 -p tcp --dport 80 -j ACCEPT
-A FORWARD --in-interface swp1 -p tcp --dport 80 -j ACCEPT

[ebtables]
-A INPUT -p IPv4 -j ACCEPT
-A FORWARD -p IPv4 -j ACCEPT

You can use wildcards or variables to specify chain and interface lists to ease administration of rules.

Currently only swp+ and bond+ are supported as wildcard names. There might be kernel restrictions in supporting more complex wildcards like swp1+ etc.

swp+ rules are applied as an aggregate, not per port. If you want to apply per port policing, specify a specific port instead of the wildcard.

INGRESS = swp+
INPUT_PORT_CHAIN = INPUT,FORWARD

[iptables]
-A $INPUT_PORT_CHAIN --in-interface $INGRESS -p tcp --dport 80 -j ACCEPT

[ip6tables]
-A $INPUT_PORT_CHAIN --in-interface $INGRESS -p tcp --dport 80 -j ACCEPT

[ebtables]
-A INPUT -p IPv4 -j ACCEPT

You can write ACL rules for the system into multiple files under the default /etc/cumulus/acl/policy.d/ directory. The ordering of rules during installation follows the sort order of the files based on their file names.

Use multiple files to stack rules. The example below shows two rules files separating rules for management and datapath traffic:

cumulus@switch:~$ ls /etc/cumulus/acl/policy.d/
00sample_mgmt.rules 01sample_datapath.rules
cumulus@switch:~$ cat /etc/cumulus/acl/policy.d/00sample_mgmt.rules

INGRESS_INTF = swp+
INGRESS_CHAIN = INPUT

[iptables]
# protect the switch management
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -s 10.0.14.2 -d 10.0.15.8 -p tcp -j ACCEPT
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -s 10.0.11.2 -d 10.0.12.8 -p tcp -j ACCEPT
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -d 10.0.16.8 -p udp -j DROP

cumulus@switch:~$ cat /etc/cumulus/acl/policy.d/01sample_datapath.rules
INGRESS_INTF = swp+
INGRESS_CHAIN = INPUT, FORWARD

[iptables]
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -s 192.0.2.5 -p icmp -j ACCEPT
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -s 192.0.2.6 -d 192.0.2.4 -j DROP
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -s 192.0.2.2 -d 192.0.2.8 -j DROP

Install all ACL policies under a directory:

cumulus@switch:~$ sudo cl-acltool -i -P ./rules
Reading files under rules
Reading rule file ./rules/01_http_rules.txt ...
Processing rules in file ./rules/01_http_rules.txt ...
Installing acl policy ...
Done.

Apply all rules and policies included in /etc/cumulus/acl/policy.conf:

cumulus@switch:~$ sudo cl-acltool -i

In addition to ensuring that the rules and policies referenced by /etc/cumulus/acl/policy.conf are installed, this will remove any currently active rules and policies that are not contained in the files referenced by /etc/cumulus/acl/policy.conf.

Specify the Policy Files to Install

By default, Cumulus Linux installs any .rules file you configure in /etc/cumulus/acl/policy.d/. To add other policy files to an ACL, you need to include them in /etc/cumulus/acl/policy.conf. For example, for Cumulus Linux to install a rule in a policy file called 01_new.datapathacl, add include /etc/cumulus/acl/policy.d/01_new.rules to policy.conf, as in this example:

cumulus@switch:~$ sudo nano /etc/cumulus/acl/policy.conf

#
# This file is a master file for acl policy file inclusion
#
# Note: This is not a file where you list acl rules.
#
# This file can contain:
# - include lines with acl policy files
#   example:
#     include <filepath>
#
# see manpage cl-acltool(5) and cl-acltool(8) for how to write policy files 
#

include /etc/cumulus/acl/policy.d/01_new.datapathacl

Hardware Limitations on Number of Rules

The maximum number of rules that can be handled in hardware is a function of the following factors:

If the maximum number of rules for a particular table is exceeded, cl-acltool -i generates the following error:

error: hw sync failed (sync_acl hardware installation failed) Rolling back .. failed.

In the tables below, the default rules count toward the limits listed. The raw limits below assume only one ingress and one egress table are present.

Broadcom Tomahawk Limits

Direction Atomic Mode IPv4 Rules Atomic Mode IPv6 Rules Nonatomic Mode IPv4 Rules Nonatomic Mode IPv6 Rules
Ingress raw limit 512 512 1024 1024
Ingress limit with default rules 256 (36 default) 256 (29 default) 768 (36 default) 768 (29 default)
Egress raw limit 256 0 512 0
Egress limit with default rules 256 (29 default) 0 512 (29 default) 0

Broadcom Trident3 Limits

The Trident3 ASIC is divided into 12 slices, organized into 4 groups for ACLs. Each group contains 3 slices. Each group can support a maximum of 768 rules. You cannot mix IPv4 and IPv6 rules within the same group. IPv4 and MAC rules can be programmed into the same group.

Direction Atomic Mode IPv4 Rules Atomic Mode IPv6 Rules Nonatomic Mode IPv4 Rules Nonatomic Mode IPv6 Rules
Ingress raw limit 768 768 2304 2304
Ingress limit with default rules 768 (44 default) 768 (41 default) 2304 (44 default) 2304 (41 default)
Egress raw limit 512 0 512 0
Egress limit with default rules 512 (28 default) 0 512 (28 default) 0

Broadcom Trident II+ Limits

Direction Atomic Mode IPv4 Rules Atomic Mode IPv6 Rules Nonatomic Mode IPv4 Rules Nonatomic Mode IPv6 Rules
Ingress raw limit 4096 4096 8192 8192
Ingress limit with default rules 2048 (36 default) 3072 (29 default) 6144 (36 default) 6144 (29 default)
Egress raw limit 256 0 512 0
Egress limit with default rules 256 (29 default) 0 512 (29 default) 0

Broadcom Trident II Limits

Direction Atomic Mode IPv4 Rules Atomic Mode IPv6 Rules Nonatomic Mode IPv4 Rules Nonatomic Mode IPv6 Rules
Ingress raw limit 1024 1024 2048 2048
Ingress limit with default rules 512 (36 default) 768 (29 default) 1536 (36 default) 1536 (29 default)
Egress raw limit 256 0 512 0
Egress limit with default rules 256 (29 default) 0 512 (29 default) 0

Broadcom Helix4 Limits

Direction Atomic Mode IPv4 Rules Atomic Mode IPv6 Rules Nonatomic Mode IPv4 Rules Nonatomic Mode IPv6 Rules
Ingress raw limit 1024 512 2048 1024
Ingress limit with default rules 768 (36 default) 384 (29 default) 1792 (36 default) 896 (29 default)
Egress raw limit 256 0 512 0
Egress limit with default rules 256 (29 default) 0 512 (29 default) 0

Mellanox Spectrum Limits

The Mellanox Spectrum ASIC has one common TCAM for both ingress and egress, which can be used for other non-ACL-related resources. However, the number of supported rules varies with the TCAM profile specified for the switch.

Profile Atomic Mode IPv4 Rules Atomic Mode IPv6 Rules Nonatomic Mode IPv4 Rules Nonatomic Mode IPv6 Rules
default 500 250 1000 500
ipmc-heavy 750 500 1500 1000
acl-heavy 1750 1000 3500 2000
ipmc-max 1000 500 2000 1000
ip-acl-heavy 6000 0 12000 0

  • Even though the table above specifies that zero IPv6 rules are supported with the ip-acl-heavy profile, Cumulus Linux does not prevent you from configuring IPv6 rules. However, there is no guarantee that IPv6 rules work under the ip-acl-heavy profile.
  • The ip-acl-heavy profile shows an updated number of supported atomic mode and nonatomic mode IPv4 rules. The previously published numbers were 7500 for atomic mode and 15000 for nonatomic mode IPv4 rules.

Supported Rule Types

The iptables/ip6tables/ebtables construct tries to layer the Linux implementation on top of the underlying hardware but they are not always directly compatible. Here are the supported rules for chains in iptables, ip6tables and ebtables.

To learn more about any of the options shown in the tables below, run iptables -h [name of option]. The same help syntax works for options for ip6tables and ebtables.

Click to see an example of help syntax for an ebtables target
root@leaf1# ebtables -h tricolorpolice
<...snip...>
tricolorpolice option:
--set-color-mode STRING setting the mode in blind or aware
--set-cir INT setting committed information rate in kbits per second
--set-cbs INT setting committed burst size in kbyte
--set-pir INT setting peak information rate in kbits per second
--set-ebs INT setting excess burst size in kbyte
--set-conform-action-dscp INT setting dscp value if the action is accept for conforming packets
--set-exceed-action-dscp INT setting dscp value if the action is accept for exceeding packets
--set-violate-action STRING setting the action (accept/drop) for violating packets
--set-violate-action-dscp INT setting dscp value if the action is accept for violating packets
Supported chains for the filter table:
INPUT FORWARD OUTPUT

iptables and ip6tables Rule Support

Rule Element Supported Unsupported
Matches Src/Dst, IP protocol
In/out interface
IPv4: icmp, ttl,
IPv6: icmp6, frag, hl,
IP common: tcp (with flags), udp, multiport, DSCP, addrtype
Rules with input/output Ethernet interfaces are ignored
Inverse matches
Standard Targets ACCEPT, DROP RETURN, QUEUE, STOP, Fall Thru, Jump
Extended Targets LOG (IPv4/IPv6); UID is not supported for LOG
TCP SEQ, TCP options or IP options
ULOG
SETQOS
DSCP
Unique to Cumulus Linux:
SPAN
ERSPAN (IPv4/IPv6)
POLICE
TRICOLORPOLICE
SETCLASS

ebtables Rule Support

Rule Element Supported Unsupported
Matches ether type
input interface/wildcard
output interface/wildcard
src/dst MAC
IP: src, dest, tos, proto, sport, dport
IPv6: tclass, icmp6: type, icmp6: code range, src/dst addr, sport, dport
802.1p (CoS)
VLAN
Inverse matches
Proto length
Standard Targets ACCEPT, DROP Return, Continue, Jump, Fall Thru
Extended Targets Ulog
log
Unique to Cumulus Linux:
span
erspan
police
tricolorpolice
setclass

Other Unsupported Rules

IPv6 Egress Rules on Broadcom Switches

Cumulus Linux supports IPv6 egress rules in ip6tables on Broadcom switches. Because there are no slices to allocate in the egress TCAM for IPv6, the matches are implemented using a combination of the ingress IPv6 slice and the existing egress IPv4 MAC slice:

For example, the -A FORWARD --out-interface vlan100 -p icmp6 -j ACCEPT rule is split into the following:

  • IPv6 egress rules in ip6tables are not supported on Hurricane2 switches.
  • You cannot match both input and output interfaces in the same rule.
  • The egress TCAM IPv4 MAC slice is shared with other rules, which constrains the scale to a much lower limit.

Caveats

Splitting rules across the ingress TCAM and the egress TCAM causes the ingress IPv6 part of the rule to match packets going to all destinations, which can interfere with the regular expected linear rule match in a sequence. For example:

A higher rule can prevent a lower rule from being matched unexpectedly:

Rule 1: -A FORWARD --out-interface vlan100 -p icmp6 -j ACCEPT

Rule 2: -A FORWARD --out-interface vlan101 -p icmp6 -s 01::02 -j ACCEPT

Rule 1 matches all icmp6 packets from to all out interfaces in the ingress TCAM.

This prevents rule 2 from getting matched, which is more specific but with a different out interface. Make sure to put more specific matches above more general matches even if the output interfaces are different.

When you have two rules with the same output interface, the lower rule might match unexpectedly depending on the presence of the previous rules.

Rule 1: -A FORWARD --out-interface vlan100 -p icmp6 -j ACCEPT

Rule 2: -A FORWARD --out-interface vlan101 -s 00::01 -j DROP

Rule 3: -A FORWARD --out -interface vlan101 -p icmp6 -j ACCEPT

Rule 3 still matches for an icmp6 packet with sip 00:01 going out of vlan101. Rule 1 interferes with the normal function of rule 2 and/or rule 3.

When you have two adjacent rules with the same match and different output interfaces, such as:

Rule 1: -A FORWARD --out-interface vlan100 -p icmp6 -j ACCEPT

Rule 2: -A FORWARD --out-interface vlan101 -p icmp6 -j DROP

Rule 2 will never be match on ingress. Both rules share the same mark.

Matching Untagged Packets (Trident3 Switches)

Untagged packets do not have an associated VLAN to match on egress; therefore, the match must be on the underlying layer 2 port. For example, for a bridge configured with pvid 100, member port swp1s0 and swp1s1, and SVI vlan100, the output interface match on vlan100 has to be expanded into each member port. The -A FORWARD -o vlan100 -p icmp6 -j ACCEPT rule must be specified as two rules:

Rule 1: -A FORWARD -o swp1s0 -p icmp6 -J ACCEPT

Rule 2: -A FORWARD -o swp1s1 -p icmp6 -j ACCEPT

Matching on an egress port matches all packets egressing the port, tagged as well as untagged. Therefore, to match only untagged traffic on the port, you must specify additional rules above this rule to prevent tagged packets matching the rule. This is true for bridge member ports as well as regular layer 2 ports. In the example rule above, if vlan101 is also present on the bridge, add a rule above rule 1 and rule 2 to protect vlan101 tagged traffic:

Rule 0: -A FORWARD -o vlan101 -p icmp6 -j ACCEPT

Rule 1: -A FORWARD -o swp1s0 -p icmp6 -j ACCEPT

Rule 2: -A FORWARD -o swp1s1 -p icmp6 -j ACCEPT

For a standalone port or subinterface on swp1s2:

Rule 0: -A FORWARD -o swp1s2.101 -p icmp6 -j ACCEPT

Rule 1: -A FORWARD -o swp1s2 -p icmp6 -j ACCEPT

Common Examples

Control Plane and Data Plane Traffic

You can configure quality of service for traffic on both the control plane and the data plane. By using QoS policers, you can rate limit traffic so incoming packets get dropped if they exceed specified thresholds.

Counters on POLICE ACL rules in iptables do not currently show the packets that are dropped due to those rules.

Use the POLICE target with iptables. POLICE takes these arguments:

For example, to rate limit the incoming traffic on swp1 to 400 packets per second with a burst of 100 packets per second and set the class of the queue for the policed traffic as 0, set this rule in your appropriate .rules file:

-A INPUT --in-interface swp1 -j POLICE --set-mode pkt --set-rate 400 --set-burst 100 --set-class 0

Here is another example of control plane ACL rules to lock down the switch. You specify them in /etc/cumulus/acl/policy.d/00control_plane.rules:

View the contents of the file ...
INGRESS_INTF = swp+
INGRESS_CHAIN = INPUT
INNFWD_CHAIN = INPUT,FORWARD
MARTIAN_SOURCES_4 = "240.0.0.0/5,127.0.0.0/8,224.0.0.0/8,255.255.255.255/32"
MARTIAN_SOURCES_6 = "ff00::/8,::/128,::ffff:0.0.0.0/96,::1/128"

# Custom Policy Section
SSH_SOURCES_4 = "192.168.0.0/24"
NTP_SERVERS_4 = "192.168.0.1/32,192.168.0.4/32"
DNS_SERVERS_4 = "192.168.0.1/32,192.168.0.4/32"
SNMP_SERVERS_4 = "192.168.0.1/32"

[iptables]
-A $INNFWD_CHAIN --in-interface $INGRESS_INTF -s $MARTIAN_SOURCES_4 -j DROP
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p ospf -j POLICE --set-mode pkt --set-rate 2000 --set-burst 2000 --set-class 7
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p tcp --dport bgp -j POLICE --set-mode pkt --set-rate 2000 --set-burst 2000 --set-class 7
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p tcp --sport bgp -j POLICE --set-mode pkt --set-rate 2000 --set-burst 2000 --set-class 7
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p icmp -j POLICE --set-mode pkt --set-rate 100 --set-burst 40 --set-class 2
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p udp --dport bootps:bootpc -j POLICE --set-mode pkt --set-rate 100 --set-burst 100 --set-class 2
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p tcp --dport bootps:bootpc -j POLICE --set-mode pkt --set-rate 100 --set-burst 100 --set-class 2
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p igmp -j POLICE --set-mode pkt --set-rate 300 --set-burst 100 --set-class 6

# Custom policy
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p tcp --dport 22 -s $SSH_SOURCES_4 -j ACCEPT
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p udp --sport 123 -s $NTP_SERVERS_4 -j ACCEPT
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p udp --sport 53 -s $DNS_SERVERS_4 -j ACCEPT
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p udp --dport 161 -s $SNMP_SERVERS_4 -j ACCEPT


# Allow UDP traceroute when we are the current TTL expired hop 
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p udp --dport 1024:65535 -m ttl --ttl-eq 1 -j ACCEPT
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -j DROP

Set DSCP on Transit Traffic

The examples here use the mangle table to modify the packet as it transits the switch. DSCP is expressed in decimal notation in the examples below.

[iptables]

#Set SSH as high priority traffic.
-t mangle -A FORWARD -p tcp --dport 22  -j DSCP --set-dscp 46

#Set everything coming in SWP1 as AF13
-t mangle -A FORWARD --in-interface swp1 -j DSCP --set-dscp 14

#Set Packets destined for 10.0.100.27 as best effort
-t mangle -A FORWARD -d 10.0.100.27/32 -j DSCP --set-dscp 0

#Example using a range of ports for TCP traffic
-t mangle -A FORWARD -p tcp -s 10.0.0.17/32 --sport 10000:20000 -d 10.0.100.27/32 --dport 10000:20000 -j DSCP --set-dscp 34

Verify DSCP Values on Transit Traffic

The examples here use the DSCP match criteria in combination with other IP, TCP, and interface matches to identify traffic and count the number of packets.

[iptables]

#Match and count the packets that match SSH traffic with DSCP EF
-A FORWARD -p tcp --dport 22 -m dscp --dscp 46 -j ACCEPT

#Match and count the packets coming in SWP1 as AF13
-A FORWARD --in-interface swp1 -m dscp --dscp 14 -j ACCEPT
#Match and count the packets with a destination 10.0.0.17 marked best effort
-A FORWARD -d 10.0.100.27/32 -m dscp --dscp 0 -j ACCEPT

#Match and count the packets in a port range with DSCP AF41
-A FORWARD -p tcp -s 10.0.0.17/32 --sport 10000:20000 -d 10.0.100.27/32 --dport 10000:20000 -m dscp --dscp 34 -j ACCEPT

Check the Packet and Byte Counters for ACL Rules

To verify the counters using the above example rules, first send test traffic matching the patterns through the network. The following example generates traffic with mz (or mausezahn), which can be installed on host servers or even on Cumulus Linux switches. After traffic is sent to validate the counters, they are matched on switch1 using cl-acltool.

Policing counters do not increment on switches with the Spectrum ASIC.

# Send 100 TCP packets on host1 with a DSCP value of EF with a destination of host2 TCP port 22:

cumulus@host1$ mz eth1 -A 10.0.0.17 -B 10.0.100.27 -c 100 -v -t tcp "dp=22,dscp=46"
  IP:  ver=4, len=40, tos=184, id=0, frag=0, ttl=255, proto=6, sum=0, SA=10.0.0.17, DA=10.0.100.27,
      payload=[see next layer]
  TCP: sp=0, dp=22, S=42, A=42, flags=0, win=10000, len=20, sum=0,
      payload=

# Verify the 100 packets are matched on switch1

cumulus@switch1$ sudo cl-acltool -L ip
-------------------------------
Listing rules of type iptables:
-------------------------------
TABLE filter :
Chain INPUT (policy ACCEPT 9314 packets, 753K bytes)
  pkts bytes target     prot opt in     out     source               destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
  pkts bytes target     prot opt in     out     source               destination
  100  6400 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:ssh DSCP match 0x2e
    0     0 ACCEPT     all  --  swp1   any     anywhere             anywhere             DSCP match 0x0e
    0     0 ACCEPT     all  --  any    any     10.0.0.17            anywhere             DSCP match 0x00
    0     0 ACCEPT     tcp  --  any    any     10.0.0.17            10.0.100.27          tcp spts:webmin:20000
    dpts:webmin:2002

# Send 100 packets with a small payload on host1 with a DSCP value of AF13 with a destination of host2:

cumulus@host1$ mz eth1 -A 10.0.0.17 -B 10.0.100.27 -c 100 -v -t ip
  IP:  ver=4, len=20, tos=0, id=0, frag=0, ttl=255, proto=0, sum=0, SA=10.0.0.17, DA=10.0.100.27,
      payload=

# Verify the 100 packets are matched on switch1

cumulus@switch1$ sudo cl-acltool -L ip
-------------------------------
Listing rules of type iptables:
-------------------------------
TABLE filter :
Chain INPUT (policy ACCEPT 9314 packets, 753K bytes)
  pkts bytes target     prot opt in     out     source               destination
  chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
  pkts bytes target     prot opt in     out     source               destination
  100  6400 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:ssh DSCP match 0x2e
  100  7000 ACCEPT     all  --  swp3   any     anywhere             anywhere             DSCP match 0x0e
  100  6400 ACCEPT     all  --  any    any     10.0.0.17            anywhere             DSCP match 0x00
    0     0 ACCEPT     tcp  --  any    any     10.0.0.17            10.0.100.27          tcp spts:webmin:20000 dpts:webmin:2002

# Send 100 packets on host1 with a destination of host2:

cumulus@host1$ mz eth1 -A 10.0.0.17 -B 10.0.100.27 -c 100 -v -t ip
 IP:  ver=4, len=20, tos=56, id=0, frag=0, ttl=255, proto=0, sum=0, SA=10.0.0.17, DA=10.0.100.27,
     payload=

# Verify the 100 packets are matched on switch1

cumulus@switch1$ sudo cl-acltool -L ip
-------------------------------
Listing rules of type iptables:
-------------------------------
TABLE filter :
Chain INPUT (policy ACCEPT 9314 packets, 753K bytes)
  pkts bytes target     prot opt in     out     source               destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
  pkts bytes target     prot opt in     out     source               destination
  100  6400 ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:ssh DSCP match 0x2e
  100  7000 ACCEPT     all  --  swp3   any     anywhere             anywhere             DSCP match 0x0e
    0     0 ACCEPT     all  --  any    any     10.0.0.17            anywhere             DSCP match 0x00
    0     0 ACCEPT     tcp  --  any    any     10.0.0.17            10.0.100.27          tcp spts:webmin:20000 dpts:webmin:2002Still working

Filter Specific TCP Flags

The example solution below creates rules on the INPUT and FORWARD chains to drop ingress IPv4 and IPv6 TCP packets when the SYN bit is set and the RST, ACK, and FIN bits are reset. The default for the INPUT and FORWARD chains allows all other packets. The ACL is applied to ports swp20 and swp21. After configuring this ACL, new TCP sessions that originate from ingress ports swp20 and swp21 are not allowed. TCP sessions that originate from any other port are allowed.

INGRESS_INTF = swp20,swp21

[iptables]
-A INPUT,FORWARD --in-interface $INGRESS_INTF -p tcp --syn -j DROP
[ip6tables]
-A INPUT,FORWARD --in-interface $INGRESS_INTF -p tcp --syn -j DROP

The --syn flag in the above rule matches packets with the SYN bit set and the ACK, RST, and FIN bits are cleared. It is equivalent to using -tcp-flags SYN,RST,ACK,FIN SYN. For example, you can write the above rule as:

-A INPUT,FORWARD --in-interface $INGRESS_INTF -p tcp --tcp-flags SYN,RST,ACK,FIN SYN -j DROP

Control Who Can SSH into the Switch

Run the following NCLU commands to control who can SSH into the switch. In the following example, 10.0.0.11/32 is the interface IP address (or loopback IP address) of the switch and 10.255.4.0/24 can SSH into the switch.

cumulus@switch:~$ net add acl ipv4 test priority 10 accept source-ip 10.255.4.0/24 dest-ip 10.0.0.11/32
cumulus@switch:~$ net add acl ipv4 test priority 20 drop source-ip any dest-ip 10.0.0.11/32
cumulus@switch:~$ net add control-plane acl ipv4 test inbound
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Cumulus Linux does not support the keyword iprouter (typically used for traffic sent to the CPU, where the destination MAC address is that of the router but the destination IP address is not the router).

Example Scenario

The following example scenario demonstrates how several different rules are applied.

Following are the configurations for the two switches used in these examples. The configuration for each switch appears in /etc/network/interfaces on that switch.

Switch 1 Configuration

cumulus@switch1:~$ net show configuration files
...
/etc/network/interfaces
=======================

auto swp1
iface swp1

auto swp2
iface swp2

auto swp3
iface swp3

auto swp4
iface swp4

auto bond2
iface bond2
  bond-slaves swp3 swp4

auto br-untagged
iface br-untagged
  address 10.0.0.1/24
  bridge_ports swp1 bond2
  bridge_stp on

auto br-tag100
iface br-tag100
  address 10.0.100.1/24
  bridge_ports swp2.100 bond2.100
  bridge_stp on
...

Switch 2 Configuration

cumulus@switch2:~$ net show configuration files
...
/etc/network/interfaces
=======================

auto swp3
iface swp3

auto swp4
iface swp4

auto br-untagged
iface br-untagged
  address 10.0.0.2/24
  bridge_ports bond2
  bridge_stp on

auto br-tag100
iface br-tag100
  address 10.0.100.2/24
  bridge_ports bond2.100
  bridge_stp on

auto bond2
iface bond2
  bond-slaves swp3 swp4
...

Egress Rule

The following rule blocks any TCP traffic with destination port 200 going from host1 or host2 through the switch (corresponding to rule 1 in the diagram above).

[iptables] -A FORWARD -o bond2 -p tcp --dport 200 -j DROP

Ingress Rule

The following rule blocks any UDP traffic with source port 200 going from host1 through the switch (corresponding to rule 2 in the diagram above).

[iptables] -A FORWARD -i swp2 -p udp --sport 200 -j DROP

Input Rule

The following rule blocks any UDP traffic with source port 200 and destination port 50 going from host1 to the switch (corresponding to rule 3 in the diagram above).

[iptables] -A INPUT -i swp1 -p udp --sport 200 --dport 50 -j DROP

Output Rule

The following rule blocks any TCP traffic with source port 123 and destination port 123 going from Switch 1 to host2 (corresponding to rule 4 in the diagram above).

[iptables] -A OUTPUT -o br-tag100 -p tcp --sport 123 --dport 123 -j DROP

Combined Rules

The following rule blocks any TCP traffic with source port 123 and destination port 123 going from any switch port egress or generated from Switch 1 to host1 or host2 (corresponding to rules 1 and 4 in the diagram above).

[iptables] -A OUTPUT,FORWARD -o swp+ -p tcp --sport 123 --dport 123 -j DROP

This also becomes two ACLs and is the same as:

[iptables]
-A FORWARD -o swp+ -p tcp --sport 123 --dport 123 -j DROP 
-A OUTPUT -o swp+ -p tcp --sport 123 --dport 123 -j DROP

Layer 2-only Rules/ebtables

The following rule blocks any traffic with source MAC address 00:00:00:00:00:12 and destination MAC address 08:9e:01:ce:e2:04 going from any switch port egress/ingress.

[ebtables] -A FORWARD -s 00:00:00:00:00:12 -d 08:9e:01:ce:e2:04 -j DROP

Caveats and Errata

Not All Rules Supported

Not all iptables, ip6tables, or ebtables rules are supported. Refer to the Supported Rules section above for specific rule support.

Input Chain Rules on Broadcom Switches

Broadcom switches evaluate both IPv4 and IPv6 packets against INPUT chain iptables rules. For example, when you install the following rule, the switch drops both IPv6 and IPv4 packets with destination port 22.

[iptables]
-A INPUT -p tcp --dport 22 -j DROP

To work around this issue, use ebtables with IPv4 or IPv6 headers instead of the iptables and ip6tables generic INPUT chain DROP. For example:

[ebtables]
-A INPUT -i swp+ -p IPv4 --ip-protocol tcp --ip-destination-port 22 -j DROP
[ebtables]
-A INPUT -i swp+ -p IPv6 --ip6-protocol tcp --ip6-destination-port 22 -j DROP

ACL Log Policer Limits Traffic

To protect the CPU from overloading, traffic copied to the CPU is limited to 1 pkt/s by an ACL Log Policer.

Bridge Traffic Limitations

Bridge traffic that matches LOG ACTION rules are not logged in syslog; the kernel and hardware identify packets using different information.

Log Actions Cannot Be Forwarded

Logged packets cannot be forwarded. The hardware cannot both forward a packet and send the packet to the control plane (or kernel) for logging. To emphasize this, a log action must also have a drop action.

Broadcom Range Checker Limitations

Broadcom platforms have only 24 range checkers. This is a separate resource from the total number of ACLs allowed. If you are creating a large ACL configuration, use port ranges for large ranges of more than 5 ports.

Inbound LOG Actions Only for Broadcom Switches

On Broadcom-based switches, LOG actions can only be done on inbound interfaces (the ingress direction), not on outbound interfaces (the egress direction).

SPAN Sessions that Reference an Outgoing Interface

SPAN sessions that reference an outgoing interface create mirrored packets based on the ingress interface before the routing/switching decision. For an example, see the SPAN Sessions that Reference an Outgoing Interface in the Network Troubleshooting chapter.

Tomahawk Hardware Limitations

Rate Limiting per Pipeline, Not Global

On Tomahawk switches, the field processor (FP) polices on a per-pipeline basis instead of globally, as with a Trident II switch. If packets come in to different switch ports that are on different pipelines on the ASIC, they might be rate limited differently.

For example, your switch is set so BFD is rate limited to 2000 packets per second. When the BFD packets are received on port1/pipe1 and port2/pipe2, they are each rate limited at 2000 pps; the switch is rate limiting at 4000 pps overall. Because there are four pipelines on a Tomahawk switch, you might see a fourfold increase of your configured rate limits.

Atomic Update Mode Enabled by Default

In Cumulus Linux, atomic update mode is enabled by default. If you have Tomahawk switches and plan to use SPAN and/or mangle rules, you must disable atomic update mode.

To do so, enable nonatomic update mode by setting the value for acl.non_atomic_update_mode to TRUE in /etc/cumulus/switchd.conf, then restart switchd.

acl.non_atomic_update_mode = TRUE

Packets Undercounted during ACL Updates

On Tomahawk switches, when updating egress FP rules, some packets do no get counted. This results in an underreporting of counts during ping-pong or incremental switchover.

Trident II+ Hardware Limitations

On a Trident II+ switch, the TCAM allocation for ACLs is limited to 2048 rules in atomic mode for a default setup instead of 4096, as advertised for ingress rules.

Trident3 Hardware Limitations

TCAM Allocation

On a Trident3 switch, the TCAM allocation for ACLs is limited to 2048 rules in atomic mode for a default setup instead of 4096, as advertised for ingress rules.

Enable Nonatomic Mode

On a Trident3 switch, you must enable nonatomic update mode before you can configure ERSPAN. To do so, set the value for acl.non_atomic_update_mode to TRUE in /etc/cumulus/switchd.conf, then restart switchd.

acl.non_atomic_update_mode = TRUE

Egress ACL Rules

On Trident3 switches, egress ACL rules matching on the output SVI interface match layer 3 routed packets only, not bridged packets. To match layer 2 traffic, use egress bridge member port-based rules.

iptables Interactions with cl-acltool

Because Cumulus Linux is a Linux operating system, the iptables commands can be used directly. However, consider using cl-acltool instead because:

For example, running the following command works:

cumulus@switch:~$ sudo iptables -A INPUT -p icmp --icmp-type echo-request -j DROP

And the rules appear when you run cl-acltool -L:

cumulus@switch:~$ sudo cl-acltool -L ip
-------------------------------
Listing rules of type iptables:
-------------------------------
TABLE filter :
Chain INPUT (policy ACCEPT 72 packets, 5236 bytes)
pkts bytes target  prot opt in   out   source    destination

0     0 DROP    icmp --  any  any   anywhere  anywhere      icmp echo-request

However, running cl-acltool -i or reboot removes them. To ensure all rules that can be in hardware are hardware accelerated, place them in the /etc/cumulus/acl/policy.conf file, then run cl-acltool -i.

Mellanox Spectrum Hardware Limitations

Due to hardware limitations in the Spectrum ASIC, BFD policers are shared between all BFD-related control plane rules. Specifically the following default rules share the same policer in the 00control_plan.rules file:

[iptables]
-A $INGRESS_CHAIN -p udp --dport $BFD_ECHO_PORT -j POLICE --set-mode pkt --set-rate 2000 --set-burst 2000
-A $INGRESS_CHAIN -p udp --dport $BFD_PORT -j POLICE --set-mode pkt --set-rate 2000 --set-burst 2000
-A $INGRESS_CHAIN -p udp --dport $BFD_MH_PORT -j POLICE --set-mode pkt --set-rate 2000 --set-burst 2000

[ip6tables]
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p udp --dport $BFD_ECHO_PORT -j POLICE --set-mode pkt --set-rate 2000 --set-burst 2000 --set-class 7
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p udp --dport $BFD_PORT -j POLICE --set-mode pkt --set-rate 2000 --set-burst 2000 --set-class 7
-A $INGRESS_CHAIN --in-interface $INGRESS_INTF -p udp --dport $BFD_MH_PORT -j POLICE --set-mode pkt --set-rate 2000 --set-burst 2000 --set-class 7

To work around this limitation, set the rate and burst of all 6 of these rules to the same values, using the --set-rate and --set-burst options.

Where to Assign Rules

Generic Error Message Displayed after ACL Rule Installation Failure

After an ACL rule installation failure, a generic error message like the following is displayed:

cumulus@switch:$ sudo cl-acltool -i -p 00control_plane.rules
Using user provided rule file 00control_plane.rules
Reading rule file 00control_plane.rules ...
Processing rules in file 00control_plane.rules ...
error: hw sync failed (sync_acl hardware installation failed)
Installing acl policy... Rolling back ..
failed.

Dell S3048-ON Supports only 24K MAC Addresses

The Dell S3048-ON has a limit of 24576 MAC address entries instead of 32K for other 1G switches.

Mellanox Spectrum ASICs and INPUT Chain Rules

On switches with Mellanox Spectrum ASICs, INPUT chain rules are implemented using a trap mechanism. Packets headed to the CPU are assigned trap IDs. The default INPUT chain rules are mapped to these trap IDs. However, if a packet matches multiple traps, they are resolved by an internal priority mechanism that might be different from the rule priorities. Packets might not get policed by the default expected rule, but by another rule instead. For example, ICMP packets headed to the CPU are policed by the LOCAL rule instead of the ICMP rule. Also, multiple rules might share the same trap. In this case the policer that is applied is the largest of the policer values.

To work around this issue, create rules on the INPUT and FORWARD chains (INPUT,FORWARD).

Hardware Policing of Packets in the Input Chain

On certain platforms, there are limitations on hardware policing of packets in the INPUT chain. To work around these limitations, Cumulus Linux supports kernel based policing of these packets in software using limit/hashlimit matches. Rules with these matches are not hardware offloaded, but are ignored during hardware install.

ACLs Do not Match when the Output Port on the ACL is a Subinterface

Packets don’t get matched when a subinterface is configured as the output port. The ACL matches on packets only if the primary port is configured as an output port. If a subinterface is set as an output or egress port, the packets match correctly.

For example:

-A FORWARD --out-interface swp49s1.100 -j ACCEPT

Mellanox Switches and Egress ACL Matching on Bonds

On the Mellanox switch, ACL rules that match on an outbound bond interface are not supported. For example, the following rule is not supported:

[iptables]
-A FORWARD --out-interface <bond_intf> -j DROP

To work around this issue, duplicate the ACL rule on each physical port of the bond. For example:

[iptables]
-A FORWARD --out-interface <bond-member-port-1> -j DROP
-A FORWARD --out-interface <bond-member-port-2> -j DROP

Default Cumulus Linux ACL Configuration

The Cumulus Linux default ACL configuration is split into three parts: IP tables, IPv6 tables, and EB tables. The sections below describe the default configurations for each part. You can see the default file by clicking the Default ACL Configuration link:

Default ACL Configuration
cumulus@switch:~$ sudo cl-acltool -L all
-------------------------------
Listing rules of type iptables:
-------------------------------
TABLE filter :
Chain INPUT (policy ACCEPT 167 packets, 16481 bytes)
    pkts bytes target     prot opt in     out     source               destination
      0     0 DROP       all  --  swp+   any     240.0.0.0/5          anywhere
      0     0 DROP       all  --  swp+   any     loopback/8           anywhere
      0     0 DROP       all  --  swp+   any     base-address.mcast.net/8  anywhere
      0     0 DROP       all  --  swp+   any     255.255.255.255      anywhere
      0     0 SETCLASS   udp  --  swp+   any     anywhere             anywhere             udp dpt:3785 SETCLASS  class:7
      0     0 POLICE     udp  --  any    any     anywhere             anywhere             udp dpt:3785 POLICE  mode:pkt rate:2000 burst:2000
      0     0 SETCLASS   udp  --  swp+   any     anywhere             anywhere             udp dpt:3784 SETCLASS  class:7
      0     0 POLICE     udp  --  any    any     anywhere             anywhere             udp dpt:3784 POLICE  mode:pkt rate:2000 burst:2000
      0     0 SETCLASS   udp  --  swp+   any     anywhere             anywhere             udp dpt:4784 SETCLASS  class:7
      0     0 POLICE     udp  --  any    any     anywhere             anywhere             udp dpt:4784 POLICE  mode:pkt rate:2000 burst:2000
      0     0 SETCLASS   ospf --  swp+   any     anywhere             anywhere             SETCLASS  class:7
      0     0 POLICE     ospf --  any    any     anywhere             anywhere             POLICE  mode:pkt rate:2000 burst:2000
      0     0 SETCLASS   tcp  --  swp+   any     anywhere             anywhere             tcp dpt:bgp SETCLASS  class:7
      0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp dpt:bgp POLICE  mode:pkt rate:2000 burst:2000
      0     0 SETCLASS   tcp  --  swp+   any     anywhere             anywhere             tcp spt:bgp SETCLASS  class:7
      0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp spt:bgp POLICE  mode:pkt rate:2000 burst:2000
      0     0 SETCLASS   tcp  --  swp+   any     anywhere             anywhere             tcp dpt:5342 SETCLASS  class:7
      0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp dpt:5342 POLICE  mode:pkt rate:2000 burst:2000
      0     0 SETCLASS   tcp  --  swp+   any     anywhere             anywhere             tcp spt:5342 SETCLASS  class:7
      0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp spt:5342 POLICE  mode:pkt rate:2000 burst:2000
      0     0 SETCLASS   icmp --  swp+   any     anywhere             anywhere             SETCLASS  class:2
      1    84 POLICE     icmp --  any    any     anywhere             anywhere             POLICE  mode:pkt rate:100 burst:40
      0     0 SETCLASS   udp  --  swp+   any     anywhere             anywhere             udp dpts:bootps:bootpc SETCLASS  class:2
      0     0 POLICE     udp  --  any    any     anywhere             anywhere             udp dpt:bootps POLICE  mode:pkt rate:100 burst:100
      0     0 POLICE     udp  --  any    any     anywhere             anywhere             udp dpt:bootpc POLICE  mode:pkt rate:100 burst:100
      0     0 SETCLASS   tcp  --  swp+   any     anywhere             anywhere             tcp dpts:bootps:bootpc SETCLASS  class:2
      0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp dpt:bootps POLICE  mode:pkt rate:100 burst:100
      0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp dpt:bootpc POLICE  mode:pkt rate:100 burst:100
      0     0 SETCLASS   udp  --  swp+   any     anywhere             anywhere             udp dpt:10001 SETCLASS  class:3
      0     0 POLICE     udp  --  any    any     anywhere             anywhere             udp dpt:10001 POLICE  mode:pkt rate:2000 burst:2000
      0     0 SETCLASS   igmp --  swp+   any     anywhere             anywhere             SETCLASS  class:6
      1    32 POLICE     igmp --  any    any     anywhere             anywhere             POLICE  mode:pkt rate:300 burst:100
      0     0 POLICE     all  --  swp+   any     anywhere             anywhere             ADDRTYPE match dst-type LOCAL POLICE  mode:pkt rate:1000 burst:1000 class:0
      0     0 POLICE     all  --  swp+   any     anywhere             anywhere             ADDRTYPE match dst-type IPROUTER POLICE  mode:pkt rate:400 burst:100 class:0
      0     0 SETCLASS   all  --  swp+   any     anywhere             anywhere             SETCLASS  class:0

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
    pkts bytes target     prot opt in     out     source               destination
      0     0 DROP       all  --  swp+   any     240.0.0.0/5          anywhere
      0     0 DROP       all  --  swp+   any     loopback/8           anywhere
      0     0 DROP       all  --  swp+   any     base-address.mcast.net/8  anywhere
      0     0 DROP       all  --  swp+   any     255.255.255.255      anywhere

Chain OUTPUT (policy ACCEPT 107 packets, 12590 bytes)
    pkts bytes target     prot opt in     out     source               destination

TABLE mangle :
Chain PREROUTING (policy ACCEPT 172 packets, 17871 bytes)
    pkts bytes target     prot opt in     out     source               destination

Chain INPUT (policy ACCEPT 172 packets, 17871 bytes)
    pkts bytes target     prot opt in     out     source               destination

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
    pkts bytes target     prot opt in     out     source               destination

Chain OUTPUT (policy ACCEPT 111 packets, 18134 bytes)
    pkts bytes target     prot opt in     out     source               destination

Chain POSTROUTING (policy ACCEPT 111 packets, 18134 bytes)
    pkts bytes target     prot opt in     out     source               destination


TABLE raw :
Chain PREROUTING (policy ACCEPT 173 packets, 17923 bytes)
    pkts bytes target     prot opt in     out     source               destination

    Chain OUTPUT (policy ACCEPT 112 packets, 18978 bytes)
     pkts bytes target     prot opt in     out     source               destination


--------------------------------
Listing rules of type ip6tables:
--------------------------------
TABLE filter :
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
    pkts bytes target    prot opt in     out     source               destination
      0     0 DROP       all      swp+   any     ip6-mcastprefix/8    anywhere
      0     0 DROP       all      swp+   any     ::/128               anywhere
      0     0 DROP       all      swp+   any     ::ffff:0.0.0.0/96    anywhere
      0     0 DROP       all      swp+   any     localhost/128        anywhere
      0     0 POLICE     udp      swp+   any     anywhere             anywhere             udp dpt:3785 POLICE  mode:pkt rate:2000 burst:2000 class:7
      0     0 POLICE     udp      swp+   any     anywhere             anywhere             udp dpt:3784 POLICE  mode:pkt rate:2000 burst:2000 class:7
      0     0 POLICE     udp      swp+   any     anywhere             anywhere             udp dpt:4784 POLICE  mode:pkt rate:2000 burst:2000 class:7
      0     0 POLICE     ospf     swp+   any     anywhere             anywhere             POLICE  mode:pkt rate:2000 burst:2000 class:7
      0     0 POLICE     tcp      swp+   any     anywhere             anywhere             tcp dpt:bgp POLICE  mode:pkt rate:2000 burst:2000 class:7
      0     0 POLICE     tcp      swp+   any     anywhere             anywhere             tcp spt:bgp POLICE  mode:pkt rate:2000 burst:2000 class:7
      0     0 POLICE     ipv6-icmp    swp+   any     anywhere             anywhere             ipv6-icmp router-solicitation POLICE  mode:pkt rate:100 burst:100 class:2
      0     0 POLICE     ipv6-icmp    swp+   any     anywhere             anywhere             ipv6-icmp router-advertisement POLICE  mode:pkt rate:500 burst:500 class:2
      0     0 POLICE     ipv6-icmp    swp+   any     anywhere             anywhere             ipv6-icmp neighbour-solicitation POLICE  mode:pkt rate:400 burst:400 class:2
      0     0 POLICE     ipv6-icmp    swp+   any     anywhere             anywhere             ipv6-icmp neighbour-advertisement POLICE  mode:pkt rate:400 burst:400 class:2
      0     0 POLICE     ipv6-icmp    swp+   any     anywhere             anywhere             ipv6-icmptype 130 POLICE  mode:pkt rate:200 burst:100 class:6
      0     0 POLICE     ipv6-icmp    swp+   any     anywhere             anywhere             ipv6-icmptype 131 POLICE  mode:pkt rate:200 burst:100 class:6
      0     0 POLICE     ipv6-icmp    swp+   any     anywhere             anywhere             ipv6-icmptype 132 POLICE  mode:pkt rate:200 burst:100 class:6
      0     0 POLICE     ipv6-icmp    swp+   any     anywhere             anywhere             ipv6-icmptype 143 POLICE  mode:pkt rate:200 burst:100 class:6
      0     0 POLICE     ipv6-icmp    swp+   any     anywhere             anywhere             POLICE  mode:pkt rate:64 burst:40 class:2
      0     0 POLICE     udp      swp+   any     anywhere             anywhere             udp dpts:dhcpv6-client:dhcpv6-server POLICE  mode:pkt rate:100 burst:100 class:2
      0     0 POLICE     tcp      swp+   any     anywhere             anywhere             tcp dpts:dhcpv6-client:dhcpv6-server POLICE  mode:pkt rate:100 burst:100 class:2
      0     0 POLICE     all      swp+   any     anywhere             anywhere             ADDRTYPE match dst-type LOCAL POLICE  mode:pkt rate:1000 burst:1000 class:0
      0     0 POLICE     all      swp+   any     anywhere             anywhere             ADDRTYPE match dst-type IPROUTER POLICE  mode:pkt rate:400 burst:100 class:0
      0     0 SETCLASS   all      swp+   any     anywhere             anywhere             SETCLASS  class:0

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
    pkts bytes target    prot opt in     out     source               destination
      0     0 DROP       all      swp+   any     ip6-mcastprefix/8    anywhere
      0     0 DROP       all      swp+   any     ::/128               anywhere
      0     0 DROP       all      swp+   any     ::ffff:0.0.0.0/96    anywhere
      0     0 DROP       all      swp+   any     localhost/128        anywhere

Chain OUTPUT (policy ACCEPT 5 packets, 408 bytes)
    pkts bytes target     prot opt in     out     source               destination


TABLE mangle :
Chain PREROUTING (policy ACCEPT 7 packets, 718 bytes)
    pkts bytes target     prot opt in     out     source               destination

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
    pkts bytes target     prot opt in     out     source               destination

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
    pkts bytes target     prot opt in     out     source               destination

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
    pkts bytes target     prot opt in     out     source               destination

Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)
    pkts bytes target     prot opt in     out     source               destination


TABLE raw :
Chain PREROUTING (policy ACCEPT 7 packets, 718 bytes)
    pkts bytes target     prot opt in     out     source               destination

Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
    pkts bytes target     prot opt in     out     source               destination

-------------------------------
Listing rules of type ebtables:
-------------------------------
TABLE filter :
Bridge table: filter

Bridge chain: INPUT, entries: 16, policy: ACCEPT
-d BGA -i swp+ -j setclass --class 7 , pcnt = 0 -- bcnt = 0
-d BGA -j police --set-mode pkt --set-rate 2000 --set-burst 2000 , pcnt = 0 -- bcnt = 0
-d 1:80:c2:0:0:2 -i swp+ -j setclass --class 7 , pcnt = 0 -- bcnt = 0
-d 1:80:c2:0:0:2 -j police --set-mode pkt --set-rate 2000 --set-burst 2000 , pcnt = 0 -- bcnt = 0
-d 1:80:c2:0:0:e -i swp+ -j setclass --class 6 , pcnt = 0 -- bcnt = 0
-d 1:80:c2:0:0:e -j police --set-mode pkt --set-rate 200 --set-burst 200 , pcnt = 0 -- bcnt = 0
-d 1:0:c:cc:cc:cc -i swp+ -j setclass --class 6 , pcnt = 0 -- bcnt = 0
-d 1:0:c:cc:cc:cc -j police --set-mode pkt --set-rate 200 --set-burst 200 , pcnt = 0 -- bcnt = 0
-p ARP -i swp+ -j setclass --class 2 , pcnt = 0 -- bcnt = 0
-p ARP -j police --set-mode pkt --set-rate 400 --set-burst 100 , pcnt = 0 -- bcnt = 0
-d 1:0:c:cc:cc:cd -i swp+ -j setclass --class 7 , pcnt = 0 -- bcnt = 0
-d 1:0:c:cc:cc:cd -j police --set-mode pkt --set-rate 2000 --set-burst 2000 , pcnt = 0 -- bcnt = 0
-p IPv4 -i swp+ -j ACCEPT , pcnt = 0 -- bcnt = 0
-p IPv6 -i swp+ -j ACCEPT , pcnt = 0 -- bcnt = 0
-i swp+ -j setclass --class 0 , pcnt = 0 -- bcnt = 0
-j police --set-mode pkt --set-rate 100 --set-burst 100 , pcnt = 0 -- bcnt = 0

Bridge chain: FORWARD, entries: 0, policy: ACCEPT

Bridge chain: OUTPUT, entries: 0, policy: ACCEPT

IP Tables

Action/Value Protocol/IP Address
Drop
Destination IP: Any
Source IPv4:
240.0.0.0/5
loopback/8
224.0.0.0/4
255.255.255.255
Set class: 7
Police: Packet rate 2000 burst 2000
Source IP: Any
Destination IP: Any
Protocol:
UDP/BFD Echo
UDP/BFD Control
UDP BFD Multihop Control
OSPF
TCP/BGP (spt dpt 179)
TCP/MLAG (spt dpt 5342)
Set Class: 6
Police: Rate 300 burst 100
Source IP: Any
Destination IP: Any
Protocol:
IGMP
Set class: 2
Police: Rate 100 burst 40
Source IP : Any
Destination IP: Any
Protocol:
ICMP
Set class: 2
Police: Rate 100 burst 100
Source IP: Any
Destination IP: Any
Protocol:
UDP/bootpc, bootps
Set class: 0
Police: Rate 1000 burst 1000
Source IP: Any
Destination IP: Any
ADDRTYPE match dst-type LOCAL
Note: LOCAL is any local address -> Receiving a packet with a destination matching a local IP address on the switch will go to the CPU.
Set class: 0
Police: Rate 400 burst 100
Source IP: Any
Destination IP: Any
ADDRTYPE match dst-type IPROUTER
Note: IPROUTER is any unresolved address -> On a l2/l3 boundary receiving a packet from L3 and needs to go to CPU in order to ARP for the destination.
Set class 0 All

Set class is internal to the switch - it does not set any precedence bits.

IPv6 Tables

Action/Value Protocol/IP Address
Drop Source IPv6:
ff00::/8
::
::ffff:0.0.0.0/96
localhost
Set class: 7
Police: Packet rate 2000 burst 2000
Source IPv6: Any
Destination IPv6: Any
Protocol:
UDP/BFD Echo
UDP/BFD Control
UDP BFD Multihop Control
OSPF
TCP/BGP (spt dpt 179)
Set class: 6
Police: Packet Rte: 200 burst 100
Source IPv6: Any
Destination IPv6: Any
Protocol:
Multicast Listener Query (MLD)
Multicast
Listener Report (MLD)
Multicast Listener Done (MLD
Multicast Listener Report V2
Set class: 2
Police: Packet rate: 100 burst 100
Source IPv6: Any
Destination IPv6: Any
Protocol:
ipv6-icmp router-solicitation
Set class: 2
Police: Packet rate: 500 burst 500
Source IPv6: Any
Destination IPv6: Any
Protocol:
ipv6-icmp router-advertisement POLICE
Set class: 2
Police: Packet rate: 400 burst 400
Source IPv6: Any
Destination IPv6: Any
Protocol:
ipv6-icmp neighbour-solicitation
ipv6-icmp neighbour-advertisement
Set class: 2
Police: Packet rate: 64 burst: 40
Source IPv6: Any
Destination IPv6: Any
Protocol:
Ipv6 icmp
Set class: 2
Police: Packet rate: 100 burst: 100
Source IPv6: Any
Destination IPv6: Any
Protocol:
UDP/dhcpv6-client:dhcpv6-server (Spts & dpts)
Police: Packet rate: 1000 burst 1000
Source IPv6: Any
Destination IPv6: Any
ADDRTYPE match dst-type LOCAL
Note: LOCAL is any local address -> Receiving a packet with a destination matching a local IPv6 address on the switch will go to the CPU.
Set class: 0
Police: Packet rate: 400 burst 100
ADDRTYPE match dst-type IPROUTER
Note: IPROUTER is an unresolved address -> On a l2/l3 boundary receiving a packet from L3 and needs to go to CPU in order to ARP for the destination.
Set class 0 All

Set class is internal to the switch - it does not set any precedence bits.

EB Tables

Action/Value Protocol/MAC Address
Set Class: 7
Police: packet rate: 2000 burst rate:2000
Any switchport input interface
BDPU
LACP=
Cisco PVST
Set Class: 6
Police: packet rate: 200 burst rate: 200
Any switchport input inteface
LLDP
CDP
Set Class: 2
Police: packet rate: 400 burst rate: 100
Any switchport input interface
ARP
Catch All:
Allow all traffic
Any switchport input interface
IPv4
IPv6
Catch All (applied at end):
Set class: 0
Police: packet rate 100 burst rate 100
Any switchport
ALL OTHER

Set class is internal to the switch. It does not set any precedence bits.

Filtering Learned MAC Addresses

On Broadcom switches, a MAC address is learned on a bridge regardless of whether or not a received packet is dropped by an ACL. This is due to how the hardware learns MAC addresses and occurs before the ACL lookup. This can be a security or resource problem as the MAC address table has the potential to get filled with bogus MAC addresses; a malfunctioning host, network error, loop, or malicious attack on a shared layer 2 platform can create an outage for other hosts if the same MAC address is learned on another port.

To prevent this from happening, Cumulus Linux filters frames before MAC learning occurs. Because MAC addresses and their port/VLAN associations are known at configuration time, you can create static MAC addresses, then create ingress ACLs to whitelist traffic from these MAC addresses and drop traffic otherwise.

This feature is specific to switches on the Broadcom platform only; on switches with Mellanox Spectrum ASICs, the input port ACL does not have these issues when learning MAC addresses.

Create a configuration similar to the following, where you associate a port and VLAN with a given MAC address, adding each one to the bridge:

cumulus@switch:~$ net add bridge bridge vids 100,200,300
cumulus@switch:~$ net add bridge bridge pvid 1
cumulus@switch:~$ net add bridge bridge ports swp1-3
cumulus@switch:~$ net add bridge pre-up bridge fdb add 00:00:00:00:00:11 dev swp1 master static vlan 100
cumulus@switch:~$ net add bridge pre-up bridge fdb add 00:00:00:00:00:22 dev swp2 master static vlan 200
cumulus@switch:~$ net add bridge pre-up bridge fdb add 00:00:00:00:00:33 dev swp3 master static vlan 300
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following configuration in the /etc/network/interfaces file:

auto swp1
iface swp1

auto swp2
iface swp2

auto swp3
iface swp3

auto bridge
iface bridge
    bridge-ports swp1 swp2 swp3
    bridge-pvid 1
    bridge-vids 100 200 300
    bridge-vlan-aware yes
    pre-up bridge fdb add 00:00:00:00:00:11 dev swp1 master static vlan 100
    pre-up bridge fdb add 00:00:00:00:00:22 dev swp2 master static vlan 200
    pre-up bridge fdb add 00:00:00:00:00:33 dev swp3 master static vlan 300

If you need to list many MAC addresses, you can run a script to create the same configuration. For example, create a script called macs.txt and put in the bridge fdb add commands for each MAC address you need to configure:

cumulus@switch:~$ cat /etc/networks/macs.txt
#!/bin/bash
bridge fdb add 00:00:00:00:00:11 dev swp1 master static vlan 100
bridge fdb add 00:00:00:00:00:22 dev swp2 master static vlan 200
bridge fdb add 00:00:00:00:00:33 dev swp3 master static vlan 300
bridge fdb add 00:00:00:00:00:44 dev swp4 master static vlan 400
bridge fdb add 00:00:00:00:00:55 dev swp5 master static vlan 500
bridge fdb add 00:00:00:00:00:66 dev swp6 master static vlan 600

Then create the configuration using NCLU:

cumulus@switch:~$ net add bridge bridge vids 100,200,300
cumulus@switch:~$ net add bridge bridge pvid 1
cumulus@switch:~$ net add bridge bridge ports swp1-3
cumulus@switch:~$ net add bridge pre-up /etc/networks/macs.txt
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following configuration in the /etc/network/interfaces file:

auto swp1
iface swp1

auto swp2
iface swp2

auto swp3
iface swp3

auto swp4
iface swp4

auto swp5
iface swp5

auto swp6
iface swp6

auto bridge
iface bridge
    bridge-ports swp1 swp2 swp3 swp4 swp5 swp6
    bridge-pvid 1
    bridge-vids 100 200 300
    bridge-vlan-aware yes
    pre-up bridge fdb add 00:00:00:00:00:11 dev swp1 master static vlan 100
    pre-up bridge fdb add 00:00:00:00:00:22 dev swp2 master static vlan 200
    pre-up bridge fdb add 00:00:00:00:00:33 dev swp3 master static vlan 300
    pre-up bridge fdb add 00:00:00:00:00:44 dev swp4 master static vlan 400
    pre-up bridge fdb add 00:00:00:00:00:55 dev swp5 master static vlan 500
    pre-up bridge fdb add 00:00:00:00:00:66 dev swp6 master static vlan 600

Interactions with EVPN

If you are using EVPN, local static MAC addresses added to the local FDB are exported as static MAC addresses to remote switches. Remote MAC addresses are added as MAC addresses to the remote FDB.

Services and Daemons in Cumulus Linux

Services (also known as daemons) and processes are at the heart of how a Linux system functions. Most of the time, a service takes care of itself; you just enable and start it, then let it run. However, because a Cumulus Linux switch is a Linux system, you can dig deeper if you like. Services can start multiple processes as they run. Services are important to monitor on a Cumulus Linux switch.

You manage services in Cumulus Linux in the following ways:

systemd and the systemctl Command

In general, you manage services using systemd via the systemctl command. You use it with any service on the switch to start, stop, restart, reload, enable, disable, reenable, or get the status of the service.

cumulus@switch:~$ sudo systemctl start | stop | restart | status | reload | enable | disable | reenable SERVICENAME.service

For example to restart networking, run the command:

cumulus@switch:~$ sudo systemctl restart networking.service

The service name is written after the systemctl subcommand, not before it.

To show all the services currently running, run the systemctl status command. For example:

cumulus@switch:~$ sudo systemctl status
● switch
    State: running
      Jobs: 0 queued
    Failed: 0 units
    Since: Thu 2019-01-10 00:19:34 UTC; 23h ago
    CGroup: /
            ├─init.scope
            │ └─1 /sbin/init
            └─system.slice
              ├─haveged.service
              │ └─234 /usr/sbin/haveged --Foreground --verbose=1 -w 1024
              ├─sysmonitor.service
              │ ├─  658 /bin/bash /usr/lib/cumulus/sysmonitor
              │ └─26543 sleep 60
              ├─systemd-udevd.service
              │ └─218 /lib/systemd/systemd-udevd
              ├─system-ntp.slice
              │ └─ntp@mgmt.service
              │   └─vrf
              │     └─mgmt
              │       └─12108 /usr/sbin/ntpd -n -u ntp:ntp -g
              ├─cron.service
              │ └─274 /usr/sbin/cron -f -L 38
              ├─system-serial\x2dgetty.slice
              │ └─serial-getty@ttyS0.service
              │   └─745 /sbin/agetty -o -p -- \u --keep-baud 115200,38400,9600 ttyS0 vt220
              ├─nginx.service
              │ ├─332 nginx: master process /usr/sbin/nginx -g daemon on; master_process on;
              │ └─333 nginx: worker process
              ├─auditd.service
              │ └─235 /sbin/auditd
              ├─rasdaemon.service
              │ └─275 /usr/sbin/rasdaemon -f -r
              ├─clagd.service
              │ └─11443 /usr/bin/python /usr/sbin/clagd --daemon 169.254.1.2 peerlink.4094 44:39:39:ff:40:9
              --priority 100 --vxlanAnycas
              ├─switchd.service
              │ └─430 /usr/sbin/switchd -vx
              ...

systemctl Subcommands

systemctl has a number of subcommands that perform a specific operation on a given service.

There is often little reason to interact with the services directly using these commands. If a critical service crashes or encounters an error, it is automatically respawned by systemd. systemd is effectively the caretaker of services in modern Linux systems and is responsible for starting all the necessary services at boot time.

Ensure a Service Starts after Multiple Restarts

By default, systemd is configured to try to restart a particular service only a certain number of times within a given interval before the service fails to start at all. The settings, StartLimitInterval (which defaults to 10 seconds) and StartBurstLimit (which defaults to 5 attempts) are stored in the service script; however, many services override these defaults, sometimes with much longer times. For example, switchd.service sets StartLimitInterval=10m and StartBurstLimit=3; therefore, if you restart switchd more than 3 times in 10 minutes, it does not start.

When the restart fails for this reason, you see a message similar to the following:

Job for switchd.service failed. See 'systemctl status switchd.service' and 'journalctl -xn' for details.

systemctl status switchd.service shows output similar to:

Active: failed (Result: start-limit) since Thu 2016-04-07 21:55:14 UTC; 15s ago

To clear this error, run systemctl reset-failed switchd.service. If you know you are going to restart frequently (multiple times within the StartLimitInterval), you can run the same command before you issue the restart request. This also applies to stop followed by start.

Keep systemd Services from Hanging after Starting

If you start, restart, or reload any systemd service that can be started from another systemd service, you must use the --no-block option with systemctl. Otherwise, that service or even the switch itself might hang after starting or restarting.

Identify Active Listener Ports for IPv4 and IPv6

You can identify the active listener ports under both IPv4 and IPv6 using the netstat command:

cumulus@switch:~$ netstat -nlp --inet --inet6
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:53              0.0.0.0:*               LISTEN      444/dnsmasq
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      874/sshd
tcp6       0      0 :::53                   :::*                    LISTEN      444/dnsmasq
tcp6       0      0 :::22                   :::*                    LISTEN      874/sshd
udp        0      0 0.0.0.0:28450           0.0.0.0:*                           839/dhclient
udp        0      0 0.0.0.0:53              0.0.0.0:*                           444/dnsmasq
udp        0      0 0.0.0.0:68              0.0.0.0:*                           839/dhclient
udp        0      0 192.168.0.42:123        0.0.0.0:*                           907/ntpd
udp        0      0 127.0.0.1:123           0.0.0.0:*                           907/ntpd
udp        0      0 0.0.0.0:123             0.0.0.0:*                           907/ntpd
udp        0      0 0.0.0.0:4784            0.0.0.0:*                           909/ptmd
udp        0      0 0.0.0.0:3784            0.0.0.0:*                           909/ptmd
udp        0      0 0.0.0.0:3785            0.0.0.0:*                           909/ptmd
udp6       0      0 :::58352                :::*                                839/dhclient
udp6       0      0 :::53                   :::*                                444/dnsmasq
udp6       0      0 fe80::a200:ff:fe00::123 :::*                                907/ntpd
udp6       0      0 ::1:123                 :::*                                907/ntpd
udp6       0      0 :::123                  :::*                                907/ntpd
udp6       0      0 :::4784                 :::*                                909/ptmd
udp6       0      0 :::3784                 :::*                                909/ptmd

Identify Services Currently Active or Stopped

To determine which services are currently active or stopped, run the cl-service-summary command:

cumulus@switch:~$ cl-service-summary
Service cron               enabled    active
Service ssh                enabled    active
Service syslog             enabled    active
Service asic-monitor       enabled    inactive
Service clagd              enabled    inactive
Service cumulus-poe                   inactive
Service lldpd              enabled    active
Service mstpd              enabled    active
Service neighmgrd          enabled    active
Service netd               enabled    active
Service netq-agent         enabled    active
Service ntp                enabled    active
Service portwd             enabled    active
Service ptmd               enabled    active
Service pwmd               enabled    active
Service smond              enabled    active
Service switchd            enabled    active
Service sysmonitor         enabled    active
Service rdnbrd             disabled   inactive
Service frr                enabled    inactive
...

You can also run the systemctl list-unit-files --type service command to list all services on the switch and see which ones are enabled:

cumulus@switch:~$ systemctl list-unit-files --type service
UNIT FILE                              STATE
aclinit.service                        enabled
acltool.service                        enabled
acpid.service                          disabled
asic-monitor.service                   enabled
auditd.service                         enabled
autovt@.service                        disabled
bmcd.service                           disabled
bootlog.service                        enabled
bootlogd.service                       masked  
bootlogs.service                       masked  
bootmisc.service                       masked  
checkfs.service                        masked  
checkroot-bootclean.service            masked  
checkroot.service                      masked
clagd.service                          enabled
console-getty.service                  disabled
console-shell.service                  disabled
container-getty@.service               static  
cron.service                           enabled
cryptdisks-early.service               masked  
cryptdisks.service                     masked  
cumulus-aclcheck.service               static  
cumulus-core.service                   static  
cumulus-fastfailover.service           enabled
cumulus-firstboot.service              disabled
cumulus-platform.service               enabled  
...

Identify Essential Services

If you need to know which services are required to run when the switch boots, run:

cumulus@switch:~$ systemctl list-dependencies --before basic.target

To see which services are needed for networking, run:

cumulus@switch:~$ systemctl list-dependencies --after network.target
   ├─switchd.service
   ├─wd_keepalive.service
   └─network-pre.target

To identify the services needed for a multi-user environment, run:

cumulus@switch:~$ systemctl list-dependencies --before multi-user.target

 ●  ├─bootlog.service
   ├─systemd-readahead-done.service
   ├─systemd-readahead-done.timer
   ├─systemd-update-utmp-runlevel.service
   └─graphical.target
   └─systemd-update-utmp-runlevel.service

Important Services

The following table lists the most important services in Cumulus Linux.

Service Name Description Affects Forwarding?
switchd Hardware abstraction daemon. Synchronizes the kernel with the ASIC. YES
sx_sdk Interfaces with the Spectrum ASIC. Only on Spectrum switches. YES
portwd Port watch daemon. Broadcom switches only. Reads pluggable information over the I2C bus. Identifies and classifies the modules that are inserted into the system. Manages setting related to the module types that are inserted. YES, eventually, if modules are added or removed
frr FRRouting. Handles routing protocols. There are separate processes for each routing protocol, such as bgpd and ospfd. YES if routing
clag Cumulus link aggregation daemon. Handles MLAG. YES if using MLAG
neighmgrd Keeps neighbor entries refreshed, snoops on ARP and ND packets if ARP suppression is on, and refreshes VRR MAC addresses. YES
mstpd Spanning tree protocol daemon. YES if using layer 2
ptmd Prescriptive Topology Manager. Verifies cabling based on LLDP output. Also sets up BFD sessions. YES if using BFD
netd NCLU back end. NO
rsyslog Handles logging of syslog messages. NO
ntp Network time protocol. NO
ledmgrd LED manager. Reads the state of system LEDs. NO
sysmonitor Watches and logs critical system load (free memory, disk, CPU). NO
lldpd Handles Tx/Rx of LLDP information. NO
smond Reads platform sensors and fan information from pwmd. NO
pwmd Reads and sets fan speeds. NO

Configuring switchd

switchd is the daemon at the heart of Cumulus Linux. It communicates between the switch and Cumulus Linux, and all the applications running on Cumulus Linux.

The switchd configuration is stored in /etc/cumulus/switchd.conf.

The switchd File System

switchd also exports a file system, mounted on /cumulus/switchd, that presents all the switchd configuration options as a series of files arranged in a tree structure. To show the contents, run the tree /cumulus/switchd command. The following example shows output for a switch with one switch port configured:

cumulus@switch:~$ sudo tree /cumulus/switchd/
/cumulus/switchd/
├── clear
│   └── stats
│       ├── vlan
│       └── vxlan
├── config
│   ├── acl
│   │   ├── flow_based_mirroring
│   │   ├── non_atomic_update_mode
│   │   ├── optimize_hw
│   │   └── vxlan_tnl_arp_punt_disable
│   ├── arp
│   │   ├── drop_during_failed_state
│   │   └── next_hops
│   ├── bridge
│   │   ├── broadcast_frame_to_cpu
│   │   └── optimized_mcast_flood
│   ├── buf_util
│   │   ├── measure_interval
│   │   └── poll_interval
│   ├── coalesce
│   │   ├── offset
│   │   ├── reducer
│   │   └── timeout
│   ├── disable_internal_hw_err_restart
│   ├── disable_internal_parity_restart
│   ├── hal
│   │   └── bcm
│   │       ├── l3
│   │       │   └── per_vlan_router_mac_lookup_for_vrrp
│   │       ├── linkscan_interval
│   │       ├── logging
│   │       │   └── l3mc
│   │       ├── per_vlan_router_mac_lookup
│   │       └── vxlan_support
│   ├── ignore_non_swps
│   ├── interface
│   │   ├── swp1
│   │   │   ├── ethtool_mode
│   │   │   ├── interface_mode
│   │   │   ├── port_security
│   │   │   │   ├── enable
│   │   │   │   ├── mac_limit
│   │   │   │   ├── static_mac
│   │   │   │   ├── sticky_aging
│   │   │   │   ├── sticky_mac
│   │   │   │   ├── sticky_timeout
│   │   │   │   ├── violation_mode
│   │   │   │   └── violation_timeout
│   │   │   └── storm_control
│   │   │       ├── broadcast
│   │   │       ├── multicast
│   │   │       └── unknown_unicast
...

Configure switchd Parameters

To configure the switchd parameters, edit the /etc/cumulus/switchd.conf file. An example is provided below.

cumulus@switch:~$ sudo nano /etc/cumulus/switchd.conf
#
# /etc/cumulus/switchd.conf - switchd configuration file
#

# Statistic poll interval (in msec)
#stats.poll_interval = 2000

# Buffer utilization poll interval (in msec), 0 means disable
#buf_util.poll_interval = 0

# Buffer utilization measurement interval (in mins)
#buf_util.measure_interval = 0

# Optimize ACL HW resources for better utilization
#acl.optimize_hw = FALSE

# Enable Flow based mirroring.
#acl.flow_based_mirroring = TRUE

# Enable non atomic acl update
acl.non_atomic_update_mode = FALSE

# Send ARPs for next hops
#arp.next_hops = TRUE

# Kernel routing table ID, range 1 - 2^31, default 254
#route.table = 254
...

When you update the /etc/cumulus/switchd.conf file, you must restart switchd for the changes to take effect. See Restart switchd, below.

Restart switchd

Whenever you modify a switchd hardware configuration file (for example, you update any *.conf file that requires making a change to the switching hardware, like /etc/cumulus/datapath/traffic.conf), you must restart the switchd service for the change to take effect:

cumulus@switch:~$ sudo systemctl restart switchd.service

You do not have to restart the switchd service when you update a network interface configuration (for example, when you edit the /etc/network/interfaces file).

Restarting the switchd service causes all network ports to reset in addition to resetting the switch hardware configuration. NVIDIA recommends that you reboot the switch instead of restarting the switchd service to minimize traffic impact when redundant switches are present with MLAG.

Power over Ethernet - PoE

Cumulus Linux supports Power over Ethernet (PoE) and PoE+, so certain Cumulus Linux switches can supply power from Ethernet switch ports to enabled devices over the Ethernet cables that connect them. PoE is capable of powering devices up to 15W, while PoE+ can power devices up to 30W. Configuration for power negotiation is done over LLDP.

The currently supported platforms include:

PoE Basics

PoE functionality is provided by the cumulus-poe package. When a powered device is connected to the switch via an Ethernet cable:

Power is available as follows:

PSU 1 PSU 2 PoE Power Budget
920W x 750W
x 920W 750W
920W 920W 1650W

The AS4610-54P has an LED on the front panel to indicate PoE status:

Link state and PoE state are completely independent of each other. When a link is brought down on a particular port using ip link <port> down, power on that port is not turned off; however, LLDP negotiation is not possible.

Configure PoE

You use the poectl command utility to configure PoE on a switch that supports the feature. You can:

The PoE configuration resides in /etc/cumulus/poe.conf. The file lists all the switch ports, whether PoE is enabled for those ports and the priority for each port.

Sample poe.conf File ...
[enable]
swp1 = enable
swp2 = enable
swp3 = enable
swp4 = enable
swp5 = enable
swp6 = enable
swp7 = enable
swp8 = enable
swp9 = enable
swp10 = enable
swp11 = enable
swp12 = enable
swp13 = enable
swp14 = enable
swp15 = enable
swp16 = enable
swp17 = enable
swp18 = enable
swp19 = enable
swp20 = enable
swp21 = enable
swp22 = enable
swp23 = enable
swp24 = enable
swp25 = enable
swp26 = enable
swp27 = enable
swp28 = enable
swp29 = enable
swp30 = enable
swp31 = enable
swp32 = enable
swp33 = enable
swp34 = enable
swp35 = enable
swp36 = enable
swp37 = enable
swp38 = enable
swp39 = enable
swp40 = enable
swp41 = enable
swp42 = enable
swp43 = enable
swp44 = enable
swp45 = enable
swp46 = enable
swp47 = enable
swp48 = enable

[priority]
swp1 = low
swp2 = low
swp3 = low
swp4 = low
swp5 = low
swp6 = low
swp7 = low
swp8 = low
swp9 = low
swp10 = low
swp11 = low
swp12 = low
swp13 = low
swp14 = low
swp15 = low
swp16 = low
swp17 = low
swp18 = low
swp19 = low
swp20 = low
swp21 = low
swp22 = low
swp23 = low
swp24 = low
swp25 = low
swp26 = low
swp27 = low
swp28 = low
swp29 = low
swp30 = low
swp31 = low
swp32 = low
swp33 = low
swp34 = low
swp35 = low
swp36 = low
swp37 = low
swp38 = low
swp39 = low
swp40 = low
swp41 = low
swp42 = low
swp43 = low
swp44 = low
swp45 = low
swp46 = low
swp47 = low
swp48 = low

By default, PoE and PoE+ are enabled on all Ethernet/1G switch ports, and these ports are set with a low priority. Switch ports can have low, high or critical priority.

There is no additional configuration for PoE+.

To change the priority for one or more switch ports, run poectl -p swp# [low|high|critical]. For example:

cumulus@switch:~$ sudo poectl -p swp1-swp5,swp7 high

To disable PoE for one or more ports, run poectl -d [port_numbers]:

cumulus@switch:~$ sudo poectl -d swp1-swp5,swp7

To display PoE information for a set of switch ports, run poectl -i [port_numbers]:

cumulus@switch:~$ sudo poectl -i swp10-swp13
Port          Status            Allocated    Priority  PD type      PD class   Voltage   Current    Power
-----   --------------------   -----------   -------- -----------   --------   -------   -------   ---------
swp10   connected              negotiating   low      IEEE802.3at   4          53.5 V     25 mA    3.9 W
swp11   searching              n/a           low      IEEE802.3at   none        0.0 V      0 mA    0.0 W
swp12   connected              n/a           low      IEEE802.3at   2          53.5 V     25 mA    1.4 W
swp13   connected              51.0 W        low      IEEE802.3at   4          53.6 V     72 mA    3.8 W

The Status can be one of the following:

The Allocated column displays how much PoE power has been allocated to the port, which can be one of the following:

To see all the PoE information for a switch, run poectl -s:

cumulus@switch:~$ poectl -s
System power:
  Total:      730.0 W
  Used:        11.0 W
  Available:  719.0 W
Connected ports:
  swp11, swp24, swp27, swp48

The set commands (priority, enable, disable) either succeed silently or display an error message if the command fails.

The poectl command takes the following arguments:

Argument Description
-h, --help Show this help message and exit
-i, --port-info
<port-list>
Returns detailed information for the specified ports. You can specify a range of ports. For example: -i swp1-swp5,swp10.
Note: On an Edge-Core AS4610-54P switch, the voltage reported by the poectl -i command and measured through a power meter connected to the device varies by 5V. The current and power readings are correct and no difference is seen for them.
-a, --all Returns PoE status and detailed information for all ports.
-p, --priority
<port-list> <priority>
Sets priority for the specified ports: low, high, critical.
-d, --disable-ports <port-list> Disables PoE operation on the specified ports.
-e, --enable-ports <port-list> Enables PoE operation on the specified ports.
-s, --system Returns PoE status for the entire switch.
-r, --reset <port-list> Performs a hardware reset on the specified ports. Use this if one or more ports are stuck in an error state. This does not reset any configuration settings for the specified ports.
-v, --version Displays version information.
-j, --json Displays output in JSON format.
--save Saves the current configuration. The saved configuration is automatically loaded on system boot.
--load Loads and applies the saved configuration.

Troubleshooting

You can troubleshoot PoE and PoE+ using the following utilities and files:

LLDP requires network connectivity, so verify that the link is up.

cumulus@switch:~$ net show interface swp20
    Name    MAC                Speed      MTU  Mode
--  ------  -----------------  -------  -----  ---------
UP  swp20   44:38:39:00:00:04  1G        1500  Access/L2

View LLDP Information Using lldpcli

You can run lldpcli to view the LLDP information that has been received on a switch port. For example:

cumulus@switch:~$ sudo lldpcli show neighbors ports swp20 protocol lldp hidden details
-------------------------------------------------------------------------------
LLDP neighbors:
-------------------------------------------------------------------------------
Interface:    swp20, via: LLDP, RID: 2, Time: 0 day, 00:03:34
  Chassis:
    ChassisID:    mac 68:c9:0b:25:54:7c
    SysName:      ihm-ubuntu
    SysDescr:     Ubuntu 14.04.2 LTS Linux 3.14.4+ #1 SMP Thu Jun 26 00:54:44 UTC 2014 armv7l
    MgmtIP:       fe80::6ac9:bff:fe25:547c
    Capability:   Bridge, off
    Capability:   Router, off
    Capability:   Wlan, off
    Capability:   Station, on
  Port:
    PortID:       mac 68:c9:0b:25:54:7c
    PortDescr:    eth0
    PMD autoneg:  supported: yes, enabled: yes
      Adv:          10Base-T, HD: yes, FD: yes
      Adv:          100Base-TX, HD: yes, FD: yes
      MAU oper type: 100BaseTXFD - 2 pair category 5 UTP, full duplex mode
    MDI Power:    supported: yes, enabled: yes, pair control: no
      Device type:  PD
      Power pairs:  spare
      Class:        class 4
      Power type:   2
      Power Source: Primary power source
      Power Priority: low
      PD requested power Value: 51000
      PSE allocated power Value: 51000
  UnknownTLVs: 
    TLV:          OUI: 00,01,42, SubType: 1, Len: 1 05
    TLV:          OUI: 00,01,42, SubType: 1, Len: 1 0D
-------------------------------------------------------------------------------

View LLDP Information Using tcpdump

You can use tcpdump to view the LLDP frames being transmitted and received. For example:

cumulus@switch:~$ sudo tcpdump -v -v -i swp20 ether proto 0x88cc
tcpdump: listening on swp20, link-type EN10MB (Ethernet), capture size 262144 bytes
18:41:47.559022 LLDP, length 211
    Chassis ID TLV (1), length 7
      Subtype MAC address (4): 00:30:ab:f2:d7:a5 (oui Unknown)
      0x0000:  0400 30ab f2d7 a5
    Port ID TLV (2), length 6
      Subtype Interface Name (5): swp20
      0x0000:  0573 7770 3230
    Time to Live TLV (3), length 2: TTL 120s
      0x0000:  0078
    System Name TLV (5), length 13: dni-3048up-09
      0x0000:  646e 692d 3330 3438 7570 2d30 39
    System Description TLV (6), length 68
      Cumulus Linux version 3.0.1~1466303042.2265c10 running on dni 3048up
      0x0000:  4375 6d75 6c75 7320 4c69 6e75 7820 7665
      0x0010:  7273 696f 6e20 332e 302e 317e 3134 3636
      0x0020:  3330 3330 3432 2e32 3236 3563 3130 2072
      0x0030:  756e 6e69 6e67 206f 6e20 646e 6920 3330
      0x0040:  3438 7570
    System Capabilities TLV (7), length 4
      System  Capabilities [Bridge, Router] (0x0014)
      Enabled Capabilities [Router] (0x0010)
      0x0000:  0014 0010
    Management Address TLV (8), length 12
      Management Address length 5, AFI IPv4 (1): 10.0.3.190
      Interface Index Interface Numbering (2): 2
      0x0000:  0501 0a00 03be 0200 0000 0200
    Management Address TLV (8), length 24
      Management Address length 17, AFI IPv6 (2): fe80::230:abff:fef2:d7a5
      Interface Index Interface Numbering (2): 2
      0x0000:  1102 fe80 0000 0000 0000 0230 abff fef2
      0x0010:  d7a5 0200 0000 0200
    Port Description TLV (4), length 5: swp20
      0x0000:  7377 7032 30
    Organization specific TLV (127), length 9: OUI IEEE 802.3 Private (0x00120f)
      Link aggregation Subtype (3)
        aggregation status [supported], aggregation port ID 0
      0x0000:  0012 0f03 0100 0000 00
    Organization specific TLV (127), length 9: OUI IEEE 802.3 Private (0x00120f)
      MAC/PHY configuration/status Subtype (1)
        autonegotiation [supported, enabled] (0x03)
        PMD autoneg capability [10BASE-T fdx, 100BASE-TX fdx, 1000BASE-T fdx] (0x2401)
        MAU type 100BASEFX fdx (0x0012)
      0x0000:  0012 0f01 0324 0100 12
    Organization specific TLV (127), length 12: OUI IEEE 802.3 Private (0x00120f)
      Power via MDI Subtype (2)
        MDI power support [PSE, supported, enabled], power pair spare, power class class4
      0x0000:  0012 0f02 0702 0513 01fe 01fe
    Organization specific TLV (127), length 5: OUI Unknown (0x000142)
      0x0000:  0001 4201 0d
    Organization specific TLV (127), length 5: OUI Unknown (0x000142)
      0x0000:  0001 4201 01
    End TLV (0), length 0

Log poed Events in syslog

The poed service logs the following events to syslog when:

Configuring a Global Proxy

You configure global HTTP and HTTPS proxies in the /etc/profile.d/ directory of Cumulus Linux. To do so, set the http_proxy and https_proxy variables, which tells the switch the address of the proxy server to use to fetch URLs on the command line. This is useful for programs such as apt/apt-get, curl and wget, which can all use this proxy.

  1. In a terminal, create a new file in the /etc/profile.d/ directory. In the code example below, the file is called proxy.sh, and is created using the text editor nano.

    cumulus@switch:~$ sudo nano /etc/profile.d/proxy.sh
    
  2. Add a line to the file to configure either an HTTP or an HTTPS proxy, or both.

    http_proxy=http://myproxy.domain.com:8080
    export http_proxy
    
    https_proxy=https://myproxy.domain.com:8080
    export https_proxy
    
  3. Create a file in the /etc/apt/apt.conf.d directory and add the following lines to the file for acquiring the HTTP and HTTPS proxies; the example below uses http_proxy as the file name:

    cumulus@switch:~$ sudo nano /etc/apt/apt.conf.d/http_proxy
    Acquire::http::Proxy "http://myproxy.domain.com:8080";
    Acquire::https::Proxy "https://myproxy.domain.com:8080";
    
  4. Add the proxy addresses to /etc/wgetrc; you may have to uncomment the http_proxy and https_proxy lines:

    cumulus@switch:~$ sudo nano /etc/wgetrc
    ...
    https_proxy = https://myproxy.domain.com:8080
    http_proxy = http://myproxy.domain.com:8080
    ...
    
  5. Run the source command, to execute the file in the current environment:

    cumulus@switch:~$ source /etc/profile.d/proxy.sh
    

The proxy is now configured. The echo command can be used to confirm aproxy is set up correctly:

Set up an apt package cache

HTTP API

Cumulus Linux implements an HTTP application programing interface to NCLU. Instead of accessing Cumulus Linux using SSH, you can interact with the switch using an HTTP client, such as cURL, HTTPie or a web browser.

HTTP API Basics

The supporting software for the API is installed with Cumulus Linux.

To enable the HTTP API service, run the following systemd command:

cumulus@switch:~$ sudo systemctl enable restserver

Use the systemctl start and systemctl stop commands to start or stop the HTTP API service:

cumulus@switch:~$ sudo systemctl start restserver
cumulus@switch:~$ sudo systemctl stop restserver

Use the systemctl disable command to disable the HTTP API service from running at startup:

cumulus@switch:~$ sudo systemctl disable restserver

Each service runs as a background daemon.

Configuration

To configure the HTTP API services, edit the /etc/nginx/sites-available/nginx-restapi.conf configuration file, enter in the IP address in which the REST API will listen on and then run the command sudo systemctl restart nginx.

IP and Port Settings

You can modify the IP:port combinations to which services listen by changing the parameters of the listen directive(s). By default, nginx-restapi.conf has only one listen parameter.

All URLs must use HTTPS instead of HTTP.

For more information on the listen directive, refer to the NGINX documentation.

Security

Authentication

The default configuration requires all HTTP requests from external sources (not internal switch traffic) to set the HTTP Basic Authentication header.

The user and password must correspond to a user on the host switch.

Transport Layer Security

All traffic must be secured in transport using TLSv1.2 by default. Cumulus Linux contains a self-signed certificate and private key used server-side in this application so that it works out of the box, but using your own certificates and keys is highly recommended. Certificates must be in the PEM format.

For step by step documentation for generating self-signed certificates and keys, and installing them to the switch, refer to the Ubuntu Certificates and Security documentation.

Do not copy the cumulus.pem or cumulus.key files. After installation, edit the ssl_certificate and ssl_certificate_key values in the configuration file for your hardware.

cURL Examples

This section includes several example cURL commands you can use to send HTTP requests to a host. The following settings are used for these examples:

Requests for NCLU require setting the Content-Type request header to be set to application/json.

The cURL -k flag is necessary when the server uses a self-signed certificate. This is the default configuration (see the Security section). To display the response headers, include the -D flag in the command.

To retrieve a list of all available HTTP endpoints:

cumulus@switch:~$ curl -X GET -k -u user:pw https://192.168.0.32:8080

To run net show counters on the host as a remote procedure call:

cumulus@switch:~$ curl -X POST -k -u user:pw -H "Content-Type: application/json" -d '{"cmd": "show counters"}' https://192.168.0.32:8080/nclu/v1/rpc

Caveats

The /etc/restapi.conf file is not listed in the net show configuration files command output.

Layer 1 and Switch Ports

This section discusses how to configure network interfaces and DHCP delays and servers. The Prescriptive Topology Manager (PTM) cabling verification tool is also discussed.

Interface Configuration and Management

ifupdown is the network interface manager for Cumulus Linux. Cumulus Linux uses an updated version of this tool, ifupdown2.

For more information on network interfaces, see Switch Port Attributes.

By default, ifupdown is quiet. Use the verbose option (-v) to show commands as they are executed when bringing an interface down or up.

Basic Commands

To bring up the physical connection to an interface or apply changes to an existing interface, run the sudo ifup <interface> command. The following example command brings up the physical connection to swp1:

cumulus@switch:~$ sudo ifup swp1

To bring down the physical connection to a single interface, run the sudo ifdown <interface> command. The following example command brings down the physical connection to swp1:

cumulus@switch:~$ sudo ifdown swp1

The ifdown command always deletes logical interfaces after bringing them down. When you bring down the physical connection to an interface, it is brought back up automatically after any future reboots or configuration changes with ifreload -a.

To administratively bring the interface up or down; for example, to bring down a port, bridge, or bond but not the physical connection for a port, bridge, or bond, you can use --admin-state option. Alternatively, you can use NCLU commands.

When you put an interface into an admin down state, the interface remains down after any future reboots or configuration changes with ifreload -a.

To put an interface into an admin down state, run the net add interface <interface> link down command.

cumulus@switch:~$ net add interface swp1 link down
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following configuration in the /etc/network/interfaces file:

auto swp1
iface swp1
    link-down yes

To bring the interface back up, run the net del interface <interface> link down command.

cumulus@switch:~$ net del interface swp1 link down
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To put an interface into an admin down state, run the sudo ifdown <interface> --admin-state command:

cumulus@switch:~$ sudo ifdown swp1 --admin-state

These commands create the following configuration in the /etc/network/interfaces file:

auto swp1
iface swp1
    link-down yes

To bring the interface back up, run the sudo ifup <interface> --admin-state command:

cumulus@switch:~$ sudo ifup swp1 --admin-state

To see the link and administrative state, use the ip link show command. In the following example, swp1 is administratively UP and the physical link is UP (LOWER_UP flag).

cumulus@switch:~$ ip link show dev swp1
3: swp1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 500
    link/ether 44:38:39:00:03:c1 brd ff:ff:ff:ff:ff:ff

For additional information on interface administrative state and physical state, refer to this knowledge base article.

ifupdown2 Interface Classes

ifupdown2 enables you to group interfaces into separate classes, where a class is a user-defined label that groups interfaces that share a common function (such as uplink, downlink or compute). You specify classes in the /etc/network/interfaces file.

The most common class is auto, which you configure like this:

auto swp1
iface swp1

You can add other classes using the allow prefix. For example, if you have multiple interfaces used for uplinks, you can define a class called uplinks:

auto swp1
allow-uplink swp1
iface swp1 inet static
    address 10.1.1.1/31

auto swp2
allow-uplink swp2
iface swp2 inet static
    address 10.1.1.3/31

This allows you to perform operations on only these interfaces using the --allow=uplinks option. You can still use the -a options because these interfaces are also in the auto class:

cumulus@switch:~$ sudo ifup --allow=uplinks
cumulus@switch:~$ sudo ifreload -a

If you are using Management VRF, you can use the special interface class called mgmt and put the management interface into that class. The management VRF must have an IPv6 address in addition to an IPv4 address to work correctly.

The mgmt interface class is not supported with NCLU commands.

allow-mgmt eth0
iface eth0 inet dhcp
    vrf mgmt

allow-mgmt mgmt
iface mgmt
    address 127.0.0.1/8
    address ::1/128
    vrf-table auto

All ifupdown2 commands (ifup, ifdown, ifquery, ifreload) can take a class. Include the --allow=<class> option when you run the command. For example, to reload the configuration for the management interface described above, run:

cumulus@switch:~$ sudo ifreload --allow=mgmt

Use the -a option to bring up or down all interfaces that are marked with the common auto class in the /etc/network/interfaces file.

To administratively bring up all interfaces marked auto, run:

cumulus@switch:~$ sudo ifup -a

To administratively bring down all interfaces marked auto, run:

cumulus@switch:~$ sudo ifdown -a

To reload all network interfaces marked auto, use the ifreload command. This command is equivalent to running ifdown then ifup; however, ifreload skips unchanged configurations:

cumulus@switch:~$ sudo ifreload -a

Certain syntax checks are done by default. As a precaution, apply configurations only if the syntax check passes. Use the following compound command:

cumulus@switch:~$ sudo bash -c "ifreload -s -a && ifreload -a"

For more information, see the individual man pages for ifup(8), ifdown(8), ifreload(8).

Configure a Loopback Interface

Cumulus Linux has a loopback interface preconfigured in the /etc/network/interfaces file. When the switch boots up, it has a loopback interface called lo, which is up and assigned an IP address of 127.0.0.1.

The loopback interface lo must always be specified in the /etc/network/interfaces file and must always be up.

ifupdown Behavior with Child Interfaces

By default, ifupdown recognizes and uses any interface present on the system that is listed as a dependent of an interface (for example, a VLAN, bond, or physical interface). You are not required to list interfaces in the interfaces file unless they need a specific configuration for MTU, link speed, and so on. If you need to delete a child interface, delete all references to that interface from the interfaces file.

In the following example, swp1 and swp2 do not need an entry in the interfaces file. The following stanzas defined in /etc/network/interfaces provide the exact same configuration:

With Child Interfaces Defined:

auto swp1
iface swp1

auto swp2
iface swp2

auto bridge
iface bridge
    bridge-vlan-aware yes
    bridge-ports swp1 swp2
    bridge-vids 1-100
    bridge-pvid 1
    bridge-stp on

Without Child Interfaces Defined

auto bridge
iface bridge
    bridge-vlan-aware yes
    bridge-ports swp1 swp2
    bridge-vids 1-100
    bridge-pvid 1
    bridge-stp on

In the following example, swp1.100 and swp2.100 do not need an entry in the interfaces file. The following stanzas defined in /etc/network/interfaces provide the exact same configuration:

With Child Interfaces Defined

auto swp1.100
iface swp1.100

auto swp2.100
iface swp2.100

auto br-100
iface br-100
    address 10.0.12.2/24
    address 2001:dad:beef::3/64
    bridge-ports swp1.100 swp2.100
    bridge-stp on

Without Child Interfaces Defined

auto br-100
iface br-100
    address 10.0.12.2/24
    address 2001:dad:beef::3/64
    bridge-ports swp1.100 swp2.100
    bridge-stp on

For more information about bridges in traditional mode and bridges in VLAN-aware mode, read this knowledge base article.

ifupdown2 Interface Dependencies

ifupdown2 understands interface dependency relationships. When you run ifup and ifdown with all interfaces, the commands always run with all interfaces in dependency order. When you run ifup and ifdown with the interface list on the command line, the default behavior is to not run with dependents; however, if there are any built-in dependents, they will be brought up or down.

To run with dependents when you specify the interface list, use the --with-depends option. The --with-depends option walks through all dependents in the dependency tree rooted at the interface you specify. Consider the following example configuration:

auto bond1
iface bond1
    address 100.0.0.2/16
    bond-slaves swp29 swp30

auto bond2
iface bond2
    address 100.0.0.5/16
    bond-slaves swp31 swp32

auto br2001
iface br2001
    address 12.0.1.3/24
    bridge-ports bond1.2001 bond2.2001
    bridge-stp on

The ifup --with-depends br2001 command brings up all dependents of br2001: bond1.2001, bond2.2001, bond1, bond2, bond1.2001, bond2.2001, swp29, swp30, swp31, swp32.

cumulus@switch:~$ sudo ifup --with-depends br2001

The ifdown --with-depends br2001 command brings down all dependents of br2001: bond1.2001, bond2.2001, bond1, bond2, bond1.2001, bond2.2001, swp29, swp30, swp31, swp32.

cumulus@switch:~$ sudo ifdown --with-depends br2001

ifdown2 always deletes logical interfaces after bringing them down. Use the --admin-state option if you only want to administratively bring the interface up or down. In the above example, ifdown br2001 deletes br2001.

To guide you through which interfaces will be brought down and up, use the --print-dependency option.

For example, run ifquery --print-dependency=list -a to show the dependency list for all interfaces:

cumulus@switch:~$ sudo ifquery --print-dependency=list -a
lo : None
eth0 : None
bond0 : ['swp25', 'swp26']
bond1 : ['swp29', 'swp30']
bond2 : ['swp31', 'swp32']
br0 : ['bond1', 'bond2']
bond1.2000 : ['bond1']
bond2.2000 : ['bond2']
br2000 : ['bond1.2000', 'bond2.2000']
bond1.2001 : ['bond1']
bond2.2001 : ['bond2']
br2001 : ['bond1.2001', 'bond2.2001']
swp40 : None
swp25 : None
swp26 : None
swp29 : None
swp30 : None
swp31 : None
swp32 : None

To print the dependency list of a single interface, run the ifquery --print-dependency=list <interface> command. The following example command shows the dependency list for br2001:

cumulus@switch:~$ sudo ifquery --print-dependency=list br2001
br2001 : ['bond1.2001', 'bond2.2001']
bond1.2001 : ['bond1']
bond2.2001 : ['bond2']
bond1 : ['swp29', 'swp30']
bond2 : ['swp31', 'swp32']
swp29 : None
swp30 : None
swp31 : None
swp32 : None

To show the dependency information for an interface in dot format, run the ifquery --print-dependency=dot <interface> command. The following example command shows the dependency information for interface br2001 in dot format:

cumulus@switch:~$ sudo ifquery --print-dependency=dot br2001
/* Generated by GvGen v.0.9 (http://software.inl.fr/trac/wiki/GvGen) */
digraph G {
    compound=true;
    node1 [label="br2001"];
    node2 [label="bond1.2001"];
    node3 [label="bond2.2001"];
    node4 [label="bond1"];
    node5 [label="bond2"];
    node6 [label="swp29"];
    node7 [label="swp30"];
    node8 [label="swp31"];
    node9 [label="swp32"];
    node1->node2;
    node1->node3;
    node2->node4;
    node3->node5;
    node4->node6;
    node4->node7;
    node5->node8;
    node5->node9;
}

You can use dot to render the graph on an external system where dot is installed.

To print the dependency information of the entire interfaces file, run the following command:

cumulus@switch:~$ sudo ifquery --print-dependency=dot -a >interfaces_all.dot

Subinterfaces

On Linux, an interface is a network device that can be either physical, like a switch port (for example, swp1) or virtual, like a VLAN (for example, vlan100). A VLAN subinterface is a VLAN device on an interface, and the VLAN ID is appended to the parent interface using dot (.) VLAN notation. For example, a VLAN with ID 100 that is a subinterface of swp1 is named swp1.100. The dot VLAN notation for a VLAN device name is a standard way to specify a VLAN device on Linux. Many Linux configuration tools, such as ifupdown2 and its predecessor ifupdown, recognize such a name as a VLAN interface name.

A VLAN subinterface only receives traffic tagged for that VLAN; therefore, swp1.100 only receives packets tagged with VLAN 100 on switch port swp1. Similarly, any packets transmitted from swp1.100 are tagged with VLAN 100.

In an MLAG configuration, the peer link interface that connects the two switches in the MLAG pair has a VLAN subinterface named 4094 by default if you configured the subinterface with NCLU. The peerlink.4094 subinterface only receives traffic tagged for VLAN 4094.

ifup and Upper (Parent) Interfaces

When you run ifup on a logical interface (like a bridge, bond or VLAN interface), if the ifup results in the creation of the logical interface, it implicitly tries to execute on the interface’s upper (or parent) interfaces as well.

Consider this example configuration:

auto br100
iface br100
    bridge-ports bond1.100 bond2.100

auto bond1
iface bond1
    bond-slaves swp1 swp2

If you run ifdown bond1, ifdown deletes bond1 and the VLAN interface on bond1 (bond1.100); it also removes bond1 from the bridge br100. Next, when you run ifup bond1, it creates bond1 and the VLAN interface on bond1 (bond1.100); it also executes ifup br100 to add the bond VLAN interface (bond1.100) to the bridge br100.

There can be cases where an upper interface (like br100) is not in the right state, which can result in warnings. The warnings are mostly harmless.

If you want to disable these warnings, you can disable the implicit upper interface handling by setting skip_upperifaces=1 in the /etc/network/ifupdown2/ifupdown2.conf file.

With skip_upperifaces=1, you have to explicitly execute ifup on the upper interfaces. In this case, you will have to run ifup br100 after an ifup bond1 to add bond1 back to bridge br100.

Although specifying a subinterface like swp1.100 and then running ifup swp1.100 results in the automatic creation of the swp1 interface in the kernel, specify the parent interface swp1 as well. A parent interface is one where any physical layer configuration can reside, such as link-speed 1000 or link-duplex full. If you only create swp1.100 and not swp1, then you cannot run ifup swp1 because you did not specify it.

Configure IP Addresses

To configure IP addresses, run the following commands.

The following commands configure three IP addresses for swp1: two IPv4 addresses, and one IPv6 address.

cumulus@switch:~$ net add interface swp1 ip address 12.0.0.1/30
cumulus@switch:~$ net add interface swp1 ip address 12.0.0.2/30
cumulus@switch:~$ net add interface swp1 ipv6 address 2001:DB8::1/126
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following code snippet in the /etc/network/interfaces file:

auto swp1
iface swp1
    address 12.0.0.1/30
    address 12.0.0.2/30
    address 2001:DB8::1/126

You can specify both IPv4 and IPv6 addresses for the same interface.

For IPv6 addresses, you can create or modify the IP address for an interface using either :: or 0:0:0 notation. Both of the following examples are valid:

cumulus@switch:~$ net add bgp neighbor 2620:149:43:c109:0:0:0:5 remote-as internal
cumulus@switch:~$ net add interface swp1 ipv6 address 2001:DB8::1/126

NCLU adds the address method and address family when needed, specifically when you are creating DHCP or loopback interfaces.

auto lo
iface lo inet loopback

In the /etc/network/interfaces file, list all IP addresses under the iface section. The following command example adds IP address 10.0.0.1/30 and 10.0.0.2/30 to swp1.

auto swp1
iface swp1
    address 10.0.0.1/30
    address 10.0.0.2/30

The address method and address family are not mandatory; they default to inet/inet6 and static. However, you must specify inet/inet6 when you are creating DHCP or loopback interfaces.

auto lo
iface lo inet loopback

You can specify both IPv4 and IPv6 addresses in the same iface stanza:

auto swp1
iface swp1
    address 192.0.2.1/30
    address 192.0.2.2/30
    address 2001:DB8::1/126

A runtime configuration is non-persistent, which means the configurationyou create here does not persist after you reboot the switch.

To make non-persistent changes to interfaces at runtime, use ip addr add:

cumulus@switch:~$ sudo ip addr add 192.0.2.1/30 dev swp1
cumulus@switch:~$ sudo ip addr add 2001:DB8::1/126 dev swp1

To remove an addresses from an interface, use ip addr del:

cumulus@switch:~$ sudo ip addr del 192.0.2.1/30 dev swp1
cumulus@switch:~$ sudo ip addr del 2001:DB8::1/126 dev swp1

For more details on the options available to manage and query interfaces, see man ip.

To show the assigned IP address on an interface, run the ip addr show command. The following example command shows the assigned IP address on swp1.

cumulus@switch:~$ ip addr show dev swp1
3: swp1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 500
    link/ether 44:38:39:00:03:c1 brd ff:ff:ff:ff:ff:ff
    inet 192.0.2.1/30 scope global swp1
    inet 192.0.2.2/30 scope global swp1
    inet6 2001:DB8::1/126 scope global tentative
        valid_lft forever preferred_lft forever

Specify IP Address Scope

ifupdown2 does not honor the configured IP address scope setting in the /etc/network/interfaces file, treating all addresses as global. It does not report an error. Consider this example configuration:

auto swp2
iface swp2
    address 35.21.30.5/30
    address 3101:21:20::31/80
    scope link

When you run ifreload -a on this configuration, ifupdown2 considers all IP addresses as global.

cumulus@switch:~$ ip addr show swp2
5: swp2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 74:e6:e2:f5:62:82 brd ff:ff:ff:ff:ff:ff
inet 35.21.30.5/30 scope global swp2
valid_lft forever preferred_lft forever
inet6 3101:21:20::31/80 scope global 
valid_lft forever preferred_lft forever
inet6 fe80::76e6:e2ff:fef5:6282/64 scope link 
valid_lft forever preferred_lft forever

To work around this issue, configure the IP address scope:

Run the following commands:

cumulus@switch:~$ net add interface swp6 post-up ip address add 71.21.21.20/32 dev swp6 scope site
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following code snippet in the /etc/network/interfaces file:

auto swp6
iface swp6
    post-up ip address add 71.21.21.20/32 dev swp6 scope site

In the /etc/network/interfaces file, configure the IP address scope using post-up ip address add <address> dev <interface> scope <scope>. For example:

auto swp6
iface swp6
    post-up ip address add 71.21.21.20/32 dev swp6 scope site

Then run the ifreload -a command on this configuration.

The following configuration shows the correct scope:

cumulus@switch:~$ ip addr show swp6
9: swp6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 74:e6:e2:f5:62:86 brd ff:ff:ff:ff:ff:ff
inet 71.21.21.20/32 scope site swp6
valid_lft forever preferred_lft forever
inet6 fe80::76e6:e2ff:fef5:6286/64 scope link
valid_lft forever preferred_lft forever

Purge Existing IP Addresses on an Interface

By default, ifupdown2 purges existing IP addresses on an interface. If you have other processes that manage IP addresses for an interface, you can disable this feature.

To disable IP address purge on an interface, run the following commands:

cumulus@switch:~$ net add interface swp1 address-purge no
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following configuration snippet in the /etc/network/interfaces file:

auto swp1
iface swp1
    address-purge no

In the /etc/network/interfaces file, add address-purge no to the interface configuration. The following example command disables IP address purge on swp1.

cumulus@switch:~# sudo nano /etc/network/interfaces

auto swp1
iface swp1
    address-purge no

Purging existing addresses on interfaces with multiple iface stanzas is not supported. Doing so can result in the configuration of multiple addresses for an interface after you change an interface address and reload the configuration with ifreload -a. If this happens, you must shut down and restart the interface with ifup and ifdown, or manually delete superfluous addresses with ip address delete specify.ip.address.here/mask dev DEVICE. See also the Caveats and Errata section below for cautions about using multiple iface stanzas for the same interface.

Specify User Commands

You can specify additional user commands in the /etc/network/interfaces file. The interface stanzas in /etc/network/interfaces can have a command that runs at pre-up, up, post-up, pre-down, down, and post-down:

To add a command to an interface stanza, run the following commands:

cumulus@switch:~$ net add interface swp1 post-up /sbin/foo bar
cumulus@switch:~$ net add interface ip address 12.0.0.1/30
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following configuration in the /etc/network/interfaces file:

auto swp1
iface swp1
    address 12.0.0.1/30
    post-up /sbin/foo bar

If your post-up command also starts, restarts, or reloads any systemd service, you must use the --no-block option with systemctl. Otherwise, that service or even the switch itself might hang after starting or restarting. For example, to restart the dhcrelay service after bringing up VLAN 100, first run:

cumulus@switch:~$ net add vlan 100 post-up systemctl --no-block restart dhcrelay.service

This command creates the following configuration in the /etc/network/interfaces file:

auto bridge
iface bridge
    bridge-vids 100
    bridge-vlan-aware yes

auto vlan100 iface vlan100 post-up systemctl –no-block restart dhcrelay.service vlan-id 100 vlan-raw-device bridge

To add a command to an interface stanza, add the command in the /etc/network/interfaces file. For example:

cumulus@switch:~# sudo nano /etc/network/interfaces

auto swp1
iface swp1
    address 12.0.0.1/30
    up /sbin/foo bar

If your post-up command also starts, restarts, or reloads any systemd service, you must use the --no-block option with systemctl. Otherwise, that service or even the switch itself might hang after starting or restarting. For example, to restart the dhcrelay service after bringing up a VLAN, the /etc network/interfaces configuration looks like this:

auto bridge.100
iface bridge.100 
    post-up systemctl --no-block restart dhcrelay.service

You can add any valid command in the sequence to bring an interface up or down; however, limit the scope to network-related commands associated with the particular interface. For example, it does not make sense to install a Debian package on ifup of swp1, even though it is technically possible. See man interfaces for more details.

Source Interface File Snippets

Sourcing interface files helps organize and manage the interfaces file. For example:

cumulus@switch:~$ sudo cat /etc/network/interfaces
# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet dhcp

source /etc/network/interfaces.d/bond0

The contents of the sourced file used above are:

cumulus@switch:~$ sudo cat /etc/network/interfaces.d/bond0
auto bond0
iface bond0
    address 14.0.0.9/30
    address 2001:ded:beef:2::1/64
    bond-slaves swp25 swp26

Use Globs for Port Lists

Globs define a range of ports.

NCLU supports globs to define port lists (a range of ports). You must use commas to separate different ranges of ports in the NCLU command; for example:

cumulus@switch:~$ net add bridge bridge ports swp1-4,6,10-12
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands produce the following snippet in the /etc/network/interfaces file. The file renders the list of ports individually.

...

auto bridge
iface bridge
    bridge-ports swp1 swp2 swp3 swp4 swp6 swp10 swp11 swp12
    bridge-vlan-aware yes
auto swp1
iface swp1

auto swp2
iface swp2

auto swp3
iface swp3

auto swp4
iface swp4

auto swp6
iface swp6

auto swp10
iface swp10

auto swp11
iface swp11

auto swp12
iface swp12

Use the glob keyword to specify bridge ports and bond slaves:

auto br0
iface br0
    bridge-ports glob swp1-6.100

auto br1
iface br1
    bridge-ports glob swp7-9.100  swp11.100 glob swp15-18.100

Mako Templates

ifupdown2 supports Mako-style templates. The Mako template engine is run over the interfaces file before parsing.

While ifupdown2 supports Mako templates, NCLU does not understand them. As a result, NCLU cannot read or write to the /etc/network/interfaces file.

Use the template to declare cookie-cutter bridges in the interfaces file:

And use it to declare addresses in the interfaces file:

%for i in [1,12]:
auto swp${i}
iface swp${i}
    address 10.20.${i}.3/24

In Mako syntax, use square brackets ([1,12]) to specify a list of individual numbers (in this case, 1 and 12). Use range(1,12) to specify a range of interfaces.

You can test your template and confirm it evaluates correctly by running mako-render /etc/network/interfaces.

To comment out content in Mako templates, use double hash marks (##). For example:

## % for i in range(1, 4):
## auto swp${i}
## iface swp${i}
## % endfor
##

For more examples of configuring Mako templates, read this knowledge base article.

Run ifupdown Scripts under /etc/network/ with ifupdown2

Unlike the traditional ifupdown system, ifupdown2 does not run scripts installed in /etc/network/*/ automatically to configure network interfaces.

To enable or disable ifupdown2 scripting, edit the addon_scripts_support line in the /etc/network/ifupdown2/ifupdown2.conf file. 1 enables scripting and 2 disables scripting. The following example enables scripting.

cumulus@switch:~$ sudo nano /etc/network/ifupdown2/ifupdown2.conf
# Support executing of ifupdown style scripts.
# Note that by default python addon modules override scripts with the same name
addon_scripts_support=1

ifupdown2 sets the following environment variables when executing commands:

Add Descriptions to Interfaces

You can add descriptions to interfaces configured in the /etc/network/interfaces file by using the alias keyword.

The following commands create an alias for swp1:

cumulus@switch:~$ net add interface swp1 alias hypervisor_port_1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following code snippet:

auto swp1
iface swp1
    alias hypervisor_port_1

In the /etc/network/interfaces file, add a description using the alias keyword:

cumulus@switch:~# sudo nano /etc/network/interfaces

auto swp1
iface swp1
    alias swp1 hypervisor_port_1

You can query the interface description.

To show the description (alias) for an interface, run the net show interface <interface> command. The following example command shows the description for swp1:

cumulus@switch$ net show interface swp1
    Name   MAC                Speed     MTU   Mode
--  ----   -----------------  -------   -----  ---------
UP  swp1   44:38:39:00:00:04  1G        1500   Access/L2
Alias
-----
hypervisor_port_1

To show the interface description (alias) for all interfaces on the switch, run the net show interface alias command. For example:

cumulus@switch:~$ net show interface alias
State    Name            Mode              Alias
-----    -------------   -------------     ------------------
UP       bond01          LACP
UP       bond02          LACP
UP       bridge          Bridge/L2
UP       eth0            Mgmt
UP       lo              Loopback          loopback interface
UP       mgmt            Interface/L3
UP       peerlink        LACP
UP       peerlink.4094   SubInt/L3
UP       swp1            BondMember        hypervisor_port_1
UP       swp2            BondMember        to Server02
...

To show the interface description for all interfaces on the switch in JSON format, run the net show interface alias json command.

To show the description (alias) for an interface, run the ip link show command. The alias appears on the alias line:

cumulus@switch$ ip link show swp1
3: swp1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT qlen 500
    link/ether aa:aa:aa:aa:aa:bc brd ff:ff:ff:ff:ff:ff
    alias hypervisor_port_1

Interface descriptions also appear in the SNMP OID IF-MIB::ifAlias .

  • Aliases are limited to 256 characters.
  • Avoid using apostrophes or non-ASCII characters in the alias string. Cumulus Linux does not parse these characters.

Caveats and Errata

Even though ifupdown2 supports the inclusion of multiple iface stanzas for the same interface, use a single iface stanza for each interface. If you must specify more than one iface stanza; for example, if the configuration for a single interface comes from many places, like a template or a sourced file, make sure the stanzas do not specify the same interface attributes. Otherwise, unexpected behavior can result.

In the following example, swp1 is configured in two places: the /etc/network/interfaces file and the /etc/network/interfaces.d/speed_settings file. ifupdown2 correctly parses this configuration because the same attributes are not specified in multiple iface stanzas.

cumulus@switch:~$ sudo cat /etc/network/interfaces

source /etc/network/interfaces.d/speed_settings

auto swp1
iface swp1
  address 10.0.14.2/24

cumulus@switch:~$ cat /etc/network/interfaces.d/speed_settings

auto swp1
iface swp1
  link-speed 1000
  link-duplex full

You cannot purge existing addresses on interfaces with multiple iface stanzas.

ifupdown2 and sysctl

For sysctl commands in the pre-up, up, post-up, pre-down, down, and post-down lines that use the $IFACE variable, if the interface name contains a dot (.), ifupdown2 does not change the name to work with sysctl. For example, the interface name bridge.1 is not converted to bridge/1.

Interface Name Limitations

Interface names are limited to 15 characters in length, the first character cannot be a number and the name cannot include a dash (-). In addition, any name that matches with the regular expression .{0,13}\-v.* is not supported.

If you encounter issues, remove the interface name from the /etc/network/interfaces file, then restart the networking.service.

cumulus@switch:~$ sudo nano /etc/network/interfaces
cumulus@switch:~$ sudo systemctl restart networking.service

Switch Port Attributes

Cumulus Linux exposes network interfaces for several types of physical and logical devices:

Each physical network interface (port) has a number of configurable settings:

Most of these settings are configured automatically for you, depending upon your switch ASIC; however, you must always set MTU manually.

For NVIDIA Spectrum ASICs, the firmware configures FEC, link speed, duplex mode and auto-negotiation automatically, following a predefined list of parameter settings until the link comes up. You can disable FEC if necessary, which forces the firmware to not try any FEC options.

For Broadcom-based switches, enable auto-negotiation on each port. When enabled, Cumulus Linux automatically configures the best link parameter settings based on the module type (speed, duplex, auto-negotiation, and FEC, where supported).

This topic describes the auto-negotiation, link speed, duplex mode, MTU, and FEC settings and provides a table showing the default configuration for various port and cable types. Breakout port configuration, logical switch port limitations, and troubleshooting is also provided.

Auto-negotiation

By default on a Broadcom-based switch, auto-negotiation is disabled - except on 10G and 1000BASE-T fixed copper switch ports, where it is required for links to work. For RJ-45 SFP adapters, you need to manually configure the desired link speed and auto-negotiation as described in the default settings table below.

If you disable auto-negotiation later or never enable it, then you have to configure any settings that deviate from the port default - such as duplex mode, FEC, and link speed settings.

Some module types support auto-negotiation while others do not. To enable a simpler configuration, Cumulus Linux allows you to configure auto-negotiation on all port types on Broadcom switches; the port configuration software then configures the underlying hardware according to its capabilities.

If you do decide to disable auto-negotiation, be aware of the following:

  • You must manually set any non-default link speed, duplex, pause, and FEC.
  • Disabling auto-negotiation on a 1G optical cable prevents detection of single fiber breaks.
  • You cannot disable auto-negotiation on 1GT or 10GT fixed copper switch ports.

For 1000BASE-T RJ-45 SFP adapters, auto-negotiation is automatically done on the SFP PHY, so enabling auto-negotiation on the port settings is not required. You must manually configure these ports using the settings below.

Depending upon the connector used for a port, enabling auto-negotiation also enables forward error correction (FEC), if the cable requires it (see the table below). The correct FEC mode is set based on the speed of the cable when auto-negotiation is enabled.

To configure auto-negotiation for a switch:

Run the net add interface <interface> link autoneg command. The following example commands enable auto-negotiation for the swp1 interface:

cumulus@switch:~$ net add interface swp1 link autoneg on
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
  1. Edit the /etc/network/interfaces file. The following example disables auto-negotiation for the swp1 interface.

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    
    auto swp1
    iface swp1
        link-autoneg off
    
  2. Run the ifreload -a command to load the updated configuration:

    cumulus@switch:~$ sudo ifreload -a
    

    Runtime Configuration (Advanced)

    You can use ethtool to configure auto-negotiation. The following example command enables auto-negotiation for the swp1 interface:

    ethtool -s swp1 speed 10000 duplex full autoneg on|off
    

A runtime configuration is non-persistent. The configuration you create does not persist after you reboot the switch.

Any time you enable auto-negotiation, Cumulus Linux restores the default configuration settings specified in the table below.

Port Speed and Duplex Mode

Cumulus Linux supports both half- and full-duplex configurations. Half-duplex is supported only with speeds of less than 1G.

Supported port speeds include 100M, 1G, 10G, 25G, 40G, 50G and 100G. In Cumulus Linux, you set the speed on Broadcom-based switch in Mbps, where the setting for 1G is 1000, 40G is 40000, and 100G is 100000.

You can configure ports to the following speeds (unless there are restrictions in the /etc/cumulus/ports.conf file of a particular platform).

Switch Port Type
Other Configurable Speeds
1G 100 Mb
10G 1 Gigabit (1000 Mb)
40G 4x10G (10G lanes) creates four 1-lane ports each running at 10G
100G 50G or 2x50G (25G lanes) - 50G creates one 2-lane port running at 25G and 2x50G creates two 2-lane ports each running at 25G
40G (10G lanes) creates one 4-lane port running at 40G
4x25G (25G lanes) creates four 1-lane ports each running at 25G
4x10G (10G lanes) creates four 1-lane ports each running at 10G

  • On Lenovo NE2572O switches, swp1 through swp8 only support 25G speed.
  • For 10G and 1G SFPs inserted in a 25G port on a Broadcom platform, you must edit the /etc/cumulus/ports.conf file and configure the four ports in the same core to be 10G. See Caveats and Errata.
  • A switch with the Maverick ASIC limits multicast traffic by the lowest speed port that has joined a particular group. For example, if you are sending 100G multicast through and subscribe with one 100G and one 25G port, traffic on both egress ports is limited to 25Gbps. If you remove the 25G port from the group, traffic correctly forwards at 100Gbps.

To configure the port speed and duplex mode:

Run the net add interface <interface> link speed command. The following commands configure the port speed for the swp1 interface. The duplex mode setting defaults to full. You only need to specify link duplex if you want to set half-duplex mode.

cumulus@switch:~$ net add interface swp1 link speed 10000
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The above commands create the following /etc/network/interfaces file code snippet:

auto swp1
iface swp1
    link-speed 10000

The following commands configure the port speed and set half-duplex mode for the swp1 interface.

cumulus@switch:~$ net add interface swp1 link speed 100 
cumulus@switch:~$ net add interface swp1 link duplex half
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The above commands create the following /etc/network/interfaces file code snippet:

auto swp1
iface swp1
    link-speed 100
    link-duplex half

Edit the /etc/network/interfaces file to create a persistent configuration for the port speeds:

  1. Add the appropriate lines for each switch port stanza. The following example shows that the port speed for the swp1 interface is set to 10G and the duplex mode is set to full.

If you specify the port speed in the /etc/network/interfaces file, you must also specify the duplex mode setting; otherwise, the interface defaults to half duplex.

```
cumulus@switch:~$ sudo nano /etc/network/interfaces

auto swp1
iface swp1
    address 10.1.1.1/24
    link-speed 10000
    link-duplex full
```
  1. Run the ifreload -a command to load the updated configuration:

    cumulus@switch:~$ sudo ifreload -a
    

    Runtime Configuration (Advanced)

    You can use ethtool to configure the port speed and duplex mode for your switch ports. You must specify both the port speed and the duplex mode in the ethtool command; auto-negotiation is optional.

    The following example command sets the port speed to 10G and duplex mode to full on the swp1 interface:

    cumulus@switch:~$  ethtool -s swp1 speed 10000 duplex full
    

A runtime configuration is non-persistent. The configuration you create does not persist after you reboot the switch.

MTU

Interface MTU applies to traffic traversing the management port, front panel or switch ports, bridge, VLAN subinterfaces, and bonds (both physical and logical interfaces). MTU is the only interface setting that you must set manually.

In Cumulus Linux, ifupdown2 assigns 1500 as the default MTU setting. On a Mellanox switch, the initial MTU value set by the driver is 9238. After you configure the interface, the default MTU setting is 1500.

To change the MTU setting, run the following commands:

Run the net add interface <interface> mtu command. The following example command sets the MTU to 9000 for the swp1 interface.

cumulus@switch:~$ net add interface swp1 mtu 9000
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following code snippet:

auto swp1
iface swp1
    mtu 9000
  1. Edit the /etc/network/interfaces file. The following example sets MTU to 9000 for the swp1 interface.

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    
    auto swp1
    iface swp1
        mtu 9000
    
  2. Run the ifreload -a command to load the updated configuration:

    cumulus@switch:~$ sudo ifreload -a
    

    Runtime Configuration (Advanced)

    Run the ip link set command. The following example command sets the swp1 interface to MTU 9000.

    cumulus@switch:~$ sudo ip link set dev swp1 mtu 9000
    

A runtime configuration is non-persistent. The configuration you create does not persist after you reboot the switch.

Some switches might not support the same maximum MTU setting in hardware for both the management interface (eth0) and the data plane ports.

Set a Policy for Global System MTU

For a global policy to set MTU, create a policy document (called mtu.json). For example:

cumulus@switch:~$ sudo cat /etc/network/ifupdown2/policy.d/mtu.json
{
  "address": {"defaults": { "mtu": "9216" }
            }
}

The policies and attributes in any file in /etc/network/ifupdown2/policy.d/ override the default policies and attributes in /var/lib/ifupdown2/policy.d/.

MTU for a Bridge

The MTU setting is the lowest MTU of any interface that is a member of the bridge (every interface specified in bridge-ports in the bridge configuration of the /etc/network/interfaces file). There is no need to specify an MTU on the bridge. Consider this bridge configuration:

auto bridge
iface bridge
    bridge-ports bond1 bond2 bond3 bond4 peer5
    bridge-vids 100-110
    bridge-vlan-aware yes

For a bridge to have an MTU of 9000, set the MTU for each of the member interfaces (bond1 to bond 4, and peer5), to 9000 at minimum.

When configuring MTU for a bond, configure the MTU value directly under the bond interface; the configured value is inherited by member links/slave interfaces. If you need a different MTU on the bond, set it on the bond interface, as this ensures the slave interfaces pick it up. There is no need to specify MTU on the slave interfaces.

VLAN interfaces inherit their MTU settings from their physical devices or their lower interface; for example, swp1.100 inherits its MTU setting from swp1. Therefore, specifying an MTU on swp1 ensures that swp1.100 inherits the MTU setting for swp1.

If you are working with VXLANs, the MTU for a virtual network interface (VNI must be 50 bytes smaller than the MTU of the physical interfaces on the switch, as those 50 bytes are required for various headers and other data. Also, consider setting the MTU much higher than 1500.

The MTU for an SVI interface, such as vlan100, is derived from the bridge. When you use NCLU to change the MTU for an SVI and the MTU setting is higher than it is for the other bridge member interfaces, the MTU for all bridge member interfaces changes to the new setting. If you need to use a mixed MTU configuration for SVIs, (if some SVIs have a higher MTU and some lower), set the MTU for all member interfaces to the maximum value, then set the MTU on the specific SVIs that need to run at a lower MTU.

To show the MTU setting for an interface:

Run the net show interface <interface> command:

cumulus@switch:~$ net show interface swp1
    Name    MAC                Speed      MTU  Mode
--  ------  -----------------  -------  -----  ---------
UP  swp1    44:38:39:00:00:04  1G        1500  Access/L2

Run the ip link show <interface> command:

cumulus@switch:~$ ip link show dev swp1
3: swp1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 500
   link/ether 44:38:39:00:03:c1 brd ff:ff:ff:ff:ff:ff

FEC

Forward Error Correction (FEC) is an encoding and decoding layer that enables the switch to detect and correct bit errors introduced over the cable between two interfaces. Because 25G transmission speeds can introduce a higher than acceptable bit error rate (BER) on a link, FEC is required or recommended for 25G, 4x25G, and 100G link speeds.

For the link to come up, the two interfaces on each end must use the same FEC setting.

There is a very small latency overhead required for FEC. For most applications, this small amount of latency is preferable to error packet retransmission latency.

There are two FEC types:

Cumulus Linux includes additional FEC options:

  • While Auto FEC is the default setting on the Mellanox Spectrum switch, do not explicitly configure the fec auto option on the switch as this leads to a link flap whenever you run net commit or ifreload -a.
  • The Trident II switch does not support FEC.
  • The Tomahawk switch does not support RS FEC or auto-negotiation of FEC on 25G lanes that are broken out (Tomahawk pre-dates 802.3by). If you are using a 4x25G breakout DAC or AOC on a Tomahawk switch, you can configure either Base-R FEC or no FEC, and choose cables appropriate for that limitation (CA-25G-S, CA-25G-N or fiber). Tomahawk+, Tomahawk2, Trident3 and Maverick switches do not have this limitation.

For 25G DAC, 4x25G Breakouts DAC and 100G DAC cables, the IEEE 802.3by specification creates 3 classes:

The IEEE classification is based on various dB loss measurements and minimum achievable cable length. You can build longer and shorter cables if they comply to the dB loss and BER requirements.

If a cable is manufactured to CA-25G-S classification and FEC is not enabled, the BER might be unacceptable in a production network. It is important to set the FEC according to the cable class (or better) to have acceptable bit error rates. See Determining Cable Class below.

You can check bit errors using cl-netstat (RX_ERR column) or ethtool -S (HwIfInErrors counter) after a large amount of traffic has passed through the link. A non-zero value indicates bit errors. Expect error packets to be zero or extremely low compared to good packets. If a cable has an unacceptable rate of errors with FEC enabled, replace the cable.

For 25G, 4x25G Breakout, and 100G Fiber modules and AOCs, there is no classification of 25G cable types for dB loss, BER or length. FEC is recommended but might not be required if the BER is low enough.

Determine Cable Class of 100G and 25G DACs

You can determine the cable class for 100G and 25G DACs from the Extended Specification Compliance Code field (SFP28: 0Ah, byte 35, QSFP28: Page 0, byte 192) in the cable EEPROM programming.

For 100G DACs, most manufacturers use the 0x0Bh 100GBASE-CR4 or 25GBASE-CR CA-L value (the 100G DAC specification predates the IEEE 802.3by 25G DAC specification). RS FEC is the expected setting for 100G DAC but might not be required with shorter or better cables.

A manufacturer’s EEPROM setting might not match the dB loss on a cable or the actual bit error rates that a particular cable introduces. Use the designation as a guide, but set FEC according to the bit error rate tolerance in the design criteria for the network. For most applications, the highest mutual FEC ability of both end devices is the best choice.

You can determine for which grade the manufacturer has designated the cable as follows.

For the SFP28 DAC, run the following command:

cumulus@switch:~$ sudo ethtool -m swp35 hex on | grep 0020 | awk '{ print $6}'
0c

The values at location 0x0024 are:

For the QSFP28 DAC, run the following command:

cumulus@switch:~$ sudo ethtool -m swp51s0 hex on | grep 00c0 | awk '{print $2}'
0b

The values at 0x00c0 are:

In each example below, the Compliance field is derived using the method described above and is not visible in the ethool -m output.

3meter cable that does not require FEC 
(CA-N)  
Cost: More expensive  
Cable size: 26AWG (Note that AWG does not necessarily correspond to overall dB loss or BER performance)  
Compliance Code: 25GBASE-CR CA-N

3meter cable that requires Base-R FEC 
(CA-S)  
Cost: Less expensive  
Cable size: 26AWG  
Compliance Code: 25GBASE-CR CA-S

When in doubt, consult the manufacturer directly to determine the cable classification.

Spectrum ASIC FEC Behavior

The firmware in a Spectrum ASIC applies FEC configuration to 25G and 100G cables based on the cable type and whether the peer switch also has a Spectrum ASIC.

When the link is between two switches with Spectrum ASICs:

Cable Type
FEC Mode
25G optical cables Base-R/FC-FEC
25G 1,2 meters: CA-N, loss <13db Base-R/FC-FEC
25G 2.5,3 meters: CA-S, loss <16db Base-R/FC-FEC
25G 2.5,3,4,5 meters: CA-L, loss > 16db RS-FEC
100G DAC or optical RS-FEC

When linking to a non-Spectrum peer, the firmware lets the peer decide. The Spectrum ASIC supports RS-FEC (for both 100G and 25G), Base-R/FC-FEC (25G only), or no-FEC (for both 100G and 25G).

Cable Type
FEC Mode
25G pptical cables Let peer decide
25G 1,2 meters: CA-N, loss <13db Let peer decide
25G 2.5,3 meters: CA-S, loss <16db Let peer decide
25G 2.5,3,4,5 meters: CA-L, loss > 16db Let peer decide
100G Let peer decide: RS-FEC or No FEC

How Does Cumulus Linux use FEC?

This depends upon the make of the switch you are using.

A Spectrum switch enables FEC automatically when it powers up; that is, the setting is fec auto. The port firmware tests and determines the correct FEC mode to bring the link up with the neighbor. It is possible to get a link up to a Spectrum switch without enabling FEC on the remote device as the switch eventually finds a working combination to the neighbor without FEC.

On a Broadcom switch, Cumulus Linux does not enable FEC by default; that is, the setting is fec off. Configure FEC explicitly to match the configured FEC on the link neighbor. On 100G DACs, you can configure link-autoneg so that the port attempts to negotiate FEC settings with the remote peer.

The following sections describe how to show the current FEC mode, and to enable and disable FEC.

Show the Current FEC Mode

Cumulus Linux returns different output for the ethtool --show-fec command, depending upon whether you are using a Broadcom or Mellanox Spectrum switch.

On a Broadcom switch, the --show-fec output tells you exactly what you configured, even if the link is down due to a FEC mismatch with the neighbor.

On a Spectrum switch, the --show-fec output tells you the current active state of FEC only if the link is up; that is, if the FEC modes matches that of the neighbor. If the link is not up, the value displays None, which is not valid.

To show the FEC mode currently enabled on a given switch port, run the ethtool --show-fec <interface> command.

cumulus@switch:~$ sudo ethtool --show-fec swp1
FEC parameters for swp1:
Configured FEC encodings: Auto
Active FEC encoding: Off

Enable or Disable FEC

To enable Reed Solomon (RS) FEC on a link:

Run the net add interface <interface> link fec rs command. For example:

cumulus@switch:~$ sudo net add interface swp1 link fec rs
cumulus@switch:~$ sudo net pending
cumulus@switch:~$ sudo net commit
  1. Edit the /etc/network/interfaces file. The following example enables RS FEC for the swp1 interface (link-fec rs):

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    
    auto swp1
    iface swp1
        link-autoneg off
        link-speed 100000
        link-fec rs
    
  2. Run the ifreload -a command to load the updated configuration:

    cumulus@switch:~$ sudo ifreload -a
    

    Runtime Configuration (Advanced)

    Run the ethtool --set-fec <interface> encoding RS command. For example:

    cumulus@switch:~$ sudo ethtool --set-fec swp1 encoding RS
    

A runtime configuration is non-persistent. The configuration you create does not persist after you reboot the switch.

To enable Base-R/FireCode FEC on a link:

Run the net add interface <interface> link fec baser command. For example:

cumulus@switch:~$ sudo net add interface swp1 link fec baser
cumulus@switch:~$ sudo net pending
cumulus@switch:~$ sudo net commit
  1. Edit the /etc/network/interfaces file. The following example enables Base-R FEC for the swp1 interface (link-fec baser):

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    
    auto swp1
    iface swp1
        link-autoneg off
        link-speed 100000
        link-fec baser
    
  2. Run the ifreload -a command to load the updated configuration:

    cumulus@switch:~$ sudo ifreload -a
    

    Runtime Configuration (Advanced)

    Run the ethtool --set-fec <interface> encoding baser command. For example:

    cumulus@switch:~$ sudo ethtool --set-fec swp1 encoding BaseR
    

A runtime configuration is non-persistent. The configuration you create does not persist after you reboot the switch.

To enable FEC with Auto-negotiation:

FEC with auto-negotiation is supported on DACs only.

Run the net add interface <interface> link autoneg on command. The following example command enables FEC with auto-negotiation on the swp1 interface:

cumulus@switch:~$ sudo net add interface swp1 link autoneg on
cumulus@switch:~$ sudo net pending
cumulus@switch:~$ sudo net commit
  1. Edit the /etc/network/interfaces file and set auto-negotiation to on. For example:

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    
    auto swp1
    iface swp1
        link-autoneg on
    
  2. Run the ifreload -a command to load the updated configuration:

    cumulus@switch:~$ sudo ifreload -a
    

    Runtime Configuration (Advanced)

    You can use ethtool to enable FEC with auto-negotiation. For example:

    ethtool -s swp1 speed 10000 duplex full autoneg on
    

A runtime configuration is non-persistent. The configuration you create does not persist after you reboot the switch.

To show the FEC and auto-negotiation settings for an interface, run the following command:

cumulus@switch:~$ sudo ethtool swp1 | egrep 'FEC|auto'
Supports auto-negotiation: Yes
Supported FEC modes: RS
Advertised auto-negotiation: Yes
Advertised FEC modes: RS
Link partner advertised auto-negotiation: Yes
Link partner advertised FEC modes: Not reported

To disable FEC on a link:

Run the net add interface <interface> link fec off command. For example:

cumulus@switch:~$ sudo net add interface swp1 link fec off
cumulus@switch:~$ sudo net pending
cumulus@switch:~$ sudo net commit
  1. Edit the /etc/network/interfaces file. The following example disables Base-R FEC for the swp1 interface (link-fec baser):

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    
    auto swp1
    iface swp1
    link-fec off
    
  2. Run the ifreload -a command to load the updated configuration:

    cumulus@switch:~$ sudo ifreload -a
    

    Runtime Configuration (Advanced)

    Run the ethtool --set-fec <interface> encoding off command. For example:

    cumulus@switch:~$ sudo ethtool --set-fec swp1 encoding off
    

A runtime configuration is non-persistent. The configuration you create does not persist after you reboot the switch.

Interface Configuration Recommendations for Broadcom Platforms

The recommended configuration for each type of interface is described in the following table. These are the link settings that are applied to the port hardware when auto-negotiation is enabled on a Broadcom-based switch. If further troubleshooting is required to bring a link up, use the table below as a guide to set the link parameters.

Except as noted below, the settings for both sides of the link are expected to be the same.

Spectrum switches automatically configure these settings following a predefined list of parameter settings until the link comes up.

Speed Auto-negotiation FEC Setting Manual Configuration Examples Notes
100BASE-T (RJ-45 SFP adapter) Off N/A NCLU commands
$ net add interface swp1 link speed 100
$ net add interface swp1 link autoneg off
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg off
   link-speed 100
The module has two sets of electronics: the port side, which communicates with the switch ASIC and the RJ-45 adapter side.

Auto-negotiation is always used on the RJ-45 adapter side of the link by the PHY built into the module. This is independent of the switch setting. Set auto-negotiation to off.

Auto-negotiation must be enabled on the server side in this scenario.
100BASE-T on a 1G fixed copper port On N/A NCLU commands
$ net add interface swp1 link speed 100
$net add interface swp1 link autoneg on
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   ink-autoneg on
   link-speed 100
10M or 100M speeds are possible with auto-negotiation off on both sides.

Testing on an Edgecore AS4610-54P showed the ASIC reporting auto-negotiation as on.

Power over Ethernet might require auto-negotiation to be on.
1000BASE-T (RJ-45 SFP adapter) Off N/A NCLU commands
$ net add interface swp1 link speed 1000
$ net add interface swp1 link autoneg off
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg off
   link-speed 1000
The module has two sets of electronics: the port side, which communicates with the switch ASIC and the RJ-45 side.

Auto-negotiation is always used on the RJ-45 side of the link by the PHY built into the module. This is independent of the switch setting. Set auto-negotiation to off.

Auto-negotiation must be enabled on the server side.
1000BASE-T on a 1G fixed copper port On N/A NCLU commands
$ net add interface swp1 link speed 1000
$ net add interface swp1 link autoneg on
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg on
   link-speed 1000
1000BASE-T on a 10G fixed copper port On N/A NCLU commands
$ net add interface swp1 link speed 1000
$ net add interface swp1 link autoneg on
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg on
   link-speed 1000
1000BASE-SX 1000BASE-LX (1G Fiber) Recommended On N/A NCLU commands
$ net add interface swp1 link speed 1000
$ net add interface swp1 link autoneg on
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg on
   link-speed 1000
Without auto-negotiation, the link stays up when there is a single fiber break.

See the limitation discussed in 10G and 1G SFPs Inserted in a 25G Port below.
10GBASE-T (RJ-45 SFP Module) Off N/A NCLU commands
$ net add interface swp1 link speed 10000
$ net add interface swp1 link autoneg off
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg off
   link-speed 10000
The module has two sets of electronics - the port side, which communicates to the switch ASIC and the RJ-45 side.

Auto-negotiation is always used on the RJ-45 side of the link by the PHY built into the module. This is independent of the switch setting. Set link-autoneg to off.

Auto-negotiation needs to be enabled on the server side.
10GBASE-T fixed copper port On N/A NCLU commands
$ net add interface swp1 link speed 10000
$ net add interface swp1 link autoneg on
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg on
   link-speed 10000
10GBASE-CR
10GBASE-LR
10GBASE-SR
10G AOC
Off N/A NCLU commands
$ net add interface swp1 link speed 10000
$ net add interface swp1 link autoneg off
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg off
   link-speed 10000
40GBASE-CR4 Recommended On Disable NCLU commands
$ net add interface swp1 link speed 40000
$ net add interface swp1 link autoneg on
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg on
   link-speed 40000
40G standards mandate auto-negotiation be enabled for DAC connections.
40GBASE-SR4
40GBASE-LR4
40G AOC
Off Disable NCLU commands
$ net add interface swp1 link speed 40000
$ net add interface swp1 link autoneg off
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg off
   link-speed 40000
100GBASE-CR4 On auto-negotiated NCLU commands
$ net add interface swp1 link speed 100000
$ net add interface swp1 link autoneg on
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg on
   link-speed 100000
100GBASE-SR4
100G AOC
Off RS NCLU commands
$ net add interface swp1 link speed 100000
$ net add interface swp1 link autoneg off
$ net add interface swp1 link fec rs
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg off
   link-speed 100000
   link-fec rs
100GBASE-LR4 Off None NCLU commands
$ net add interface swp1 link speed 100000
$ net add interface swp1 link autoneg off
$ net add interface swp1 link fec off
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg off
   link-speed 100000
   link-fec off
25GBASE-CR On auto-negotiated NCLU commands
$ net add interface swp1 link speed 25000
$ net add interface swp1 link autoneg on
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg on
   link-speed 25000
Tomahawk predates 802.3by. It does not support RS FEC or auto-negotiation of RS FEC on a 25G port or subport. It does support Base-R FEC.
25GBASE-SR Off RS NCLU commands
$ net add interface swp1 link speed 25000
$ net add interface swp1 link autoneg off
$ net add interface swp1 link fec rs
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg off
   link-speed 25000
   link-fec rs
Tomahawk predates 802.3by and does not support RS FEC on a 25G port or subport; however it does support Base-R FEC. The configuration for Base-R FEC is as follows:
NCLU commands
$ net add interface swp1 link speed 25000
$ net add interface swp1 link autoneg off
$ net add interface swp1 link fec baser

Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg off
   link-speed 25000
   link-fec baser

Configure FEC to the setting that the cable requires.
25GBASE-LR Off None NCLU commands
$ net add interface swp1 link speed 25000
$ net add interface swp1 link autoneg off
$ net add interface swp1 link fec off
Configuration in /etc/network/interfaces
auto swp1
iface swp1
   link-autoneg off
    link-speed 25000
   link-fec off

Default Policies for Interface Settings

Instead of configuring settings for each individual interface, you can specify a policy for all interfaces on a switch or tailor custom settings for each interface. Create a file in /etc/network/ifupdown2/policy.d/ and populate the settings accordingly. The following example shows a file called address.json.

cumulus@switch:~$ cat /etc/network/ifupdown2/policy.d/address.json
{
    "ethtool": {
        "defaults": {
            "link-duplex": "full"
        },
        "iface_defaults": {
            "swp1": {
                "link-autoneg": "on",
                "link-speed": "1000"
          },
            "swp16": {
                "link-autoneg": "off",
                "link-speed": "10000"
            },
            "swp50": {
                "link-autoneg": "off",
                "link-speed": "100000",
                "link-fec": "rs"
            }
        }
    },
    "address": {
        "defaults": { "mtu": "9000" },
        "iface_defaults": {
            "eth0": {"mtu": "1500"}
        }
    }
}

Setting the default MTU also applies to the management interface. Be sure to add the iface_defaults to override the MTU for eth0, to remain at 1500 for Broadcom switches or 9238 for Mellanox switches.

Breakout Ports

Cumulus Linux lets you:

  • For Broadcom switches with ports that support 100G speeds, you cannot have more than 128 logical ports.

  • Port ganging is not supported on Mellanox switches with the Spectrum ASIC.

  • Mellanox switches with the Spectrum ASIC have a limit of 64 logical ports. 64-port Broadcom switches with the Tomahawk2 ASIC have a limit of 128 total logical ports. If you want to break ports out to 4x25G or 4x10G, you must configure the logical ports as follows:

    • You can only break out odd-numbered ports into four logical ports.
    • You must disable the next even-numbered port. For example, if you break out port 11 into four logical ports, you must disable port 12.

    These restrictions do not apply to a 2x50G breakout configuration or to the Mellanox SN2100 and SN2010 switches.

Configure a Breakout Port

To configure a breakout port:

This example command breaks out the 100G port on swp1 into four 25G ports.

cumulus@switch:~$ net add interface swp1 breakout 4x25G
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To break out swp1 into four 10G ports, run the net add interface swp1 breakout 4x10G command.

On Mellanox switches with the Spectrum ASIC and 64-port Broadcom switches, you need to disable the next port. The following example command disables swp2.

cumulus@switch:~$ net add interface swp2 breakout disabled
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands break out swp1 into four 25G interfaces in the /etc/cumulus/ports.conf file and create four interfaces in the /etc/network/interfaces file:

cumulus@switch:~$ cat /etc/network/interfaces
...
auto swp1s0
iface swp1s0

auto swp1s1
iface swp1s1

auto swp1s2
iface swp1s2

auto swp1s3
iface swp1s3
...

When you commit your change, switchd restarts to apply the changes. The restart interrupts network services.

  1. Edit the /etc/cumulus/ports.conf file to configure the port breakout. The following example breaks out the 100G port on swp1 into four 25G ports. To break out swp1 into four 10G ports, use 1=4x10G. On Mellanox switches with the Spectrum ASIC and 64-port Broadcom switches with the Tomahawk2 ASIC, you need to disable the next port. The example also disables swp2.

    cumulus@switch:~$ sudo cat /etc/cumulus/ports.conf
    ...
    1=4x25G
    2=disabled
    3=100G
    4=100G
    ...
    

    The /etc/cumulus/ports.conf file varies across different hardware platforms.

  2. Configure the breakout ports in the /etc/network/interfaces file. The following example shows the swp1 breakout ports (swp1s0, swp1s1, swp1s2, and swp1s3).

cumulus@switch:~$ sudo cat /etc/network/interfaces
...
auto swp1s0
iface swp1s0

auto swp1s1
iface swp1s1

auto swp1s2
iface swp1s2

auto swp1s3
iface swp1s3
...
  1. Restart switchd with the sudo systemctl restart switchd.service command. The restart interrupts network services.

Remove a Breakout Port

To remove a breakout port:

  1. Run the net del interface <interface> command. For example:

    cumulus@switch:~$ net del interface swp1s0
    cumulus@switch:~$ net del interface swp1s1
    cumulus@switch:~$ net del interface swp1s2
    cumulus@switch:~$ net del interface swp1s3
    cumulus@switch:~$ net pending
    cumulus@switch:~$ net commit
    
  2. Manually edit the /etc/cumulus/ports.conf file to configure the interface for the original speed. For example:

    cumulus@switch:~$ sudo nano /etc/cumulus/ports.conf
    ...
    
    1=100G
    2=100G
    3=100G
    4=100G
    ...
    
  3. Restart switchd with the sudo systemctl restart switchd.service command. The restart interrupts network services.

  1. Edit the /etc/cumulus/ports.conf file to configure the interface for the original speed.

    cumulus@switch:~$ sudo nano /etc/cumulus/ports.conf
    ...
    
    1=100G
    2=100G
    3=100G
    4=100G
    ...
    
  2. Restart switchd with the sudo systemctl restart switchd.service command. The restart interrupts network services.

Combine Four 10G Ports into One 40G Port

You can gang (combine) four 10G ports into one 40G port for use with a breakout cable, provided you follow these requirements:

  • Port ganging is not supported on Mellanox switches with the Spectrum ASIC.
  • The /etc/cumulus/ports.conf file varies across different hardware platforms.

To gang swp1 through swp4 into a 40G port, run the following commands:

cumulus@switch:~$ net add int swp1-4 breakout /4
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following configuration snippet in the /etc/cumulus/ports.conf file:

# SFP+ ports#
# <port label 1-48> = [10G|40G/4]
1=40G/4
2=40G/4
3=40G/4
4=40G/4
5=10G

To gang swp1 through swp4 into a 40G port, edit the /etc/cumulus/ports.conf file as shown below:

# SFP+ ports#
# <port label 1-48> = [10G|40G/4]
1=40G/4
2=40G/4
3=40G/4
4=40G/4
5=10G

Restart switchd with the following command:

cumulus@switch:~$ sudo systemctl restart switchd.service

Restarting the switchd service causes all network ports to reset, interrupting network services, in addition to resetting the switch hardware configuration.

Logical Switch Port Limitations

100G and 40G switches can support a certain number of logical ports, depending on the manufacturer; these include:

Before you configure any logical/unganged ports on a switch, check the limitations listed in /etc/cumulus/ports.conf; this file is specific to each manufacturer.

The following example shows the logical port limitation provided in the Dell Z9254F-ON ports.conf file. The maximum number of ports for this switch is 128.

# ports.conf --
#
#   configure port speed, aggregation, and subdivision.
#
# The Dell Z9264F has:
#      64 QSFP28 ports numbered 1-64
#         These ports are configurable as 100G, 50G, 40G, or split into
#         2x50G, 4x25G, or 4x10G ports.
#
# NOTE:  You must restart switchd for any changes to take effect.
# Only "odd-numbered " port can be split into 4 interfaces and if an odd-numbered
# port is split in a 4X configuration, the port adjacent to it (even-numbered port)
# has to be set to "disabled " in this file. When splitting a port into two
# interfaces, like 2x50G, it is NOT required that the adjacent port be
# disabled. For example, when splitting port 11 into 4 10G interfaces, port
# 12 must be configured as "disabled" like this:
#
#   11=4x10G
#   12=disabled

# QSFP28 ports
#
# <port label> = [100G|50G|40G|2x50G|4x25G|4x10G|disabled]

Mellanox SN2700 and SN2700B switches have a limit of 64 logical ports in total. However, the logical ports must be configured in a specific way. See the note above.

Verification and Troubleshooting Commands

Statistics

To show high-level interface statistics, run the net show interface command:

cumulus@switch:~$ net show interface swp1

    Name    MAC                Speed      MTU  Mode
--  ------  -----------------  -------  -----  ---------
UP  swp1    44:38:39:00:00:04  1G        1500  Access/L2

Vlans in disabled State
-------------------------
br0

Counters      TX    RX
----------  ----  ----
errors         0     0
unicast        0     0
broadcast      0     0
multicast      0     0

LLDP
------  ----  ---------------------------
swp1    ====  44:38:39:00:00:03(server01)

To show low-level interface statistics, run the following ethtool command:

cumulus@switch:~$ sudo ethtool -S swp1
NIC statistics:
      HwIfInOctets: 21870
      HwIfInUcastPkts: 0
      HwIfInBcastPkts: 0
      HwIfInMcastPkts: 243
      HwIfOutOctets: 1148217
      HwIfOutUcastPkts: 0
      HwIfOutMcastPkts: 11353
      HwIfOutBcastPkts: 0
      HwIfInDiscards: 0
      HwIfInL3Drops: 0
      HwIfInBufferDrops: 0
      HwIfInAclDrops: 0
      HwIfInBlackholeDrops: 0
      HwIfInDot3LengthErrors: 0
      HwIfInErrors: 0
      SoftInErrors: 0
      HwIfOutErrors: 0
      HwIfOutQDrops: 0
      HwIfOutNonQDrops: 0
      SoftOutErrors: 0
      SoftOutDrops: 0
      SoftOutTxFifoFull: 0
      HwIfOutQLen: 0

Query SFP Port Information

To verify SFP settings, run the ethtool -m command. The following example shows the vendor, type and power output for the swp4 interface.

cumulus@switch:~$ sudo ethtool -m swp4 | egrep 'Vendor|type|power\s+:'
        Transceiver type                          : 10G Ethernet: 10G Base-LR
        Vendor name                               : FINISAR CORP.
        Vendor OUI                                : 00:90:65
        Vendor PN                                 : FTLX2071D327
        Vendor rev                                : A
        Vendor SN                                 : UY30DTX
        Laser output power                        : 0.5230 mW / -2.81 dBm
        Receiver signal average optical power     : 0.7285 mW / -1.38 dBm

Caveats and Errata

Port Speed and the ifreload -a Command

When configuring port speed or break outs in the /etc/cumulus/ports.conf file, you need to run the ifreload -a command to reload the configuration after restarting switchd in the following cases:

Port Speed Configuration

If you change the port speed in the /etc/cumulus/ports.conf file but the speed is also configured for that port in the /etc/network/interfaces file, after you edit the /etc/cumulus/ports.conf file and restart switchd, you must also run the ifreload -a command so that the /etc/network/interfaces file is also updated with your change.

10G and 1G SFPs Inserted in a 25G Port

For 10G and 1G SFPs inserted in a 25G port on a Broadcom platform, you must configure the four ports in the same core to be 10G. Each set of four 25G ports are controlled by a single core; therefore, each core must run at the same clock speed. The four ports must be in sequential order; for example, swp1, swp2, swp3, and swp4, unless a particular core grouping is specified in the /etc/cumulus/ports.conf file.

  1. Edit the /etc/cumulus/ports.conf file and configure the four ports to be 10G. 1G SFPs are clocked at 10G speeds; therefore, for 1G SFPs, the /etc/cumulus/ports.conf file entry must also specify 10G. Currently you cannot use NCLU commands for this step.

    ...
    # SFP28 ports
    #
    # <port label 1-48> = [25G|10G|100G/4|40G/4]
    1=25G
    2=25G
    3=25G
    4=25G
    5=10G
    6=10G
    7=10G
    8=10G
    9=25G
    ...
    

    You cannot use ethtool -s speed XX (or ifreload -a after setting the speed in the /etc/network/interfaces file) to change the port speed unless the four ports in a core group are already configured to 10G and switchd has been restarted. If the ports are still in 25G mode, using ethtool or ifreload to change the speed to 10G or 1G returns an error (and a return code of 255).

    If you change the speed with ethtool to a setting already in use in the /etc/cumulus/ports.conf file, ethtool (and ifreload -a) do not return an error and no changes are made.

  2. Restart switchd.

  3. If you want to set the speed of any SFPs to 1G, set the port speed to 1000 Mbps using NCLU commands; this is not necessary for 10G SFPs. You don’t need to set the port speed to 1G for all four ports. For example, if you intend only for swp5 and swp6 to use 1G SFPs, do the following:

    cumulus@switch:~$ net add interface swp5-swp6 link speed 1000
    cumulus@switch:~$ net pending
    cumulus@switch:~$ net commit
    

100G switch ASICs do not support 1000Base-X auto-negotiation (Clause 37), which is recommended for 1G fiber optical modules. As a result, single fiber breaks cannot be detected when using 1G optical modules on these switches.

The auto-negotiation setting must be the same on both sides of the connection. If using 1G fiber modules in 25G SFP28 ports, ensure auto-negotiation is disabled on the link partner interface as well.

Timeout Error on Quanta LY8 and LY9 Switches

On Quanta T5048-LY8 and T3048-LY9 switches, an Operation timed out error occurs when you remove and reinsert a QSFP module.

You cannot remove the QSFPx2 module while the switch is powered on; it is not hot-swappable. However, if an Operation timed out error occurs, restart switchd to bring the link up. Be aware that this disrupts your network.

On the T3048-LY9, run the following commands:

cumulus@switch:~$ sudo echo 0 > qsfpd_power_enable/value
cumulus@switch:~$ sudo rmmod quanta_ly9_rangeley_platform
cumulus@switch:~$ sudo modprobe quanta_ly9_rangeley_platform
cumulus@switch:~$ sudo systemctl restart switchd.service

On the T5048-LY8, run the following commands:

cumulus@switch:~$ sudo echo 0 > qsfpd_power_enable/value
cumulus@switch:~$ sudo systemctl restart switchd.service

swp33 and swp34 Disabled on Some Switches

The front SFP+ ports (swp33 and swp34) are disabled in Cumulus Linux on the following switches:

These ports appear as disabled in the /etc/cumulus/ports.conf file.

200G Interfaces on the Dell S5248F Switch

On the Dell S5248F switch, the 2x200G QSFP-DD interfaces labeled 49/50 and 51/52 are not supported natively at 200G speeds. The interfaces are supported with 100G cables; however, you can only use one 100G from each QSFP-DD port. The upper QSFP-DD port is named swp49 and the lower QSFP-DD port is named swp52.

QSFP+ Ports on the Dell S5232F Switch

Cumulus Linux does not support the 2x10G QSFP+ ports on the Dell S5232F switch.

QSFP+ Ports on the Dell S4148T Switch

On the Dell S4148T switch, the two QSFP+ ports are set to disabled by default and the four QSFP28 ports are configured for 100G. The following example shows the default settings in the /etc/cumulus/ports.conf file for this switch:

cumulus@switch:~$ sudo cat /etc/cumulus/ports.conf
...
# QSFP+ ports
#
# <port label 27-28> = [4x10G|40G]
27=disabled
28=disabled
# QSFP28 ports
#
# <port label 25-26, 29-30> = [4x10G|4x25G|2x50G|40G|50G|100G]
25=100G
26=100G
29=100G
30=100G

To enable the two QSFP+ ports, you must configure all four QSFP28 ports for either 40G or 4x10G. You cannot use either of the QSFP+ ports if any of the QSFP28 ports are configured for 100G.

The following example shows the /etc/cumulus/ports.conf file with all four QSFP28 ports configured for 40G and both QSFP+ ports enabled:

cumulus@switch:~$ sudo cat /etc/cumulus/ports.conf
...
# QSFP+ ports
#
# <port label 27-28> = [4x10G|40G]
27=40G
28=40G
# QSFP28 ports
#
# <port label 25-26, 29-30> = [4x10G|4x25G|2x50G|40G|50G|100G]
25=40G
26=40G
29=40G
30=40G

To disable the QSFP+ ports, you must set the ports to disabled. Do not comment out the lines as this prevents switchd from restarting.

1000BASE-T Modules Not Supported on Certain Edgecore and Cumulus Express Switches

1000BASE-T modules are not supported on the following switches:

After rebooting the Melllanox SN2100 switch, eth0 always has a speed of 100Mb/s. If you bring the interface down and then back up again, the interface negotiates 1000Mb. This only occurs the first time the interface comes up.

To work around this issue, add the following commands to the /etc/rc.local file to flap the interface automatically when the switch boots:

modprobe -r igb
sleep 20
modprobe igb

On the EdgeCore AS7326-56X switch, all four switch ports in each port group must be set to the same link speed; otherwise, the links do not come up. These ports are set to 25G by default, but can also be set to 10G. The port groups on this switch are as follows, where each row is a port group:

For example, if you configure port 19 for 10G, you must also configure ports 16, 17 and 21 for 10G.

Additionally, you can gang each port group together as a 100G or 40G port. When ganged together, one port (based on the arrangement of the ports) is designated as the gang leader. This port’s number is used to configure the ganged ports and is marked with an asterisk (*) above.

The EdgeCore AS7326-56X is a 48x25G + 8x100G + 2x10G switch. The dedicated 10G ports are not currently supported in Cumulus Linux. However, you can configure all other ports to run at 10G speeds.

The Lenovo NE2572O switch has external retimers on swp1 through swp8. Currently, these ports only support a speed of 25G.

The following switches that use Serial over LAN technology (SOL) do not support eth0 speed or auto-negotiation changes:

Delay in Reporting Interface as Operational Down

When you remove two transceivers simultaneously from a switch, both interfaces show the carrier down status immediately. However, it takes one second for the second interface to show the operational down status. In addition, the services on this interface also take an extra second to come down.

Mellanox Spectrum-2 and Tomahawk-based Switches Support Different FEC Modes

The Mellanox Spectrum-2 (25G) switch only supports RS FEC. The Tomahawk-based switch only supports BASE-R FEC. These two switches do not share compatible FEC modes and do not interoperate reliably.

Maverick Switches with Modules that Don’t Support Auto-negotiation

On a Maverick switch, if auto-negotiation is configured on a 10G interface and the installed module does not support auto-negotiation (for example, 10G DAC, 10G Optical, 1G RJ45 SFP), the link breaks. To work around this issue, disable auto-negotiation on interfaces where it is not supported.

Dell Z9264F-ON 10G Interfaces are Unsupported

The Dell Z9264F-ON has 64x100G + 2x 10G SFP+ ports. The 2x 10G SFP+ ports are not supported in Cumulus Linux.

ifplugd

ifplugd is an Ethernet link-state monitoring daemon that executes user-specified scripts to configure an Ethernet device when a cable is plugged in, or automatically unconfigure an Ethernet device when a cable is removed. Follow the steps below to install and configure the ifplugd daemon.

Install ifplugd

You can install this package even if the switch is not connected to the internet, as it is contained in the cumulus-local-apt-archive repository that is embedded in the Cumulus Linux disk image.

To install ifplugd:

  1. Update the switch before installing the daemon:

    cumulus@switch:~$ sudo -E apt-get update
    
  2. Install the ifplugd package:

    cumulus@switch:~$ sudo -E apt-get install ifplugd
    

Configure ifplugd

After you install ifplugd, you must edit two configuration files:

The example configuration below configures ifplugd to bring down all uplinks when the peer bond goes down in an MLAG environment.

  1. Open /etc/default/ifplugd in a text editor and configure the file as appropriate. Add the peerbond name before you save the file.

    INTERFACES="peerbond"
    HOTPLUG_INTERFACES=""
    ARGS="-q -f -u0 -d1 -w -I"
    SUSPEND_ACTION="stop"
    
  2. Open the /etc/ifplugd/action.d/ifupdown file in a text editor. Configure the script, then save the file.

    #!/bin/sh
    set -e
    case "$2" in
    up)
           clagrole=$(clagctl | grep "Our Priority" | awk '{print $8}')
           if [ "$clagrole" = "secondary" ]
           then
               #List all the interfaces below to bring up when clag peerbond comes up.
               for interface in swp1 bond1 bond3 bond4
               do
                   echo "bringing up : $interface"  
                   ip link set $interface up
               done
            fi
        ;;
    down)
           clagrole=$(clagctl | grep "Our Priority" | awk '{print $8}')
           if [ "$clagrole" = "secondary" ]
           then
               #List all the interfaces below to bring down when clag peerbond goes down.
               for interface in swp1 bond1 bond3 bond4
               do
                   echo "bringing down : $interface"
                   ip link set $interface down
               done
           fi
        ;;
    esac
    
  3. Restart the ifplugd daemon to implement the changes:

    cumulus@switch:~$ sudo systemctl restart ifplugd.service
    

Caveats and Errata

The default shell for ifplugd is dash (/bin/sh) instead of bash, as it provides a faster and more nimble shell. However, dash contains fewer features than bash (for example, dash is unable to handle multiple uplinks).

Buffer and Queue Management

Hardware datapath configuration manages packet buffering, queueing and scheduling in hardware. To configure priority groups, and assign the scheduling alogorithm and weights, you edit the /etc/cumulus/datapath/traffic.conf.

The /usr/lib/python2.7/dist-packages/cumulus/__chip_config/[bcm|mlx]/datapath.conf assigns buffer space and egress queues. The default thresholds defined in the datapath.conf file are intended for data center environments, but certain workloads may require additional tuning. It is best to make small, incremental changes to validate the changes with your application performance. Be sure to back up the original file before making changes.

Each packet is assigned to an ASIC Class of Service (CoS) value based on the priority value of the packet stored in the 802.1p (Class of Service) or DSCP (Differentiated Services Code Point) header field. The choice to schedule packets based on COS or DSCP is a configurable option in the /etc/cumulus/datapath/traffic.conf file.

Priority groups include:

The scheduler is configured to use a hybrid scheduling algorithm. It applies strict priority to control traffic queues and a weighted round robin selection from the remaining queues. Unicast packets and multicast packets with the same priority value are assigned to separate queues, which are assigned equal scheduling weights.

You can configure Quality of Service (QoS) for switches on the following platforms only:

  • Broadcom Tomahawk, Trident II, Trident II+ and Trident3
  • Mellanox Spectrum and Spectrum-2

Example Configuration File

The following example /etc/cumulus/datapath/traffic.conf datapath configuration file applies to 10G, 40G, and 100G switches on Broadcom Tomahawk, Trident II, Trident II+, or Trident3 and Mellanox Spectrum platforms only.

click to see traffic.conf file
cumulus@switch:~$ sudo cat /etc/cumulus/datapath/traffic.conf
#
# /etc/cumulus/datapath/traffic.conf
#

# packet header field used to determine the packet priority level
# fields include {802.1p, dscp}
traffic.packet_priority_source_set = [802.1p,dscp]

# remark packet priority value
# fields include {802.1p, none}
# remark packet priority value
# fields include {802.1p, dscp}
traffic.packet_priority_remark_set = [802.1p,dscp]

# packet priority remark values assigned from each internal cos value
# internal cos values {cos_0..cos_7}
# (internal cos 3 has been reserved for CPU-generated traffic)
#
# 802.1p values = {0..7}

traffic.cos_0.priority_remark.8021p = [1]
traffic.cos_1.priority_remark.8021p = [0]
traffic.cos_2.priority_remark.8021p = [3]
traffic.cos_3.priority_remark.8021p = [2]
traffic.cos_4.priority_remark.8021p = [4]
traffic.cos_5.priority_remark.8021p = [5]
traffic.cos_6.priority_remark.8021p = [7]
traffic.cos_7.priority_remark.8021p = [6]

# dscp values = {0..63}
traffic.cos_0.priority_remark.dscp = [1]
traffic.cos_1.priority_remark.dscp = [9]
traffic.cos_2.priority_remark.dscp = [17]
traffic.cos_3.priority_remark.dscp = [25]
traffic.cos_4.priority_remark.dscp = [33]
traffic.cos_5.priority_remark.dscp = [41]
traffic.cos_6.priority_remark.dscp = [49]
traffic.cos_7.priority_remark.dscp = [57]

# Per-port remark packet fields and mapping: applies to the designated set of ports.
remark.port_group_list = [remark_port_group]
remark.remark_port_group.packet_priority_remark_set = [802.1p,dscp]
remark.remark_port_group.port_set = swp1-swp4,swp6
remark.remark_port_group.cos_0.priority_remark.dscp = [2]
remark.remark_port_group.cos_1.priority_remark.dscp = [10]
remark.remark_port_group.cos_2.priority_remark.dscp = [18]
remark.remark_port_group.cos_3.priority_remark.dscp = [26]
remark.remark_port_group.cos_4.priority_remark.dscp = [34]
remark.remark_port_group.cos_5.priority_remark.dscp = [42]
remark.remark_port_group.cos_6.priority_remark.dscp = [50]
remark.remark_port_group.cos_7.priority_remark.dscp = [58]

# packet priority values assigned to each internal cos value
# internal cos values {cos_0..cos_7}
# (internal cos 3 has been reserved for CPU-generated traffic)
#
# 802.1p values = {0..7}
traffic.cos_0.priority_source.8021p = [0]
traffic.cos_1.priority_source.8021p = [1]
traffic.cos_2.priority_source.8021p = [2]
traffic.cos_3.priority_source.8021p = []
traffic.cos_4.priority_source.8021p = [3,4]
traffic.cos_5.priority_source.8021p = [5]
traffic.cos_6.priority_source.8021p = [6]
traffic.cos_7.priority_source.8021p = [7]

# dscp values = {0..63}
traffic.cos_0.priority_source.dscp = [0,1,2,3,4,5,6,7]
traffic.cos_1.priority_source.dscp = [8,9,10,11,12,13,14,15]
traffic.cos_2.priority_source.dscp = []
traffic.cos_3.priority_source.dscp = []
traffic.cos_4.priority_source.dscp = []
traffic.cos_5.priority_source.dscp = []
traffic.cos_6.priority_source.dscp = []
traffic.cos_7.priority_source.dscp = [56,57,58,59,60,61,62,63]

# Per-port source packet fields and mapping: applies to the designated set of ports.
source.port_group_list = [source_port_group]
source.source_port_group.packet_priority_source_set = [802.1p,dscp]
source.source_port_group.port_set = swp1-swp4,swp6
source.source_port_group.cos_0.priority_source.8021p = [7]
source.source_port_group.cos_1.priority_source.8021p = [6]
source.source_port_group.cos_2.priority_source.8021p = [5]
source.source_port_group.cos_3.priority_source.8021p = [4]
source.source_port_group.cos_4.priority_source.8021p = [3]
source.source_port_group.cos_5.priority_source.8021p = [2]
source.source_port_group.cos_6.priority_source.8021p = [1]
source.source_port_group.cos_7.priority_source.8021p = [0]

# priority groups
traffic.priority_group_list = [control, service, bulk]

# internal cos values assigned to each priority group
# each cos value should be assigned exactly once
# internal cos values {0..7}
priority_group.control.cos_list = [7]
priority_group.service.cos_list = [2]
priority_group.bulk.cos_list = [0,1,3,4,5,6]

# to configure priority flow control on a group of ports:
# -- assign cos value(s) to the cos list
# -- add or replace a port group names in the port group list
# -- for each port group in the list
#    -- populate the port set, e.g.
#       swp1-swp4,swp8,swp50s0-swp50s3
#    -- set a PFC buffer size in bytes for each port in the group
#    -- set the xoff byte limit (buffer limit that triggers PFC frame transmit to start)
#    -- set the xon byte delta (buffer limit that triggers PFC frame transmit to stop)
#    -- enable PFC frame transmit and/or PFC frame receive
# priority flow control
# pfc.port_group_list = [pfc_port_group]
# pfc.pfc_port_group.cos_list = []
# pfc.pfc_port_group.port_set = swp1-swp4,swp6
# pfc.pfc_port_group.port_buffer_bytes = 25000
# pfc.pfc_port_group.xoff_size = 10000
# pfc.pfc_port_group.xon_delta = 2000
# pfc.pfc_port_group.tx_enable = true
# pfc.pfc_port_group.rx_enable = true

# to configure pause on a group of ports:
# -- add or replace port group names in the port group list
# -- for each port group in the list
#    -- populate the port set, e.g.
#       swp1-swp4,swp8,swp50s0-swp50s3
#    -- set a pause buffer size in bytes for each port in the group
#    -- set the xoff byte limit (buffer limit that triggers pause frames transmit to start)
#    -- set the xon byte delta (buffer limit that triggers pause frames transmit to stop)

# link pause
# link_pause.port_group_list = [pause_port_group]
# link_pause.pause_port_group.port_set = swp1-swp4,swp6
# link_pause.pause_port_group.port_buffer_bytes = 25000
# link_pause.pause_port_group.xoff_size = 10000
# link_pause.pause_port_group.xon_delta = 2000
# link_pause.pause_port_group.rx_enable = true
# link_pause.pause_port_group.tx_enable = true

# scheduling algorithm: algorithm values = {dwrr}
scheduling.algorithm = dwrr

# traffic group scheduling weight
# weight values = {0..127}
# '0' indicates strict priority
priority_group.control.weight = 0
priority_group.service.weight = 32
priority_group.bulk.weight = 16

# To turn on/off Denial of service (DOS) prevention checks
dos_enable = false

# Cut-through is disabled by default on all chips with the exception of
# Spectrum. On Spectrum cut-through cannot be disabled.
#cut_through_enable = false

# Enable resilient hashing
#resilient_hash_enable = FALSE

# Resilient hashing flowset entries per ECMP group
# Valid values - 64, 128, 256, 512, 1024
#resilient_hash_entries_ecmp = 128

# Enable symmetric hashing
#symmetric_hash_enable = TRUE

# Set sflow/sample ingress cpu packet rate and burst in packets/sec
# Values: {0..16384}
#sflow.rate = 16384  
#sflow.burst = 16384

#Specify the maximum number of paths per route entry.
#  Maximum paths supported is 200.
#  Default value 0 takes the number of physical ports as the max path size.
#ecmp_max_paths = 0

#Specify the hash seed for Equal cost multipath entries
# Default value 0
# Value Rang: {0..4294967295}
#ecmp_hash_seed = 42

# Specify the forwarding table resource allocation profile, applicable
# only on platforms that support universal forwarding resources.
#
# /usr/cumulus/sbin/cl-rsource-query reports the allocated table sizes
# based on the profile setting.
#
#   Values: one of {'default', 'l2-heavy', 'v4-lpm-heavy', 'v6-lpm-heavy'}
#   Default value: 'default'
#   Note: some devices may support more modes, please consult user
#         guide for more details
#
#forwarding_table.profile = default

On switches with Spectrum ASICs, you must enable packet priority remark on the ingress port. A packet received on a remark-enabled port is remarked according to the priority mapping configured on the egress port. If you configure packet priority remark the same way on every port, the default configuration example above is correct. However, per-port customized configurations require two port groups: one for the ingress ports and one for the egress ports, as below:

remark.port_group_list = [ingress_remark_group, egress_remark_group]
remark.ingress_remark_group.packet_priority_remark_set = [dscp]
remark.remark_port_group.port_set = swp1-swp4,swp6
remark.egress_remark_group.port_set = swp10-swp20
remark.egress_remark_group.cos_0.priority_remark.dscp = [2]
remark.egress_remark_group.cos_1.priority_remark.dscp = [10]
remark.egress_remark_group.cos_2.priority_remark.dscp = [18]
remark.egress_remark_group.cos_3.priority_remark.dscp = [26]
remark.egress_remark_group.cos_4.priority_remark.dscp = [34]
remark.egress_remark_group.cos_5.priority_remark.dscp = [42]
remark.egress_remark_group.cos_6.priority_remark.dscp = [50]
remark.egress_remark_group.cos_7.priority_remark.dscp = [58]

On Broadcom switches, if you modify the configuration in the /etc/cumulus/datapath/traffic.conf file, you must restart switchd for the changes to take effect; run the cumulus@switch:~$ sudo systemctl restart switchd.service command.

On Mellanox switches with the Spectrum ASIC, the following options in the /etc/cumulus/datapath/traffic.conf file do not require you to restart switchd. However, you must run the echo 1 > /cumulus/switchd/config/traffic/reload command after you change the options.

Configure Traffic Marking through ACL Rules

You can mark traffic for egress packets through iptables or ip6tables rule classifications. To enable these rules, you do one of the following:

To enable traffic marking, use cl-acltool. Add the -p option to specify the location of the policy file. By default, if you do not include the -p option, cl-acltool looks for the policy file in /etc/cumulus/acl/policy.d/.

The iptables-/ip6tables-based marking is supported with the following action extension:

-j SETQOS --set-dscp 10 --set-cos 5

For ebtables, the setqos keyword must be in lowercase, as in:

[ebtables]
-A FORWARD -o swp5 -j setqos --set-cos 5

You can specify one of the following targets for SETQOS/setqos:

Option Description
--set-cos INT Sets the datapath resource/queuing class value. Values are defined in IEEE P802.1p.
--set-dscp value Sets the DSCP field in packet header to a value, which can be either a decimal or hex value.
--set-dscp-class class Sets the DSCP field in the packet header to the value represented by the DiffServ class value. This class can be EF, BE or any of the CSxx or AFxx classes.

You can specify either --set-dscp or --set-dscp-class, but not both.

Here are two example rules:

[iptables]
-t mangle -A FORWARD --in-interface swp+ -p tcp --dport bgp -j SETQOS --set-dscp 10 --set-cos 5

[ip6tables]
-t mangle -A FORWARD --in-interface swp+ -j SETQOS --set-dscp 10

You can put the rule in either the mangle table or the default filter table; the mangle table and filter table are put into separate TCAM slices in the hardware.

To put the rule in the mangle table, include -t mangle; to put the rule in the filter table, omit -t mangle.

Priority Flow Control

Priority flow control, as defined in the IEEE 802.1Qbb standard, provides a link-level flow control mechanism that can be controlled independently for each Class of Service (CoS) with the intention to ensure no data frames are lost when congestion occurs in a bridged network.

PFC is not supported on switches with the Helix4 ASIC.

PFC is a layer 2 mechanism that prevents congestion by throttling packet transmission. When PFC is enabled for received packets on a set of switch ports, the switch detects congestion in the ingress buffer of the receiving port and signals the upstream switch to stop sending traffic. If the upstream switch has PFC enabled for packet transmission on the designated priorities, it responds to the downstream switch and stops sending those packets for a period of time.

PFC operates between two adjacent neighbor switches; it does not provide end-to-end flow control. However, when an upstream neighbor throttles packet transmission, it could build up packet congestion and propagate PFC frames further upstream: eventually the sending server could receive PFC frames and stop sending traffic for a time.

The PFC mechanism can be enabled for individual switch priorities on specific switch ports for RX and/or TX traffic. The switch port’s ingress buffer occupancy is used to measure congestion. If congestion is present, the switch transmits flow control frames to the upstream switch. Packets with priority values that do not have PFC configured are not counted during congestion detection; neither do they get throttled by the upstream switch when it receives flow control frames.

PFC congestion detection is implemented on the switch using xoff and xon threshold values for the specific ingress buffer which is used by the targeted switch priorities. When a packet enters the buffer and the buffer occupancy is above the xoff threshold, the switch transmits an Ethernet PFC frame to the upstream switch to signal packet transmission should stop. When the buffer occupancy drops below the xon threshold, the switch sends another PFC frame upstream to signal that packet transmission can resume. (PFC frames contain a quanta value to indicate a timeout value for the upstream switch: packet transmission can resume after the timer has expired, or when a PFC frame with quanta == 0 is received from the downstream switch.)

After the downstream switch has sent a PFC frame upstream, it continues to receive packets until the upstream switch receives and responds to the PFC frame. The downstream ingress buffer must be large enough to store those additional packets after the xoff threshold has been reached.

Priority flow control is fully supported on both Broadcom and Mellanox switches.

PFC is disabled by default in Cumulus Linux. To enable priority flow control (PFC), you must configure the following settings in the /etc/cumulus/datapath/traffic.conf file on the switch:

The following configuration example shows PFC configured for ports swp1 through swp4 and swp6:

# to configure priority flow control on a group of ports:
# -- assign cos value(s) to the cos list
# -- add or replace a port group names in the port group list
# -- for each port group in the list
#    -- populate the port set, e.g.
#       swp1-swp4,swp8,swp50s0-swp50s3
#    -- set a PFC buffer size in bytes for each port in the group
#    -- set the xoff byte limit (buffer limit that triggers PFC frame transmit to start)
#    -- set the xon byte delta (buffer limit that triggers PFC frame transmit to stop)
#    -- enable PFC frame transmit and/or PFC frame receive
# priority flow control
pfc.port_group_list = [pfc_port_group]
pfc.pfc_port_group.cos_list = []
pfc.pfc_port_group.port_set = swp1-swp4,swp6
pfc.pfc_port_group.port_buffer_bytes = 25000
pfc.pfc_port_group.xoff_size = 10000
pfc.pfc_port_group.xon_delta = 2000
pfc.pfc_port_group.tx_enable = true
pfc.pfc_port_group.rx_enable = true

Port Groups

A port group refers to one or more sequences of contiguous ports. You can define multiple port groups by adding:

You can specify the set of ports in a port group in comma-separate sequences of contiguous ports; you can see which ports are contiguous in the /var/lib/cumulus/porttab file. The syntax supports:

...
swp2
swp3
swp4
swp5
swp6s0
swp6s1
swp6s2
swp6s3
swp7
...

On a Broadcom switch, restart switchd with the sudo systemctl restart switchd.service command to allow the PFC configuration changes to take effect. On a Mellanox switch with the Spectrum ASIC, restarting switchd is not necessary.

The PAUSE frame is a flow control mechanism that halts the transmission of the transmitter for a specified period of time. A server or other network node within the data center may be receiving traffic faster than it can handle it, thus the PAUSE frame. In Cumulus Linux, you can configure individual ports to execute link pause by:

Link pause is disabled by default. To enabling link pause, you must configure settings in the /etc/cumulus/datapath traffic.conf file.

What’s the difference between link pause and priority flow control?

  • Priority flow control is applied to an individual priority group for a specific ingress port.
  • Link pause (also known as port pause or global pause) is applied to all the traffic for a specific ingress port.

Here is an example configuration that enables both types of link pause for swp1 through swp4 and swp6:

# to configure pause on a group of ports:
# -- add or replace port group names in the port group list
# -- for each port group in the list
#    -- populate the port set, e.g.
#       swp1-swp4,swp8,swp50s0-swp50s3
#    -- set a pause buffer size in bytes for each port in the group
#    -- set the xoff byte limit (buffer limit that triggers pause frames transmit to start)
#    -- set the xon byte delta (buffer limit that triggers pause frames transmit to stop)

# link pause
link_pause.port_group_list = [pause_port_group]
link_pause.pause_port_group.port_set = swp1-swp4,swp6
link_pause.pause_port_group.port_buffer_bytes = 25000
link_pause.pause_port_group.xoff_size = 10000
link_pause.pause_port_group.xon_delta = 2000
link_pause.pause_port_group.rx_enable = true
link_pause.pause_port_group.tx_enable = true

On a Broadcom switch, restart switchd with the sudo systemctl restart switchd.service command to allow the PFC configuration changes to take effect. On a Mellanox switch with the Spectrum ASIC, restarting switchd is not necessary.

Cut-through Mode and Store and Forward Switching

Cut-through mode is disabled in Cumulus Linux by default on switches with Broadcom ASICs. With cut-though mode enabled and link pause is asserted, Cumulus Linux generates a TOVR and TUFL ERROR; certain error counters increment on a given physical port.

cumulus@switch:~$ sudo ethtool -S swp49 | grep Error
HwIfInDot3LengthErrors: 0
HwIfInErrors: 0
HwIfInDot3FrameErrors: 0
SoftInErrors: 0
SoftInFrameErrors: 0
HwIfOutErrors: 35495749
SoftOutErrors: 0

cumulus@switch:~$ sudo ethtool -S swp50 | grep Error
HwIfInDot3LengthErrors: 3038098
HwIfInErrors: 297595762
HwIfInDot3FrameErrors: 293710518

To work around this issue, disable link pause or disable cut-through mode in the /etc/cumulus/datapath/traffic.conf file.

To disable link pause, comment out the link_pause* section in the /etc/cumulus/datapath/traffic.conf file:

cumulus@switch:~$ sudo nano /etc/cumulus/datapath/traffic.conf 
#link_pause.port_group_list = [port_group_0]
#link_pause.port_group_0.port_set = swp45-swp54
#link_pause.port_group_0.rx_enable = true
#link_pause.port_group_0.tx_enable = true

To enable store and forward switching, set cut_through_enable to false in the /etc/cumulus/datapath/traffic.conf file:

cumulus@switch:~$ sudo nano /etc/cumulus/datapath/traffic.conf
cut_through_enable = false

On switches using Broadcom Tomahawk, Trident II, Trident II+, and Trident3 ASICs, Cumulus Linux supports store and forward switching but does not support cut-through mode.

On switches with the Mellanox Spectrum ASIC, Cumulus Linux supports cut-through mode but does not support store and forward switching.

Congestion Notification

Explicit Congestion Notification (ECN) is defined by RFC 3168. ECN enables the Cumulus Linux switch to mark a packet to signal impending congestion instead of dropping the packet, which is how TCP typically behaves when ECN is not enabled.

ECN is a layer 3 end-to-end congestion notification mechanism only. Packets can be marked as ECN-capable transport (ECT) by the sending server. If congestion is observed by any switch while the packet is getting forwarded, the ECT-enabled packet can be marked by the switch to indicate the congestion. The end receiver can respond to the ECN-marked packets by signaling the sending server to slow down transmission. The sending server marks a packet ECT by setting the least 2 significant bits in an IP header DiffServ (ToS) field to 01 or 10. A packet that has the least 2 significant bits set to 00 indicates a non-ECT-enabled packet.

The ECN mechanism on a switch only marks packets to notify the end receiver. It does not take any other action or change packet handling in any way, nor does it respond to packets that have already been marked ECN by an upstream switch.

On Trident II switches only, if ECN is enabled on a specific queue, the ASIC also enables RED on the same queue. If the packet is ECT marked (the ECN bits are 01 or 10), the ECN mechanism executes as described above. However, if it is entering an ECN-enabled queue but is not ECT marked (the ECN bits are 00), then the RED mechanism uses the same threshold and probability values to decide whether to drop the packet. Packets entering a non-ECN-enabled queue do not get marked or dropped due to ECN or RED in any case.

ECN is implemented on the switch using minimum and maximum threshold values for the egress queue length. When a packet enters the queue and the average queue length is between the minimum and maximum threshold values, a configurable probability value will determine whether the packet will be marked. If the average queue length is above the maximum threshold value, the packet is always marked.

The downstream switches with ECN enabled perform the same actions as the traffic is received. If the ECN bits are set, they remain set. The only way to overwrite ECN bits is to set the ECN bits to 11.

ECN is supported on Broadcom Tomahawk, Tomahawk2, Trident II, Trident II+ and Trident3, and Mellanox Spectrum ASICs.

Click to learn how to configure ECN

ECN is disabled by default in Cumulus Linux. You can enable ECN for individual switch priorities on specific switch ports in the /etc/cumulus/datapath/traffic.conf file:

  • Specify the name of the port group in ecn.port_group_list in brackets; for example, ecn.port_group_list = [ecn_port_group].
  • Assign a CoS value to the port group in ecn.ecn_port_group.cos_list. If the CoS value of a packet matches the value of this setting, then ECN is applied. Note that ecn_port_group is the name of a port group you specified above.
  • Populate the port group with its member ports (ecn.ecn_port_group.port_set), where ecn_port_group is the name of the port group you specified above. Congestion is measured on the egress port queue for the ports listed here, using the average queue length: if congestion is present, a packet entering the queue may be marked to indicate that congestion was observed. Marking a packet involves setting the least 2 significant bits in the IP header DiffServ (ToS) field to 11.
  • The switch priority value(s) are mapped to specific egress queues for the target switch ports.
  • The ecn.ecn_port_group.probability value indicates the probability of a packet being marked if congestion is experienced.

The following configuration example shows ECN configured for ports swp1 through swp4 and swp6:

# Explicit Congestion Notification
# to configure ECN on a group of ports:
# -- add or replace port group names in the port group list
# -- assign cos value(s) to the cos list  *ECN will only be applied to traffic matching this COS*
# -- for each port group in the list
#    -- populate the port set, e.g.
#       swp1-swp4,swp8,swp50s0-swp50s3
  ecn.port_group_list = [ecn_port_group]
  ecn.ecn_port_group.cos_list = [0]
  ecn.ecn_port_group.port_set = swp1-swp4,swp6
  ecn.ecn_port_group.min_threshold_bytes = 40000
  ecn.ecn_port_group.max_threshold_bytes = 200000
  ecn.ecn_port_group.probability = 100

On a Broadcom switch, restart switchd with the sudo systemctl restart switchd.service command to allow the PFC configuration changes to take effect. On a Mellanox switch with the Spectrum ASIC, restarting switchd is not necessary.

Check Interface Buffer Status

iptables-extensions man page

Hardware-enabled DDOS Protection

It is crucial to protect the control plane on the switch to ensure that the proper control plane applications have access to the CPU. Failure to do so increases vulnerabilities to a Denial of Service (DOS attack. Cumulus Linux provides control plane protection by default. In addition, you can configure DDOS protection to protect data plane, control plane, and management plane traffic on the switch. You can configure Cumulus Linux to drop packets that match one or more of the following criteria while incurring no performance impact:

DDOS protection is not supported on Broadcom Hurricane2 and Mellanox Spectrum ASICs.

Configure DDOS Protection

  1. Open the /etc/cumulus/datapath/traffic.conf file in a text editor.

  2. Enable DOS prevention checks by setting the dos_enable value to true:

    # To turn on/off Denial of Service (DOS) prevention checks
    dos_enable = true
    
  3. Open the /usr/lib/python2.7/dist-packages/cumulus/__chip_config/bcm/datapath.conf file in a text editor. Set any of the DOS checks to true. For example:

    cumulus@switch:~$ sudo nano /usr/lib/python2.7/dist-packages/cumulus/__chip_config/bcm/datapath.conf
    # Enabling/disabling Denial of service (DOS) prevetion checks
    # To change the default configuration:
    # enable/disable the individual DOS checks.
    dos.sip_eq_dip = true
    dos.smac_eq_dmac = true
    dos.tcp_hdr_partial = true
    dos.tcp_syn_frag = true
    dos.tcp_ports_eq = true
    dos.tcp_flags_syn_fin = true
    dos.tcp_flags_fup_seq0 = true
    dos.tcp_offset1 = true
    dos.tcp_ctrl0_seq0 = true
    dos.udp_ports_eq = true
    dos.icmp_frag = true
    dos.icmpv4_length = true
    dos.icmpv6_length = true
    dos.ipv6_min_frag = true
    

    Configuring any of the following settings affects the BFD echo function. For example, if you enable dos.udp_ports_eq, all the BFD packets are dropped because the BFD protocol uses the same source and destination UDP ports.

    dos.sip_eq_dip
    dos.smac_eq_dmac
    dos.tcp_ctrl0_seq0
    dos.tcp_flags_fup_seq0
    dos.tcp_flags_syn_fin
    dos.tcp_ports_eq
    dos.tcp_syn_frag
    dos.udp_ports_eq
    

  4. Restart switchd:

    cumulus@switch:~$ sudo systemctl restart switchd.service
    

DHCP Relays

DHCP is a client/server protocol that automatically provides IP hosts with IP addresses and other related configuration information. A DHCP relay (agent) is a host that forwards DHCP packets between clients and servers. DHCP relays forward requests and replies between clients and servers that are not on the same physical subnet.

This topic describes how to configure DHCP relays for IPv4 and IPv6. Configurations on the server hosts, DHCP relays, and DHCP server are provided using the following topology:

The dhcpd and dhcrelay services are disabled by default. After you finish configuring the DHCP relays and servers, you need to start those services. If you intend to run these services within a VRF, follow these steps.

Configure IPv4 DHCP Relays

To configure IPv4 DHCP relays, run the following commands.

You configure a DHCP relay on a per-VLAN basis, specifying the SVI, not the parent bridge. In the example below, you specify vlan1 as the SVI for VLAN 1 but you do not specify the bridge named bridge in this case.

Specify the IP address of each DHCP server and the interfaces that are used as the uplinks. In the example commands below, the DHCP server IP address is 172.16.1.102, VLAN 1 (the SVI is vlan1) and the uplinks are swp51 and swp52. As per RFC 3046, you can specify as many server IP addresses that can fit in 255 octets. You can specify each address only once.

cumulus@switch:~$ net add dhcp relay interface swp51
cumulus@switch:~$ net add dhcp relay interface swp52
cumulus@switch:~$ net add dhcp relay interface vlan1
cumulus@switch:~$ net add dhcp relay server 172.16.1.102
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

These commands create the following configuration in the /etc/default/isc-dhcp-relay file:

SERVERS="172.16.1.102"
INTF_CMD="-i vlan1 -i swp51 -i swp52"
OPTIONS=""

Enable, then restart the dhcrelay service so the configuration persists between reboots:

cumulus@switch:~$ sudo systemctl enable dhcrelay.service
cumulus@switch:~$ sudo systemctl restart dhcrelay.service
  1. Edit the /etc/default/isc-dhcp-relay file to add the IP address of the DHCP server and both interfaces participating in DHCP relay (facing the server and facing the client). In the example below, the DHCP server IP address is 172.16.1.102, VLAN 1 (the SVI is vlan1) and the uplinks are swp51 and swp52. If the client-facing interface is a bridge port, specify the switch virtual interface (SVI) name if using a VLAN-aware bridge (for example, bridge.100), or the bridge name if using traditional bridging (for example, br100).

    cumulus@switch:~$ sudo nano /etc/default/isc-dhcp-relay
    SERVERS="172.16.1.102"
    INTF_CMD="-i vlan1 -i swp51 -i swp52"
    OPTIONS=""
    
  2. Enable then restart the dhcrelay service so that the configuration persists between reboots:

    cumulus@switch:~$ sudo systemctl enable dhcrelay.service
    cumulus@switch:~$ sudo systemctl restart dhcrelay.service
    

To see the DHCP relay status, use the systemctl status dhcrelay.service command:

cumulus@switch:~$ sudo systemctl status dhcrelay.service
● dhcrelay.service - DHCPv4 Relay Agent Daemon
    Loaded: loaded (/lib/systemd/system/dhcrelay.service; enabled)
    Active: active (running) since Fri 2016-12-02 17:09:10 UTC; 2min 16s ago
      Docs: man:dhcrelay(8)
Main PID: 1997 (dhcrelay)
    CGroup: /system.slice/dhcrelay.service
            └─1997 /usr/sbin/dhcrelay --nl -d -q -i vlan1 -i swp51 -i swp52 172.16.1.102

DHCP Agent Information Option (Option 82)

Cumulus Linux supports DHCP Agent Information Option 82, which allows a DHCP relay to insert circuit or relay specific information into a request that is being forwarded to a DHCP server. Two sub-options are provided:

To enable the DHCP Agent Information Option, you configure the -a option. By default, when you enable this option, the Circuit ID is the printable name of the interface on which the client request is received, typically an SVI. The Remote ID is the System MAC of the device on which DHCP relay is running.

NCLU commands are not currently available for this feature. Use the following Linux commands.

Make sure to restart the dhcrelay service to apply the new configuration:

cumulus@switch:~$ sudo systemctl restart dhcrelay.service

Control the Gateway IP Address with RFC 3527

When DHCP relay is required in an environment that relies on an anycast gateway (such as EVPN), a unique IP address is necessary on each device for return traffic. By default, in a BGP unnumbered environment with DHCP relay, the source IP address is set to the loopback IP address and the gateway IP address (giaddr) is set as the SVI IP address. However with anycast traffic, the SVI IP address is not unique to each rack; it is typically shared amongst all racks. Most EVPN ToR deployments only possess a single unique IP address, which is the loopback IP address.

RFC 3527 enables the DHCP server to react to these environments by introducing a new parameter to the DHCP header called the link selection sub-option, which is built by the DHCP relay agent. The link selection sub-option takes on the normal role of the giaddr in relaying to the DHCP server which subnet is correlated to the DHCP request. When using this sub-option, the giaddr continues to be present but only relays the return IP address that is to be used by the DHCP server; the giaddr becomes the unique loopback IP address.

When enabling RFC 3527 support, you can specify an interface, such as the loopback interface or a switch port interface to be used as the giaddr. The relay picks the first IP address on that interface. If the interface has multiple IP addresses, you can specify a specific IP address for the interface.

RFC 3527 is supported for IPv4 DHCP relays only.

The following illustration demonstrates how you can control the giaddr with RFC 3527.

To enable RFC 3527 support and control the giaddr, run the following commands.

  1. Run the net add dhcp relay giaddr-interface command with the interface/IP address you want to use. The following example uses the first IP address on the loopback interface as the giaddr:

    cumulus@switch:~$ net add dhcp relay giaddr-interface lo
    

    The above command creates the following configuration in the /etc/default/isc-dhcp-relay file:

    # Additional options that are passed to the DHCP relay daemon?
    OPTIONS="-U lo"
    

The first IP address on the loopback interface is typically the 127.0.0.1 address. Use more specific syntax, as shown in the next example.

The following example uses IP address 10.0.0.1 on the loopback interface as the giaddr:

cumulus@switch:~$ net add dhcp relay giaddr-interface lo 10.0.0.1

The above command creates the following configuration in the /etc/default/isc-dhcp-relay file:

# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-U 10.0.0.1%lo"

The following example uses the first IP address on swp2 as the giaddr:

   cumulus@switch:~$ net add dhcp relay giaddr-interface swp2

The above command creates the following configuration in the /etc/default/isc-dhcp-relay file:

# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-U swp2"

The following example uses IP address 10.0.0.3 on swp2 as the giaddr:

cumulus@switch:~$ net add dhcp relay giaddr-interface swp2 10.0.0.3

The above command creates the following configuration in the /etc/default/isc-dhcp-relay file:

# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-U 10.0.0.3%swp2"
  1. Restart the dhcrelay service to apply the configuration change:

    cumulus@switch:~$ sudo systemctl restart dhcrelay.service
    
  1. Edit the /etc/default/isc-dhcp-relay file and provide the -U option with the interface or IP address you want to use as the giaddr. The following example uses the first IP address on the loopback interface as the giaddr:

    cumulus@switch:~$ sudo nano /etc/default/isc-dhcp-relay
    ...
    # Additional options that are passed to the DHCP relay daemon?
    OPTIONS="-U lo"
    

The first IP address on the loopback interface is typically the 127.0.0.1 address. Use more specific syntax, as shown in the next example.

The following example uses IP address 10.0.0.1 on the loopback interface as the giaddr:

cumulus@switch:~$ sudo nano /etc/default/isc-dhcp-relay
...
# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-U 10.0.0.1%lo"

The following example uses the first IP address on swp2 as the giaddr:

cumulus@switch:~$ sudo nano /etc/default/isc-dhcp-relay
...
# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-U swp2"

The following example uses IP address 10.0.0.3 on swp2 as the giaddr:

cumulus@switch:~$ sudo nano /etc/default/isc-dhcp-relay
...
# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-U 10.0.0.3%swp2"
  1. Restart the dhcrelay service to apply the configuration change :

    cumulus@switch:~$ sudo systemctl restart dhcrelay.service
    

When enabling RFC 3527 support, you can specify an interface such as the loopback interface or swp interface for the gateway address. The interface you use must be reachable in the tenant VRF that it is servicing and must be unique to the switch. In EVPN symmetric routing, fabrics running an anycast gateway that use the same SVI IP address on multiple leaf switches need a unique IP address for the VRF interface and must include the layer 3 VNI for this VRF in the DHCP Relay configuration. For example:

cumulus@leaf01:mgmt:~$ cat /etc/default/isc-dhcp-relay-RED
SERVERS="10.1.10.104"
INTF_CMD=" -i vlan10 -i vlan20 -i vlan4001"
OPTIONS="-U RED"

Gateway IP Address as Source IP for Relayed DHCP Packets (Advanced)

You can configure the dhcrelay service to forward IPv4 (only) DHCP packets to a DHCP server and ensure that the source IP address of the relayed packet is the same as the gateway IP address.

This option impacts all relayed IPv4 packets globally.

To use the gateway IP address as the source IP address:

Run these commands:

cumulus@leaf:~$ net add dhcp relay use-giaddr-as-src
cumulus@leaf:~$ net pending
cumulus@leaf:~$ net commit
  1. Edit the /etc/default/isc-dhcp-relay file to add --giaddr-src to the OPTIONS line. An example is shown below.

    cumulus@switch:~$ sudo nano /etc/default/isc-dhcp-relay
    SERVERS="172.16.1.102"
    INTF_CMD="-i vlan1 -i swp51 -i swp52 -U swp2"
    OPTIONS="--giaddr-src"
    
  2. Restart the dhcrelay service to apply the configuration change :

    cumulus@switch:~$ sudo systemctl restart dhcrelay.service
    

Configure IPv6 DHCP Relays

NCLU commands are not currently available to configure IPv6 relays.

  1. Edit the /etc/default/isc-dhcp-relay6 file to add the upstream and downstream interfaces. In the example below, the SVI is vlan1, and the interfaces are swp51 and swp52.

    cumulus@switch:$ sudo nano /etc/default/isc-dhcp-relay6 
    SERVERS=" -u 2001:db8:100::2%swp51 -u 2001:db8:100::2%swp52"
    INTF_CMD="-l vlan1"
    
  2. Enable, then restart the dhcrelay6 service so that the configuration persists between reboots:

    cumulus@switch:~$ sudo systemctl enable dhcrelay6.service
    cumulus@switch:~$ sudo systemctl restart dhcrelay6.service
    

To see the status of the IPv6 DHCP relay, use the systemctl status dhcrelay6.service command:

cumulus@switch:~$ sudo systemctl status dhcrelay6.service
● dhcrelay6.service - DHCPv6 Relay Agent Daemon
    Loaded: loaded (/lib/systemd/system/dhcrelay6.service; disabled)
    Active: active (running) since Fri 2016-12-02 21:00:26 UTC; 1s ago
      Docs: man:dhcrelay(8)
  Main PID: 6152 (dhcrelay)
    CGroup: /system.slice/dhcrelay6.service
            └─6152 /usr/sbin/dhcrelay -6 --nl -d -q -l vlan1 -u 2001:db8:100::2 swp51 -u 2001:db8:100::2 swp52

Configure Multiple DHCP Relays

Cumulus Linux supports multiple DHCP relay daemons on a switch to enable relaying of packets from different bridges to different upstream interfaces.

To configure multiple DHCP relay daemons on a switch:

  1. Create a configuration file in the /etc/default directory for each DHCP relay daemon. Use the naming scheme isc-dhcp-relay-<dhcp-name> for IPv4 or isc-dhcp-relay6-<dhcp-name> for IPv6. An example configuration file for IPv4 is shown below:

    # Defaults for isc-dhcp-relay initscript
    # sourced by /etc/init.d/isc-dhcp-relay
    # installed at /etc/default/isc-dhcp-relay by the maintainer scripts
    
    #
    # This is a POSIX shell fragment
    #
    
    # What servers should the DHCP relay forward requests to?
    SERVERS="102.0.0.2"
    # On what interfaces should the DHCP relay (dhrelay) serve DHCP requests?
    # Always include the interface towards the DHCP server.
    # This variable requires a -i for each interface configured above.
    # This will be used in the actual dhcrelay command
    # For example, "-i eth0 -i eth1"
    INTF_CMD="-i swp2s2 -i swp2s3"
    
    # Additional options that are passed to the DHCP relay daemon?
    OPTIONS=""
    

    An example configuration file for IPv6 is shown below:

    # Defaults for isc-dhcp-relay6 initscript
    # sourced by /etc/init.d/isc-dhcp-relay6
    # installed at /etc/default/isc-dhcp-relay6 by the maintainer scripts
    
    #
    # This is a POSIX shell fragment
    #
    
    # Specify upstream and downstream interfaces
    # For example, "-u eth0 -l swp1"
    INTF_CMD=""
    
    # Additional options that are passed to the DHCP relay daemon?
    OPTIONS=""
    
  2. Run the following command to start a dhcrelay instance, where <dhcp-name> is the instance name or number.

    cumulus@switch:~$ sudo systemctl start dhcrelay@<dhcp-name>
    

Configure a DHCP Relay with VRR

The configuration procedure for DHCP relay with VRR is the same as documented above.

The DHCP relay must run on the SVI and not on the -v0 interface.

Troubleshooting

If you are experiencing issues with DHCP relay, you can check if there is a problem with systemd:

The above commands manually activate the DHCP relay process and they do not persist when you reboot the switch.

To see how DHCP relay is working on your switch, run the journalctl command:

cumulus@switch:~$ sudo journalctl -l -n 20 | grep dhcrelay
Dec 05 20:58:55 leaf01 dhcrelay[6152]: sending upstream swp52
Dec 05 20:58:55 leaf01 dhcrelay[6152]: sending upstream swp51
Dec 05 20:58:55 leaf01 dhcrelay[6152]: Relaying Reply to fe80::4638:39ff:fe00:3 port 546 down.
Dec 05 20:58:55 leaf01 dhcrelay[6152]: Relaying Reply to fe80::4638:39ff:fe00:3 port 546 down.
Dec 05 21:03:55 leaf01 dhcrelay[6152]: Relaying Renew from fe80::4638:39ff:fe00:3 port 546 going up.
Dec 05 21:03:55 leaf01 dhcrelay[6152]: sending upstream swp52
Dec 05 21:03:55 leaf01 dhcrelay[6152]: sending upstream swp51
Dec 05 21:03:55 leaf01 dhcrelay[6152]: Relaying Reply to fe80::4638:39ff:fe00:3 port 546 down.
Dec 05 21:03:55 leaf01 dhcrelay[6152]: Relaying Reply to fe80::4638:39ff:fe00:3 port 546 down.

To specify a time period with the journalctl command, use the --since flag:

cumulus@switch:~$ sudo journalctl -l --since "2 minutes ago" | grep dhcrelay
Dec 05 21:08:55 leaf01 dhcrelay[6152]: Relaying Renew from fe80::4638:39ff:fe00:3 port 546 going up.
Dec 05 21:08:55 leaf01 dhcrelay[6152]: sending upstream swp52
Dec 05 21:08:55 leaf01 dhcrelay[6152]: sending upstream swp51

Configuration Errors

If you configure DHCP relays by editing the /etc/default/isc-dhcp-relay file manually instead of running NCLU commands, you might introduce configuration errors that can cause the switch to crash.

For example, if you see an error similar to the following, there might be a space between the DHCP server address and the interface used as the uplink.

Core was generated by /usr/sbin/dhcrelay --nl -d -i vx-40 -i vlan100 10.0.0.4 -U 10.0.1.2  %vlan120.
Program terminated with signal SIGSEGV, Segmentation fault.

To resolve the issue, manually edit the /etc/default/isc-dhcp-relay file to remove the space, then run the systemctl restart dhcrelay.service command to restart the dhcrelay service and apply the configuration change.

Caveats and Errata

Interface Names Cannot Be Longer than 14 Characters

The dhcrelay command does not bind to an interface if the interface’s name is longer than 14 characters. To work around this issue, change the interface name to be 14 or fewer characters if dhcrelay is required to bind to it.

This is a known limitation in dhcrelay.

DHCP Servers

A DHCP Server automatically provides and assigns IP addresses and other network parameters to client devices. It relies on the Dynamic Host Configuration Protocol to respond to broadcast requests from clients.

This topic describes how to configure a DHCP server for IPv4 and IPv6. Configurations on the hosts, DHCP relay and DHCP server are provided using the following topology. The DHCP server is a switch running Cumulus Linux; however, the DHCP server can also be located on a dedicated server in your environment.

The dhcpd and dhcrelay services are disabled by default. After you finish configuring the DHCP relays and servers, you need to start those services. If you intend to run these services within a VRF, including the management VRF, follow these steps.

For information about DHCP relays, refer to DHCP Relays.

Configure the DHCP Server on Cumulus Linux Switches

To configure the DHCP server on a Cumulus Linux switch for IPv4 and IPv6, you need to edit the /etc/dhcp/dhcp.conf and /etc/dhcp/dhcpd6.conf configuration files. Sample configurations are provided as a starting point.

You must include two pools in the DHCP configuration files:

Configure the IPv4 DHCP Server

In a text editor, edit the /etc/dhcp/dhcpd.conf file. Use following configuration as an example:

cumulus@switch:~$ cat /etc/dhcp/dhcpd.conf
ddns-update-style none;

default-lease-time 600;
max-lease-time 7200;

subnet 10.0.100.0 netmask 255.255.255.0 {
}
subnet 10.0.1.0 netmask 255.255.255.0 {
      range 10.0.1.50 10.0.1.60;
}

Edit the /etc/default/isc-dhcp-server configuration file so that the DHCP server launches when the system boots. Here is an example configuration:

cumulus@switch:~$ cat /etc/default/isc-dhcp-server
DHCPD_CONF="-cf /etc/dhcp/dhcpd.conf"

INTERFACES="swp1"

Enable and start the dhcpd service:

cumulus@switch:~$ sudo systemctl enable dhcpd.service
cumulus@switch:~$ sudo systemctl start dhcpd.service

Configure the IPv6 DHCP Server

In a text editor, edit the /etc/dhcp/dhcpd6.conf file. Use following configuration as an example:

cumulus@switch:~$ cat /etc/dhcp/dhcpd6.conf
ddns-update-style none;

default-lease-time 600;
max-lease-time 7200;

subnet6 2001:db8:100::/64 {
}
subnet6 2001:db8:1::/64 {
    range6 2001:db8:1::100 2001:db8:1::200;
}

Edit the /etc/default/isc-dhcp-server6 file so that the DHCP server launches when the system boots. Here is an example configuration:

cumulus@switch:~$ cat /etc/default/isc-dhcp-server6
DHCPD_CONF="-cf /etc/dhcp/dhcpd6.conf"

INTERFACES="swp1"

Enable and start the dhcpd6 service:

cumulus@switch:~$ sudo systemctl enable dhcpd6.service
cumulus@switch:~$ sudo systemctl start dhcpd6.service

Assign Port-Based IP Addresses

You can assign an IP address and other DHCP options based on physical location or port regardless of MAC address to clients that are attached directly to the Cumulus Linux switch through a switch port. This is helpful when swapping out switches and servers; you can avoid the inconvenience of collecting the MAC address and sending it to the network administrator to modify the DHCP server configuration.

Edit the /etc/dhcp/dhcpd.conf file and add the interface name ifname to assign an IP address through DHCP. The following provides an example:

host myhost {
    ifname "swp1" ;
    fixed-address 10.10.10.10 ;
}

Troubleshooting

The DHCP server determines if a DHCP request is a relay or a non-relay DHCP request. You can run the following command to see the DHCP request:

cumulus@server02:~$ sudo tail /var/log/syslog | grep dhcpd
2016-12-05T19:03:35.379633+00:00 server02 dhcpd: Relay-forward message from 2001:db8:101::1 port 547, link address 2001:db8:101::1, peer address fe80::4638:39ff:fe00:3
2016-12-05T19:03:35.380081+00:00 server02 dhcpd: Advertise NA: address 2001:db8:1::110 to client with duid 00:01:00:01:1f:d8:75:3a:44:38:39:00:00:03 iaid = 956301315 valid for 600 seconds
2016-12-05T19:03:35.380470+00:00 server02 dhcpd: Sending Relay-reply to 2001:db8:101::1 port 547

802.1X Interfaces

The IEEE 802.1X protocol provides a method of authenticating a client (called a supplicant) over wired media. It also provides access for individual MAC addresses on a switch (called the authenticator) after those MAC addresses have been authenticated by an authentication server, typically a RADIUS (Remote Authentication Dial In User Service, defined by RFC 2865) server.

A Cumulus Linux switch acts as an intermediary between the clients connected to the wired ports and the authentication server, which is reachable over the existing network. EAPOL (Extensible Authentication Protocol (EAP) over LAN - EtherType value of 0x888E, defined by RFC 3748) operates on top of the data link layer; the switch uses EAPOL to communicate with supplicants connected to the switch ports.

Cumulus Linux implements 802.1X through the Debian hostapd package, which has been modified to provide the PAE (port access entity).

Supported Features and Limitations

Configure the RADIUS Server

Before you configure any interfaces for 802.1X, configure the RADIUS server.

Do not use a Cumulus Linux switch as the RADIUS server.

To add a popular and freely available RADIUS server called FreeRADIUS on a Debian server, do the following:

root@radius:~# apt-get update
root@radius:~# apt-get install freeradius

When installed and configured, the FreeRADIUS server can serve Cumulus Linux running hostapd as a RADIUS client.

For more information, see the FreeRADIUS documentation.

Configure 802.1X Interfaces

All the 802.1X interfaces share the same RADIUS server settings. Make sure you configure the RADIUS server before you configure the 802.1X interfaces. See Configure the RADIUS Server above.

To configure an 802.1X interface, you need to set the following parameters, then enable 802.1X on the interface:

Configure 802.1X Interfaces for a VLAN-aware Bridge

NCLU handles all the 802.1X interface configuration, updating hostapd and other components so you do not have to manually modify configuration files.

  1. Create a simple interface bridge configuration on the switch and add the switch ports that are members of the bridge. You can use glob syntax to add a range of interfaces. The MAB and parking VLAN configurations require interfaces to be bridge access ports. The VLAN-aware bridge must be named bridge and there can be only one VLAN-aware bridge on a switch.

    cumulus@switch:~$ net add bridge bridge ports swp1-4
    
  2. Add the 802.1X RADIUS server IP address and shared secret:

    cumulus@switch:~$ net add dot1x radius server-ip 127.0.0.1
      cumulus@switch:~$ net add dot1x radius shared-secret mysecret
    

    You can specify a VRF for outgoing RADIUS accounting and authorization packets. The following example specifies a VRF called blue:

    cumulus@switch:~$ net add dot1x radius server-ip 127.0.0.1 vrf blue
    cumulus@switch:~$ net add dot1x radius shared-secret mysecret
    
  3. Enable 802.1X on the interfaces, then review and commit the new configuration:

    cumulus@switch:~$ net add interface swp1-4 dot1x
    cumulus@switch:~$ net pending
    cumulus@switch:~$ net commit
    

    To assign a tagged VLAN for voice devices and assign different VLANs to the devices based on authorization, run these commands:

    cumulus@switch:~$ net add interface swp1-4 dot1x voice-enable
    cumulus@switch:~$ net add interface swp1-4 dot1x voice-enable vlan 200
    cumulus@switch:~$ net pending 
    cumulus@switch:~$ net commit
    
  1. Edit the /etc/network/interfaces file to create a simple interface bridge configuration on the switch and add the switch ports that are members of the bridge. The MAB and parking VLAN configurations require interfaces to be bridge access ports. The VLAN-aware bridge must be named bridge and there can be only one VLAN-aware bridge on a switch. The following example shows that swp1 thru swp4 are members of the bridge.

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    ...
    auto bridge
    iface bridge
        bridge-ports swp1 swp2 swp3 swp4
        bridge-vlan-aware yes
    ...
    
  2. Edit the /etc/hostapd.conf file to configure 802.1X settings. The example below sets:

    • The IP address of the 802.1X RADIUS server to 127.0.0.1 (auth_server_addr=127.0.0.1). You can specify a VRF for outgoing RADIUS accounting and authorization packets (for example, to specify a VRF called blue: auth_server_addr=127.0.0.1%blue).
    • The shared secret to mysecret (auth_server_shared_secret=mysecret).
    • 802.1X on swp1 thru swp4 (interfaces=swp1,swp2,swp3,swp4).
    cumulus@switch:~$ sudo nano /etc/hostapd.conf
    ...
    interfaces=swp1,swp2,swp3,swp4
    mab_interfaces=
    parking_vlan_interfaces=
    parking_vlan_id=
    mab_activation_delay=30
    eap_reauth_period=0
    eap_send_identity=0
    ctrl_interface=/var/run/hostapd
    nas_identifier=localhost
    auth_server_addr=127.0.0.1
    auth_server_port=1812
    auth_server_shared_secret=mysecret
    acct_server_addr=
    acct_server_port=1813
    acct_server_shared_secret=mysecret
    ...
    
  3. Enable then restart the hostapd service so that the configuration persists between reboots:

    cumulus@switch:~$ sudo systemctl enable hostapd
    cumulus@switch:~$ sudo systemctl restart hostapd
    

Configure 802.1X Interfaces for a Traditional Mode Bridge

NCLU and hostapd might change traditional mode configurations on the bridge-ports line in the /etc/network/interface file by adding or deleting special 802.1X traditional mode bridge-ports configuration stanzas in /etc/network/interfaces.d/. The source configuration command in /etc/network/interfaces must include these special configuration filenames. It must include at least source /etc/network/interfaces.d/*.intf so that these files are sourced during an ifreload.

  1. Create uplink ports. The following example uses bonds:

    cumulus@switch:~$ net add bond bond1 bond slaves swp5-6
    cumulus@switch:~$ net add bond bond2 bond slaves swp7-8
    
  2. Create a traditional mode bridge configuration on the switch and add the switch ports that are members of the bridge. A traditional bridge cannot be named **** bridge as that name is reserved for the single VLAN-aware bridge on the switch. You can use glob syntax to add a range of interfaces.

    cumulus@switch:~$ net add bridge bridge1 ports swp1-4
    
  3. Create bridge associations with the parking VLAN ID and the dynamic VLAN IDs. In this example, 600 is used for the parking VLAN ID and 700 is used for the dynamic VLAN ID:

    cumulus@switch:~$ net add bridge br-vlan600 ports bond1.600
    cumulus@switch:~$ net add bridge br-vlan700 ports bond2.700
    
  4. Add the 802.1X RADIUS server IP address and shared secret:

    cumulus@switch:~$ net add dot1x radius server-ip 127.0.0.1
    cumulus@switch:~$ net add dot1x radius shared-secret mysecret
    

    You can specify a VRF for outgoing RADIUS accounting and authorization packets.The following example specifies a VRF called blue:

    cumulus@switch:~$ net add dot1x radius server-ip 127.0.0.1 vrf blue
    cumulus@switch:~$ net add dot1x radius shared-secret mysecret
    
  5. Enable 802.1X on the interfaces, then review and commit the new configuration:

    cumulus@switch:~$ net add interface swp1-2 dot1x
    cumulus@switch:~$ net pending
    cumulus@switch:~$ net commit
    
  1. Edit the /etc/network/interfaces file to create uplink ports and create a traditional mode bridge configuration on the switch.

    a. Create uplink ports. The following example uses bonds:

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    ...
    auto bond1
    iface bond1
          bond-slaves swp5 swp6
    auto bond2
    iface bond2
          bond-slaves swp7 swp8
    ...
    

    b. Create a traditional mode bridge configuration on the switch and add the switch ports that are members of the bridge. You must also create bridge associations with the parking VLAN ID and the dynamic VLAN IDs. In this example, 600 is used for the parking VLAN ID and 700 is used for the dynamic VLAN ID.

    A traditional bridge cannot be named **** bridge as that name is reserved for the single VLAN-aware bridge on the switch. You can use glob syntax to add a range of interfaces.

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    ...
    auto bridge1
    iface bridge1
          bridge-ports swp1-swp4
          bridge-vlan-aware no
    
    auto br-vlan600
    iface br-vlan600
          bridge-ports bond1.600
          bridge-vlan-aware no
    
    auto br-vlan700
    iface br-vlan700
          bridge-ports bond1.700
          bridge-vlan-aware no
    
  2. Edit the /etc/hostapd.conf file to configure 802.1X settings. The example below sets:

    • The IP address of the 802.1X RADIUS server to 127.0.0.1 (auth_server_addr=127.0.0.1). You can specify a VRF for outgoing RADIUS accounting and authorization packets (for example, to specify a VRF called blue: auth_server_addr=127.0.0.1%blue).
    • The shared secret to mysecret (auth_server_shared_secret=mysecret).
    • 802.1X on swp1, swp2, swp3, and swp4 (interfaces=swp1,swp2,swp3,swp4).
    cumulus@switch:~$ sudo nano /etc/hostapd.conf
    ...
    interfaces=swp1,swp2,swp3,swp4
    mab_interfaces=
    parking_vlan_interfaces=
    parking_vlan_id=
    mab_activation_delay=30
    eap_reauth_period=0
    eap_send_identity=0
    ctrl_interface=/var/run/hostapd
    nas_identifier=localhost
    auth_server_addr=127.0.0.1
    auth_server_port=1812
    auth_server_shared_secret=mysecret
    acct_server_addr=
    acct_server_port=1813
    acct_server_shared_secret=testing123
    ...
    
  3. Enable then restart the hostapd service so that the configuration persists between reboots:

    cumulus@switch:~$ sudo systemctl enable hostapd
    cumulus@switch:~$ sudo systemctl restart hostapd
    

Configure the Linux Supplicants

A sample FreeRADIUS server configuration needs to contain the entriesfor users host1 and host2 on swp1 and swp2 for them to be placed in a VLAN.

host1 Cleartext-Password := "host1password"
host2 Cleartext-Password := "host2password"

After being configured, each supplicant needs the proper credentials:

user@host1:~# cat /etc/wpa_supplicant.conf

ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=0
eapol_version=2
ap_scan=0
network={
        key_mgmt=IEEE8021X
        eap=TTLS MD5
        identity="host1"
        anonymous_identity="host1"
        password="host1password"
        phase1="auth=MD5"
        eapol_flags=0
}
user@host2:~# cat /etc/wpa_supplicant.conf

ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=0
eapol_version=2
ap_scan=0
network={
        key_mgmt=IEEE8021X
        eap=TTLS MD5
        identity="host2"
        anonymous_identity="host2"
        password="host2password"
        phase1="auth=MD5"
        eapol_flags=0
  }

To test that a supplicant (client) can communicate with the Cumulus Linux Authenticator switch, install the wpasupplicant package:

root@radius:~# apt-get update
root@radius:~# apt-get install wpasupplicant

And run the following command from the supplicant:

root@host1:/home/cumulus# wpa_supplicant -c /etc/wpa_supplicant.conf -D wired -i swp1
Successfully initialized wpa_supplicant
swp1: Associated with 01:80:c2:00:00:03
swp1: CTRL-EVENT-EAP-STARTED EAP authentication started
swp1: CTRL-EVENT-EAP-PROPOSED-METHOD vendor=0 method=4
swp1: CTRL-EVENT-EAP-METHOD EAP vendor 0 method 4 (MD5) selected
swp1: CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully
swp1: CTRL-EVENT-CONNECTED - Connection to 01:80:c2:00:00:03 compl

Or from another supplicant:

root@host2:/home/cumulus# wpa_supplicant -c /etc/wpa_supplicant.conf -D wired -i swp1
Successfully initialized wpa_supplicant
swp1: Associated with 01:80:c2:00:00:03
swp1: CTRL-EVENT-EAP-STARTED EAP authentication started
swp1: CTRL-EVENT-EAP-PROPOSED-METHOD vendor=0 method=4
swp1: CTRL-EVENT-EAP-METHOD EAP vendor 0 method 4 (MD5) selected
swp1: CTRL-EVENT-EAP-SUCCESS EAP authentication completed successfully
swp1: CTRL-EVENT-CONNECTED - Connection to 01:80:c2:00:00:03 comp

Configure Accounting and Authentication Ports

You can configure the accounting and authentication ports in Cumulus Linux. The default values are 1813 for the accounting port and 1812 for the authentication port. You can also change the reauthentication period for Extensible Authentication Protocol (EAP). The period defaults to 0 (no re-authentication is performed by the switch).

To use different ports:

The following example commands change:

  • The authentication port to 2812
  • The accounting port to 2813
  • The reauthentication period for EAP to 86400
cumulus@switch:~$ net add dot1x radius authentication-port 2812
cumulus@switch:~$ net add dot1x radius accounting-port 2813
cumulus@switch:~$ net add dot1x eap-reauth-period 86400
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/hostapd.conf file to change the accounting and authentication ports.The example below sets:

  • The accounting port to 2813 (auth_server_port=2813)
  • The authentication port to 2812
  • The reauthentication period for EAP to 86400 (eap_reauth_period=86400)
cumulus@switch:~$ sudo nano /etc/hostapd.conf
...
eap_reauth_period=86400
eap_send_identity=0
ctrl_interface=/var/run/hostapd
nas_identifier=localhost
auth_server_addr=127.0.0.1
auth_server_port=2812
auth_server_shared_secret=mysecret
acct_server_addr=
acct_server_port=2813
...

Restart the hostapd service :

cumulus@switch:~$ sudo systemctl restart hostapd

Configure MAC Authentication Bypass

MAC authentication bypass (MAB) enables bridge ports to allow devices to bypass authentication based on their MAC address. This is useful for devices that do not support PAE, such as printers or phones. You can change the MAB activation delay from the default of 30 seconds, but the delay must be between 5 and 30 seconds. After the delay limit is reached, the port enters MAB mode.

MAB must be configured on both the RADIUS server and the RADIUS client (the Cumulus Linux switch).

When using a VLAN-aware bridge, the switch port must be part of bridge named bridge.

To configure MAB:

Enable a bridge port for MAB. The following example commands enable bridge port swp1 for MAB:

cumulus@switch:~$ net add interface swp1 dot1x mab
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/hostapd.conf file to enable a bridge port for MAB. The following example enables bridge port swp1 for MAB.

cumulus@switch:~$ sudo nano hostapd.conf
...
mab_interfaces=swp1
parking_vlan_interfaces=
parking_vlan_id=
mab_activation_delay=20
...

Restart the hostapd service:

cumulus@switch:~$ sudo systemctl restart hostapd

Configure a Parking VLAN

If a non-authorized supplicant tries to communicate with the switch, you can route traffic from that device to a different VLAN and associate that VLAN with one of the switch ports to which the supplicant is attached.

For VLAN-aware bridges, the parking VLAN is assigned by manipulating the PVID of the switch port. For traditional mode bridges, Cumulus Linux identifies the bridge associated with the parking VLAN ID and moves the switch port into that bridge. If an appropriate bridge is not found for the move, the port remains in an unauthenticated state where no packets can be received or transmitted.

When using a VLAN-aware bridge, the switch port must be part of bridge named bridge.

Run the following commands:

cumulus@switch:~$ net add dot1x parking-vlan-id 777
cumulus@switch:~$ net add interface swp1 dot1x parking-vlan
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

If the authentication for swp1 fails, the port is moved to the parking VLAN:

cumulus@switch:~$ net show dot1x interface swp1 details

Interface  MAC Address        Attribute                     Value
---------  -----------------  ----------------------------  -----------------
swp1       00:02:00:00:00:08  Status Flags                  [PARKED_VLAN]
                              Username                      vlan60
                              Authentication Type           MD5
                              VLAN                          777
                              Session Time (seconds)        24772
                              EAPOL Frames RX               9
                              EAPOL Frames TX               12
                              EAPOL Start Frames RX         1
                              EAPOL Logoff Frames RX        0
                              EAPOL Response ID Frames RX   4
                              EAPOL Response Frames RX      8
                              EAPOL Request ID Frames TX    4
                              EAPOL Request Frames TX       8
                              EAPOL Invalid Frames RX       0
                              EAPOL Length Error Frames Rx  0
                              EAPOL Frame Version           2
                              EAPOL Auth Last Frame Source  00:02:00:00:00:08
                              EAPOL Auth Backend Responses  8
                              RADIUS Auth Session ID        C2FED91A39D8D605

The following output shows a parking VLAN association failure. A VLAN association failure only occurs with traditional mode bridges when there is no traditional bridge available with a parking VLAN ID-tagged subinterface (notice the [UNKNOWN_BR] status in the output):

cumulus@switch:~$ net show dot1x interface swp3 details

Interface  MAC Address        Attribute                     Value
---------  -----------------  ----------------------------  -------------------------
swp1       00:02:00:00:00:08  Status Flags                  [PARKED_VLAN][UNKNOWN_BR]
                              Username                      vlan60
                              Authentication Type           MD5
                              VLAN                          777
                              Session Time (seconds)        24599
                              EAPOL Frames RX               3
                              EAPOL Frames TX               3
                              EAPOL Start Frames RX         1
                              EAPOL Logoff Frames RX        0
                              EAPOL Response ID Frames RX   1
                              EAPOL Response Frames RX      2
                              EAPOL Request ID Frames TX    1
                              EAPOL Request Frames TX       2
                              EAPOL Invalid Frames RX       0
                              EAPOL Length Error Frames Rx  0
                              EAPOL Frame Version           2
                              EAPOL Auth Last Frame Source  00:02:00:00:00:08
                              EAPOL Auth Backend Responses  2
                              RADIUS Auth Session ID        C2FED91A39D8D605

Edit the /etc/hostapd.conf file to add the parking VLAN ID and port. The following example adds the parking VLAN ID 777 (parking_vlan_id=777) and port swp1 (parking_vlan_interfaces=swp1)

cumulus@switch:~$ sudo nano hostapd.conf
...
parking_vlan_interfaces=swp1
parking_vlan_id=777
...

If the authentication for swp1 fails, the port is moved to the parking VLAN.

Configure Dynamic VLAN Assignments

A common requirement for campus networks is to assign dynamic VLANs to specific users in combination with IEEE 802.1x. After authenticating a supplicant, the user is assigned a VLAN based on the RADIUS configuration.

For VLAN-aware bridges, the dynamic VLAN is assigned by manipulating the PVID of the switch port. For traditional mode bridges, Cumulus Linux identifies the bridge associated with the dynamic VLAN ID and moves the switch port into that bridge. If an appropriate bridge is not found for the move, the port remains in an unauthenticated state where no packets can be received or transmitted.

To enable dynamic VLAN assignment globally, where VLAN attributes sent from the RADIUS server are applied to the bridge:

Run the following commands:

cumulus@switch:~$ net add dot1x dynamic-vlan
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

You can specify the require option in the command so that VLAN attributes are required. If VLAN attributes do not exist in the access response packet returned from the RADIUS server, the user is not authorized and has no connectivity. If the RADIUS server returns VLAN attributes but the user has an incorrect password, the user is placed in the parking VLAN (if you have configured parking VLAN).

cumulus@switch:~$ net add dot1x dynamic-vlan require
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following example shows a typical RADIUS configuration (shown for FreeRADIUS, not typically configured or run on the Cumulus Linux device) for a user with dynamic VLAN assignment:

# # VLAN 100 Client Configuration for Freeradius RADIUS Server.
# # This is not part of the CL configuration.
vlan100client Cleartext-Password := "client1password"
      Service-Type = Framed-User,
      Tunnel-Type = VLAN,
      Tunnel-Medium-Type = "IEEE-802",
      Tunnel-Private-Group-ID = 100

Verify the configuration (notice the [AUTHORIZED] status in the output):

cumulus@switch:~$ net show dot1x interface swp1 details

Interface  MAC Address        Attribute                     Value
---------  -----------------  ----------------------------  --------------------------
swp1       00:02:00:00:00:08  Status Flags                  [DYNAMIC_VLAN][AUTHORIZED]
                              Username                      host1
                              Authentication Type           MD5
                              VLAN                          888
                              Session Time (seconds)        799
                              EAPOL Frames RX               3
                              EAPOL Frames TX               3
                              EAPOL Start Frames RX         1
                              EAPOL Logoff Frames RX        0
                              EAPOL Response ID Frames RX   1
                              EAPOL Response Frames RX      2
                              EAPOL Request ID Frames TX    1
                              EAPOL Request Frames TX       2
                              EAPOL Invalid Frames RX       0
                              EAPOL Length Error Frames Rx  0
                              EAPOL Frame Version           2
                              EAPOL Auth Last Frame Source  00:02:00:00:00:08
                              EAPOL Auth Backend Responses  2
                              RADIUS Auth Session ID        939B1A53B624FC56
cumulus@switch:~$ net show dot1x interface summary

Interface  MAC Address        Username      State         Authentication Type  MAB  VLAN
---------  -----------------  ------------  ------------  -------------------  ---  ----
swp1       00:02:00:00:00:08  000200000008  AUTHORIZED    unknown              NO   888

The following output shows a dynamic VLAN association failure. VLAN association failure only occurs with traditional mode bridges when there is no traditional bridge available with a parking VLAN ID-tagged subinterface in it (notice the [UNKNOWN_BR] status in the output):

cumulus@switch:~$ net show dot1x interface swp1 details

Interface  MAC Address        Attribute                     Value
---------  -----------------  ----------------------------  --------------------------------------
swp1       00:02:00:00:00:08  Status Flags                  [DYNAMIC_VLAN][AUTHORIZED][UNKNOWN_BR]
                              Username                      host2
                              Authentication Type           MD5
                              VLAN                          888
                              Session Time (seconds)        11
                              EAPOL Frames RX               3
                              EAPOL Frames TX               3
                              EAPOL Start Frames RX         1
                              EAPOL Logoff Frames RX        0
                              EAPOL Response ID Frames RX   1
                              EAPOL Response Frames RX      2
                              EAPOL Request ID Frames TX    1
                              EAPOL Request Frames TX       2
                              EAPOL Invalid Frames RX       0
                              EAPOL Length Error Frames Rx  0
                              EAPOL Frame Version           2
                              EAPOL Auth Last Frame Source  00:02:00:00:00:08
                              EAPOL Auth Backend Responses  2
                              RADIUS Auth Session ID        BDF731EF2B765B78

Edit the /etc/hostapd.conf file to add the following options:

  • dynamic_vlan=1 (Specify dynamic_vlan=2 if you want VLAN attributes to be required. If VLAN attributes do not exist in the access response packet returned from the RADIUS server, the user is not authorized and has no connectivity. If the RADIUS server returns VLAN attributes but the user has an incorrect password, the user is placed in the parking VLAN, if you have configured parking VLAN).
  • radius_das_port=
  • radius_das_time_window=300
  • radius_das_require_event_timestamp=1
  • radius_das_require_message_authenticator=1

Remove the eap_send_identity=0 option. For example:

cumulus@switch:~$ sudo nano /etc/hostapd.conf
eap_server=0
ieee8021x=1
driver=wired
dynamic_vlan=1
interfaces=swp1,swp2,swp3,swp4
mab_interfaces=
parking_vlan_interfaces=swp1
parking_vlan_id=777
mab_activation_delay=30
eap_reauth_period=0
ctrl_interface=/var/run/hostapd
nas_identifier=localhost
auth_server_addr=127.0.0.1
auth_server_port=1812
auth_server_shared_secret=mysecret
acct_server_addr=
acct_server_port=1813
acct_server_shared_secret=
radius_das_port=
radius_das_time_window=300
radius_das_require_event_timestamp=1
radius_das_require_message_authenticator=1

Restart the hostapd service :

cumulus@switch:~$ sudo systemctl restart hostapd

The following example shows a typical RADIUS configuration (shown for FreeRADIUS, not typically configured or run on the Cumulus Linux device) for a user with dynamic VLAN assignment:

# # VLAN 100 Client Configuration for Freeradius RADIUS Server.
# # This is not part of the CL configuration.
vlan100client Cleartext-Password := "client1password"
      Service-Type = Framed-User,
      Tunnel-Type = VLAN,
      Tunnel-Medium-Type = "IEEE-802",
      Tunnel-Private-Group-ID = 100

To disable dynamic VLAN assignment, where VLAN attributes sent from the RADIUS server are ignored and users are authenticated based on existing credentials:

Run the net del dot1x dynamic-vlan command:

cumulus@switch:~$ net del dot1x dynamic-vlan
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/hostapd.conf file to remove the following options:

  • dynamic_vlan=1
  • radius_das_port=
  • radius_das_time_window=300
  • radius_das_require_event_timestamp=1
  • radius_das_require_message_authenticator=1

Add the eap_send_identity=0 option. The following example shows the options in the /etc/hostapd.conf file

cumulus@switch:~$ sudo nano /etc/hostapd.conf
eap_server=0
ieee8021x=1
driver=wired
interfaces=
mab_interfaces=
parking_vlan_interfaces=swp1
parking_vlan_id=777
mab_activation_delay=30
eap_reauth_period=0
eap_send_identity=0
ctrl_interface=/var/run/hostapd
nas_identifier=localhost
auth_server_addr=127.0.0.1
auth_server_port=1812
auth_server_shared_secret=mysecret
acct_server_addr=
acct_server_port=1813
acct_server_shared_secret=

Restart the hostapd service.

cumulus@switch:~$ sudo systemctl restart hostapd

Enabling or disabling dynamic VLAN assignment restarts hostapd, which forces existing, authorized users to re-authenticate.

Configure MAC Addresses per Port

You can specify the maximum number of authenticated MAC addresses allowed on a port.

Run the net add dot1x max-number-stations <value> command. You can specify any number between 0 and 255. The default value is 4.

cumulus@switch:~$ net add dot1x max-number-stations 10
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/hostapd.conf file to add the max_num_sta= option. For example:

cumulus@switch:~$ sudo nano /etc/hostapd.conf
eap_server=0
ieee8021x=1
driver=wired
dynamic_vlan=1
max_num_sta=10
interfaces=swp1,swp2,swp3,swp4
mab_interfaces=
parking_vlan_interfaces=swp1
parking_vlan_id=777
mab_activation_delay=30
eap_reauth_period=0
ctrl_interface=/var/run/hostapd
nas_identifier=localhost
auth_server_addr=127.0.0.1
auth_server_port=1812
auth_server_shared_secret=mysecret
acct_server_addr=
acct_server_port=1813
acct_server_shared_secret=
radius_das_port=
radius_das_time_window=300
radius_das_require_event_timestamp=1
radius_das_require_message_authenticator=1

Restart the hostapd service :

cumulus@switch:~$ sudo systemctl restart hostapd

Configure EAP Requests from the Switch

Cumulus Linux provides the send-eap-request-id option, which you can use to trigger EAP packets to be sent from the host side of a connection. For example, this option is required in a configuration where a PC connected to a phone attempts to send EAP packets to the switch via the phone but the PC does not receive a response from the switch (the phone might not be ready to forward packets to the switch after a reboot). Because the switch does not receive EAP packets, it attempts to authorize the PC with MAB instead of waiting for the packets. In this case, the PC might be placed into a parking VLAN to isolate it. To remove the PC from the parking VLAN, the switch needs to send an EAP request to the PC to trigger EAP.

To configure the switch send an EAP request, run these commands:

cumulus@switch:~$ net add dot1x send-eap-request-id
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Only run this command if MAB is configured on an interface.

The PC might attempt 802.1X authorization through the bridged connection in the back of the phone before the phone completes MAB authorization. In this case, 802.1X authorization fails.

The net del dot1x send-eap-request-id command disables this feature.

RADIUS Change of Authorization and Disconnect Requests

Extensions to the RADIUS protocol (RFC 5176) enable the Cumulus Linux switch to act as a Dynamic Authorization Server (DAS) by listening for Change of Authorization (CoA) requests from the RADIUS server (Dynamic Authorization Client (DAC)) and taking action when needed, such as bouncing a port or terminating a user session. The IEEE 802.1x server (hostapd) running on Cumulus Linux has been adapted to handle these additional, unsolicited RADIUS requests.

Configure DAS

To configure DAS, provide the UDP port (3799 is the default port), the IP address, and the secret key for the DAS client.

The following example commands set the UDP port to the default port, the IP address of the DAS client to 10.0.2.228, and the secret key to myclientsecret:

cumulus@switch:~$ net add dot1x radius das-port default
cumulus@switch:~$ net add dot1x radius das-client-ip 10.0.2.228 das-client-secret mysecret123
cumulus@switch:~$ net commit

You can specify a VRF so that incoming RADIUS disconnect and CoA commands are received and acknowledged on the correct interface when VRF is configured. The following example specifies VRF blue:

cumulus@switch:~$ net add dot1x radius das-port default
cumulus@switch:~$ net add dot1x radius das-client-ip 10.0.2.228 vrf blue das-client-secret mysecret123
cumulus@switch:~$ net commit

You can configure up to four DAS clients to be authorized to send CoA commands. For example:

cumulus@switch:~$ net add dot1x radius das-port default
cumulus@switch:~$ net add dot1x radius das-client-ip 10.20.250.53 das-client-secret mysecret1
cumulus@switch:~$ net add dot1x radius das-client-ip 10.0.1.7 das-client-secret mysecret2
cumulus@switch:~$ net add dot1x radius das-client-ip 10.20.250.99 das-client-secret mysecret3
cumulus@switch:~$ net add dot1x radius das-client-ip 10.10.0.0.2 das-client-secret mysecret4
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To see DAS configuration information, run the net show configuration dot1x command. For example:

cumulus@switch:~$ net show configuration dot1x

dot1x
  mab-activation-delay 5
  eap-reauth-period 0
  parking-vlan-id 100
  dynamic-vlan

  radius
    accounting-port 1813
    das-client-ip 10.0.2.228 das-client-secret mysecret123
    authentication-port 1812
    das-port 3799

Edit the /etc/hostapd.conf file to add the following options to configure the UDP port, the IP address and secret key for the DAS client:

  • radius_das_port
  • radius_das_client

The following example sets the UDP port to the default port, the IP address of the DAS client to 10.0.2.228, and the secret key to mysecret123:

cumulus@switch:~$ sudo nano /etc/hostapd.conf
...
radius_das_port=3799
radius_das_client=10.0.2.228 mysecret123

You can specify a VRF so that incoming RADIUS disconnect and CoA commands are received and acknowledged on the correct interface when VRF is configured. The following example specifies VRF blue:

cumulus@switch:~$ sudo nano /etc/hostapd.conf
...
radius_das_port=3799
radius_das_client=10.0.2.228%blue mysecret123

You can configure up to four DAS clients to be authorized to send CoA commands. For example:

cumulus@switch:~$ sudo nano /etc/hostapd.conf
...
radius_das_port=3799
radius_das_client=10.20.250.53 mysecret1 
radius_das_client=10.0.1.7 mysecret2
radius_das_client=10.20.250.99 mysecret3
radius_das_client=10.10.0.0.2 mysecret4

Restart the hostapd service:

cumulus@switch:~$ sudo systemctl restart hostapd

You can disable DAS in Cumulus Linux at any time by running the following commands:

cumulus@switch:~$ net del dot1x radius das-port
cumulus@switch:~$ net del dot1x radius das-client-ip
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/hostapd.conf file to remove the following options:

  • radius_das_port
  • radius_das_client

Restart the hostapd service:

cumulus@switch:~$ sudo systemctl restart hostapd

Terminate a User Session

From the DAC, users can create a disconnect message using the radclient utility (included in the Debian freeradius-utils package) on the RADIUS server or other authorized client. A disconnect message is sent as an unsolicited RADIUS Disconnect-Request packet to the switch to terminate a user session and discard all associated session context. The Disconnect-Request packet is used when the RADIUS server wants to disconnect the user after the session has been accepted by the RADIUS Access-Accept packet.

This is an example of a disconnect message created using the radclient utility:

$ echo "Acct-Session-Id=D91FE8E51802097" > disconnect-packet.txt
$ ## OPTIONAL ## echo "User-Name=somebody" >> disconnect-packet.txt
$ echo "Message-Authenticator=1" >> disconnect-packet.txt
$ echo "Event-Timestamp=1532974019" >> disconnect-packet.txt
# now send the packet with the radclient utility (from freeradius-utils deb package)
$ cat disconnect-packet.txt | radclient -x 10.0.0.1:3799 disconnect myclientsecret

To prevent unauthorized servers from disconnecting users, the Disconnect-Request packet must include certain identification attributes (described below). For a session to be disconnected, all parameters must match their expected values at the switch. If the parameters do not match, the switch discards the Disconnect-Request packet and sends a Disconnect-NAK (negative acknowledgment message).

RADIUS DAS: Acct-Session-Id match
RADIUS DAS: No matches remaining after User-Name check
hostapd_das_find_global_sta: checking ifname=swp2
RADIUS DAS: No matches remaining after Acct-Session-Id check
RADIUS DAS: No matching session found
DAS: Session not found for request from 10.10.0.1:58385
DAS: Reply to 10.10.0.1:58385

The following is an example of the Disconnect-Request packet received by the switch:

RADIUS Protocol
Code: Disconnect-Request (40)
Packet identifier: 0x4f (79)
Length: 53
Authenticator: c0e1fa75fdf594a1cfaf35151a43c6a7
Attribute Value Pairs
AVP: t=Acct-Session-Id(44) l=17 val=D91FE8E51802097
AVP: t=User-Name(1) l=10 val=somebody
AVP: t=Message-Authenticator(80) l=18 val=38cb3b6896623b4b7d32f116fa976cdc
AVP: t=Event-Timestamp(55) l=6 val=1532974019
AVP: t=NAS-IP-Address(4) l=6 val=10.0.0.1

Bounce a Port

You can create a CoA bounce-host-port message from the RADIUS server using the radclient utility (included in the Debian freeradius-utils package). The bounce port can cause a link flap on an authentication port, which triggers DHCP renegotiation from one or more hosts connected to the port.

The following is an example of a Cisco AVPair CoA bounce-host-port message sent from the radclient utility:

$ echo "Acct-Session-Id=D91FE8E51802097" > bounce-packet.txt
$ ## OPTIONAL ## echo "User-Name=somebody" >> bounce-packet.txt
$ echo "Message-Authenticator=1" >> bounce-packet.txt
$ echo "Event-Timestamp=1532974019" >> bounce-packet.txt
$ echo "cisco-avpair='subscriber:command=bounce-host-port' " >> bounce-packet.txt
$ cat bounce-packet.txt | radclient -x 10.0.0.1:3799 coa myclientsecret

The message received by the switch is:

RADIUS Protocol
Code: CoA-Request (43)
Packet identifier: 0x3a (58)
Length: 96
Authenticator: 6480d710802329269d5cae6a59bcfb59
Attribute Value Pairs
AVP: t=Acct-Session-Id(44) l=17 val=D91FE8E51802097
Type: 44
Length: 17
Acct-Session-Id: D91FE8E51802097
AVP: t=User-Name(1) l=10 val=somebody
Type: 1
Length: 10
User-Name: somebody
AVP: t=NAS-IP-Address(4) l=6 val=10.0.0.1
Type: 4
Length: 6
NAS-IP-Address: 10.0.0.1
AVP: t=Vendor-Specific(26) l=43 vnd=ciscoSystems(9)
Type: 26
Length: 43
Vendor ID: ciscoSystems (9)
VSA: t=Cisco-AVPair(1) l=37 val=subscriber:command=bounce-host-port
Type: 1
Length: 37
Cisco-AVPair: subscriber:command=bounce-host-port

Configure the NAS IP Address

You can send the NAS IPv4 or IPv6 address in access request and accounting packets. You can only configure one NAS IP address on the switch, which is used for all interface authorizations.

To configure the NAS IP address, run the following commands:

The following command example sets the NAS IP address to 10.0.0.1:

cumulus@switch:~$ net add dot1x radius nas-ip-address 10.0.0.1

Edit the /etc/hostapd.conf file and configure the own_ip_addr setting with the NAS IP address:

cumulus@switch:~$ sudo nano /etc/hostapd.conf
...
interfaces=swp1,swp2,swp3,swp4
mab_interfaces=
parking_vlan_interfaces=
parking_vlan_id=
mab_activation_delay=30
eap_reauth_period=0
eap_send_identity=0
ctrl_interface=/var/run/hostapd
own_ip_addr=10.0.0.1

Enable, then restart the hostapd service so that the configuration persists between reboots:

cumulus@switch:~$ sudo systemctl enable hostapd
cumulus@switch:~$ sudo systemctl restart hostapd

To delete the NAS IP address, either run the NCLU net del dot1x radius nas-ip-address command or edit the /etc/hostapd.conf file.

Troubleshooting

To check connectivity between two supplicants, ping one host from the other:

root@host1:/home/cumulus# ping 198.150.0.2
PING 11.0.0.2 (11.0.0.2) 56(84) bytes of data.
64 bytes from 11.0.0.2: icmp_seq=1 ttl=64 time=0.604 ms
64 bytes from 11.0.0.2: icmp_seq=2 ttl=64 time=0.552 ms
^C
--- 11.0.0.2 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1000ms
rtt min/avg/max/mdev = 0.552/0.578/0

You can run net show dot1x with the following options for more data:

To check to see which MAC addresses have been authorized by RADIUS:

cumulus@switch:~$ net show dot1x macs
Interface     Attribute   Value
-----------   -------------  -----------------
swp1          MAC Addresses  00:02:00:00:00:01
swp2          No Data
swp3          No Data
swp4          No Data

To check the port detail counters:

cumulus@switch:~$ net show dot1x port-details

Interface  Attribute                                  Value
-----------  ----------------------------------------     ---------
swp1        Mac Addresses                              00:02:00:00:00:01
            authMultiSessionId                         96703ADC82D77DF2
            connected_time                             182
            dot1xAuthEapolFramesRx                     3
            dot1xAuthEapolFramesTx                     3
            dot1xAuthEapolLogoffFramesRx               0
            dot1xAuthEapolReqFramesTx                  2
            dot1xAuthEapolReqIdFramesTx                1
            dot1xAuthEapolRespFramesRx                 2
            dot1xAuthEapolRespIdFramesRx               1
            dot1xAuthEapolStartFramesRx                1
            dot1xAuthInvalidEapolFramesRx              0
            dot1xAuthLastEapolFrameSource              00:02:00:00:00:01
            dot1xAuthLastEapolFrameVersion             2
            dot1xAuthPaeState                          5
            dot1xAuthQuietPeriod                       60
            dot1xAuthReAuthEnabled                     FALSE
            dot1xAuthReAuthPeriod                      0
            dot1xAuthServerTimeout                     30
            dot1xAuthSessionAuthenticMethod            1
            dot1xAuthSessionId                         1B50FE8939FD9F5E
            dot1xAuthSessionTerminateCause             999
            dot1xAuthSessionTime                       182
            dot1xAuthSessionUserName                   testing
            dot1xPaePortProtocolVersion                2
            last_eap_type_as                           4 (MD5)
            last_eap_type_sta                          4 (MD5)

To check RADIUS counters:

cumulus@switch:~$ net show dot1x radius-details swp1

Interface  Attribute                                   Value
-----------  ----------------------------------------    ---------
swp1       radiusAccClientRequests                      1
           radiusAccClientResponses                     1
           radiusAccClientServerPortNumber              1813
           radiusAccServerAddress                       127.0.0.1
           radiusAuthClientAccessAccepts                1
           radiusAuthClientAccessChallenges             1
           radiusAuthClientAccessRejects                0
           radiusAuthClientAccessRequests               0
           radiusAuthClientServerPortNumber             1812
           radiusAuthServerAddress                      127.0.0.1
           radiusAuthServerIndex                        1

...

You can also check logging with the journalctl command:

cumulus@switch:~$ sudo journalctl -f -u hostapd
Apr 19 22:17:11 switch hostapd[12462]: swp1: interface state UNINITIALIZED->ENABLED
Apr 19 22:17:11 switch hostapd[12462]: swp1: AP-ENABLED
Apr 19 22:17:11 switch hostapd[12462]: Reading rule file /etc/cumulus/acl/policy.d/00control_ps ...
Apr 19 22:17:11 switch hostapd[12462]: Processing rules in file /etc/cumulus/acl/policy.d/00...
Apr 19 22:17:12 switch hostapd[12462]: Reading rule file /etc/cumulus/acl/policy.d/100_dot1x...
Apr 19 22:17:12 switch hostapd[12462]: Processing rules in file /etc/cumulus/acl/policy.d/ ..
Apr 19 22:17:12 switch hostapd[12462]: Reading rule file /etc/cumulus/acl/policy.d/99control
Apr 19 22:17:12 switch hostapd[12462]: Processing rules in file /etc/cumulus/acl/policy.d/99
Apr 19 22:17:12 switch hostapd[12462]: Installing acl policy
Apr 19 22:17:12 switch hostapd[12462]: done. 

You can perform more advanced troubleshooting with the following commands.

To increase the debug level in hostapd, copy over the hostapd service file, then add -d, -dd or -ddd to the ExecStart line in the hostapd.service file:

cumulus@switch:~$ cp /lib/systemd/system/hostapd.service /etc/systemd/system/hostapd.service
cumulus@switch:~$ sudo nano /etc/systemd/system/hostapd.service
...
ExecStart=/usr/sbin/hostapd -ddd -c /etc/hostapd.conf
...

To watch debugs with journalctl as supplicants attempt to connect:

cumulus@switch:~$ sudo journalctl -n 1000  -u hostapd      # see the last 1000 lines of hostapd debug logging
cumulus@switch:~$ sudo journalctl -f -u hostapd            # continuous tail of the hostapd daemon debug logging

To check ACL rules in /etc/cumulus/acl/policy.d/100_dot1x_swpX.rules before and after a supplicant attempts to authenticate:

cumulus@switch:~$ sudo cl-acltool -L eb | grep swpXX
cumulus@switch:~$ sudo cl-netstat | grep swpXX           # look at interface counters

To check tc rules in /var/lib/hostapd/acl/tc_swpX.rules with:

cumulus@switch:~$ sudo tc -s filter show dev swpXX parent 1:
cumulus@switch:~$ sudo tc -s filter show dev swpXX parent ffff:

Prescriptive Topology Manager - PTM

In data center topologies, right cabling is a time-consuming endeavor and is error prone. Prescriptive Topology Manager (PTM) is a dynamic cabling verification tool to help detect and eliminate such errors. It takes a Graphviz-DOT specified network cabling plan (something many operators already generate), stored in a topology.dot file, and couples it with runtime information derived from LLDP to verify that the cabling matches the specification. The check is performed on every link transition on each node in the network.

You can customize the topology.dot file to control ptmd at both the global/network level and the node/port level.

PTM runs as a daemon, named ptmd.

For more information, see man ptmd(8).

Supported Features

Configure PTM

ptmd verifies the physical network topology against a DOT-specified network graph file, /etc/ptm.d/topology.dot.

PTM supports undirected graphs.

At startup, ptmd connects to lldpd, the LLDP daemon, over a Unix socket and retrieves the neighbor name and port information. It then compares the retrieved port information with the configuration information that it read from the topology file. If there is a match, it is a PASS, else it is a FAIL.

PTM performs its LLDP neighbor check using the PortID ifname TLV information.

Basic Topology Example

This is a basic example DOT file and its corresponding topology diagram. Use the same topology.dot file on all switches and do not split the file per device; this allows for easy automation by pushing/pulling the same exact file on each device.

graph G {
    "spine1":"swp1" -- "leaf1":"swp1";
    "spine1":"swp2" -- "leaf2":"swp1";
    "spine2":"swp1" -- "leaf1":"swp2";
    "spine2":"swp2" -- "leaf2":"swp2";
    "leaf1":"swp3" -- "leaf2":"swp3";
    "leaf1":"swp4" -- "leaf2":"swp4";
    "leaf1":"swp5s0" -- "server1":"eth1";
    "leaf2":"swp5s0" -- "server2":"eth1";
}

ptmd Scripts

ptmd executes scripts at /etc/ptm.d/if-topo-pass and /etc/ptm.d/if-topo-failfor each interface that goes through a change and runs if-topo-pass when an LLDP or BFD check passes or if-topo-fails when the check fails. The scripts receive an argument string that is the result of the ptmctl command, described in the ptmd commands below.

Modify these default scripts as needed.

Configuration Parameters

You can configure ptmd parameters in the topology file. The parameters are classified as host-only, global, per-port/node and templates.

Host-only Parameters

Host-only parameters apply to the entire host on which PTM is running. You can include the hostnametype host-only parameter, which specifies if PTM uses only the host name (hostname) or the fully-qualified domain name (fqdn) while looking for the self-node in the graph file. For example, in the graph file below PTM ignores the FQDN and only looks for switch04 because that is the host name of the switch on which it is running:

Always wrap the hostname in double quotes; for example, "www.example.com" to prevent ptmd from failing.

To avoid errors when starting the ptmd process, make sure that /etc/hosts and /etc/hostname both reflect the hostname you are using in the topology.dot file.

graph G {
          hostnametype="hostname"
          BFD="upMinTx=150,requiredMinRx=250"
          "cumulus":"swp44" -- "switch04.cumulusnetworks.com":"swp20"
          "cumulus":"swp46" -- "switch04.cumulusnetworks.com":"swp22"
}

In this next example, PTM compares using the FQDN and looks for switch05.cumulusnetworks.com, which is the FQDN of the switch ion which it is running:

graph G {
          hostnametype="fqdn"
          "cumulus":"swp44" -- "switch05.cumulusnetworks.com":"swp20"
          "cumulus":"swp46" -- "switch05.cumulusnetworks.com":"swp22"
}

Global Parameters

Global parameters apply to every port listed in the topology file. There are two global parameters: LLDP and BFD. LLDP is enabled by default; if no keyword is present, default values are used for all ports. However, BFD is disabled if no keyword is present, unless there is a per-port override configured. For example:

graph G {
          LLDP=""
          BFD="upMinTx=150,requiredMinRx=250,afi=both"
          "cumulus":"swp44" -- "qct-ly2-04":"swp20"
          "cumulus":"swp46" -- "qct-ly2-04":"swp22"
}

Per-port Parameters

Per-port parameters provide finer-grained control at the port level. These parameters override any global or compiled defaults. For example:

graph G {
          LLDP=""
          BFD="upMinTx=300,requiredMinRx=100"
          "cumulus":"swp44" -- "qct-ly2-04":"swp20" [BFD="upMinTx=150,requiredMinRx=250,afi=both"]
          "cumulus":"swp46" -- "qct-ly2-04":"swp22"
}

Templates

Templates provide flexibility in choosing different parameter combinations and applying them to a given port. A template instructs ptmd to reference a named parameter string instead of a default one. There are two parameter strings ptmd supports:

For example:

graph G {
          LLDP=""
          BFD="upMinTx=300,requiredMinRx=100"
          BFD1="upMinTx=200,requiredMinRx=200"
          BFD2="upMinTx=100,requiredMinRx=300"
          LLDP1="match_type=ifname"
          LLDP2="match_type=portdescr"
          "cumulus":"swp44" -- "qct-ly2-04":"swp20" [BFD="bfdtmpl=BFD1", LLDP="lldptmpl=LLDP1"]
          "cumulus":"swp46" -- "qct-ly2-04":"swp22" [BFD="bfdtmpl=BFD2", LLDP="lldptmpl=LLDP2"]
          "cumulus":"swp46" -- "qct-ly2-04":"swp22"
}

In this template, LLDP1 and LLDP2 are templates for LLDP parameters. BFD1 and BFD2 are templates for BFD parameters.

Supported BFD and LLDP Parameters

ptmd supports the following BFD parameters:

The following is an example of a topology with BFD applied at the port level:

graph G {
          "cumulus-1":"swp44" -- "cumulus-2":"swp20" [BFD="upMinTx=300,requiredMinRx=100,afi=v6"]
          "cumulus-1":"swp46" -- "cumulus-2":"swp22" [BFD="detectMult=4"]
}

ptmd supports the following LLDP parameters:

The following is an example of a topology with LLDP applied at the port level:

graph G {
          "cumulus-1":"swp44" -- "cumulus-2":"swp20" [LLDP="match_hostname=fqdn"]
          "cumulus-1":"swp46" -- "cumulus-2":"swp22" [LLDP="match_type=portdescr"]
}

When you specify match_hostname=fqdn, ptmd will match the entire FQDN, (cumulus-2.domain.com in the example below). If you do not specify anything for match_hostname, ptmd matches based on hostname only, (cumulus-3 below), and ignores the rest of the URL:

graph G { 
          "cumulus-1":"swp44" -- "cumulus-2.domain.com":"swp20" [LLDP="match_hostname=fqdn"] 
          "cumulus-1":"swp46" -- "cumulus-3":"swp22" [LLDP="match_type=portdescr"] 
}

Bidirectional Forwarding Detection (BFD)

BFD provides low overhead and rapid detection of failures in the paths between two network devices. It provides a unified mechanism for link detection over all media and protocol layers. Use BFD to detect failures for IPv4 and IPv6 single or multihop paths between any two network devices, including unidirectional path failure detection. For information about configuring BFD using PTM, see BFD.

The FRRouting routing suite enables additional checks to ensure that routing adjacencies are formed only on links that have connectivity conformant to the specification, as determined by ptmd.

You only need to do this to check link state; you do not need to enable PTM to determine BFD status.

When the global ptm-enable option is enabled, every interface has an implied ptm-enable line in the configuration stanza in the interfaces file.

To enable the global ptm-enable option, run the following FRRouting command:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# ptm-enable
switch(config)# end
switch# write memory
switch# exit
cumulus@switch:~$

To disable the checks, delete the ptm-enable parameter from the interface:

cumulus@switch:~$ net del interface swp51 ptm-enable
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh
switch# conf t
switch(config)# interface swp51
switch(config-if)# no ptm-enable
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

If you need to reenable PTM for that interface:

cumulus@switch:~$ net add interface swp51 ptm-enable
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh
switch# conf t
switch(config)# interface swp51
switch(config-if)# ptm-enable

switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

With PTM enabled on an interface, the zebra daemon connects to ptmd over a Unix socket. Any time there is a change of status for an interface, ptmd sends notifications to zebra. Zebra maintains a ptm-status flag per interface and evaluates routing adjacency based on this flag. To check the per-interface ptm-status:

cumulus@switch:~$ net show interface swp1

Interface swp1 is up, line protocol is up
  Link ups:       0    last: (never)
  Link downs:     0    last: (never)
  PTM status: disabled
  vrf: Default-IP-Routing-Table
  index 3 metric 0 mtu 1550 
  flags: <UP,BROADCAST,RUNNING,MULTICAST>
  HWaddr: c4:54:44:bd:01:41
switch# show interface swp1
Interface swp1 is up, line protocol is up
  Link ups:       0    last: (never)
  Link downs:     0    last: (never)
  PTM status: disabled
  vrf: Default-IP-Routing-Table
  index 3 metric 0 mtu 1550 
  flags: <UP,BROADCAST,RUNNING,MULTICAST>
  HWaddr: c4:54:44:bd:01:41
...

ptmd Service Commands

PTM sends client notifications in CSV format.

To start or restart the ptmd service, run the following command. The topology.dot file must be present for the service to start.

cumulus@switch:~$ sudo systemctl start|restart|force-reload ptmd.service

To instruct ptmd to read the topology.dot file again to apply the new configuration to the running state without restarting:

cumulus@switch:~$ sudo systemctl reload ptmd.service

To stop the ptmd service:

cumulus@switch:~$ sudo systemctl stop ptmd.service

To retrieve the current running state of ptmd:

cumulus@switch:~$ sudo systemctl status ptmd.service

ptmctl Commands

ptmctl is a client of ptmd that retrieves the operational state of the ports configured on the switch and information about BFD sessions from ptmd. ptmctl parses the CSV notifications sent by ptmd. See man ptmctl for more information.

ptmctl Examples

The examples below contain the following keywords in the output of the cbl status column:

cbl status Keyword Definition
pass The interface is defined in the topology file, LLDP information is received on the interface, and the LLDP information for the interface matches the information in the topology file.
fail The interface is defined in the topology file, LLDP information is received on the interface, and the LLDP information for the interface does not match the information in the topology file.
N/A The interface is defined in the topology file, but no LLDP information is received on the interface. The interface might be down or disconnected, or the neighbor is not sending LLDP packets.
The N/A and fail status might indicate a wiring problem to investigate.
The N/A status is not shown when you use the -l option with ptmctl; only interfaces that are receiving LLDP information are shown.

For basic output, use ptmctl without any options:

cumulus@switch:~$ sudo ptmctl

-------------------------------------------------------------
port  cbl     BFD     BFD                  BFD    BFD
      status  status  peer                 local  type
-------------------------------------------------------------
swp1  pass    pass    11.0.0.2             N/A    singlehop
swp2  pass    N/A     N/A                  N/A    N/A
swp3  pass    N/A     N/A                  N/A    N/A  

For more detailed output, use the -d option:

cumulus@switch:~$ sudo ptmctl -d

--------------------------------------------------------------------------------------
port  cbl    exp     act      sysname  portID  portDescr  match  last    BFD   BFD
      status nbr     nbr                                  on     upd     Type  state  
--------------------------------------------------------------------------------------
swp45 pass   h1:swp1 h1:swp1  h1       swp1    swp1       IfName 5m: 5s  N/A   N/A
swp46 fail   h2:swp1 h2:swp1  h2       swp1    swp1       IfName 5m: 5s  N/A   N/A

#continuation of the output
-------------------------------------------------------------------------------------------------
BFD   BFD       det_mult  tx_timeout  rx_timeout  echo_tx_timeout  echo_rx_timeout  max_hop_cnt
peer  DownDiag
-------------------------------------------------------------------------------------------------
N/A   N/A       N/A       N/A         N/A         N/A              N/A              N/A
N/A   N/A       N/A       N/A         N/A         N/A              N/A              N/A

To return information on active BFD sessions ptmd is tracking, use the -b option:

cumulus@switch:~$ sudo ptmctl -b

----------------------------------------------------------
port  peer        state  local         type       diag

----------------------------------------------------------
swp1  11.0.0.2    Up     N/A           singlehop  N/A  
N/A   12.12.12.1  Up     12.12.12.4    multihop   N/A

To return LLDP information, use the -l option. It returns only the active neighbors currently being tracked by ptmd.

cumulus@switch:~$ sudo ptmctl -l

---------------------------------------------
port  sysname  portID  port   match  last
                       descr  on     upd
---------------------------------------------
swp45 h1       swp1    swp1   IfName 5m:59s
swp46 h2       swp1    swp1   IfName 5m:59s 

To return detailed information on active BFD sessions ptmd is tracking, use the -b and -d option (results are for an IPv6-connected peer):

cumulus@switch:~$ sudo ptmctl -b -d

----------------------------------------------------------------------------------------
port  peer                 state  local  type       diag  det   tx_timeout  rx_timeout  
                                                          mult
----------------------------------------------------------------------------------------
swp1  fe80::202:ff:fe00:1  Up     N/A    singlehop  N/A   3     300         900
swp1  3101:abc:bcad::2     Up     N/A    singlehop  N/A   3     300         900

#continuation of output
---------------------------------------------------------------------
echo        echo        max      rx_ctrl  tx_ctrl  rx_echo  tx_echo
tx_timeout  rx_timeout  hop_cnt
---------------------------------------------------------------------
0           0           N/A      187172   185986   0        0
0           0           N/A      501      533      0        0

ptmctl Error Outputs

If there are errors in the topology file or there is no session, PTM returns appropriate outputs. Typical error strings are:

Topology file error [/etc/ptm.d/topology.dot] [cannot find node cumulus] -
please check /var/log/ptmd.log for more info

Topology file error [/etc/ptm.d/topology.dot] [cannot open file (errno 2)] -
please check /var/log/ptmd.log for more info

No Hostname/MgmtIP found [Check LLDPD daemon status] -
please check /var/log/ptmd.log for more info

No BFD sessions . Check connections

No LLDP ports detected. Check connections

Unsupported command

For example:

cumulus@switch:~$ sudo ptmctl
-------------------------------------------------------------------------
cmd         error
-------------------------------------------------------------------------
get-status  Topology file error [/etc/ptm.d/topology.dot]
            [cannot open file (errno 2)] - please check /var/log/ptmd.log 
            for more info

If you encounter errors with the topology.dot file, you can use dot (included in the Graphviz package) to validate the syntax of the topology file.

Open the topology file with Graphviz to ensure that it is readable and that the file format is correct.

If you edit topology.dot file from a Windows system, be sure to double check the file formatting; there might be extra characters that keep the graph from working correctly.

Caveats and Errata

When PTMD is incorrectly in a failure state and the Zebra interface is enabled, PIF BGP sessions do not establish the route, but the subinterface on top of it does establish routes.

If the subinterface is configured on the physical interface and the physical interface is incorrectly marked as being in a PTM FAIL state, routes on the physical interface are not processed in FRR, but the subinterface is working.

Port Security

Port security is a layer 2 traffic control feature that enables you to manage network access from end-users. Use port security to:

You can specify what action to take when there is a port security violation (drop packets or put the port into ADMIN down state) and add a timeout for the action to take effect.

  • Port security is supported on Broadcom switches only.
  • Layer 2 interfaces in trunk or access mode are currently supported. However, interfaces in a bond are not supported.

Configure MAC Address Options

To limit port access to a specific MAC address, run the following commands.

The example commands configure swp1 to allow access to MAC address 00:02:00:00:00:05:

cumulus@switch:~$ net add interface swp1 port-security allowed-mac 00:02:00:00:00:05

You can specify only one MAC address with the NCLU command. To specify multiple MAC addresses, set the interface.<port>.port_security.static_mac parameter in the /etc/cumulus/switchd.d/port_security.conf file. See Configure Port Security Manually below.

To enable sticky MAC on a port, where the first learned MAC address on the port is the only MAC address allowed, run the following commands.

You can add a timeout value so that after the time specified, the MAC address ages out and no longer has access to the port. The default aging timeout value is 1800 seconds. You can specify a value between 0 and 3600 seconds.

The example commands enable sticky MAC on interface swp1, set the timeout value to 2000 seconds, and enable aging.

cumulus@switch:~$ net add interface swp1 port-security sticky-mac
cumulus@switch:~$ net add interface swp1 port-security sticky-mac timeout 2000
cumulus@switch:~$ net add interface swp1 port-security sticky-mac aging
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To limit the number of MAC addresses that are allowed to access a port, run the following commands. You can specify a number between 0 and 512. The default is 32.

The example commands configure swp1 to limit access to 40 MAC addresses:

cumulus@switch:~$ net add interface swp1 port-security mac-limit 40
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Configure Security Violation Actions

You can configure the action you want to take when there is a security violation on a port:

You can also set a timeout value between 0 and 3600 seconds for the action to take effect. The default is 1800 seconds.

The following example commands put swp1 into ADMIN down state when there is a security violation and set the timeout value to 3600 seconds:

cumulus@switch:~$ net add interface swp1 port-security violation shutdown
cumulus@switch:~$ net add interface swp1 port-security violation timeout 3600
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Enable Port Security Settings

After you configure the port security settings to suit your needs, you can enable security on a port with the following commands:

cumulus@switch:~$ net add interface swp1 port-security
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To disable port security on a port, run the net del interface <interface> port-security command.

Configure Port Security Manually

You can edit the /etc/cumulus/switchd.d/port_security.conf file manually to configure port security instead of running the NCLU commands shown above. This procedure is useful if you use configuration scripts.

Add the configuration settings you want to use to the /etc/cumulus/switchd.d/port_security.conf file, then restart switchd to apply the changes.

Setting
Description
interface.<port>.port_security.enable 1 enables security on the port. 0 disables security on the port.
interface.<port>.port_security.mac_limit The maximum number of MAC addresses allowed to access the port. You can specify a number between 0 and 512. The default is 32.
interface.<port>.port_security.static_mac The specific MAC addresses allowed to access the port. You can specify multiple MAC addresses. Separate each MAC address with a space.
interface.<port>.port_security.sticky_mac 1 enables sticky MAC, where the first learned MAC address on the port is the only MAC address allowed. 0 disables sticky MAC.
interface.<port>.port_security.sticky_timeout The time period after which the first learned MAC address ages out and no longer has access to the port. The default aging timeout value is 30 minutes. You can specify a value between 0 and 60 minutes.
interface.<port>.port_security.sticky_aging 1 enables sticky MAC aging. 0 disables sticky MAC aging.
interface.<port>.port_security.violation_mode The violation mode: 0 (shutdown) puts a port into ADMIN down state. 1 (restrict) drops packets.
interface.<port>.port_security.violation_timeout The number of seconds after which the violation mode times out. You can specify a value between 0 and 3600 seconds. The default value is 1800 seconds.

An example /etc/cumulus/switchd.d/port_security.conf configuration file is shown here:

cumulus@switch:~$ sudo nano /etc/cumulus/switchd.d/port_security.conf
interface.swp1.port_security.enable = 1
interface.swp1.port_security.mac_limit = 32
interface.swp1.port_security.static_mac = 00:02:00:00:00:05 00:02:00:00:00:06
interface.swp1.port_security.sticky_mac = 1
interface.swp1.port_security.sticky_timeout = 2000
interface.swp1.port_security.sticky_aging = 1
interface.swp1.port_security.violation_mode = 0
interface.swp1.port_security.violation_timeout = 3600
...

Show Port Security Configuration

To show port security settings for all ports:

cumulus@switch:~$ net show port-security
Interface  Port security  MAC limit  Sticky MAC  Sticky MAC aging  Sticky MAC timeout  Violation mode  Timeout
---------  -------------  ---------  ----------  ----------------  ------------------  --------------  -------
swp1       ENABLED        40         ENABLED     ENABLED           2000                Shutdown        3600
swp2       Disabled       NA         NA          NA                NA                  Restrict        1800
swp3       Disabled       NA         NA          NA                NA                  Restrict        1800
swp4       Disabled       NA         NA          NA                NA                  Restrict        1800
swp5       Disabled       NA         NA          NA                NA                  Restrict        1800
swp6       Disabled       NA         NA          NA                NA                  Restrict        1800
...

To show port security settings for a specific port:

cumulus@switch:~$ net show port-security swp1
Interface           swp1
Port security       Enabled
Mac limit           40
Sticky mac          ENABLED
Sticky MAC aging    Enabled
Sticky MAC timeout  1440
Violation mode      Shutdown
Violation timeout   3600
Mac addresses
00:02:00:00:00:05
00:02:00:00:00:06

Layer 2

This section describes layer 2 configuration, such as Ethernet bridging, bonding, spanning tree protocol, multi-chassis link aggregation (MLAG), link layer discovery protocol (LLDP), LACP bypass, virtual router redundancy (VRR) and IGMP and MLD snooping.

Spanning Tree and Rapid Spanning Tree

Spanning tree protocol (STP) identifies links in the network and shuts down redundant links, preventing possible network loops and broadcast radiation on a bridged network. STP also provides redundant links for automatic failover when an active link fails. STP is enabled by default in Cumulus Linux for both VLAN-aware and traditional bridges.

Cumulus Linux supports RSTP, PVST, and PVRST modes:

STP for a Traditional Mode Bridge

Per VLAN Spanning Tree (PVST) creates a spanning tree instance for a bridge. Rapid PVST (PVRST) supports RSTP enhancements for each spanning tree instance. To use PVRST with a traditional bridge, you must create a bridge corresponding to the untagged native VLAN and all the physical switch ports must be part of the same VLAN.

For maximum interoperability, when connected to a switch that has a native VLAN configuration, the native VLAN must be configured to be VLAN 1 only.

STP for a VLAN-aware Bridge

VLAN-aware bridges operate in RSTP mode only. RSTP on VLAN-aware bridges works with other modes in the following ways:

RSTP and STP

If a bridge running RSTP (802.1w) receives a common STP (802.1D) BPDU, it falls back to 802.1D automatically.

RSTP and PVST

The RSTP domain sends BPDUs on the native VLAN, whereas PVST sends BPDUs on a per VLAN basis. For both protocols to work together, you need to enable the native VLAN on the link between the RSTP to PVST domain; the spanning tree is built according to the native VLAN parameters.

The RSTP protocol does not send or parse BPDUs on other VLANs, but floods BPDUs across the network, enabling the PVST domain to maintain its spanning-tree topology and provide a loop-free network.

RSTP and MST

RSTP works with MST seamlessly, creating a single instance of spanning tree that transmits BPDUs on the native VLAN.

RSTP treats the MST domain as one giant switch, whereas MST treats the RSTP domain as a different region. To enable proper communication between the regions, MST creates a Common Spanning Tree (CST) that connects all the boundary switches and forms the overall view of the MST domain. Because changes in the CST need to be reflected in all regions, the RSTP tree is included in the CST to ensure that changes on the RSTP domain are reflected in the CST domain. This does cause topology changes on the RSTP domain to impact the rest of the network but keeps the MST domain informed of every change occurring in the RSTP domain, ensuring a loop-free network.

Configure the root bridge within the MST domain by changing the priority on the relevant MST switch. When MST detects an RSTP link, it falls back into RSTP mode. The MST domain chooses the switch with the lowest cost to the CST root bridge as the CIST root bridge.

RSTP with MLAG

More than one spanning tree instance enables switches to load balance and use different links for different VLANs. With RSTP, there is only one instance of spanning tree. To better utilize the links, you can configure MLAG on the switches connected to the MST or PVST domain and set up these interfaces as an MLAG port. The PVST or MST domain thinks it is connected to a single switch and utilizes all the links connected to it. Load balancing is based on the port channel hashing mechanism instead of different spanning tree instances and uses all the links between the RSTP to the PVST or MST domains. For information about configuring MLAG, see Multi-Chassis Link Aggregation - MLAG.

Optional Configuration

There are a number of ways to customize STP in Cumulus Linux. Exercise caution when changing the settings below to prevent malfunctions in STP loop avoidance.

Spanning Tree Priority

If you have a multiple spanning tree instance (MSTI 0, also known as a common spanning tree, or CST), you can set the tree priority for a bridge. The bridge with the lowest priority is elected the root bridge. The priority must be a number between 0 and 61440, and must be a multiple of 4096. The default is 32768.

To set the tree priority, run the following commands:

The following example command sets the tree priority to 8192:

cumulus@switch:~$ net add bridge stp treeprio 8192
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Configure the tree priority (mstpctl-treeprio) under the bridge stanza in the /etc/network/interfaces file, then run the ifreload -a command. The following example command sets the tree priority to 8192:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    # bridge-ports includes all ports related to VxLAN and CLAG.
    # does not include the Peerlink.4094 subinterface
    bridge-ports bond01 bond02 peerlink vni13 vni24 vxlan4001
    bridge-pvid 1
    bridge-vids 13 24
    bridge-vlan-aware yes
    mstpctl-treeprio 8192
...
cumulus@switch:~$ ifreload -a

Cumulus Linux supports MSTI 0 only. It does not support MSTI 1 through 15.

PortAdminEdge (PortFast Mode)

PortAdminEdge is equivalent to the PortFast feature offered by other vendors. It enables or disables the initial edge state of a port in a bridge.

All ports configured with PortAdminEdge bypass the listening and learning states to move immediately to forwarding.

PortAdminEdge mode might cause loops if it is not used with the BPDU guard feature.

It is common for edge ports to be configured as access ports for a simple end host; however, this is not mandatory. In the data center, edge ports typically connect to servers, which might pass both tagged and untagged traffic.

To configure PortAdminEdge mode:

The following example commands configure PortAdminEdge and BPDU guard for swp5.

cumulus@switch:~$ net add interface swp5 stp bpduguard
cumulus@switch:~$ net add interface swp5 stp portadminedge
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Configure PortAdminEdge and BPDU guard under the switch port interface stanza in the /etc/network/interfaces file, then run the ifreload -a command. The following example configures PortAdminEdge and BPD guard on swp5.

cumulus@switch:~$ sudo nano /etc/netowrk/interfaces
...
auto swp5
iface swp5
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
...
cumulus@switch:~$ sudo ifreload -a

Runtime Configuration (Advanced)

A runtime configuration is non-persistent, which means the configuration you create here does not persist after you reboot the switch.

To configure PortAdminEdge and BPDU guard at runtime, run the following commands:

cumulus@switch:~$ sudo mstpctl setportadminedge br2 swp1 yes
cumulus@switch:~$ sudo mstpctl setbpduguard br2 swp1 yes

PortAutoEdge

PortAutoEdge is an enhancement to the standard PortAdminEdge (PortFast) mode, which allows for the automatic detection of edge ports. PortAutoEdge enables and disables the auto transition to and from the edge state of a port in a bridge.

Edge ports and access ports are not the same. Edge ports transition directly to the forwarding state and skip the listening and learning stages. Upstream topology change notifications are not generated when an edge port link changes state. Access ports only forward untagged traffic; however, there is no such restriction on edge ports, which can forward both tagged and untagged traffic.

When a BPDU is received on a port configured with PortAutoEdge, the port ceases to be in the edge port state and transitions into a normal STP port. When BPDUs are no longer received on the interface, the port becomes an edge port, and transitions through the discarding and learning states before resuming forwarding.

PortAutoEdge is enabled by default in Cumulus Linux.

To disable PortAutoEdge for an interface:

The following example commands disable PortAutoEdge on swp1:

cumulus@switch:~$ net add interface swp1 stp portautoedge no
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the switch port interface stanza in the /etc/network/interfaces file to add the mstpctl-portautoedge no line, then run the ifreload -a command. The following example disables PortAutoEdge on swp1:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto swp1
iface swp1
    alias to Server01
    # Port to Server02
    mstpctl-portautoedge no
...
cumulus@switch:~$ sudo ifreload -a

To reenable PortAutoEdge for an interface:

The following example commands reenable PortAutoEdge on swp1:

cumulus@switch:~$ net del interface swp1 stp portautoedge no
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
Edit the switch port interface stanza in the /etc/network/interfaces file to remove mstpctl-portautoedge no, then run the ifreload -a command.

BPDU Guard

You can configure BPDU guard to protect the spanning tree topology from unauthorized switches affecting the forwarding path. For example, if you add a new switch to an access port off a leaf switch and this new switch is configured with a low priority, it might become the new root switch and affect the forwarding path for the entire layer 2 topology.

To configure BPDU guard:

The following example commands set BPDU guard for swp5:

cumulus@switch:~$ net add interface swp5 stp bpduguard
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the switch port interface stanza in the /etc/network/interfaces file to add the mstpctl-bpduguard yes line, then run the ifreload -a command. The following example sets BPDU guard for interface swp5:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto swp5
iface swp5
    mstpctl-bpduguard yes
...
cumulus@switch:~$ sudo ifreload -a

If a BPDU is received on the port, STP brings down the port and logs an error in /var/log/syslog. The following is a sample error:

mstpd: error, MSTP_IN_rx_bpdu: bridge:bond0 Recvd BPDU on BPDU Guard Port - Port Down

To determine whether BPDU guard is configured, or if a BPDU has been received:

cumulus@switch:~$ net show bridge spanning-tree | grep bpdu
  bpdu guard port    yes                bpdu guard error     yes
cumulus@switch:~$ mstpctl showportdetail bridge bond0
bridge:bond0 CIST info
  enabled            no                      role                 Disabled
  port id            8.001                   state                discarding
  external port cost 305                     admin external cost  0
  internal port cost 305                     admin internal cost  0
  designated root    8.000.6C:64:1A:00:4F:9C dsgn external cost   0
  dsgn regional root 8.000.6C:64:1A:00:4F:9C dsgn internal cost   0
  designated bridge  8.000.6C:64:1A:00:4F:9C designated port      8.001
  admin edge port    no                      auto edge port       yes
  oper edge port     no                      topology change ack  no
  point-to-point     yes                     admin point-to-point auto
  restricted role    no                      restricted TCN       no
  port hello time    10                      disputed             no
  bpdu guard port    yes                      bpdu guard error     yes
  network port       no                      BA inconsistent      no
  Num TX BPDU        3                       Num TX TCN           2
  Num RX BPDU        488                     Num RX TCN           2
  Num Transition FWD 1                       Num Transition BLK   2
  bpdufilter port    no
  clag ISL           no                      clag ISL Oper UP     no
  clag role          unknown                 clag dual conn mac   0:0:0:0:0:0
  clag remote portID F.FFF                   clag system mac      0:0:0:0:0:0

The only way to recover a port that has been placed in the disabled state is to manually bring up the port with the sudo ifup <interface> command. See Interface Configuration and Management for more information about ifupdown.

Bringing up the disabled port does not correct the problem if the configuration on the connected end-station has not been resolved.

Bridge Assurance

On a point-to-point link where RSTP is running, if you want to detect unidirectional links and put the port in a discarding state, you can enable bridge assurance on the port by enabling a port type network. The port is then in a bridge assurance inconsistent state until a BPDU is received from the peer. You need to configure the port type network on both ends of the link for bridge assurance to operate properly.

Bridge assurance is disabled by default.

To enable bridge assurance on an interface:

The following example commands enable bridge assurance on swp1:

cumulus@switch:~$ net add interface swp1 stp portnetwork
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the switch port interface stanza in the /etc/network/interfaces file to add the mstpctl-portnetwork yes line, then run the ifreload -a command. The following example enables bridge assurance on swp5:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto swp5
iface swp5
    mstpctl-portnetwork yes
...
cumulus@switch:~$ sudo ifreload -a

Runtime Configuration (Advanced)

A runtime configuration is non-persistent, which means the configuration you create here does not persist after you reboot the switch.

To enable bridge assurance at runtime, run mstpctl:

cumulus@switch:~$ sudo mstpctl setportnetwork br1007 swp1.1007 yes

cumulus@switch:~$ sudo mstpctl showportdetail br1007 swp1.1007 | grep network
  network port       yes                     BA inconsistent      yes

To monitor logs for bridge assurance messages, run the following command:

cumulus@switch:~$ sudo grep -in assurance /var/log/syslog | grep mstp
  1365:Jun 25 18:03:17 mstpd: br1007:swp1.1007 Bridge assurance inconsistent

BPDU Filter

You can enable bpdufilter on a switch port, which filters BPDUs in both directions. This disables STP on the port as no BPDUs are transiting.

Using BDPU filter might cause layer 2 loops. Use this feature deliberately and with extreme caution.

To configure the BPDU filter on an interface:

The following example commands configure the BPDU filter on swp6:

cumulus@switch:~$ net add interface swp6 stp portbpdufilter
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the switch port interface stanza in the /etc/network/interfaces file to add the mstpctl-portbpdufilter yes line, then run the ifreload -a command. The following example configures BPDU filter on swp6:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto swp6
iface swp6
    mstpctl-portbpdufilter yes
...
cumulus@switch:~$ sudo ifreload -a

Runtime Configuration (Advanced)

A runtime configuration is non-persistent, which means the configuration you create here does not persist after you reboot the switch.

To enable BPDU filter at runtime, run mstpctl. For example:

cumulus@switch:~$ sudo mstpctl setportbpdufilter br100 swp1.100=yes swp2.100=yes

Parameter List

Spanning tree parameters are defined in the IEEE 802.1D and 802.1Q specifications.

The table below describes the STP configuration parameters available in Cumulus Linux. For a comparison of STP parameter configuration between mstpctl and other vendors, read this knowledge base article.

Most of these parameters are blacklisted in the ifupdown_blacklist section of the /etc/netd.conf file. Before you configure these parameters, you must edit the file to remove them from the blacklist.

Parameter
NCLU Command
Description
mstpctl-maxage net add bridge stp maxage <seconds> Sets the maximum age of the bridge in seconds. The default is 20. The maximum age must meet the condition 2 * (Bridge Forward Delay - 1 second) >= Bridge Max Age.
mstpctl-ageing net add bridge stp ageing <seconds> Sets the Ethernet (MAC) address ageing time for the bridge in seconds when the running version is STP, but not RSTP/MSTP. The default is 1800.
mstpctl-fdelay net add bridge stp fdelay <seconds> Sets the bridge forward delay time in seconds. The default value is 15. The bridge forward delay must meet the condition 2 * (Bridge Forward Delay - 1 second) >= Bridge Max Age.
mstpctl-maxhops net add bridge stp maxhops <max-hops> Sets the maximum hops for the bridge. The default is 20.
mstpctl-txholdcount net add bridge stp txholdcount <hold-count> Sets the bridge transmit hold count. The default value is 6.
mstpctl-forcevers net add bridge stp forcevers RSTP|STP Sets the force STP version of the bridge to either RSTP/STP. The default is RSTP.
mstpctl-treeprio net add bridge stp treeprio <priority> Sets the tree priority of the bridge for an MSTI (multiple spanning tree instance). The priority value is a number between 0 and 61440 and must be a multiple of 4096. The bridge with the lowest priority is elected the root bridge. The default is 32768. See Spanning Tree Priority above.
Note: Cumulus Linux supports MSTI 0 only. It does not support MSTI 1 through 15.
mstpctl-hello net add bridge stp hello <seconds> Sets the bridge hello time in seconds. The default is 2.
mstpctl-portpathcost net add interface <interface> stp portpathcost <cost> Sets the port cost of the interface. The default is 0.
mstpd supports only long mode; 32 bits for the path cost.
mstpctl-treeportprio net add interface <interface> stp treeportprio <priority> Sets the priority of the interface for the MSTI. The priority value is a number between 0 and 240 and must be a multiple of 16. The default is 128.
Note: Cumulus Linux supports MSTI 0 only. It does not support MSTI 1 through 15.
mstpctl-portadminedge net add interface <interface> stp portadminedge Enables or disables the initial edge state of the interface in the bridge. The default is no.
In NCLU, to use a setting other than the default, you must specify this attribute without setting an option. See PortAdminEdge above.
mstpctl-portautoedge net add interface <interface> stp portautoedge Enables or disables the auto transition to and from the edge state of the interface in the bridge. PortAutoEdge is enabled by default. See PortAutoEdge above.
mstpctl-portp2p net add interface <interface> stp portp2p yes|no Enables or disables the point-to-point detection mode of the interface in the bridge.
mstpctl-portrestrrole net add interface <interface> stp portrestrrole Enables or disables the ability of the interface in the bridge to take the restricted role. The default is no.
To enable this feature with the NCLU command, you specify this attribute without an option (portrestrrole). To enable this feature by editing the /etc/network/interfaces file, you specify mstpctl-portrestrrole yes.
mstpctl-portrestrtcn net add interface <interface> stp portrestrtcn Enables or disables the ability of the interface in the bridge to propagate received topology change notifications. The default is no.
mstpctl-portnetwork net add interface <interface> stp portnetwork Enables or disables the bridge assurance capability for a network interface. The default is no. See Bridge Assurance above.
mstpctl-bpduguard net add interface <interface> stp bpduguard Enables or disables the BPDU guard configuration of the interface in the bridge. The default is no. See BPDU Guard above.
mstpctl-portbpdufilter net add interface <interface> stp portbpdufilter Enables or disables the BPDU filter functionality for an interface in the bridge. The default is no. See BPDU Filter above.
mstpctl-treeportcost net add interface <interface> stp treeportcost <port-cost> Sets the spanning tree port cost to a value from 0 to 255. The default is 0.

Troubleshooting

To check STP status for a bridge:

Run the net show bridge spanning-tree command:

cumulus@switch:~$ net show bridge spanning-tree
Bridge info
  enabled         yes
  bridge id       8.000.44:38:39:FF:40:94
    Priority:     32768
    Address:      44:38:39:FF:40:94
  This bridge is root.

  designated root 8.000.44:38:39:FF:40:94
    Priority:     32768
    Address:      44:38:39:FF:40:94

  root port       none
  path cost     0          internal path cost   0
  max age       20         bridge max age       20
  forward delay 15         bridge forward delay 15
  tx hold count 6          max hops             20
  hello time    2          ageing time          300
  force protocol version     rstp

INTERFACE  STATE  ROLE  EDGE
---------  -----  ----  ----
peerlink   forw   Desg  Yes
vni13      forw   Desg  Yes
vni24      forw   Desg  Yes
vxlan4001  forw   Desg  Yes

The mstpctl utility provided by the mstpd service configures STP. The mstpd daemon is an open source project used by Cumulus Linux to implement IEEE802.1D 2004 and IEEE802.1Q 2011.

The mstpd daemon starts by default when the switch boots and logs errors to /var/log/syslog.

mstpd is the preferred utility for interacting with STP on Cumulus Linux. brctl also provides certain tools for configuring STP; however, they are not as complete and output from brctl might be misleading.

To show the bridge state, run the brctl show command:

cumulus@switch:~$ sudo brctl show
  bridge name     bridge id               STP enabled     interfaces
  bridge          8000.001401010100       yes             swp1
                                                          swp4
                                                          swp5

To show the mstpd bridge port state, run the mstpctl showport bridge command:

cumulus@switch:~$ sudo mstpctl showport bridge
  E swp1 8.001 forw F.000.00:14:01:01:01:00 F.000.00:14:01:01:01:00 8.001 Desg
    swp4 8.002 forw F.000.00:14:01:01:01:00 F.000.00:14:01:01:01:00 8.002 Desg
  E swp5 8.003 forw F.000.00:14:01:01:01:00 F.000.00:14:01:01:01:00 8.003 Desg

The source code for mstpd and mstpctl was written by Vitalii Demianets and is hosted at the URL below.

Link Layer Discovery Protocol

The lldpd daemon implements the IEEE802.1AB (Link Layer Discovery Protocol, or LLDP) standard. LLDP shows you which ports are neighbors of a given port. By default, lldpd runs as a daemon and starts at system boot. lldpd command line arguments are placed in /etc/default/lldpd. All lldpd configuration options are saved in /etc/lldpd.conf or under /etc/lldpd.d/.

For more details on the command line arguments and configuration options, see man lldpd(8).

lldpd supports CDP (Cisco Discovery Protocol, v1 and v2) and logs by default into /var/log/daemon.log with an lldpd prefix.

You can use the lldpcli CLI tool to query the lldpd daemon for neighbors, statistics, and other running configuration information. See man lldpcli(8) for details.

Configure LLDP

You configure lldpd settings in /etc/lldpd.conf or /etc/lldpd.d/.

Here is an example persistent configuration:

cumulus@switch:~$ sudo cat /etc/lldpd.conf
configure lldp tx-interval 40
configure lldp tx-hold 3
configure system interface pattern *,!eth0,swp*

The last line in the example above shows that LLDP is disabled on eth0. To disable LLDP on a single port, edit the /etc/default/lldpd file. This file specifies the default options to present to the lldpd service when it starts. The following example uses the -I option to disable LLDP on swp43:

cumulus@switch:~$ sudo nano /etc/default/lldpd

# Add "-x" to DAEMON_ARGS to start SNMP subagent
# Enable CDP by default
DAEMON_ARGS="-c -I *,!swp43"

lldpd has two timers defined by the tx-interval setting that affect each switch port:

lldpd logs to /var/log/daemon.log with the lldpd prefix:

cumulus@switch:~$ sudo tail -f /var/log/daemon.log  | grep lldp
Aug  7 17:26:17 switch lldpd[1712]: unable to get system name
Aug  7 17:26:17 switch lldpd[1712]: unable to get system name
Aug  7 17:26:17 switch lldpcli[1711]: lldpd should resume operations
Aug  7 17:26:32 switch lldpd[1805]: NET-SNMP version 5.4.3 AgentX subagent connected

Example lldpcli Commands

To show all neighbors on all ports and interfaces:

cumulus@switch:~$ sudo lldpcli show neighbors
-------------------------------------------------------------------------------
LLDP neighbors:
-------------------------------------------------------------------------------
Interface:    eth0, via: LLDP, RID: 1, Time: 0 day, 17:38:08
  Chassis:
    ChassisID:    mac 08:9e:01:e9:66:5a
    SysName:      PIONEERMS22
    SysDescr:     Cumulus Linux version 4.0.0 running on quanta lb9
    MgmtIP:       192.168.0.22
    Capability:   Bridge, on
    Capability:   Router, on
  Port:
    PortID:       ifname swp47
    PortDescr:    swp47
-------------------------------------------------------------------------------
Interface:    swp1, via: LLDP, RID: 10, Time: 0 day, 17:08:27
  Chassis:
    ChassisID:    mac 00:01:00:00:09:00
    SysName:      MSP-1
    SysDescr:     Cumulus Linux version 4.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.9
    MgmtIP:       fe80::201:ff:fe00:900
    Capability:   Bridge, off
    Capability:   Router, on
  Port:
    PortID:       ifname swp1
    PortDescr:    swp1
-------------------------------------------------------------------------------
Interface:    swp2, via: LLDP, RID: 10, Time: 0 day, 17:08:27
  Chassis:
    ChassisID:    mac 00:01:00:00:09:00
    SysName:      MSP-1
    SysDescr:     Cumulus Linux version 4.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.9
    MgmtIP:       fe80::201:ff:fe00:900
    Capability:   Bridge, off
    Capability:   Router, on
  Port:
    PortID:       ifname swp2
    PortDescr:    swp2
-------------------------------------------------------------------------------
Interface:    swp3, via: LLDP, RID: 11, Time: 0 day, 17:08:27
  Chassis:
    ChassisID:    mac 00:01:00:00:0a:00
    SysName:      MSP-2
    SysDescr:     Cumulus Linux version 4.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.10
    MgmtIP:       fe80::201:ff:fe00:a00
    Capability:   Bridge, off
    Capability:   Router, on
  Port:
    PortID:       ifname swp1
    PortDescr:    swp1
-------------------------------------------------------------------------------
Interface:    swp4, via: LLDP, RID: 11, Time: 0 day, 17:08:27
  Chassis:
    ChassisID:    mac 00:01:00:00:0a:00
    SysName:      MSP-2
    SysDescr:     Cumulus Linux version 4.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.10
    MgmtIP:       fe80::201:ff:fe00:a00
    Capability:   Bridge, off
    Capability:   Router, on
  Port:
    PortID:       ifname swp2
    PortDescr:    swp2
-------------------------------------------------------------------------------
Interface:    swp49s1, via: LLDP, RID: 9, Time: 0 day, 16:55:00
  Chassis:
    ChassisID:    mac 00:01:00:00:0c:00
    SysName:      TORC-1-2
    SysDescr:     Cumulus Linux version 4.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.12
    MgmtIP:       fe80::201:ff:fe00:c00
    Capability:   Bridge, on
    Capability:   Router, on
  Port:
    PortID:       ifname swp6
    PortDescr:    swp6
-------------------------------------------------------------------------------
Interface:    swp49s0, via: LLDP, RID: 9, Time: 0 day, 16:55:00
  Chassis:
    ChassisID:    mac 00:01:00:00:0c:00
    SysName:      TORC-1-2
    SysDescr:     Cumulus Linux version 4.0.0 running on QEMU Standard PC (i440FX + PIIX, 1996)
    MgmtIP:       192.0.2.12
    MgmtIP:       fe80::201:ff:fe00:c00
    Capability:   Bridge, on
    Capability:   Router, on
  Port:
    PortID:       ifname swp5
    PortDescr:    swp5
-------------------------------------------------------------------------------

To show lldpd statistics for all ports:

cumulus@switch:~$ sudo lldpcli show statistics
----------------------------------------------------------------------
LLDP statistics:
----------------------------------------------------------------------
Interface:    eth0
  Transmitted:  9423
  Received:     17634
  Discarded:    0
  Unrecognized: 0
  Ageout:       10
  Inserted:     20
  Deleted:      10
--------------------------------------------------------------------
Interface:    swp1
  Transmitted:  9423
  Received:     6264
  Discarded:    0
  Unrecognized: 0
  Ageout:       0
  Inserted:     2
  Deleted:      0
---------------------------------------------------------------------
Interface:    swp2
  Transmitted:  9423
  Received:     6264
  Discarded:    0
  Unrecognized: 0
  Ageout:       0
  Inserted:     2
  Deleted:      0
---------------------------------------------------------------------
Interface:    swp3
  Transmitted:  9423
  Received:     6265
  Discarded:    0
  Unrecognized: 0
  Ageout:       0
  Inserted:     2
  Deleted:      0
----------------------------------------------------------------------
...

To show lldpd statistics summary for all ports:

cumulus@switch:~$ sudo lldpcli show statistics summary
---------------------------------------------------------------------
LLDP Global statistics:
---------------------------------------------------------------------
Summary of stats:
  Transmitted:  648186
  Received:     437557
  Discarded:    0
  Unrecognized: 0
  Ageout:       10
  Inserted:     38
  Deleted:      10

To show the lldpd running configuration:

cumulus@switch:~$ sudo lldpcli show running-configuration
--------------------------------------------------------------------
Global configuration:
--------------------------------------------------------------------
Configuration:
  Transmit delay: 30
  Transmit hold: 4
  Receive mode: no
  Pattern for management addresses: (none)
  Interface pattern: (none)
  Interface pattern blacklist: (none)
  Interface pattern for chassis ID: (none)
  Override description with: (none)
  Override platform with: Linux
  Override system name with: (none)
  Advertise version: yes
  Update interface descriptions: no
  Promiscuous mode on managed interfaces: no
  Disable LLDP-MED inventory: yes
  LLDP-MED fast start mechanism: yes
  LLDP-MED fast start interval: 1
  Source MAC for LLDP frames on bond slaves: local
  Portid TLV Subtype for lldp frames: ifname
--------------------------------------------------------------------
Runtime Configuration (Advanced)

A runtime configuration does not persist when you reboot the switch; all changes are lost.

To configure active interfaces:

cumulus@switch:~$ sudo lldpcli configure system interface pattern "swp*"

To configure inactive interfaces:

cumulus@switch:~$ sudo lldpcli configure system interface pattern *,!eth0,swp*

The active interface list always overrides the inactive interface list.

To reset any interface list to none:

cumulus@switch:~$ sudo lldpcli configure system interface pattern ""

Enable the SNMP Subagent in LLDP

LLDP does not enable the SNMP subagent by default. You need to edit /etc/default/lldpd and enable the -x option.

cumulus@switch:~$ sudo nano /etc/default/lldpd

# Add "-x" to DAEMON_ARGS to start SNMP subagent

# Enable CDP by default
DAEMON_ARGS="-c -x"

Change CDP Settings

Cumulus Linux provides support for CDP so that the switch can advertise information about itself with Cisco routers that do not support LLDP. By default, the Cumulus Linux switch sends CDP packets only if the peer sends CDP packets. You can change this setting by replacing -c in the /etc/default/lldpd file with one of the following options:

Option Description
-cc The Cumulus Linux switch sends CDPv1 packets even when there is no detected CDP peer.
-ccc The Cumulus Linux switch sends CDPv2 packets even when there is no detected CDP peer.
-cccc The Cumulus Linux switch disables CDPv1 and enables CDPv2.
-ccccc The Cumulus Linux switch disables CDPv1 and forces CDPv2.

The following example changes the CDP setting to -ccc so that the switch sends CDPv2 packets even when there is no detected CDP peer:

cumulus@switch:~$ sudo nano /etc/default/lldpd
...
# Enable CDP by default
DAEMON_ARGS="-ccc -x -M 4"

You must restart the lldpd service for the changes to take effect.

cumulus@switch:~$ sudo systemctl restart lldpd

Caveats and Errata

Storm Control

Storm control provides protection against excessive inbound BUM (broadcast, unknown unicast, multicast) traffic on layer 2 switch port interfaces, which can cause poor network performance.

  • Storm control is not supported on a switch with the Tomahawk2 ASIC.
  • On Broadcom switches, ARP requests over layer 2 VXLAN bypass broadcast storm control; they are forwarded to the CPU and subjected to embedded control plane QoS instead.

Configure Storm Control

To configure storm control for physical ports, edit the /etc/cumulus/switchd.conf file. For example, to enable broadcast storm control for swp1 at 400 packets per second (pps), multicast storm control at 3000 pps, and unknown unicast at 500 pps, edit the /etc/cumulus/switchd.conf file and uncomment the storm_control.broadcast, storm_control.multicast, and storm_control.unknown_unicast lines:

cumulus@switch:~$ sudo nano /etc/cumulus/switchd.conf
...
# Storm Control setting on a port, in pps, 0 means disable
interface.swp1.storm_control.broadcast = 400
interface.swp1.storm_control.multicast = 3000
interface.swp1.storm_control.unknown_unicast = 500
...

When you update the /etc/cumulus/switchd.conf file, you must restart switchd for the changes to take effect.

cumulus@switch:~$ sudo systemctl restart switchd.service

Restarting the switchd service causes all network ports to reset, interrupting network services, in addition to resetting the switch hardware configuration.

Alternatively, you can run the following commands. The configuration below takes effect immediately, but does not persist if you reboot the switch. For a persistent configuration, edit the /etc/cumulus/switchd.conf file, as described above.

cumulus@switch:~$ sudo sh -c 'echo 400 > /cumulus/switchd/config/interface/swp1/storm_control/broadcast'
cumulus@switch:~$ sudo sh -c 'echo 3000 > /cumulus/switchd/config/interface/swp1/storm_control/multicast'
cumulus@switch:~$ sudo sh -c 'echo 500 > /cumulus/switchd/config/interface/swp1/storm_control/unknown_unicast'

To use the same command above on range of interfaces you can use a for-loop from the switch CLI using the below example.

cumulus@switch:mgmt:~$ for i in {1..5}; do
> sudo sh -c "echo 400 > /cumulus/switchd/config/interface/swp$i/storm_control/broadcast"
> sudo sh -c "echo 3000 > /cumulus/switchd/config/interface/swp$i/storm_control/multicast"
> sudo sh -c "echo 500 > /cumulus/switchd/config/interface/swp$i/storm_control/unknown_unicast"
> done
cumulus@switch:mgmt:~$ 

Voice VLAN

In Cumulus Linux, a voice VLAN is a VLAN dedicated to voice traffic on a switch port. Voice VLAN is part of a trunk port with two VLANs that comprises either of the following:

The voice traffic is an 802.1q-tagged packet with a VLAN ID (that might or might not be 0) and an 802.1p (3-bit layer 2 COS) with a specific value (typically 5 is assigned for voice traffic).

Data traffic is always untagged.

Example Configuration





In this example configuration:
  • swp1 data traffic traverses the native VLAN of the bridge and the voice traffic traverses VLAN 200
  • swp2 data traffic traverses VLAN 100 and the voice traffic traverses VLAN 200
  • swp3 data traffic traverses VLAN 100 and voice traffic traverses VLAN 300

To configure the topology shown above:

cumulus@switch:~$ net add bridge bridge ports swp1-3
cumulus@switch:~$ net add bridge bridge vids 10,100,200,300
cumulus@switch:~$ net add bridge bridge pvid 10
cumulus@switch:~$ net add interface swp1 bridge voice-vlan 200
cumulus@switch:~$ net add interface swp2 bridge voice-vlan 200 data-vlan 100
cumulus@switch:~$ net add interface swp3 bridge voice-vlan 300 data-vlan 100
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file and add the following configuration:

cumulus@switch:~$ sudo nano /etc/network/interfaces

auto swp1
iface swp1
    bridge-vids 200
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    bridge-pvid 100
    bridge-vids 200
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    bridge-pvid 100
    bridge-vids 300
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto bridge
iface bridge
  bridge-ports swp1 swp2 swp3
  bridge-pvid 10
  bridge-vids 10 100 200 300
  bridge-vlan-aware yes

Troubleshooting

To show the bridge VIDs, run the net show bridge vlan command:

cumulus@switch:~$ net show bridge vlan

Interface      VLAN  Flags
-----------  ------  ---------------------
swp1             10  PVID, Egress Untagged
                200
swp2            100  PVID, Egress Untagged
                200
swp3            100  PVID, Egress Untagged
                300

To obtain MAC address information, run the NCLU net show bridge macs command or the Linux sudo brctl showmacs <bridge> command. For example:

cumulus@switch:~$ net show bridge macs

VLAN      Master    Interface    MAC                   TunnelDest  State      Flags    LastSeen
--------  --------  -----------  -----------------  -------------  ---------  -------  ----------
untagged  bridge    bridge       08:00:27:d5:00:93                 permanent           00:13:54
untagged  bridge    swp1         08:00:27:6a:ad:da                 permanent           00:13:54
untagged  bridge    swp2         08:00:27:e3:0c:a7                 permanent           00:13:54
untagged  bridge    swp3         08:00:27:9e:98:86                 permanent           00:13:54

To capture LLDP information, check syslog or use tcpdump on an interface.

Considerations

Bonding - Link Aggregation

Linux bonding provides a method for aggregating multiple network interfaces (slaves) into a single logical bonded interface (bond). Link aggregation is useful for linear scaling of bandwidth, load balancing, and failover protection.

Cumulus Linux supports two bonding modes:

Cumulus Linux uses version 1 of the LAG control protocol (LACP).

To temporarily bring up a bond even when there is no LACP partner, use LACP Bypass.

Hash Distribution

Egress traffic through a bond is distributed to a slave based on a packet hash calculation, providing load balancing over the slaves; many conversation flows are distributed over all available slaves to load balance the total traffic. Traffic for a single conversation flow always hashes to the same slave.

The hash calculation uses packet header data to choose to which slave to transmit the packet:

In a failover event, the hash calculation is adjusted to steer traffic over available slaves.

LAG Custom Hashing

On Mellanox switches, you can configure which fields are used in the LAG hash calculation. For example, if you do not want to use source or destination port numbers in the hash calculation, you can disable the source port and destination port fields.

You can configure the following fields:

To configure custom hash, edit the /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf file:

  1. To enable custom hashing, uncomment the lag_hash_config.enable = true line.
  2. To enable a field, set the field to true. To disable a field, set the field to false.
  3. Restart the switchd service:
cumulus@switch:~$ sudo systemctl restart switchd.service

The following shows an example datapath.conf file:

cumulus@switch:~$ sudo nano /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf
...
#LAG HASH config
#HASH config for LACP to enable custom fields
#Fields will be applicable for LAG hash
#calculation
#Uncomment to enable custom fields configured below
lag_hash_config.enable = true

lag_hash_config.smac = true
lag_hash_config.dmac = true
lag_hash_config.sip  = true
lag_hash_config.dip  = true
lag_hash_config.ether_type = true
lag_hash_config.vlan_id = true
lag_hash_config.sport = false
lag_hash_config.dport = false
lag_hash_config.ip_prot = true
...

Symmetric hashing is enabled by default on Mellanox switches. Make sure that the settings for the source IP (lag_hash_config.sip) and destination IP (lag_hash_config.dip) fields match, and that the settings for the source port (lag_hash_config.sport) and destination port (lag_hash_config.dport) fields match; otherwise symmetric hashing is disabled automatically. You can disable symmetric hashing manually in the /etc/cumulus/datapath/traffic.conf file by setting symmetric_hash_enable = FALSE.

You can set a unique hash seed for each switch to help avoid hash polarization. See Configure a Hash Seed to Avoid Hash Polarization.

Create a Bond

In the example below, the front panel port interfaces swp1 thru swp4 are slaves in bond0, while swp5 and swp6 are not part of bond0.

To create and configure a bond:

Run the net add bond command. The example command below creates a bond called bond0 with slaves swp1, swp2, swp3, and swp4:

cumulus@switch:~$ net add bond bond0 bond slaves swp1-4
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file and add a stanza for the bond. The example below creates a bond called bond0 with slaves swp1, swp2, swp3, and swp4:

cumulus@switch:~$ sudo nanno /etc/network/interfaces
...
auto bond0
iface bond0
    bond-slaves swp1 swp2 swp3 swp4
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

  • The bond is configured by default in IEEE 802.3ad link aggregation mode. To configure the bond in balance-xor mode, see Configuration Parameters below.
  • If the bond is not going to become part of a bridge, you need to specify an IP address.
  • The name of the bond must be compliant with Linux interface naming conventions and unique within the switch.
  • Do not use a dash (-) in the bond name.
  • Cumulus Linux does not support bond members at 200G or greater.

When networking is started on the switch, bond0 is created as MASTER and interfaces swp1 thru swp4 come up in SLAVE mode, as seen in the ip link show command:

cumulus@switch:~$ ip link show
...

3: swp1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT qlen 500
    link/ether 44:38:39:00:03:c1 brd ff:ff:ff:ff:ff:ff
4: swp2: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT qlen 500
    link/ether 44:38:39:00:03:c1 brd ff:ff:ff:ff:ff:ff
5: swp3: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT qlen 500
    link/ether 44:38:39:00:03:c1 brd ff:ff:ff:ff:ff:ff
6: swp4: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT qlen 500
    link/ether 44:38:39:00:03:c1 brd ff:ff:ff:ff:ff:ff
...

55: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT
    link/ether 44:38:39:00:03:c1 brd ff:ff:ff:ff:ff:ff

All slave interfaces within a bond have the same MAC address as the bond. Typically, the first slave added to the bond donates its MAC address as the bond MAC address, whereas the MAC addresses of the other slaves are set to the bond MAC address. The bond MAC address is used as the source MAC address for all traffic leaving the bond and provides a single destination MAC address to address traffic to the bond.

Configure Bond Options

The configuration options for a bond are are described in the table below. To configure a bond:

Run net add bond <bond-name> bond <option>. The following example sets the bond mode for bond01 to balance-xor:

cumulus@switch:~$ net add bond bond1 bond mode balance-xor
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file and add the parameter to the bond stanza, then load the new configuration. The following example sets the bond mode for bond01 to balance-xor:

cumulus@switch:~$ sudo nanno /etc/network/interfaces
...
auto bond1
iface bond1
    bond-mode balance-xor
    bond-slaves swp1 swp2 swp3 swp4
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

Each bond configuration option, except for bond slaves, is set to the recommended value by default in Cumulus Linux. Only configure an option if a different setting is needed. For more information on configuration values, refer to the Related Information section below.

Parameter Description
bond-mode 802.3ad|balance-xor Cumulus Linux supports IEEE 802.3ad link aggregation mode (802.3ad) and balance-xor mode.
The default mode is 802.3ad.

Note: When you enable balance-xor mode, the bonding of slave interfaces are static and all slave interfaces are active for load balancing and fault tolerance purposes. Packet transmission on the bond is based on the hash policy specified by xmit-hash-policy.

When using balance-xor mode to dual-connect host-facing bonds in an MLAG environment, you must configure the clag-id parameter on the MLAG bonds and it must be the same on both MLAG switches. Otherwise, the bonds are treated by the MLAG switch pair as single-connected.

Use balance-xor mode only if you cannot use LACP; LACP can detect mismatched link attributes between bond members and can even detect misconnections.
bond-slaves <interface-list> The list of slaves in the bond.
bond miimon <value> Defines how often the link state of each slave is inspected for failures. You can specify a value between 0 and 255. The default value is 100.
bond-use-carrier no Determines the link state.
bond-lacp-bypass-allow Enables LACP bypass.
bond-lacp-rate slow Sets the rate to ask the link partner to transmit LACP control packets. slow is the only option.
bond-min-links Defines the minimum number of links (between 0 and 255) that must be active before the bond is put into service. The default value is 1.

A value greater than 1 is useful if higher level services need to ensure a minimum aggregate bandwidth level before activating a bond. Keeping bond-min-links set to 1 indicates the bond must have at least one active member. If the number of active members drops below the bond-min-links setting, the bond appears to upper-level protocols as link-down. When the number of active links returns to greater than or equal to bond-min-links, the bond becomes link-up.

Show Bond Information

To show information for a bond:

Run the net show interface <bond> command:

cumulus@switch:~$ net show interface bond1
    Name    MAC                Speed    MTU    Mode
--  ------  -----------------  -------  -----  ------
UP  bond1   00:02:00:00:00:12  20G      1500   Bond


Bond Details
---------------  -------------
Bond Mode:       Balance-XOR
Load Balancing:  Layer3+4
Minimum Links:   1
In CLAG:         CLAG Inactive


    Port     Speed      TX    RX    Err    Link Failures
--  -------  -------  ----  ----  -----  ---------------
UP  swp3(P)  10G         0     0      0                0
UP  swp4(P)  10G         0     0      0                0


LLDP
-------  ----  ------------
swp3(P)  ====  swp1(p1c1h1)
swp4(P)  ====  swp2(p1c1h1)Routing
-------
  Interface bond1 is up, line protocol is up
  Link ups:       3    last: 2017/04/26 21:00:38.26
  Link downs:     2    last: 2017/04/26 20:59:56.78
  PTM status: disabled
  vrf: Default-IP-Routing-Table
  index 31 metric 0 mtu 1500
  flags: <UP,BROADCAST,RUNNING,MULTICAST>
  Type: Ethernet
  HWaddr: 00:02:00:00:00:12
  inet6 fe80::202:ff:fe00:12/64
  Interface Type Other

Run the sudo cat /proc/net/bonding/<bond> command:

cumulus@switch:~$ sudo cat /proc/net/bonding/bond01

Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011)
Bonding Mode: load balancing (xor)
Transmit Hash Policy: layer3+4 (1)
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 0
Down Delay (ms): 0


Slave Interface: swp1
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 44:38:39:00:00:03
Slave queue ID: 0

The detailed output in /proc/net/bonding/<filename> includes the actor/partner LACP information. This information is not necessary and requires you to use sudo to view the file.

Caveats and Errata

swp49 xe0 0 0 -1 0
swp50 xe1 0 0 -1 0
swp51 xe1 1 0 -1 0
swp52 xe0 1 0 -1 0

Single port member bonds, bonds with different units (xe0 or xe1, as above), or layer 3 bonds do not have this issue.

On Cumulus RMP switches, which are built with two Hurricane2 ASICs, you cannot form an LACP bond on links that terminate on different Hurricane2 ASICs.

Ethernet Bridging - VLANs

Ethernet bridges enable hosts to communicate through layer 2 by connecting all of the physical and logical interfaces in the system into a single layer 2 domain. The bridge is a logical interface with a MAC address and an MTU (maximum transmission unit). The bridge MTU is the minimum MTU among all its members. By default, the bridge’s MAC address is the MAC address of the first port in the bridge-ports list. The bridge can also be assigned an IP address, as discussed below.

Bridge members can be individual physical interfaces, bonds, or logical interfaces that traverse an 802.1Q VLAN trunk.

Use VLAN-aware mode bridges instead of traditional mode bridges. The bridge driver in Cumulus Linux is capable of VLAN filtering, which allows for configurations that are similar to incumbent network devices. For a comparison of traditional and VLAN-aware modes, read this knowledge base article.

  • Cumulus Linux does not put all ports into a bridge by default.
  • You can configure both VLAN-aware and traditional mode bridges on the same network in Cumulus Linux; however you cannot have more than one VLAN-aware bridge on a given switch.

Create a VLAN-aware Bridge

To create a VLAN-aware bridge, see VLAN-aware Bridge Mode.

Create a Traditional Mode Bridge

To create a traditional mode bridge, see Traditional Bridge Mode.

Bridge MAC Addresses

The MAC address for a frame is learned when the frame enters the bridge through an interface. The MAC address is recorded in the bridge table and the bridge forwards the frame to its intended destination by looking up the destination MAC address. The MAC entry is then maintained for a period of time defined by the bridge-ageing configuration option. If the frame is seen with the same source MAC address before the MAC entry age is exceeded, the MAC entry age is refreshed; if the MAC entry age is exceeded, the MAC address is deleted from the bridge table.

The following example output shows a MAC address table for the bridge:

cumulus@switch:~$ net show bridge macs
VLAN      Master    Interface    MAC                  TunnelDest  State      Flags    LastSeen
--------  --------  -----------  -----------------  ------------  ---------  -------  -----------------
untagged  bridge    swp1         44:38:39:00:00:03                                    00:00:15
untagged  bridge    swp1         44:38:39:00:00:04                permanent           20 days, 01:14:03

By default, Cumulus Linux stores MAC addresses in the Ethernet switching table for 1800 seconds (30 minutes). To change the amount of time MAC addresses are stored in the table, configure bridge ageing.

The following example commands set MAC address ageing to 600 seconds.

cumulus@switch:~$ net add bridge bridge ageing 600
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file and add bridge-ageing to the bridge stanza.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-ageing 600
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

Configure an SVI (Switch VLAN Interface)

Bridges can be included as part of a routing topology after being assigned an IP address. This enables hosts within the bridge to communicate with other hosts outside of the bridge through a switch VLAN interface (SVI), which provides layer 3 routing. The IP address of the bridge is typically from the same subnet as the member hosts of the bridge.

When you add an interface to a bridge, it ceases to function as a router interface and the IP address on the interface becomes unreachable.

To configure the SVI:

Run the net add bridge and net add vlan commands. The following example commands configure an SVI using swp1 and swp2, and VLAN ID 10.

cumulus@switch:~$ net add bridge bridge ports swp1-2
cumulus@switch:~$ net add vlan 10 ip address 10.100.100.1/24
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file to add the interfaces and VLAN ID you want to use. The following configures an SVI using swp1 and swp2, and VLAN ID 10. The bridge-vlan-aware parameter associates the SVI with the VLAN-aware bridge.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-vids 10
    bridge-vlan-aware yes

auto bridge.10
iface bridge.10
    address 10.100.100.1/24
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

When you configure a switch initially, all southbound bridge ports might be down; therefore, by default, the SVI is also down. You can force the SVI to always be up by disabling interface state tracking, which leaves the SVI in the UP state always, even if all member ports are down. Other implementations describe this feature as no autostate. This is beneficial if you want to perform connectivity testing.

To keep the SVI perpetually UP, create a dummy interface, then make the dummy interface a member of the bridge.

Example Configuration

Consider the following configuration, without a dummy interface in the bridge:

cumulus@switch:~$ sudo cat /etc/network/interfaces
...

auto bridge
iface bridge
    bridge-vlan-aware yes
    bridge-ports swp3
    bridge-vids 100
    bridge-pvid 1
...

With this configuration, when swp3 is down, the SVI is also down:

cumulus@switch:~$ ip link show swp3
5: swp3: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master bridge state DOWN mode DEFAULT group default qlen 1000
    link/ether 2c:60:0c:66:b1:7f brd ff:ff:ff:ff:ff:ff
cumulus@switch:~$ ip link show bridge
35: bridge: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default
    link/ether 2c:60:0c:66:b1:7f brd ff:ff:ff:ff:ff:ff

Now add the dummy interface to your network configuration:

  1. Edit the /etc/network/interfaces file and add the dummy interface stanza before the bridge stanza:
cumulus@switch:~$ sudo nano /etc/network/interfaces
...

auto dummy
iface dummy
    link-type dummy

auto bridge
iface bridge
...
  1. Add the dummy interface to the bridge-ports line in the bridge configuration:
auto bridge
iface bridge
    bridge-vlan-aware yes
    bridge-ports swp3 dummy
    bridge-vids 100
    bridge-pvid 1
  1. Save and exit the file, then reload the configuration:
cumulus@switch:~$ sudo ifreload -a

Now, even when swp3 is down, both the dummy interface and the bridge remain up:

cumulus@switch:~$ ip link show swp3
5: swp3: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master bridge state DOWN mode DEFAULT group default qlen 1000
    link/ether 2c:60:0c:66:b1:7f brd ff:ff:ff:ff:ff:ff
cumulus@switch:~$ ip link show dummy
37: dummy: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master bridge state UNKNOWN mode DEFAULT group default
    link/ether 66:dc:92:d4:f3:68 brd ff:ff:ff:ff:ff:ff
cumulus@switch:~$ ip link show bridge
35: bridge: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default
    link/ether 2c:60:0c:66:b1:7f brd ff:ff:ff:ff:ff:ff

By default, Cumulus Linux automatically generates IPv6 link-local addresses on VLAN interfaces. If you want to use a different mechanism to assign link-local addresses, you can disable this feature. You can disable link-local automatic address generation for both regular IPv6 addresses and address-virtual (macvlan) addresses.

To disable automatic address generation for a regular IPv6 address on a VLAN:

Run the net add vlan <vlan> ipv6-addrgen off command. The following example command disables automatic address generation for a regular IPv6 address on a VLAN 100.

cumulus@switch:~$ net add vlan 100 ipv6-addrgen off
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file and add the line ipv6-addrgen off to the VLAN stanza. The following example disables automatic address generation for a regular IPv6 address on VLAN 100.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto vlan100
iface vlan 100
    ipv6-addrgen off
    vlan-id 100
    vlan-raw-device bridge
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

To reenable automatic link-local address generation for a VLAN:

Run the net del vlan <vlan> ipv6-addrgen off command. The following example command reenables automatic address generation for a regular IPv6 address on VLAN 100.

cumulus@switch:~$ net del vlan 100 ipv6-addrgen off
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
  1. Edit the /etc/network/interfaces file and remove the line ipv6-addrgen off from the VLAN stanza. The following example reenables automatic address generation for a regular IPv6 address on a VLAN 100.

  2. Run the ifreload -a command to load the new configuration:

    cumulus@switch:~$ ifreload -a
    

bridge fdb Command Output

The bridge fdb command in Linux interacts with the forwarding database table (FDB), which the bridge uses to store the MAC addresses it learns and the ports on which it learns those MAC addresses. The bridge fdb show command output contains some specific keywords:

Keyword Description
self The Linux kernel FDB entry flag that indicates the FDB entry belongs to the FDB on the device referenced by the device.
For example, this FDB entry belongs to the VXLAN device vx-1000: 00:02:00:00:00:08 dev vx-1000 dst 27.0.0.10 self
master The Linux kernel FDB entry flag that indicates the FDB entry belongs to the FDB on the device’s master and the FDB entry is pointing to a master’s port.
For example, this FDB entry is from the master device named bridge and is pointing to the VXLAN bridge port vx-1001: 02:02:00:00:00:08 dev vx-1001 vlan 1001 master bridge
extern_learn The Linux kernel FDB entry flag that indicates the FDB entry is managed (or offloaded) by an external control plane, such as the BGP control plane for EVPN.

The following example shows the bridge fdb show command output:

cumulus@switch:~$ bridge fdb show | grep 02:02:00:00:00:08
02:02:00:00:00:08 dev vx-1001 vlan 1001 extern_learn master bridge
02:02:00:00:00:08 dev vx-1001 dst 27.0.0.10 self extern_learn

  • 02:02:00:00:00:08 is the MAC address learned with BGP EVPN.
  • The first FDB entry points to a Linux bridge entry that points to the VXLAN device vx-1001.
  • The second FDB entry points to the same entry on the VXLAN device and includes additional remote destination information.
  • The VXLAN FDB augments the bridge FDB with additional remote destination information.
  • All FDB entries that point to a VXLAN port appear as two entries. The second entry augments the remote destination information.

Caveats and Errata

VLAN-aware Bridge Mode

The Cumulus Linux bridge driver supports two configuration modes, one that is VLAN-aware, and one that follows a more traditional Linux bridge model.

For traditional Linux bridges, the kernel supports VLANs in the form of VLAN subinterfaces. Enabling bridging on multiple VLANs means configuring a bridge for each VLAN and, for each member port on a bridge, creating one or more VLAN subinterfaces out of that port. This mode poses scalability challenges in terms of configuration size as well as boot time and run time state management, when the number of ports times the number of VLANs becomes large.

The VLAN-aware mode in Cumulus Linux implements a configuration model for large-scale layer 2 environments, with one single instance of spanning tree protocol. Each physical bridge member port is configured with the list of allowed VLANs as well as its port VLAN ID, either primary VLAN Identifier (PVID) or native VLAN. MAC address learning, filtering and forwarding are VLAN-aware. This significantly reduces the configuration size, and eliminates the large overhead of managing the port/VLAN instances as subinterfaces, replacing them with lightweight VLAN bitmaps and state updates.

You can configure both VLAN-aware and traditional mode bridges on thesame network in Cumulus Linux; however do not have more than one VLAN-aware bridge on a given switch.

Configure a VLAN-aware Bridge

The example below shows the commands required to create a VLAN-aware bridge configured for STP that contains two switch ports and includes 3 VLANs; the tagged VLANs 100 and 200 and the untagged (native) VLAN of 1.

cumulus@switch:~$ net add bridge bridge ports swp1-2
cumulus@switch:~$ net add bridge bridge vids 100,200
cumulus@switch:~$ net add bridge bridge pvid 1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The above commands create the following code snippet in the /etc/network/interfaces file:

auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 100 200
    bridge-vlan-aware yes

Edit the /etc/network/interfaces file and add the bridge. An example configuration is shown below.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-vids 100 200
    bridge-pvid 1
    bridge-vlan-aware yes
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

The Primary VLAN Identifer (PVID) of the bridge defaults to 1. You do not have to specify bridge-pvid for a bridge or a port. However, even though this does not affect the configuration, it helps other users for readability. The following configurations are identical to each other and the configuration above:

auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-vids 1 100 200
    bridge-vlan-aware yes
auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 1 100 200
    bridge-vlan-aware yes
auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-vids 100 200
    bridge-vlan-aware yes

If you specify bridge-vids or bridge-pvid at the bridge level, these configurations are inherited by all ports in the bridge. However, specifying any of these settings for a specific port overrides the setting in the bridge.

Do not try to bridge the management port, eth0, with any switch ports (swp0, swp1 and so on). For example, if you create a bridge with eth0 and swp1, it will not work properly and might disrupt access to the management interface.

Reserved VLAN Range

For hardware data plane internal operations, the switching silicon requires VLANs for every physical port, Linux bridge, and layer 3 subinterface. Cumulus Linux reserves a range of 1000 VLANs by default; the reserved range is 3000-3999.

You can modify the reserved range if it conflicts with any user-defined VLANs, as long the new range is a contiguous set of VLANs with IDs anywhere between 2 and 4094, and the minimum size of the range is 300 VLANs.

To configure the reserved range:

  1. Open /etc/cumulus/switchd.conf in a text editor.

  2. Uncomment the following line, specify a new range, and save the file:

    resv_vlan_range
    
  3. Restart switchd to implement the change:

    cumulus@switch:~$ sudo systemctl restart switchd.service
    

    While restarting switchd, all running ports will flap, and forwarding will be interrupted.

VLAN Filtering (VLAN Pruning)

By default, the bridge port inherits the bridge VIDs. To configure a port to override the bridge VIDs:

The following example commands configure swp3 to override the bridge VIDs:

cumulus@switch:~$ net add bridge bridge ports swp1-3
cumulus@switch:~$ net add bridge bridge vids 100,200
cumulus@switch:~$ net add bridge bridge pvid 1
cumulus@switch:~$ net add interface swp3 bridge vids 200
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The above commands create the following code snippets in the /etc/network/interfaces file:

auto bridge
iface bridge
    bridge-ports swp1 swp2 swp3
    bridge-pvid 1
    bridge-vids 100 200
    bridge-vlan-aware yes

auto swp3
iface swp3
  bridge-vids 200

Edit the /etc/network/interfaces file. The following example commands configure swp3 to override the bridge VIDs:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-ports swp1 swp2 swp3
    bridge-pvid 1
    bridge-vids 100 200
    bridge-vlan-aware yes

auto swp3
iface swp3
  bridge-vids 200
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

Untagged/Access Ports

Access ports ignore all tagged packets. In the configuration below, swp1 and swp2 are configured as access ports, while all untagged traffic goes to VLAN 100:

cumulus@switch:~$ net add bridge bridge ports swp1-2
cumulus@switch:~$ net add bridge bridge vids 100,200
cumulus@switch:~$ net add bridge bridge pvid 1
cumulus@switch:~$ net add interface swp1 bridge access 100
cumulus@switch:~$ net add interface swp2 bridge access 100
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The above commands create the following code snippets in the /etc/network/interfaces file:

auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 100 200
    bridge-vlan-aware yes

auto swp1
iface swp1
    bridge-access 100

auto swp2
iface swp2
    bridge-access 100

Edit the /etc/network/interfaces file.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 100 200
    bridge-vlan-aware yes

auto swp1
iface swp1
    bridge-access 100

auto swp2
iface swp2
    bridge-access 100
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

Drop Untagged Frames

With VLAN-aware bridge mode, you can configure a switch port to drop any untagged frames. To do this, add bridge-allow-untagged no to the switch port (not to the bridge). This leaves the bridge port without a PVID and drops untagged packets.

To configure a switch port to drop untagged frames, run the net add interface swp2 bridge allow-untagged no command. The following example command configures swp2 to drop untagged frames:

cumulus@switch:~$ net add interface swp2 bridge allow-untagged no

When you check VLAN membership for that port, it shows that there is no untagged VLAN.

cumulus@switch:~$ net show bridge vlan

Interface      VLAN   Flags
-----------  ------   ---------------------
swp1              1   PVID, Egress Untagged
                 10
                100
                200
swp2             10
                100
                200

Edit the /etc/network/interfaces file to add the bridge-allow-untagged no line to the under the switch port interface stanza. The following example configures swp2 to drop untagged frames:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto swp1
iface swp1

auto swp2
iface swp2
    bridge-allow-untagged no 

auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 10 100 200
    bridge-vlan-aware yes
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ sudo ifreload -a

When you check VLAN membership for that port, it shows that there is no untagged VLAN.

cumulus@switch:~$ bridge -c vlan show
portvlan ids
swp1 1 PVID Egress Untagged
  10 100 200

swp2 10 100 200

bridge 1

VLAN Layer 3 Addressing - Switch Virtual Interfaces and Other VLAN Attributes

When configuring the VLAN attributes for the bridge, specify the attributes for each VLAN interface. If you are configuring the SVI for the native VLAN, you must declare the native VLAN and specify its IP address. Specifying the IP address in the bridge stanza itself returns an error.

The following example commands declare native VLAN 100 with IPv4 address 192.168.10.1/24 and IPv6 address 2001:db8::1/32.

cumulus@switch:~$ net add vlan 100 ip address 192.168.10.1/24
cumulus@switch:~$ net add vlan 100 ipv6 address 2001:db8::1/32
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file, then reload the configuration with the ifreload -a command. The following example declares native VLAN 100 with IPv4 address 192.168.10.1/24 and IPv6 address 2001:db8::1/32.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-ports swp1 swp2
    bridge-pvid 1
    bridge-vids 10 100 200
    bridge-vlan-aware yes

auto vlan100
iface vlan100
    address 192.168.10.1/24
    address 2001:db8::1/32
    vlan-id 100
    vlan-raw-device bridge
...

In the above configuration, if your switch is configured for multicast routing, you do not need to specify bridge-igmp-querier-src, as there is no need for a static IGMP querier configuration on the switch. Otherwise, the static IGMP querier configuration helps to probe the hosts to refresh their IGMP reports.

Configure Multiple Ports in a Range

To save time, you can specify a range of ports or VLANs instead of enumerating each one individually.

To specify a range:

In the example below, swp1-52 indicates that swp1 through swp52 are part of the bridge.

cumulus@switch:~$ net add bridge bridge ports swp1-52
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The glob keyword referenced in the bridge-ports attribute indicates that swp1 through swp52 are part of the bridge:

...
auto bridge
iface bridge
        bridge-vlan-aware yes
        bridge-ports glob swp1-52
        bridge-stp on
        bridge-vids 310 700 707 712 850 910
...

Example Configurations

The following sections provide example VLAN-aware bridge configurations.

Access Ports and Pruned VLANs

The following example configuration contains an access port and switch port that are pruned; they only sends and receive traffic tagged to and from a specific set of VLANs declared by the bridge-vids attribute. It also contains other switch ports that send and receive traffic from all the defined VLANs.

...
# ports swp3-swp48 are trunk ports which inherit vlans from the 'bridge'
# ie vlans 310,700,707,712,850,910
#
auto bridge
iface bridge
      bridge-ports swp1 swp2 swp3 ... swp51 swp52
      bridge-vids 310 700 707 712 850 910
      bridge-vlan-aware yes

auto swp1
iface swp1
      bridge-access 310
      mstpctl-bpduguard yes
      mstpctl-portadminedge yes

# The following is a trunk port that is "pruned".
# native vlan is 1, but only .1q tags of 707, 712, 850 are
# sent and received
#
auto swp2
iface swp2
      mstpctl-bpduguard yes
      mstpctl-portadminedge yes
      bridge-vids 707 712 850

# The following port is the trunk uplink and inherits all vlans
# from 'bridge'; bridge assurance is enabled using 'portnetwork' attribute
auto swp49
iface swp49
      mstpctl-portnetwork yes
      mstpctl-portpathcost 10

# The following port is the trunk uplink and inherits all vlans
# from 'bridge'; bridge assurance is enabled using 'portnetwork' attribute
 auto swp50
 iface swp50
      mstpctl-portnetwork yes
      mstpctl-portpathcost 0
...

Large Bond Set Configuration

The configuration below demonstrates a VLAN-aware bridge with a large set of bonds. The bond configurations are generated from a Mako template.

...
#
# vlan-aware bridge with bonds example
#
# uplink1, peerlink and downlink are bond interfaces.
# 'bridge' is a vlan aware bridge with ports uplink1, peerlink
# and downlink (swp2-20).
#
# native vlan is by default 1
#
# 'bridge-vids' attribute is used to declare vlans.
# 'bridge-pvid' attribute is used to specify native vlans if other than 1
# 'bridge-access' attribute is used to declare access port
#
auto lo
iface lo

auto eth0
iface eth0 inet dhcp

# bond interface
auto uplink1
iface uplink1
    bond-slaves swp32
    bridge-vids 2000-2079

# bond interface
auto peerlink
iface peerlink
    bond-slaves swp30 swp31
    bridge-vids 2000-2079 4094

# bond interface
auto downlink
iface downlink
    bond-slaves swp1
    bridge-vids 2000-2079

#
# Declare vlans for all swp ports
# swp2-20 get vlans from 2004 to 2022.
# The below uses mako templates to generate iface sections
# with vlans for swp ports
#
%for port, vlanid in zip(range(2, 20), range(2004, 2022)) :
    auto swp${port}
    iface swp${port}
      bridge-vids ${vlanid}

%endfor

# svi vlan 2000
auto bridge.2000
iface bridge.2000
    address 11.100.1.252/24

# l2 attributes for vlan 2000
auto bridge.2000
vlan bridge.2000
    bridge-igmp-querier-src 172.16.101.1

#
# vlan-aware bridge
#
auto bridge
iface bridge
    bridge-ports uplink1 peerlink downlink swp1 swp2 swp49 swp50
    bridge-vlan-aware yes

# svi peerlink vlan
auto peerlink.4094
iface peerlink.4094
    address 192.168.10.1/30
    broadcast 192.168.10.3
...

VXLANs with VLAN-aware Bridges

Cumulus Linux supports using VXLANs with VLAN-aware bridge configuration. This provides improved scalability, as multiple VXLANs can be added to a single VLAN-aware bridge. A one to one association is used between the VXLAN VNI and the VLAN, with the bridge access VLAN definition on the VXLAN and the VLAN membership definition on the local bridge member interfaces.

The configuration example below shows the differences between a VXLAN configured for traditional bridge mode and one configured for VLAN-aware mode. The configurations use head end replication (HER) together with the VLAN-aware bridge to map VLANs to VNIs.

See VXLAN Scale for information about the number of VXLANs you can configure simultaneously.

...
auto lo
iface lo inet loopback
    address 10.35.0.10/32

auto bridge
iface bridge
    bridge-ports uplink
    bridge-pvid 1
    bridge-vids 1-100
    bridge-vlan-aware yes
auto vni-10000
iface vni-10000
    alias CUSTOMER X VLAN 10
    bridge-access 10
    vxlan-id 10000
    vxlan-local-tunnelip 10.35.0.10
    vxlan-remoteip 10.35.0.34
...

Configure a Static MAC Address Entry

You can add a static MAC address entry to the layer 2 table for an interface within the VLAN-aware bridge by running a command similar to the following:

cumulus@switch:~$ sudo bridge fdb add 12:34:56:12:34:56 dev swp1 vlan 150 master static
cumulus@switch:~$ sudo bridge fdb show
44:38:39:00:00:7c dev swp1 master bridge permanent
12:34:56:12:34:56 dev swp1 vlan 150 master bridge static
44:38:39:00:00:7c dev swp1 self permanent
12:12:12:12:12:12 dev swp1 self permanent
12:34:12:34:12:34 dev swp1 self permanent
12:34:56:12:34:56 dev swp1 self permanent
12:34:12:34:12:34 dev bridge master bridge permanent
44:38:39:00:00:7c dev bridge vlan 500 master bridge permanent
12:12:12:12:12:12 dev bridge master bridge permanent

Caveats and Errata

Spanning Tree Protocol (STP)

IGMP Snooping

IGMP snooping and group membership are supported on a per-VLAN basis; however, the IGMP snooping configuration (including enable, disable, and mrouter ports) is defined on a per-bridge port basis.

VLAN Translation

A bridge in VLAN-aware mode cannot have VLAN translation enabled. Only traditional mode bridges can utilize VLAN translation.

Convert Bridges between Supported Modes

You cannot convert traditional mode bridges automatically to and from a VLAN-aware bridge. You must delete the original configuration and bring down all member switch ports before creating a new bridge.

Traditional Bridge Mode

Use a VLAN-aware bridge on your switch. Use traditional mode bridges only if you need to run more than one bridge on the switch or if you need to use PVSTP+.

Configure a Traditional Mode Bridge

The following examples show how to create a simple traditional mode bridge configuration on the switch. The example also shows some optional elements:

To configure spanning tree options for a bridge interface, refer to Spanning Tree and Rapid Spanning Tree.

The following example commands configure a traditional mode bridge called my_bridge with IP address 10.10.10.10/24. swp1, swp2, swp3, and swp4 are members of the bridge.

cumulus@switch:~$ net add bridge my_bridge ports swp1-4
cumulus@switch:~$ net add bridge my_bridge ip address 10.10.10.10/24
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file. The following example command configures a traditional mode bridge called my_bridge with IP address 10.10.10.10/24. swp1, swp2, swp3, and swp4 are members of the bridge.

...
auto swp1
iface swp1

auto swp2
iface swp2

auto swp3
iface swp3

auto swp4
iface swp4

auto my_bridge
iface my_bridge
    address 10.10.10.10/24
    bridge-ports swp1 swp2 swp3 swp4
    bridge-vlan-aware no
...

Run the ifreload -a command to reload the network configuration:

cumulus@switch:~$ sudo ifreload -a

The name of the bridge must be:

  • Compliant with Linux interface naming conventions.
  • Unique within the switch.
  • Something other than bridge, **** as Cumulus Linux reserves that name for a single VLAN-aware bridge.

Do not try to bridge the management port, eth0, with any switch ports (swp0, swp1, and so on). For example, if you create a bridge with eth0 and swp1, it does not work.

Configure Multiple Traditional Mode Bridges

You can configure multiple bridges to logically divide a switch into multiple layer 2 domains. This allows for hosts to communicate with other hosts in the same domain, while separating them from hosts in other domains.

The diagram below shows a multiple bridge configuration, where host-1 and host-2 are connected to bridge-A, while host-3 and host-4 are connected to bridge-B:

This example configuration looks like this in the /etc/network/interfaces file:

...
auto bridge-A
iface bridge-A
    bridge-ports swp1 swp2
    bridge-vlan-aware no

auto bridge-B
iface bridge-B
    bridge-ports swp3 swp4
    bridge-vlan-aware no
...

Trunks in Traditional Bridge Mode

The standard for trunking is 802.1Q. The 802.1Q specification adds a 4 byte header within the Ethernet frame that identifies the VLAN of which the frame is a member.

802.1Q also identifies an untagged frame as belonging to the native VLAN (most network devices default their native VLAN to 1). The concept of native, non-native, tagged or untagged has generated confusion due to mixed terminology and vendor-specific implementations. In Cumulus Linux:

A bridge in traditional mode has no concept of trunks, just tagged or untagged frames. With a trunk of 200 VLANs, there would need to be 199 bridges, each containing a tagged physical interface, and one bridge containing the native untagged VLAN. See the examples below for more information.

The interaction of tagged and un-tagged frames on the same trunk often leads to undesired and unexpected behavior. A switch that uses VLAN 1 for the native VLAN may send frames to a switch that uses VLAN 2 for the native VLAN, thus merging those two VLANs and their spanning tree state.

Trunk Example

To create the above example:

cumulus@switch:~$ net add bridge br-VLAN100 ports swp1.100,swp2.100
cumulus@switch:~$ net add bridge br-VLAN200 ports swp1.200,swp2.200
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Add the following configuration to the /etc/network/interfaces file:

...
auto br-VLAN100
iface br-VLAN100
   bridge-ports swp1.100 swp2.100

auto br-VLAN200
iface br-VLAN200
   bridge-ports swp1.200 swp2.200
...

VLAN Tagging Examples

You can find more examples of VLAN tagging in the VLAN tagging chapter.

Caveats

On Broadcom switches, when two VLAN subinterfaces are bridged to each other in a traditional mode bridge, switchd does not assign an internal resource ID to the subinterface, which is expected for each VLAN subinterface. To work around this issue, add a VXLAN on the bridge so that it does not require a real tunnel IP address.

VLAN Tagging

This topic shows two examples of VLAN tagging, one basic and one more advanced. They both demonstrate the streamlined interface configuration from ifupdown2.

VLAN Tagging, a Basic Example

A simple configuration demonstrating VLAN tagging involves two hosts connected to a switch.

To configure the above example, edit the /etc/network/interfaces file and add a configuration like the following:

# Config for host1

auto swp1
iface swp1

auto swp1.100
iface swp1.100

# Config for host2
# swp2 must exist to create the .1Q subinterfaces, but it is not assigned an address

auto swp2
iface swp2

auto swp2.120
iface swp2.120

auto swp2.130
iface swp2.130

VLAN Tagging, an Advanced Example

This example of VLAN tagging is more complex, involving three hosts and two switches, with a number of bridges and a bond connecting them all.

Although not explicitly designated, the bridge member ports function as 802.1Q access ports and trunk ports. In the example above, comparing Cumulus Linux with a traditional Cisco device:

To create the above configuration, edit the /etc/network/interfaces file and add a configuration like the following:

# Config for host1

# swp1 does not need an iface section unless it has a specific setting,
# it will be picked up as a dependent of swp1.100.
# And swp1 must exist in the system to create the .1q subinterfaces..
# but it is not applied to any bridge..or assigned an address.

auto swp1.100
iface swp1.100

# Config for host2
# swp2 does not need an iface section unless it has a specific setting,
# it will be picked up as a dependent of swp2.100 and swp2.120.
# And swp2 must exist in the system to create the .1q subinterfaces..
# but it is not applied to any bridge..or assigned an address.

auto swp2.100
iface swp2.100

auto swp2.120
iface swp2.120

# Config for host3
# swp3 does not need an iface section unless it has a specific setting,
# it will be picked up as a dependent of swp3.120 and swp3.130.
# And swp3 must exist in the system to create the .1q subinterfaces..
# but it is not applied to any bridge..or assigned an address.

auto swp3.120
iface swp3.120

auto swp3.130
iface swp3.130

# Configure the bond

auto bond2
iface bond2
  bond-slaves glob swp4-7

# configure the bridges

auto br-untagged
iface br-untagged
    address 10.0.0.1/24
    bridge-ports swp1 bond2
    bridge-stp on

auto br-tag100
iface br-tag100
    address 10.0.100.1/24
    bridge-ports swp1.100 swp2.100 bond2.100
    bridge-stp on

auto br-vlan120
iface br-vlan120
    address 10.0.120.1/24
    bridge-ports swp2.120 swp3.120 bond2.120
    bridge-stp on

auto v130
iface v130
    address 10.0.130.1/24
    bridge-ports swp3.130 bond2.130
    bridge-stp on

#

To verify:

cumulus@switch:~$ sudo mstpctl showbridge br-tag100
br-tag100 CIST info
  enabled         yes
  bridge id       8.000.44:38:39:00:32:8B
  designated root 8.000.44:38:39:00:32:8B
  regional root   8.000.44:38:39:00:32:8B
  root port       none
  path cost     0          internal path cost   0
  max age       20         bridge max age       20
  forward delay 15         bridge forward delay 15
  tx hold count 6          max hops             20
  hello time    2          ageing time          300
  force protocol version     rstp
  time since topology change 333040s
  topology change count      1
  topology change            no
  topology change port       swp2.100
  last topology change port  None
cumulus@switch:~$ sudo mstpctl showportdetail br-tag100  | grep -B 2 state
br-tag100:bond2.100 CIST info
  enabled            yes                     role                 Designated
  port id            8.003                   state                forwarding
--
br-tag100:swp1.100 CIST info
  enabled            yes                     role                 Designated
  port id            8.001                   state                forwarding
--
  br-tag100:swp2.100 CIST info
  enabled            yes                     role                 Designated
  port id            8.002                   state                forwarding
cumulus@switch:~$ cat /proc/net/vlan/config
VLAN Dev name    | VLAN ID
Name-Type: VLAN_NAME_TYPE_RAW_PLUS_VID_NO_PAD
bond2.100      | 100  | bond2
bond2.120      | 120  | bond2
bond2.130      | 130  | bond2
swp1.100       | 100  | swp1
swp2.100       | 100  | swp2
swp2.120       | 120  | swp2
swp3.120       | 120  | swp3
swp3.130       | 130  | swp3
cumulus@switch:~$ cat /proc/net/bonding/bond2
Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011)

Bonding Mode: IEEE 802.3ad Dynamic link aggregation
Transmit Hash Policy: layer3+4 (1)
MII Status: up
MII Polling Interval (ms): 100
Up Delay (ms): 0
Down Delay (ms): 0

802.3ad info
LACP rate: fast
Min links: 0
Aggregator selection policy (ad_select): stable
Active Aggregator Info:
    Aggregator ID: 3
    Number of ports: 4
    Actor Key: 33
    Partner Key: 33
    Partner Mac Address: 44:38:39:00:32:cf

Slave Interface: swp4
MII Status: up
Speed: 10000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 44:38:39:00:32:8e
Aggregator ID: 3
Slave queue ID: 0

Slave Interface: swp5
MII Status: up
Speed: 10000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 44:38:39:00:32:8f
Aggregator ID: 3
Slave queue ID: 0

Slave Interface: swp6
MII Status: up
Speed: 10000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 44:38:39:00:32:90
Aggregator ID: 3
Slave queue ID: 0

Slave Interface: swp7
MII Status: up
Speed: 10000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 44:38:39:00:32:91
Aggregator ID: 3
Slave queue ID: 0

A single bridge cannot contain multiple subinterfaces of the same port as members. Attempting to apply such a configuration will result in an error:

cumulus@switch:~$ sudo brctl addbr another_bridge
cumulus@switch:~$ sudo brctl addif another_bridge swp9 swp9.100
bridge cannot contain multiple subinterfaces of the same port: swp9, swp9.100

VLAN Translation

By default, Cumulus Linux does not allow VLAN subinterfaces associated with different VLAN IDs to be part of the same bridge. Base interfaces are not explicitly associated with any VLAN IDs and are exempt from this restriction.

In some cases, it may be useful to relax this restriction. For example, two servers might be connected to the switch using VLAN trunks, but the VLAN numbering provisioned on the two servers are not consistent. You can choose to just bridge two VLAN subinterfaces of different VLAN IDs from the servers. You do this by enabling the sysctl net.bridge.bridge-allow-multiple-vlans. Packets entering a bridge from a member VLAN subinterface will egress another member VLAN subinterface with the VLAN ID translated.

A bridge in VLAN-aware mode cannot have VLAN translation enabled for it; only bridges configured in traditional mode can utilize VLAN translation.

The following example enables the VLAN translation sysctl:

cumulus@switch:~$ echo net.bridge.bridge-allow-multiple-vlans = 1 | sudo tee /etc/sysctl.d/multiple_vlans.conf
net.bridge.bridge-allow-multiple-vlans = 1
cumulus@switch:~$ sudo sysctl -p /etc/sysctl.d/multiple_vlans.conf
net.bridge.bridge-allow-multiple-vlans = 1

If the sysctl is enabled and you want to disable it, run the above example, setting the sysctl net.bridge.bridge-allow-multiple-vlans to 0.

After sysctl is enabled, ports with different VLAN IDs can be added to the same bridge. In the following example, packets entering the bridge br-mix from swp10.100 will be bridged to swp11.200 with the VLAN ID translated from 100 to 200:

cumulus@switch:~$ sudo brctl addif br_mix swp10.100 swp11.200

cumulus@switch:~$ sudo brctl show br_mix
bridge name     bridge id               STP enabled     interfaces
br_mix          8000.4438390032bd       yes             swp10.100
                                                        swp11.200

Multi-Chassis Link Aggregation - MLAG

MLAG or CLAG: The Cumulus Linux implementation of MLAG is referred to by other vendors as CLAG, MC-LAG or VPC. You will even see references to CLAG in Cumulus Linux, including the management daemon, named clagd, and other options in the code, such as clag-id, which exist for historical purposes. The Cumulus Linux implementation is truly a multi-chassis link aggregation protocol, so we call it MLAG.

Multi-Chassis Link Aggregation (MLAG) enables a server or switch with a two-port bond, such as a link aggregation group (LAG), EtherChannel, port group or trunk, to connect those ports to different switches and operate as if they are connected to a single, logical switch. This provides greater redundancy and greater system throughput.

Dual-connected devices can create LACP bonds that contain links to each physical switch; active-active links from the dual-connected devices are supported even though they are connected to two different physical switches.

How Does MLAG Work?

A basic MLAG configuration looks like this:


  • The two switches, leaf01 and leaf02, known as peer switches, appear as a single device to the bond on server01.
  • server01 distributes traffic between the two links to leaf01 and leaf02 in the way you configure on the host.
  • Traffic inbound to server01 can traverse leaf01 or leaf02 and arrive at server01.

More elaborate configurations are also possible. The number of links between the host and the switches can be greater than two and does not have to be symmetrical. Additionally, because the two peer switches appear as a single switch to other bonding devices, you can also connect pairs of MLAG switches to each other in a switch-to-switch MLAG configuration:



  • leaf01 and leaf02 are also MLAG peer switches and present a two-port bond from a single logical system to spine01 and spine02.
  • spine01 and spine02 do the same as far as leaf01 and leaf02 are concerned.

Link Aggregation Control Protocol (LACP), the IEEE standard protocol for managing bonds, is used for verifying dual-connectedness. LACP runs on the dual-connected devices and on each of the MLAG peer switches. On a dual-connected device, the only configuration requirement is to create a bond that is managed by LACP.

On each of the peer switches, you must place the links that are connected to the dual-connected host or switch in the bond. This is true even if the links are a single port on each peer switch, where each port is placed into a bond, as shown below:

All of the dual-connected bonds on the peer switches have their system ID set to the MLAG system ID. Therefore, from the point of view of the hosts, each of the links in its bond is connected to the same system and so the host uses both links.

Each peer switch periodically makes a list of the LACP partner MAC addresses for all of their bonds and sends that list to its peer (using the clagd service). The LACP partner MAC address is the MAC address of the system at the other end of a bond (server01, server02, and server03 in the figure above). When a switch receives this list from its peer, it compares the list to the LACP partner MAC addresses on its switch. If any matches are found and the clag-id for those bonds match, then that bond is a dual-connected bond. You can find the LACP partner MAC address by the running net show bridge macs command.

Requirements

MLAG has these requirements:

The Edgecore Minipack AS8000 and Cumulus Express CX-11128 switches do not support MLAG.

Basic Configuration

To configure MLAG, you need to create a bond that uses LACP on the dual-connected devices and configure the interfaces (including bonds, VLANs, bridges, and peer links) on each peer switch.

Follow these steps on each peer switch in the MLAG pair:

  1. On the dual-connected device, such as a host or server that sends traffic to and from the switch, create a bond that uses LACP. The method you use varies with the type of device you are configuring.

    If you cannot use LACP in your environment, you can configure the bonds in balance-xor mode.

  2. Place every interface that connects to the MLAG pair from a dual-connected device into a bond, even if the bond contains only a single link on a single physical switch.

    The following examples place swp1 in bond1 and swp2 in bond2. The examples also add a description for the bonds (an alias), which is optional.

    cumulus@leaf01:~$ net add bond bond1 bond slaves swp1
    cumulus@leaf01:~$ net add bond bond1 alias bond1 on swp1
    cumulus@leaf01:~$ net add bond bond2 bond slaves swp2
    cumulus@leaf01:~$ net add bond bond2 alias bond2 on swp2
    cumulus@leaf01:~$ net pending
    cumulus@leaf01:~$ net commit
    

    Add the following lines to the /etc/network/interfaces file:

    cumulus@leaf01:~$ sudo nano /etc/network/interfaces
    ...
    auto bond1
    iface bond1
        alias bond1 on swp1
        bond-slaves swp1
    ...
    
    auto bond2
    iface bond2
        alias bond2 on swp2
        bond-slaves swp2
    ...
    
  3. Add a unique MLAG ID (clag-id) to each bond.

    You must specify a unique MLAG ID (clag-id) for every dual-connected bond on each peer switch so that switches know which links are dual-connected or are connected to the same host or switch. The value must be between 1 and 65535 and must be the same on both peer switches. A value of 0 disables MLAG on the bond.

    The example commands below add an MLAG ID of 1 to bond1 and 2 to bond2:

    cumulus@leaf01:~$ net add bond bond1 clag id 1
    cumulus@leaf01:~$ net add bond bond2 clag id 2
    cumulus@leaf01:~$ net pending
    cumulus@leaf01:~$ net commit
    

    In the /etc/network/interfaces file, add the line clag-id 1 to the auto bond1 stanza and clag-id 2 to auto bond2 stanza:

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    ...
    auto bond1
    iface bond1
        alias bond1 on swp1
        bond-slaves swp1
        clag-id 1
    
    auto bond2
    iface bond2
        alias bond2 on swp2
        bond-slaves swp2
        clag-id 2
    ...
    
  4. Add the bonds you created above to a bridge. The example commands below add bond1 and bond2 to a VLAN-aware bridge.

    On Mellanox switches, you must add all VLANs configured on the MLAG bond to the bridge so that traffic to the downstream device connected in MLAG is redirected successfully over the peerlink in case of an MLAG bond failure.

    cumulus@leaf01:~$ net add bridge bridge ports bond1,bond2
    cumulus@leaf01:~$ net pending
    cumulus@leaf01:~$ net commit
    

    Edit the /etc/network/interfaces file to add the bridge-ports bond1 bond2 lines to the auto bridge stanza:

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    ...
    auto bridge
    iface bridge
        bridge-ports bond1 bond2
        bridge-vlan-aware yes
    ...
    
  5. Create the inter-chassis bond and the peer link VLAN (as a VLAN subinterface). You also need to provide the peer link IP address, the MLAG bond interfaces, the MLAG system MAC address, and the backup interface.

    • By default, the NCLU command configures the inter-chassis bond with the name peerlink and the peer link VLAN with the name peerlink.4094. Use peerlink.4094 to ensure that the VLAN is independent of the bridge and spanning tree forwarding decisions.
    • The peer link IP address is an unrouteable link-local address that provides layer 3 connectivity between the peer switches.
    • Cumulus Linux provides a reserved range of MAC addresses for MLAG (between 44:38:39:ff:00:00 and 44:38:39:ff:ff:ff). Use a MAC address from this range to prevent conflicts with other interfaces in the same bridged network.
      • Do not to use a multicast MAC address.
      • Do not use the same MAC address for different MLAG pairs; make sure you specify a different MAC address for each MLAG pair in the network.
    • The backup IP address is any layer 3 backup interface for the peer link, which is used in case the peer link goes down. The backup IP address is required and must be different than the peer link IP address. It must be reachable by a route that does not use the peer link. Use the loopback or management IP address of the switch.
      Loopback or Management IP Address?
      • If your MLAG configuration has bridged uplinks (such as a campus network or a large, flat layer 2 network), use the peer switch eth0 address. When the peer link is down, the secondary switch routes towards the eth0 address using the OOB network (provided you have implemented an OOB network).
      • If your MLAG configuration has routed uplinks (a modern approach to the data center fabric network), use the peer switch loopback address. When the peer link is down, the secondary switch routes towards the loopback address using uplinks (towards the spine layer). If the primary switch is also suffering a more significant problem (for example, switchd is unresponsive or stopped), the secondary switch eventually promotes itself to primary and traffic now flows normally.

      When using BGP, to ensure IP connectivity between the loopbacks, the MLAG peer switches must use unique BGP ASNs; if they use the same ASN, you must bypass the BGP loop prevention check on the AS_PATH attribute.

    The following examples show commands for both MLAG peers (leaf01 and leaf02).

    The NCLU command is a macro command that:

    • Automatically creates the inter-chassis bond (peerlink) and the peer link VLAN subinterface (peerlink.4094), and adds the peerlink bond to the bridge
    • Configures the peer link IP address (primary is the link-local address)
    • Adds the MLAG system MAC address, the MLAG bond interfaces, and the backup IP address you specify
    cumulus@leaf01:~$ net add clag peer sys-mac 44:38:39:BE:EF:AA interface swp49-50 primary backup-ip 10.10.10.2
    cumulus@leaf01:~$ net pending
    cumulus@leaf01:~$ net commit
    

    To configure the backup link to a VRF, include the name of the VRF with the backup-ip parameter. The following example configures the backup link to VRF RED:

    cumulus@leaf01:~$ net add clag peer sys-mac 44:38:39:BE:EF:AA interface swp49-50 primary backup-ip 10.10.10.2 vrf RED
    cumulus@leaf01:~$ net pending
    cumulus@leaf01:~$ net commit
    
    cumulus@leaf02:~$ net add clag peer sys-mac 44:38:39:BE:EF:AA interface swp49-50 primary backup-ip 10.10.10.1
    cumulus@leaf02:~$ net pending
    cumulus@leaf02:~$ net commit
    

    To configure the backup link to a VRF, include the name of the VRF with the backup-ip parameter. The following example configures the backup link to VRF RED:

    cumulus@leaf02:~$ net add clag peer sys-mac 44:38:39:BE:EF:AA interface swp49-50 primary backup-ip 10.10.10.1 vrf RED
    cumulus@leaf02:~$ net pending
    cumulus@leaf02:~$ net commit
    

    Edit the /etc/network/interfaces file to add the following parameters, then run the sudo ifreload -a command.

    • The inter-chasis bond (peerlink) with two ports in the bond (swp49 and swp50 in the example command below)
    • The peerlink bond to the bridge
    • The peer link VLAN (peerlink.4094) with the backup IP address, the peer link IP address (link-local), and the MLAG system MAC address (from the reserved range of addresses).
    cumulus@leaf01:~$ sudo nano /etc/network/interfaces
    ...
    auto bridge
    iface bridge
        bridge-ports bond1 bond2 peerlink
        bridge-vlan-aware yes
    ...
    auto peerlink
    iface peerlink
        bond-slaves swp49 swp50
    

    auto peerlink.4094 iface peerlink.4094 clagd-backup-ip 10.10.10.2 clagd-peer-ip linklocal clagd-sys-mac 44:38:39:BE:EF:AA …

    To configure the backup link to a VRF, include the name of the VRF with the clagd-backup-ip parameter. The following example configures the backup link to VRF RED:

    cumulus@leaf01:~$ sudo nano /etc/network/interfaces
    ...
    auto peerlink.4094
    iface peerlink.4094
        clagd-backup-ip 10.10.10.2 vrf RED
        clagd-peer-ip linklocal
        clagd-sys-mac 44:38:39:BE:EF:AA
    ...
    

    Run the sudo ifreload -a command to apply all the configuration changes:

    cumulus@leaf01:~$ sudo ifreload -a
    
    cumulus@leaf02:~$ sudo nano /etc/network/interfaces
    ...
    auto bridge
    iface bridge
        bridge-ports bond1 bond2 peerlink
        bridge-vlan-aware yes
    ...
    auto peerlink
    iface peerlink
        bond-slaves swp49 swp50
    

    auto peerlink.4094 iface peerlink.4094 clagd-backup-ip 10.10.10.1 clagd-peer-ip linklocal clagd-sys-mac 44:38:39:BE:EF:AA …

    To configure the backup link to a VRF, include the name of the VRF with the clagd-backup-ip parameter. The following example configures the backup link to VRF RED:

    cumulus@leaf02:~$ sudo nano /etc/network/interfaces
    ...
    auto peerlink.4094
    iface peerlink.4094
        clagd-backup-ip 10.10.10.1 vrf RED
        clagd-peer-ip linklocal
        clagd-sys-mac 44:38:39:BE:EF:AA
    ...
    

    Run the sudo ifreload -a command to apply all the configuration changes:

    cumulus@leaf02:~$ sudo ifreload -a
    

  • Do not add VLAN 4094 to the bridge VLAN list; VLAN 4094 for the peer link subinterface cannot be configured as a bridged VLAN with bridge VIDs under the bridge.
  • Do not use 169.254.0.1 as the MLAG peer link IP address; Cumulus Linux uses this address exclusively for BGP unnumbered interfaces.
  • When you configure MLAG manually in the /etc/network/interfaces file, the changes take effect when you bring the peer link interface up with the sudo ifreload -a command. Do not use systemctl restart clagd.service to apply the new configuration.
  • The MLAG bond does not support layer 3 configuration.

MLAG synchronizes the dynamic state between the two peer switches but it does not synchronize the switch configurations. After modifying the configuration of one peer switch, you must make the same changes to the configuration on the other peer switch. This applies to all configuration changes, including:

Optional Configuration

This section describes optional configuration procedures.

Set Roles and Priority

Each MLAG-enabled switch in the pair has a role. When the peering relationship is established between the two switches, one switch is put into the primary role and the other into the secondary role. When an MLAG-enabled switch is in the secondary role, it does not send STP BPDUs on dual-connected links; it only sends BPDUs on single-connected links. The switch in the primary role sends STP BPDUs on all single- and dual-connected links.

By default, the role is determined by comparing the MAC addresses of the two sides of the peering link; the switch with the lower MAC address assumes the primary role. You can override this by setting the priority option for the peer link:

cumulus@leaf01:~$ net add interface peerlink.4094 clag priority 2048
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

Edit the /etc/network/interfaces file and add the clagd-priority option, then run the ifreload -a command.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto peerlink.4094
iface peerlink.4094
    clagd-peer-ip linklocal
    clagd-backup-ip 10.10.10.2
    clagd-sys-mac 44:38:39:BE:EF:AA
    clagd-priority 2048
...
cumulus@switch:~$ sudo ifreload -a

The switch with the lower priority value is given the primary role; the default value is 32768 and the range is between 0 and 65535.

When the clagd service exits during switch reboot or if you stop the service on the primary switch, the peer switch that is in the secondary role becomes the primary.

However, if the primary switch goes down without stopping the clagd service for any reason, or if the peer link goes down, the secondary switch does not change its role. If the peer switch is determined to not be alive, the switch in the secondary role rolls back the LACP system ID to be the bond interface MAC address instead of the MLAG system MAC address (clagd-sys-mac) and the switch in primary role uses the MLAG system MAC address as the LACP system ID on the bonds.

Set clagctl Timers

The clagd service has a number of timers that you can tune for enhanced performance:

Timer
Description
--reloadTimer <seconds> The number of seconds to wait for the peer switch to become active. If the peer switch does not become active after the timer expires, the MLAG bonds leave the initialization (protodown) state and become active. This provides clagd with sufficient time to determine whether the peer switch is coming up or if it is permanently unreachable.
The default is 300 seconds.
--peerTimeout <seconds> The number of seconds clagd waits without receiving any messages from the peer switch before it determines that the peer is no longer active. At this point, the switch reverts all configuration changes so that it operates as a standard non-MLAG switch. This includes removing all statically assigned MAC addresses, clearing the egress forwarding mask, and allowing addresses to move from any port to the peer port. After a message is again received from the peer, MLAG operation restarts. If this parameter is not specified, clagd uses ten times the local lacpPoll value.
--initDelay <seconds> The number of seconds clagd delays bringing up MLAG bonds and anycast IP addresses.
The default is 180 seconds.NVIDIA recommends you set this parameter to 300 seconds in a scaled environment.
--sendTimeout <seconds> The number of seconds clagd waits until the sending socket times out. If it takes longer than the sendTimeout value to send data to the peer, clagd generates an exception.
The default is 30 seconds.
--lacpPoll <seconds> The number of seconds clagd waits before obtaining local LACP information.
The default is 2 seconds.

To set a timer:

Run the net add interface peerlink.4094 clag args <timer> <value> command. The following example command sets the peerlink timer to 900 seconds:

cumulus@leaf01:~$ net add interface peerlink.4094 clag args --peerTimeout 900
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

Edit the /etc/network/interfaces file to add the clagd-args <timer> <value> line to the peerlink.4094 stanza, then run the ifreload -a command. The following example sets the peerlink timer to 900 seconds:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto peerlink.4094
iface peerlink.4094
    clagd-args --peerTimeout 900
    clagd-peer-ip linklocal
    clagd-backup-ip 10.10.10.2
    clagd-sys-mac 44:38:39:BE:EF:AA
    clagd-priority 2048
...
cumulus@switch:~$ sudo ifreload -a

Configure MLAG with a Traditional Mode Bridge

To configure MLAG with a traditional mode bridge instead of a VLAN-aware mode bridge, you must configure the peer link and all dual-connected links as untagged (native) ports on a bridge (note the absence of any VLANs in the bridge-ports line and the lack of the bridge-vlan-aware parameter below):

...
auto br0
iface br0
    bridge-ports peerlink bond1 bond2
...

The following example shows you how to allow VLAN 10 across the peer link:

...
auto br0.10
iface br0.10
    bridge-ports peerlink.10 bond1.10 bond2.10
    bridge-stp on
...

In an MLAG and traditional bridge configuration, NVIDIA recommends that you set bridge learning to off on all VLANs over the peerlink except for the layer 3 peerlink subinterface; for example:

...
auto peerlink
iface peerlink
    bridge-learning off
    
auto peerlink.1510
iface peerlink.1510
    bridge-learning off

auto peerlink.4094
iface peerlink.4094
...

Configure a Backup UDP Port

By default, Cumulus Linux uses UDP port 5342 with the backup IP address. To change the backup UDP port:

cumulus@leaf01:~$ net add interface peerlink.4094 clag args --backupPort 5400
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

Edit the /etc/network/interfaces file to add clagd-args --backupPort <port> to the auto peerlink.4094 stanza. For example:

...
auto peerlink.4094
iface peerlink.4094
    clagd-args --backupPort 5400
    clagd-backup-ip 10.10.10.2
    clagd-peer-ip linklocal
    clagd-sys-mac 44:38:39:BE:EF:AA
...

Run the sudo ifreload -a command to apply all the configuration changes:

cumulus@leaf01:~$ sudo ifreload -a

Best Practices

Follow these best practices when configuring MLAG on your switches.

MTU and MLAG

The MTU in MLAG traffic is determined by the bridge MTU. Bridge MTU is determined by the lowest MTU setting of an interface that is a member of the bridge. If you want to set an MTU other than the default of 9216 bytes, you must configure the MTU on each physical interface and bond interface that is a member of every MLAG bridge in the entire bridged domain.

The following example commands set an MTU of 1500 for each of the bond interfaces (peerlink, uplink, bond1, bond2), which are members of bridge bridge:

cumulus@switch:~$ net add bond peerlink mtu 1500
cumulus@switch:~$ net add bond uplink mtu 1500
cumulus@switch:~$ net add bond bond1 mtu 1500
cumulus@switch:~$ net add bond bond2 mtu 1500
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file, then run the ifreload -a command. For example:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-ports peerlink uplink bond1 bond2

auto peerlink
iface peerlink
    mtu 1500

auto bond1
iface bond1
    mtu 1500

auto bond2
iface bond2
    mtu 1500

auto uplink
iface uplink
    mtu 1500
...
cumulus@switch:~$ sudo ifreload -a

STP and MLAG

Always enable STP in your layer 2 network and BPDU Guard on the host-facing bond interfaces.

The peer link carries very little traffic when compared to the bandwidth consumed by dataplane traffic. In a typical MLAG configuration, most every connection between the two switches in the MLAG pair is dual-connected so the only traffic going across the peer link is traffic from the clagd process and some LLDP or LACP traffic; the traffic received on the peer link is not forwarded out of the dual-connected bonds.

However, there are some instances where a host is connected to only one switch in the MLAG pair; for example:

etermine how much bandwidth is traveling across the single-connected interfaces and allocate half of that bandwidth to the peer link. On average, one half of the traffic destined to the single-connected host arrives on the switch directly connected to the single-connected host and the other half arrives on the switch that is not directly connected to the single-connected host. When this happens, only the traffic that arrives on the switch that is not directly connected to the single-connected host needs to traverse the peer link.

In addition, you might want to add extra links to the peer link bond to handle link failures in the peer link bond itself.


  • Each host has two 10G links, with each 10G link going to each switch in the MLAG pair.
  • Each host has 20G of dual-connected bandwidth; all three hosts have a total of 60G of dual-connected bandwidth.
  • Allocate at least 15G of bandwidth to each peer link bond, which represents half of the single-connected bandwidth.

When planning for link failures for a full rack, you need only allocate enough bandwidth to meet your site strategy for handling failure scenarios. For example, for a full rack with 40 servers and two switches, you might plan for four to six servers to lose connectivity to a single switch and become single connected before you respond to the event. Therefore, if you have 40 hosts each with 20G of bandwidth dual-connected to the MLAG pair, you might allocate between 20G and 30G of bandwidth to the peer link, which accounts for half of the single-connected bandwidth for four to six hosts.

When enabling a routing protocol in an MLAG environment, it is also necessary to manage the uplinks; by default MLAG is not aware of layer 3 uplink interfaces. If there is a peer link failure, MLAG does not remove static routes or bring down a BGP or OSPF adjacency unless you use a separate link state daemon such as ifplugd.

When you use MLAG with VRR, set up a routed adjacency across the peerlink.4094 interface. If a routed connection is not built across the peer link, during an uplink failure on one of the switches in the MLAG pair, egress traffic might not be forwarded if the destination is on the switch whose uplinks are down.

To set up the adjacency, configure a BGP or OSPF unnumbered peering, as appropriate for your network.

For BGP, use a configuration like this:

cumulus@switch:~$ net add bgp neighbor peerlink.4094 interface remote-as internal
cumulus@switch:~$ net commit

For OSPF, use a configuration like this:

cumulus@switch:~$ net add interface peerlink.4094 ospf area 0.0.0.1
cumulus@switch:~$ net commit

If you are using EVPN and MLAG, you need to enable the EVPN address family across the peerlink.4094 interface as well:

cumulus@switch:~$ net add bgp neighbor peerlink.4094 interface remote-as internal
cumulus@switch:~$ net add bgp l2vpn evpn neighbor peerlink.4094 activate
cumulus@switch:~$ net commit

If you use NCLU to create an iBGP peering across the peer link, the net add bgp l2vpn evpn neighbor peerlink.4094 activate command creates a new eBGP neighborship when one is already configured for iBGP. The existing iBGP configuration is still valid.

MLAG Routing Support

In addition to the routing adjacency over the peer link, Cumulus Linux supports routing adjacencies from attached network devices to MLAG switches under the following conditions:

The router cannot:

  • Attach to the switch over a MLAG bond interface.
  • Form routing adjacencies to a virtual address (VRR or VRRP).

Configuration Examples

Basic Example

The example below shows a basic MLAG configuration, where:

cumulus@leaf01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.1/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink
    bridge-ports bond1 bond2 bond3
    bridge-vids 10 20 30  
    bridge-vlan-aware yes

auto vlan10
iface vlan10
    address 10.1.10.2/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.2/24
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.2/24
    vlan-raw-device bridge
    vlan-id 30

auto swp51
iface swp51
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.2
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf02:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.2/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink
    bridge-ports bond1 bond2 bond3
    bridge-vids 10 20 30  
    bridge-vlan-aware yes

auto vlan10
iface vlan10
    address 10.1.10.3/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.3/24
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.3/24
    vlan-raw-device bridge
    vlan-id 30

auto swp51
iface swp51
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.1
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@spine01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.101/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

MLAG and BGP Example

The example configuration below shows an MLAG configuration where:

/etc/network/interfaces

cumulus@leaf01:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.1/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink
    bridge-ports bond1 bond2 bond3
    bridge-vids 10 20 30
    bridge-vlan-aware yes

auto vlan10
iface vlan10
    address 10.1.10.2/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.2/24
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.2/24
    vlan-raw-device bridge
    vlan-id 30

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.2
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf02:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.2/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128


auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink
    bridge-ports bond1 bond2 bond3
    bridge-vids 10 20 30
    bridge-vlan-aware yes

auto vlan10
iface vlan10
    address 10.1.10.3/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.3/24
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.3/24
    vlan-raw-device bridge
    vlan-id 30

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.1
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf03:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.3/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128


auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink
    bridge-ports bond1 bond2 bond3
    bridge-vids 10 20 30
    bridge-vlan-aware yes

auto vlan10
iface vlan10
    address 10.1.10.2/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.2/24
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.2/24
    vlan-raw-device bridge
    vlan-id 30

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.4
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:BB

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf04:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.4/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink
    bridge-ports bond1 bond2 bond3
    bridge-vids 10 20 30
    bridge-vlan-aware yes

auto vlan10
iface vlan10
    address 10.1.10.3/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.3/24
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.3/24
    vlan-raw-device bridge
    vlan-id 30

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.3
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:BB

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@spine01:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.101/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt
auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine
cumulus@spine02:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.102/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

/etc/frr/frr.conf

cumulus@leaf01:~$ cat /etc/frr/frr.conf
...
service integrated-vtysh-config
!
log syslog informational
!
router bgp 65101
 bgp router-id 10.10.10.1
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 !
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
!
line vty
!
cumulus@leaf02:~$ cat /etc/frr/frr.conf
...
service integrated-vtysh-config
!
log syslog informational
!
router bgp 65101
 bgp router-id 10.10.10.2
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 !
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
!

!
line vty
!
cumulus@leaf03:~$ cat /etc/frr/frr.conf
...
service integrated-vtysh-config
!
log syslog informational
!
router bgp 65102
 bgp router-id 10.10.10.3
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 !
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
!

!
line vty
!

cumulus@leaf04:~$ cat /etc/frr/frr.conf
...
service integrated-vtysh-config
!
log syslog informational
!
router bgp 65102
 bgp router-id 10.10.10.4
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 !
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !

!
line vty
!
cumulus@spine01:~$ cat /etc/frr/frr.conf
...
service integrated-vtysh-config
!
log syslog informational
!
!
router bgp 65199
 bgp router-id 10.10.10.101
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 !
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
!

!
line vty
!
cumulus@spine02:~$ cat /etc/frr/frr.conf
...
service integrated-vtysh-config
!
log syslog informational
!
!
router bgp 65199
 bgp router-id 10.10.10.102
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 !
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
!

!
line vty
!

Troubleshooting

Use the following troubleshooting tips to check that MLAG is configured and working correctly.

Check MLAG Status

To check the status of your MLAG configuration, run the NCLU net show clag command or the Linux clagctl command. For example:

cumulus@switch:~$ net show clag
The peer is alive
    Peer Priority, ID, and Role: 4096 44:38:39:FF:00:01 primary
     Our Priority, ID, and Role: 8192 44:38:39:FF:00:02 secondary
          Peer Interface and IP: peerlink.4094 linklocal
                      Backup IP: 192.168.1.12 (inactive)
                     System MAC: 44:38:39:FF:00:01

CLAG Interfaces
Our Interface      Peer Interface     CLAG Id   Conflicts              Proto-Down Reason
----------------   ----------------   -------   --------------------   -----------------
           bond1   bond1              1         -                      -
           bond2   bond2              2         -                      -

Show All MLAG Settings

To see all MLAG settings, run the clagctl params command:

cumulus@leaf01:~$ clagctl params
clagVersion = 1.4.0
clagDataVersion = 1.4.0
clagCmdVersion = 1.1.0
peerIp = linklocal
peerIf = peerlink.4094
sysMac = 44:38:39:be:ef:aa
lacpPoll = 2
currLacpPoll = 2
peerConnect = 1
cmdConnect = 1
peerLinkPoll = 1
switchdReadyTimeout = 120
reloadTimer = 300
periodicRun = 4
priority = 1000
quiet = False
debug = 0x0
verbose = False
log = syslog
vm = True
peerPort = 5342
peerTimeout = 20
initDelay = 180
sendTimeout = 30
sendBufSize = 65536
forceDynamic = False
dormantDisable = False
redirectEnable = False
backupIp = 10.10.10.2
backupVrf = None
backupPort = 5342
vxlanAnycast = None
neighSync = True
permanentMacSync = True
cmdLine = /usr/sbin/clagd --daemon linklocal peerlink.4094 44:38:39:BE:EF:AA --priority 1000 --backupIp 10.10.10.2
peerlinkLearnEnable = False

View the MLAG Log File

By default, when running, the clagd service logs status messages to the /var/log/clagd.log file and to syslog. Example log file output is shown below:

cumulus@spine01:~$ sudo tail /var/log/clagd.log
2016-10-03T20:31:50.471400+00:00 spine01 clagd[1235]: Initial config loaded
2016-10-03T20:31:52.479769+00:00 spine01 clagd[1235]: The peer switch is active.
2016-10-03T20:31:52.496490+00:00 spine01 clagd[1235]: Initial data sync to peer done.
2016-10-03T20:31:52.540186+00:00 spine01 clagd[1235]: Role is now primary; elected
2016-10-03T20:31:54.250572+00:00 spine01 clagd[1235]: HealthCheck: role via backup is primary
2016-10-03T20:31:54.252642+00:00 spine01 clagd[1235]: HealthCheck: backup active
2016-10-03T20:31:54.537967+00:00 spine01 clagd[1235]: Initial data sync from peer done.
2016-10-03T20:31:54.538435+00:00 spine01 clagd[1235]: Initial handshake done.
2016-10-03T20:31:58.527464+00:00 spine01 clagd[1235]: leaf03-04 is now dual connected.
2016-10-03T22:47:35.255317+00:00 spine01 clagd[1235]: leaf01-02 is now dual connected.

Monitor the clagd Service

Due to the critical nature of the clagd service, systemd continuously monitors its status by receiving notify messages every 30 seconds. If the clagd service terminates or becomes unresponsive for any reason and systemd receives no messages after 60 seconds, systemd restarts the clagd service. systemd logs these failures in the /var/log/syslog file and, on the first failure, also generates a cl-supportfile.

Monitoring is configured and enabled automatically as long as the clagd service is enabled (the peer IP address (clagd-peer-ip), the MLAG system MAC address (clagd-sys-mac), and the backup IP address (clagd-backup-ip) are configured for an interface) and the clagd service is running. If you stop clagd with the systemctl stop clagd.service command, clagd monitoring also stops.

You can check if clagd is enabled and running with the cl-service-summary or the systemctl status command:

cumulus@switch:~$ cl-service-summary
Service cron               enabled    active
Service ssh                enabled    active
Service syslog             enabled    active
Service asic-monitor       enabled    inactive
Service clagd              enabled    active
...
cumulus@switch:~$ systemctl status clagd.service
 ● clagd.service - Cumulus Linux Multi-Chassis LACP Bonding Daemon
    Loaded: loaded (/lib/systemd/system/clagd.service; enabled)
    Active: active (running) since Mon 2016-10-03 20:31:50 UTC; 4 days ago
        Docs: man:clagd(8)
    Main PID: 1235 (clagd)
    CGroup: /system.slice/clagd.service
            ├─1235 /usr/bin/python /usr/sbin/clagd --daemon 169.254.255.2 peerlink.4094 44:38:39:FF:40:90 --prior...
            └─15795 /usr/share/mgmt-vrf/bin/ping6 -L -c 1 ff02::1 -I peerlink.409

Feb 01 23:19:30 leaf01 clagd[1717]: Cleanup is executing.
Feb 01 23:19:31 leaf01 clagd[1717]: Cleanup is finished
Feb 01 23:19:31 leaf01 clagd[1717]: Beginning execution of clagd version 1.3.0
Feb 01 23:19:31 leaf01 clagd[1717]: Invoked with: /usr/sbin/clagd --daemon 169.254.255.2 peerlink.4094 44:38:39:FF:40:94 --pri...168.0.12
Feb 01 23:19:31 leaf01 clagd[1717]: Role is now secondary
Feb 01 23:19:31 leaf01 clagd[1717]: Initial config loaded
Feb 01 23:19:31 leaf01 systemd[1]: Started Cumulus Linux Multi-Chassis LACP Bonding Daemon.
Feb 01 23:24:31 leaf01 clagd[1717]: HealthCheck: reload timeout.
Feb 01 23:24:31 leaf01 clagd[1717]: Role is now primary; Reload timeout
...

A large volume of packet drops across one of the peer link interfaces can be expected. These drops serve to prevent looping of BUM (broadcast, unknown unicast, multicast) packets. When a packet is received across the peer link, if the destination lookup results in an egress interface that is a dual-connected bond, the switch does not forward the packet (to prevent loops). This results in a drop being recorded on the peer link.

To check packet drops across peer link interfaces, run the following command:

Run the net show counters command. The number of dropped packets is displayed in the RX_DRP column.

cumulus@switch:~$ net show counters

Kernel Interface table
Iface            MTU    RX_OK    RX_ERR    RX_DRP    RX_OVR    TX_OK    TX_ERR    TX_DRP    TX_OVR  Flg
-------------  -----  -------  --------  --------  --------  -------  --------  --------  --------  -----
bond1           9216        0         0         0         0      542         0         0         0  BMmU
bond2           9216        0         0         0         0      542         0         0         0  BMmU
bridge          9216        0         0         0         0       17         0         0         0  BMRU
eth0            1500     5497         0         0         0      933         0         0         0  BMRU
lo             65536     1328         0         0         0     1328         0         0         0  LRU
mgmt           65536      790         0         0         0        0         0        33         0  OmRU
peerlink        9216    23626         0       520         0    23665         0         0         0  BMmRU
peerlink.4094   9216     8013         0         0         0     8017         0         0         0  BMRU
swp1            9216        5         0         0         0      553         0         0         0  BMsRU
swp2            9216        3         0         0         0      552         0         0         0  BMsRU
swp49           9216    11822         0         0         0    11852         0         0         0  BMsRU
swp50           9216    11804         0         0         0    11841         0         0         0  BMsRU
swp51           9216        0         0         0         0      292         0         0         0  BMRU

Run the ethtool -S <interface> command:

cumulus@leaf01:mgmt:~$ ethtool -S swp49
NIC statistics:
     rx_queue_0_packets: 136
     rx_queue_0_bytes: 36318
     rx_queue_0_drops: 0
     rx_queue_0_xdp_packets: 0
     rx_queue_0_xdp_tx: 0
     rx_queue_0_xdp_redirects: 0
     rx_queue_0_xdp_drops: 0
     rx_queue_0_kicks: 1
     tx_queue_0_packets: 200
     tx_queue_0_bytes: 44244
     tx_queue_0_xdp_tx: 0
     tx_queue_0_xdp_tx_drops: 0
     tx_queue_0_kicks: 195

Duplicate LACP Partner MAC Warning

When you run the clagctl command, you might see output similar to this:

bond1 bond1 52 duplicate lacp - partner mac

This occurs when you have multiple LACP bonds between the same two LACP endpoints; for example, an MLAG switch pair is one endpoint and an ESXi host is another. These bonds have duplicate LACP identifiers, which are MAC addresses. This same warning might trigger when you have a cabling or configuration error.

In addition to the standard UP and DOWN administrative states, an interface that is a member of an MLAG bond can also be in a protodown state. When MLAG detects a problem that might result in connectivity issues, it can put that interface into protodown state. Such connectivity issues include:

When an interface goes into a protodown state, it results in a local OPER DOWN (carrier down) on the interface.

To show an interface in protodown state, run the NCLU net show bridge link command or the Linux ip link show command. For example:

cumulus@switch:~$ net show bridge link
3: swp1 state DOWN: <NO-CARRIER,BROADCAST,MULTICAST,MASTER,UP> mtu 9216 master pfifo_fast master host-bond1 state DOWN mode DEFAULT qlen 500 protodown on
    link/ether 44:38:39:00:69:84 brd ff:ff:ff:ff:ff:ff

LACP Bypass

On Cumulus Linux, LACP Bypass allows a bond configured in 802.3ad mode to become active and forward traffic even when there is no LACP partner. For example, you can enable a host that does not have the capability to run LACP to PXE boot while connected to a switch on a bond configured in 802.3ad mode. After the pre-boot process completes and the host is capable of running LACP, the normal 802.3ad link aggregation operation takes over.

LACP Bypass All-active Mode

In all-active mode, when a bond has multiple slave interfaces, each bond slave interface operates as an active link while the bond is in bypass mode. This is useful during PXE boot of a server with multiple NICs, when you cannot determine beforehand which port needs to be active.

  • All-active mode is not supported on bonds that are not specified as bridge ports on the switch.
  • STP does not run on the individual bond slave interfaces when the LACP bond is in all-active mode. Only use all-active mode on host-facing LACP bonds. Configure STP BPDU guard together with all-active mode.
  • In an MLAG deployment where bond slaves of a host are connected to two switches and the bond is in all-active mode, all the slaves of bond are active on both the primary and secondary MLAG nodes.
  • priority mode, bond-lacp-bypass-period, bond-lacp-bypass-priority, and bond-lacp-bypass-all-active are not supported.

Configure LACP Bypass

To enable LACP bypass on the host-facing bond, set bond-lacp-bypass-allow to yes.

The following commands create a VLAN-aware bridge with LACP bypass enabled:

cumulus@switch:~$ net add bond bond1 bond slaves swp51s2,swp51s3
cumulus@switch:~$ net add bond bond1 clag id 1
cumulus@switch:~$ net add bond bond1 bond lacp-bypass-allow
cumulus@switch:~$ net add bond bond1 stp bpduguard
cumulus@switch:~$ net add bridge bridge ports bond1,bond2,bond3,bond4,peer5
cumulus@switch:~$ net add bridge bridge vids 100-105
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file to add the set bond-lacp-bypass-allow to yes option. The following configuration creates a VLAN-aware bridge with LACP bypass enabled:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bond1
iface bond1
    bond-lacp-bypass-allow yes
    bond-slaves swp51s2 swp51s3
    clag-id 1
    mstpctl-bpduguard yes
...
auto bridge
iface bridge
    bridge-ports bond1 bond2 bond3 bond4 peer5
    bridge-vids 100-105
    bridge-vlan-aware yes
...

Run the ifreload -a command to reload the configuration:

cumulus@switch:~$ sudo ifreload -a

To check the status of the configuration, run the following commands.

Run the net show interface <bond> command on the bond and its slave interfaces:

cumulus@switch:~$ net show interface bond1

    Name   MAC               Speed   MTU   Mode
--  ------ ----------------- ------- ----- ----------
UP  bond1  44:38:39:00:00:5b 1G      1500  Bond/Trunk

Bond Details
------------------ -------------------------
Bond Mode:         LACP
Load Balancing:    Layer3+4
Minimum Links:     1
In CLAG:           CLAG Active
LACP Sys Priority:
LACP Rate:         Fast Timeout
LACP Bypass:       LACP Bypass Not Supported

    Port       Speed     TX   RX   Err   Link Failures
-- --------   ------- ---- ---- ----- ---------------
UP swp51s2(P) 1G         0    0     0               0
UP swp51s3(P) 1G         0    0     0               0


All VLANs on L2 Port
----------------------
100-105

Untagged
----------
1

Vlans in disabled State
-------------------------
100-105

LLDP
--------   ---- ------------------
swp51s2(P) ==== swp1(spine01)
swp51s3(P) ==== swp1(spine02)

Run the ip link show command on the bond and its slave interfaces:

cumulus@switch:~$ ip link show bond1
164: bond1: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue master br0 state UP mode DORMANT group default
    link/ether c4:54:44:f6:44:5a brd ff:ff:ff:ff:ff:ff
cumulus@switch:~$ ip link show swp51s2
55: swp51s2: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond1 state UP mode DEFAULT group default qlen 1000
    link/ether c4:54:44:f6:44:5a brd ff:ff:ff:ff:ff:ff
cumulus@switch:~$ ip link show swp52s3
56: swp51s3: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond1 state UP mode DEFAULT group default qlen 1000
    link/ether c4:54:44:f6:44:5a brd ff:ff:ff:ff:ff:ff

To verify that LACP bypass is enabled on a bond and its slave interfaces, use the cat command:

cumulus@switch:~$ cat /sys/class/net/bond1/bonding/lacp_bypass
on 1
cumulus@switch:~$ cat /sys/class/net/bond1/bonding/slaves
swp51 swp52
cumulus@switch:~$ cat /sys/class/net/swp52/bonding_slave/ad_rx_bypass
1
cumulus@switch:~$ cat /sys/class/net/swp51/bonding_slave/ad_rx_bypass
1

Example LACP Bypass Configuration (Traditional Bridge Mode)

The following configuration shows LACP bypass enabled for multiple active interfaces (all-active mode) with a bridge in traditional bridge mode:

...
auto bond1
iface bond1
    bond-slaves swp3 swp4
    bond-lacp-bypass-allow 1

auto br0
iface br0
    bridge-ports bond1 bond2 bond3 bond4 peer5
    mstpctl-bpduguard bond1=yes
...

Virtual Router Redundancy - VRR and VRRP

Cumulus Linux provides the option of using Virtual Router Redundancy (VRR) or Virtual Router Redundancy Protocol (VRRP).

You cannot configure both VRR and VRRP on the same switch.

VRR

The diagram below illustrates a basic VRR-enabled network configuration.

The network includes several hosts and two routers running Cumulus Linux that are configured with multi-chassis link aggregation (MLAG).

Configure the Routers

The routers implement the layer 2 network interconnecting the hosts and the redundant routers. To configure the routers, add a bridge with the following interfaces to each router:

Cumulus Linux only supports VRR on switched virtual interfaces (SVIs). VRR is not supported on physical interfaces or virtual subinterfaces.

The example NCLU commands below create a VLAN-aware bridge interface for a VRR-enabled network:

cumulus@switch:~$ net add bridge
cumulus@switch:~$ net add vlan 500 ip address 192.0.2.252/24
cumulus@switch:~$ net add vlan 500 ip address-virtual 00:00:5e:00:01:00 192.0.2.254/24
cumulus@switch:~$ net add vlan 500 ipv6 address 2001:db8::1/32
cumulus@switch:~$ net add vlan 500 ipv6 address-virtual 00:00:5e:00:01:00 2001:db8::f/32
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file. The example file configuration below create a VLAN-aware bridge interface for a VRR-enabled network:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-vids 500
    bridge-vlan-aware yes

auto vlan500
iface vlan500
    address 192.0.2.252/24
    address 2001:db8::1/32
    address-virtual 00:00:5e:00:01:00 2001:db8::f/32 192.0.2.254/24
    vlan-id 500
    vlan-raw-device bridge
...

Run the ifreload -a command to reload the configuration:

cumulus@switch:~$ sudo ifreload -a

Configure the Hosts

Each host must have two network interfaces. The routers configure the interfaces as bonds running LACP; the hosts must also configure the two interfaces using teaming, port aggregation, port group, or EtherChannel running LACP. Configure the hosts either statically or with DHCP, with a gateway address that is the IP address of the virtual router; this default gateway address never changes.

Configure the links between the hosts and the routers in active-active mode for First Hop Redundancy Protocol.

Example VRR Configuration with MLAG

To create an MLAG configuration that incorporates VRR, use a configuration similar to the following.

The following examples uses a single virtual MAC address for all VLANs. You can add a unique MAC address for each VLAN, but this is not necessary.

cumulus@leaf01:~$ net add interface eth0 ip address 192.168.0.21
cumulus@leaf01:~$ net add bond server01 bond slaves swp1-2
cumulus@leaf01:~$ net add bond server01 clag id 1
cumulus@leaf01:~$ net add bond server01 mtu 9216
cumulus@leaf01:~$ net add bond server01 alias LACP etherchannel to uplink on server01
cumulus@leaf01:~$ net add bond peerlink bond slaves swp49-50
cumulus@leaf01:~$ net add interface peerlink.4094 peerlink.4094
cumulus@leaf01:~$ net add interface peerlink.4094 ip address 169.254.255.1/30
cumulus@leaf01:~$ net add interface peerlink.4094 clag peer-ip 169.254.255.2
cumulus@leaf01:~$ net add interface peerlink.4094 clag backup-ip 192.168.0.22
cumulus@leaf01:~$ net add interface peerlink.4094 clag sys-mac 44:38:39:FF:40:90
cumulus@leaf01:~$ net add bridge bridge ports server01,peerlink
cumulus@leaf01:~$ net add bridge stp treeprio 4096
cumulus@leaf01:~$ net add vlan 100 ip address 10.0.1.2/24
cumulus@leaf01:~$ net add vlan 100 ip address-virtual 00:00:5E:00:01:01 10.0.1.1/24
cumulus@leaf01:~$ net add vlan 200 ip address 10.0.2.2/24
cumulus@leaf01:~$ net add vlan 200 ip address-virtual 00:00:5E:00:01:01 10.0.2.1/24
cumulus@leaf01:~$ net add vlan 300 ip address 10.0.3.2/24
cumulus@leaf01:~$ net add vlan 300 ip address-virtual 00:00:5E:00:01:01 10.0.3.1/24
cumulus@leaf01:~$ net add vlan 400 ip address 10.0.4.2/24
cumulus@leaf01:~$ net add vlan 400 ip address-virtual 00:00:5E:00:01:01 10.0.4.1/24
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

These commands create the following configuration in the /etc/network/interfaces file:

auto eth0
iface eth0
    address 192.168.0.21

auto bridge
iface bridge
    bridge-ports server01 peerlink
    bridge-vids 100 200 300 400
    bridge-vlan-aware yes
    mstpctl-treeprio 4096

auto server01
iface server01
    alias LACP etherchannel to uplink on server01
    bond-slaves swp1 swp2
    clag-id 1
    mtu 9216

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    address 169.254.255.1/30
    clagd-backup-ip 192.168.0.22
    clagd-peer-ip 169.254.255.2
    clagd-sys-mac 44:38:39:FF:40:90

auto vlan100
iface vlan100
    address 10.0.1.2/24
    address-virtual 00:00:5E:00:01:01 10.0.1.1/24
    vlan-id 100
    vlan-raw-device bridge

auto vlan200
iface vlan200
    address 10.0.2.2/24
    address-virtual 00:00:5E:00:01:01 10.0.2.1/24
    vlan-id 200
    vlan-raw-device bridge

auto vlan300
iface vlan300
    address 10.0.3.2/24
    address-virtual 00:00:5E:00:01:01 10.0.3.1/24
    vlan-id 300
    vlan-raw-device bridge

auto vlan400
iface vlan400
    address 10.0.4.2/24
    address-virtual 00:00:5E:00:01:01 10.0.4.1/24
    vlan-id 400
    vlan-raw-device bridge
cumulus@leaf02:~$ net add interface eth0 ip address 192.168.0.22
cumulus@leaf02:~$ net add bond server01 bond slaves swp1-2
cumulus@leaf02:~$ net add bond server01 clag id 1
cumulus@leaf02:~$ net add bond server01 mtu 9216
cumulus@leaf02:~$ net add bond server01 alias LACP etherchannel to uplink on server01
cumulus@leaf02:~$ net add bond peerlink bond slaves swp49-50
cumulus@leaf02:~$ net add interface peerlink.4094 peerlink.4094
cumulus@leaf02:~$ net add interface peerlink.4094 ip address 169.254.255.2/30
cumulus@leaf02:~$ net add interface peerlink.4094 clag peer-ip 169.254.255.1
cumulus@leaf02:~$ net add interface peerlink.4094 clag backup-ip 192.168.0.21
cumulus@leaf02:~$ net add interface peerlink.4094 clag sys-mac 44:38:39:FF:40:90
cumulus@leaf02:~$ net add bridge bridge ports server01,peerlink
cumulus@leaf02:~$ net add bridge stp treeprio 4096
cumulus@leaf02:~$ net add vlan 100 ip address 10.0.1.3/24
cumulus@leaf02:~$ net add vlan 100 ip address-virtual 00:00:5E:00:01:01 10.0.1.1/24
cumulus@leaf02:~$ net add vlan 200 ip address 10.0.2.3/24
cumulus@leaf02:~$ net add vlan 200 ip address-virtual 00:00:5E:00:01:01 10.0.2.1/24
cumulus@leaf02:~$ net add vlan 300 ip address 10.0.3.3/24
cumulus@leaf02:~$ net add vlan 300 ip address-virtual 00:00:5E:00:01:01 10.0.3.1/24
cumulus@leaf02:~$ net add vlan 400 ip address 10.0.4.3/24
cumulus@leaf02:~$ net add vlan 400 ip address-virtual 00:00:5E:00:01:01 10.0.4.1/24
cumulus@leaf02:~$ net pending
cumulus@leaf02:~$ net commit

These commands create the following configuration in the /etc/network/interfaces file:

auto eth0
iface eth0
    address 192.168.0.22

auto bridge
iface bridge
    bridge-ports server01 peerlink
    bridge-vids 100 200 300 400
    bridge-vlan-aware yes
    mstpctl-treeprio 4096

auto server01
iface server01
    alias LACP etherchannel to uplink on server01
    bond-slaves swp1 swp2
    clag-id 1
    mtu 9216

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    address 169.254.255.1/30
    clagd-backup-ip 192.168.0.22
    clagd-peer-ip 169.254.255.2
    clagd-sys-mac 44:38:39:FF:40:90

auto vlan100
iface vlan100
    address 10.0.1.3/24
    address-virtual 00:00:5E:00:01:01 10.0.1.1/24
    vlan-id 100
    vlan-raw-device bridge

auto vlan200
iface vlan200
    address 10.0.2.3/24
    address-virtual 00:00:5E:00:01:01 10.0.2.1/24
    vlan-id 200
    vlan-raw-device bridge

auto vlan300
iface vlan300
    address 10.0.3.3/24
    address-virtual 00:00:5E:00:01:01 10.0.3.1/24
    vlan-id 300
    vlan-raw-device bridge

auto vlan400
iface vlan400
    address 10.0.4.3/24
    address-virtual 00:00:5E:00:01:01 10.0.4.1/24
    vlan-id 400
    vlan-raw-device bridge

Create a configuration similar to the following on an Ubuntu host:

auto eth0
iface eth0 inet dhcp

auto eth1
iface eth1 inet manual
    bond-master uplink

auto eth2
iface eth2 inet manual
    bond-master uplink

auto uplink
iface uplink inet static
    bond-slaves eth1 eth2
    bond-mode 802.3ad
    bond-miimon 100
    bond-lacp-rate 1
    bond-min-links 1
    bond-xmit-hash-policy layer3+4
    address 172.16.1.101
    netmask 255.255.255.0
    post-up ip route add 172.16.0.0/16 via 172.16.1.1
    post-up ip route add 10.0.0.0/8 via 172.16.1.1

auto uplink:200
iface uplink:200 inet static
    address 10.0.2.101

auto uplink:300
iface uplink:300 inet static
    address 10.0.3.101

auto uplink:400
iface uplink:400 inet static
    address 10.0.4.101

# modprobe bonding

Create a configuration similar to the following on an Ubuntu host:

auto eth0
iface eth0 inet dhcp

auto eth1
iface eth1 inet manual
    bond-master uplink

auto eth2
iface eth2 inet manual
    bond-master uplink

auto uplink
iface uplink inet static
    bond-slaves eth1 eth2
    bond-mode 802.3ad
    bond-miimon 100
    bond-lacp-rate 1
    bond-min-links 1
    bond-xmit-hash-policy layer3+4
    address 172.16.1.101
    netmask 255.255.255.0
    post-up ip route add 172.16.0.0/16 via 172.16.1.1
    post-up ip route add 10.0.0.0/8 via 172.16.1.1

auto uplink:200
iface uplink:200 inet static
    address 10.0.2.101

auto uplink:300
iface uplink:300 inet static
    address 10.0.3.101

auto uplink:400
iface uplink:400 inet static
    address 10.0.4.101

# modprobe bonding

VRRP

VRRP allows for a single virtual default gateway to be shared between two or more network devices in an active standby configuration. The VRRP router that forwards packets at any given time is called the master. If this VRRP router fails, another VRRP standby router automatically takes over as master. The master sends VRRP advertisements to other VRRP routers in the same virtual router group, which include the priority and state of the master. VRRP router priority determines the role that each virtual router plays and who becomes the new master if the master fails.

All virtual routers use 00:00:5E:00:01:XX for IPv4 gateways or 00:00:5E:00:02:XX for IPv6 gateways as their MAC address. The last byte of the address is the Virtual Router IDentifier (VRID), which is different for each virtual router in the network. This MAC address is used by only one physical router at a time, which replies with this address when ARP requests or neighbor solicitation packets are sent for the IP addresses of the virtual router.

  • Cumulus Linux supports both VRRPv2 and VRRPv3. The default protocol version is VRRPv3.
  • 255 virtual routers are supported per switch.
  • VRRP is not supported in an MLAG environment or with EVPN.
  • To configure VRRP on an SVI, you need to edit the /etc/frr/frr.conf file; NCLU commands are not supported for SVIs.

RFC 5798 describes VRRP in detail.

The following example illustrates a basic VRRP configuration.

Configure VRRP

To configure VRRP, specify the following information on each switch:

You can also set these optional parameters. If you do not set these parameters, the defaults are used:

Optional Parameter Default Value Description
priority 100 The priority level of the virtual router within the virtual router group, which determines the role that each virtual router plays and what happens if the master fails. Virtual routers have a priority between 1 and 254; the router with the highest priority becomes the master.
advertisement interval 1000 milliseconds The advertisement interval is the interval between successive advertisements by the master in a virtual router group. You can specify a value between 10 and 40950.
preempt enabled Preempt mode lets the router take over as master for a virtual router group if it has a higher priority than the current master. Preempt mode is enabled by default. To disable preempt mode, you need to edit the /etc/frr/frr.conf file and add the line no vrrp <VRID> preempt to the interface stanza, then restart the FRR service.

The NCLU commands write VRRP configuration to the /etc/network/interfaces file and the /etc/frr/frr.conf file.

The following example commands configure two switches (spine01 and spine02) that form one virtual router group (VRID 44) with IPv4 address 10.0.0.1/24 and IPv6 address 2001:0db8::1/64. spine01 is the master; it has a priority of 254. spine02 is the backup VRRP router.

A primary address is required for the parent interface to use as the source address on VRRP advertisement packets.

When you commit a change that configures a new routing service such as VRRP, the FRR daemon restarts and might interrupt network operations for other configured routing services.

spine01

cumulus@spine01:~$ net add interface swp1 ip address 10.0.0.2/24
cumulus@spine01:~$ net add interface swp1 ipv6 address 2001:0db8::2/64
cumulus@spine01:~$ net add interface swp1 vrrp 44 10.0.0.1/24
cumulus@spine01:~$ net add interface swp1 vrrp 44 2001:0db8::1/64
cumulus@spine01:~$ net add interface swp1 vrrp 44 priority 254
cumulus@spine01:~$ net add interface swp1 vrrp 44 advertisement-interval 5000
cumulus@spine01:~$ net pending
cumulus@spine01:~$ net commit

spine02

cumulus@spine02:~$ net add interface swp1 ip address 10.0.0.3/24
cumulus@spine02:~$ net add interface swp1 ipv6 address 2001:0db8::3/64
cumulus@spine02:~$ net add interface swp1 vrrp 44 10.0.0.1/24
cumulus@spine02:~$ net add interface swp1 vrrp 44 2001:0db8::1/64
cumulus@spine02:~$ net pending
cumulus@spine02:~$ net commit
  1. Edit the /etc/network/interface file to assign an IP address to the parent interface; for example:

    cumulus@spine01:~$ sudo vi /etc/network/interfaces
    ...
    auto swp1
    iface swp1
        address 10.0.0.2/24
        address 2001:0db8::2/64
    
  2. Enable the vrrpd daemon, then start the FRRouting service with the sudo systemctl start frr.service command.

  3. From the vtysh shell, configure VRRP.

    spine01

    cumulus@spine01:~$ sudo vtysh
    
    spine01# configure terminal
    spine01(config)# interface swp1
    spine01(config-if)# vrrp 44 ip 10.0.0.1
    spine01(config-if)# vrrp 44 ipv6 2001:0db8::1
    spine01(config-if)# vrrp 44 priority 254
    spine01(config-if)# vrrp 44 advertisement-interval 5000
    spine01(config-if)# end
    spine01# write memory
    spine01# exit
    

    spine02

    cumulus@spine02:~$ sudo vtysh
    
    spine02# configure terminal
    spine02(config)# interface swp1
    spine02(config-if)# vrrp 44 ip 10.0.0.1
    spine02(config-if)# vrrp 44 ipv6 2001:0db8::1
    spine02(config-if)# end
    spine02# write memory
    spine02# exit
    

The NCLU and vtysh commands save the configuration in the /etc/network/interfaces file and the /etc/frr/frr.conf file. For example:

cumulus@spine01:~$ sudo cat /etc/network/interfaces
...
auto swp1
iface swp1
    address 10.0.0.2/24
    address 2001:0db8::2/64
    vrrp 44 10.0.0.1/24 2001:0db8::1/64
...
cumulus@spine01:~$ sudo cat /etc/frr/frr.conf
...
interface swp1
vrrp 44
vrrp 44 advertisement-interval 5000
vrrp 44 priority 254
vrrp 44 ip 10.0.0.1
vrrp 44 ipv6 2001:0db8::1
...

Show VRRP Configuration

To show virtual router information on a switch, run the NCLU net show vrrp <VRID> command or the vtysh show vrrp <VRID> command. For example:

cumulus@spine01:~$ net show vrrp 44
Virtual Router ID                    44
Protocol Version                     3
Autoconfigured                       No
Shutdown                             No
Interface                            swp1
 VRRP interface (v4)                 vrrp4-3-1
VRRP interface (v6)                  vrrp6-3-1
Primary IP (v4)                      10.0.0.2
Primary IP (v6)                      2001:0db8::2
Virtual MAC (v4)                     00:00:5e:00:01:01
Virtual MAC (v6)                     00:00:5e:00:02:01
Status (v4)                          Master
Status (v6)                          Master
Priority                             254
Effective Priority (v4)              254
Effective Priority (v6)              254
Preempt Mode                         Yes
Accept Mode                          Yes
Advertisement Interval               5000 ms
Master Advertisement Interval (v4)   0 ms
Master Advertisement Interval (v6)   5000 ms
Advertisements Tx (v4)               17
Advertisements Tx (v6)               17
Advertisements Rx (v4)               0
Advertisements Rx (v6)               0
Gratuitous ARP Tx (v4)               1
Neigh. Adverts Tx (v6)               1
State transitions (v4)               2
State transitions (v6)               2
Skew Time (v4)                       0 ms
Skew Time (v6)                       0 ms
Master Down Interval (v4)            0 ms
Master Down Interval (v6)            0 ms
IPv4 Addresses                       1
. . . . . . . . . . . . . . . . . .  10.0.0.1
IPv6 Addresses                       1
. . . . . . . . . . . . . . . . . .  2001:0db8::1

IGMP and MLD Snooping

IGMP (Internet Group Management Protocol) and MLD (Multicast Listener Discovery) snooping are implemented in the bridge driver in the Cumulus Linux kernel and are enabled by default. IGMP snooping processes IGMP v1/v2/v3 reports received on a bridge port in a bridge to identify the hosts which would like to receive multicast traffic destined to that group.

IGMP and MLD snooping is supported over VXLAN bridges; however, this feature is not enabled by default. To enable IGMP and MLD over VXLAN, see Configure IGMP/MLD Snooping over VXLAN.

When an IGMPv2 leave message is received, a group specific query is sent to identify if there are any other hosts interested in that group, before the group is deleted.

An IGMP query message received on a port is used to identify the port that is connected to a router and is interested in receiving multicast traffic.

MLD snooping processes MLD v1/v2 reports, queries and v1 done messages for IPv6 groups. If IGMP or MLD snooping is disabled, multicast traffic gets flooded to all the bridge ports in the bridge. Similarly, in the absence of receivers in a VLAN, multicast traffic is flooded to all ports in the VLAN. The multicast group IP address is mapped to a multicast MAC address and a forwarding entry is created with a list of ports interested in receiving multicast traffic destined to that group.

Configure IGMP/MLD Snooping over VXLAN

Cumulus Linux supports IGMP/MLD snooping over VXLAN bridges, where VXLAN ports are set as router ports, on Broadcom switches.

To enable IGMP/MLD snooping over VXLAN:

cumulus@switch:~$ net add bridge mybridge mcsnoop yes
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge.100
vlan bridge.100
  bridge-igmp-querier-src 123.1.1.1

auto bridge
iface bridge
  bridge-ports swp1 swp2 swp3
  bridge-vlan-aware yes
  bridge-vids 100 200
  bridge-pvid 1
  bridge-mcquerier 1
...

Run the ifreload -a command to reload the configuration:

cumulus@switch:~$ sudo ifreload -a

Consider also configuring IGMP/MLD querier. See Configure IGMP/MLD Querier, below.

To disable IGMP/MLD snooping over VXLAN, run the net add bridge <bridge> mcsnoop no command.

Configure IGMP/MLD Querier

If no multicast router is sending queries to configure IGMP/MLD querier on the switch, you can add a configuration similar to the following in the /etc/network/interfaces file. To enable IGMP and MLD snooping for a bridge, set bridge-mcquerier to 1 in the bridge stanza. By default, the source IP address of IGMP queries is 0.0.0.0. To set the source IP address of the queries to be the bridge IP address, configure bridge-mcqifaddr 1.

For an explanation of the relevant parameters, see the ifupdown-addons-interfaces man page.

For a VLAN-aware bridge, use a configuration like the following:

...
auto bridge.100
vlan bridge.100
  bridge-igmp-querier-src 123.1.1.1

auto bridge
iface bridge
  bridge-ports swp1 swp2 swp3
  bridge-vlan-aware yes
  bridge-vids 100 200
  bridge-pvid 1
  bridge-mcquerier 1
...

For a VLAN-aware bridge, like bridge in the above example, to enable querier functionality for VLAN 100 in the bridge, set bridge-mcquerier to 1 in the bridge stanza and set bridge-igmp-querier-src to 123.1.1.1 in the bridge.100 stanza.

You can specify a range of VLANs as well. For example:

...
auto bridge.[1-200]
vlan bridge.[1-200]
  bridge-igmp-querier-src 123.1.1.1
...

For a bridge in traditional mode, use a configuration like the following:

...
auto br0
iface br0
  address 192.0.2.10/24
  bridge-ports swp1 swp2 swp3
  bridge-vlan-aware no
  bridge-mcquerier 1
  bridge-mcqifaddr 1
...

Disable IGMP and MLD Snooping

To disable IGMP and MLD snooping, set the bridge-mcsnoop value to 0.

cumulus@switch:~$ net add bridge bridge mcsnoop no
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file and set bridge-mcsnoop to 0 in the bridge stanza:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
  bridge-mcquerier 1
  bridge-mcsnoop 0
  bridge-ports swp1 swp2 swp3
  bridge-pvid 1
  bridge-vids 100 200
  bridge-vlan-aware yes
...

Run the ifreload -a command to reload the configuration:

cumulus@switch:~$ sudo ifreload -a

Troubleshooting

To show the IGMP/MLD snooping bridge state, run the brctl showstp <bridge> command:

cumulus@switch:~$ sudo brctl showstp bridge
  bridge
  bridge id              8000.7072cf8c272c
  designated root        8000.7072cf8c272c
  root port                 0                    path cost                  0
  max age                  20.00                 bridge max age            20.00
  hello time                2.00                 bridge hello time          2.00
  forward delay            15.00                 bridge forward delay      15.00
  ageing time             300.00
  hello timer               0.00                 tcn timer                  0.00
  topology change timer     0.00                 gc timer                 263.70
  hash elasticity        4096                    hash max                4096
  mc last member count      2                    mc init query count        2
  mc router                 1                    mc snooping                1
  mc last member timer      1.00                 mc membership timer      260.00
  mc querier timer        255.00                 mc query interval        125.00
  mc response interval     10.00                 mc init query interval    31.25
  mc querier                0                    mc query ifaddr            0
  flags

swp1 (1)
  port id                8001                    state                forwarding
  designated root        8000.7072cf8c272c       path cost                  2
  designated bridge      8000.7072cf8c272c       message age timer          0.00
  designated port        8001                    forward delay timer        0.00
  designated cost           0                    hold timer                 0.00
  mc router                 1                    mc fast leave              0
  flags

swp2 (2)
  port id                8002                    state                forwarding
  designated root        8000.7072cf8c272c       path cost                  2
  designated bridge      8000.7072cf8c272c       message age timer          0.00
  designated port        8002                    forward delay timer        0.00
  designated cost           0                    hold timer                 0.00
  mc router                 1                    mc fast leave              0
  flags

swp3 (3)
  port id                8003                    state                forwarding
  designated root        8000.7072cf8c272c       path cost                  2
  designated bridge      8000.7072cf8c272c       message age timer          0.00
  designated port        8003                    forward delay timer        8.98
  designated cost           0                    hold timer                 0.00
  mc router                 1                    mc fast leave              0
  flags

To show the groups and bridge port state, run the NCLU net show bridge mdb command or the Linux bridge mdb show command. To show detailed router ports and group information, run the bridge -d -s mdb show command:

cumulus@switch:~$ sudo bridge -d -s mdb show
  dev bridge port swp2 grp 234.10.10.10 temp 241.67
  dev bridge port swp1 grp 238.39.20.86 permanent 0.00
  dev bridge port swp1 grp 234.1.1.1 temp 235.43
  dev bridge port swp2 grp ff1a::9 permanent 0.00
  router ports on bridge: swp3

DIP-based Multicast Forwarding on Mellanox Spectrum Switches

Mellanox Spectrum Switches do not support DIP-based multicast forwarding. Do not configure the 224.0.0.x through 239.0.0.x and 224.128.0.x through 239.128.0.x IP ranges as multicast groups, which map to link-local MAC addresses (01:00:5e:00:00:xx).

Network Virtualization

VXLAN (Virtual Extensible LAN) is a standard overlay protocol that abstracts logical virtual networks from the physical network underneath. You can deploy simple and scalable layer 3 Clos architectures while extending layer 2 segments over that layer 3 network.

VXLAN uses a VLAN-like encapsulation technique to encapsulate MAC-based layer 2 Ethernet frames within layer 3 UDP packets. Each virtual network is a VXLAN logical layer 2 segment. VXLAN scales to 16 million segments - a 24-bit VXLAN network identifier (VNI ID) in the VXLAN header - for multi-tenancy.

Hosts on a given virtual network are joined together through an overlay protocol that initiates and terminates tunnels at the edge of the multi-tenant network, typically the hypervisor vSwitch or top of rack. These edge points are the VXLAN tunnel end points (VTEP).

Cumulus Linux can initiate and terminate VTEPs in hardware and supports wire-rate VXLAN. VXLAN provides an efficient hashing scheme across the IP fabric during the encapsulation process; the source UDP port is unique, with the hash based on layer 2 through layer 4 information from the original frame. The UDP destination port is the standard port 4789.

VXLAN is supported only on switches using the Broadcom Tomahawk, Trident II, Trident II+ and Trident3 chipsets, as well as the Mellanox Spectrum chipset.

VXLAN encapsulation over layer 3 subinterfaces (for example, swp3.111) or SVIs is not supported as traffic transiting through the switch may get dropped; even if the subinterface is used only for underlay traffic and does not perform VXLAN encapsulation, traffic may still get dropped. Only configure VXLAN uplinks as layer 3 interfaces without any subinterfaces (for example, swp3).

The VXLAN tunnel endpoints cannot share a common subnet; there must be at least one layer 3 hop between the VXLAN source and destination.

Caveats and Errata

Cut-through Mode and Store and Forward Switching

On switches using Broadcom Tomahawk, Trident II, Trident II+, and Trident3 ASICs, Cumulus Linux supports store and forward switching for VXLANs but does not support cut-through mode.

On switches using Mellanox Spectrum ASICs, Cumulus Linux supports cut-through mode for VXLANs but does not support store and forward switching.

MTU Size for Virtual Network Interfaces

The maximum transmission unit (MTU) size for a virtual network interface should be 50 bytes smaller than the MTU for the physical interfaces on the switch. For more information on setting MTU, read Layer 1 and Switch Port Attributes.

Layer 3 and Layer 2 VNIs Cannot Share the Same ID

A layer 3 VNI and a layer 2 VNI cannot have the same ID. If the VNI IDs are the same, the layer 2 VNI does not get created.

TC Filters

NVIDIA recommends you run TC filter commands on each VLAN interface on the VTEP to install rules to protect the UDP port that Cumulus Linux uses for VXLAN encapsulation against VXLAN hopping vulnerabilities. If you have VRR configured on the VLAN, add a similar rule for the VRR device.

The following example installs an IPv4 and an IPv6 filter on vlan10 to protect the default port 4879:

cumulus@switch:mgmt:~$ tc filter add dev vlan10 prio 1 protocol ip ingress flower ip_proto udp dst_port 4879 action drop
cumulus@switch:mgmt:~$ tc filter add dev vlan10 prio 2 protocol ipv6 ingress flower ip_proto udp dst_port 4879 action drop

The following example installs an IPv4 and an IPv6 filter on VRR device vlan10-v0 to protect port 4879:

cumulus@switch:mgmt:~$ tc filter add dev vlan10-v0 prio 1 protocol ip ingress flower ip_proto udp dst_port 4879 action drop
cumulus@switch:mgmt:~$ tc filter add dev vlan10-v0 prio 2 protocol ipv6 ingress flower ip_proto udp dst_port 4879 action drop

Ethernet Virtual Private Network - EVPN

VXLAN is the de facto technology for implementing network virtualization in the data center, enabling layer 2 segments to be extended over an IP core (the underlay). The initial definition of VXLAN (RFC 7348) did not include any control plane and relied on a flood-and-learn approach for MAC address learning.

Overview

Ethernet Virtual Private Network (EVPN) is a standards-based control plane for VXLAN defined in RFC 7432 and draft-ietf-bess-evpn-overlay that allows for building and deploying VXLANs at scale. It relies on multi-protocol BGP (MP-BGP) to exchange information and is based on BGP-MPLS IP VPNs (RFC 4364). It enables not only bridging between end systems in the same layer 2 segment but also routing between different segments (subnets). There is also inherent support for multi-tenancy. EVPN is often referred to as the means of implementing controller-less VXLAN.

The routing control plane (including EVPN) is installed as part of the FRRouting (FRR) package. For more information about FRR, refer to FRRouting Overview.

Key Features

Cumulus Linux fully supports EVPN as the control plane for VXLAN, including for both intra-subnet bridging and inter-subnet routing, and provides these key features:

The EVPN address-family is supported with both eBGP and iBGP peering. If the underlay routing is provisioned using eBGP, you can use the same eBGP session to carry EVPN routes. For example, in a typical 2-tier Clos network topology where the leaf switches are the VTEPs, if eBGP sessions are in use between the leaf and spine switches for the underlay routing, the same sessions can be used to exchange EVPN routes; the spine switches merely act as route forwarders and do not install any forwarding state as they are not VTEPs. When EVPN routes are exchanged over iBGP peering, OSPF can be used as the IGP or the next hops can also be resolved using iBGP.

For information about VXLAN routing, including platform and hardware limitations, see VXLAN Routing.

Data plane MAC learning is disabled by default on VXLAN interfaces. Do not enable MAC learning on VXLAN interfaces: EVPN is responsible for installing remote MACs.

Basic Configuration

The following sections provide the basic configuration needed to use EVPN as the control plane for VXLAN. The steps provided assume you have already configured VXLAN interfaces, attached them to a bridge, and mapped VLANs to VNIs.

In Cumulus Linux 4.0, MAC learning is disabled and ARP/ND suppression is enabled by default. This is a change from earlier Cumulus Linux releases, where MAC learning is enabled and ARP/ND suppression disabled by default. Be sure to update any configuration scripts, if necessary.

Enable EVPN between BGP Neighbors

To enable EVPN between BGP neighbors, add the address family evpn to the existing neighbor address-family activation command.

For a non-VTEP device that is merely participating in EVPN route exchange, such as a spine switch where the network deployment uses hop-by-hop eBGP or the switch is acting as an iBGP route reflector, activating the interface for the EVPN address family is the fundamental configuration needed in FRRouting.

The other BGP neighbor address family specific configurations supported for EVPN are allowas-in and route-reflector-client.

To configure an EVPN route exchange with a BGP peer, activate the peer or peer group within the EVPN address family. For example:

cumulus@leaf01:~$ net add bgp autonomous-system 65101
cumulus@leaf01:~$ net add bgp router-id 10.10.10.1
cumulus@leaf01:~$ net add bgp neighbor swp51 interface remote-as external
cumulus@leaf01:~$ net add bgp l2vpn evpn neighbor swp51 activate
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# bgp router-id 10.10.10.1
leaf01(config-router)# neighbor swp51 interface remote-as external
leaf01(config-router)# address-family l2vpn evpn
leaf01(config-router-af)# neighbor swp51 activate
leaf01(config-router-af)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

Adjust the remote-as above to be appropriate for your environment.

The above commands create the following configuration snippet in the /etc/frr/frr.conf file.

...
router bgp 65101
  neighbor swp51 interface remote-as external
  bgp router-id 10.10.10.1
address-family l2vpn evpn
  neighbor swp51 activate
...

The above configuration does not result in BGP knowing about the local VNIs defined on the system and advertising them to peers. This requires additional configuration, described in Advertise All VNIs, below.

FRR is not aware of any local VNIs and MACs, or hosts (neighbors) associated with those VNIs until you enable the BGP control plane for all VNIs configured on the switch by setting the advertise-all-vni option.

This configuration is only needed on leaf switches that are VTEPs. EVPN routes received from a BGP peer are accepted, even without this explicit EVPN configuration. These routes are maintained in the global EVPN routing table. However, they only become effective (imported into the per-VNI routing table and appropriate entries installed in the kernel) when the VNI corresponding to the received route is locally known.

cumulus@leaf01:~$ net add bgp l2vpn evpn advertise-all-vni
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# address-family l2vpn evpn
leaf01(config-router-af)# advertise-all-vni
leaf01(config-router-af)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

The above commands create the following configuration snippet in the /etc/frr/frr.conf file.

...
router bgp 65101
  bgp router-id 10.10.10.1
  neighbor swp51 interface remote-as external
address-family l2vpn evpn
  neighbor swp51 activate
  advertise-all-vni
...

EVPN and VXLAN Active-active Mode

For EVPN in VXLAN active-active mode, both switches in the MLAG pair establish EVPN peering with other EVPN speakers (for example, with spine switches if using hop-by-hop eBGP) and inform about their locally known VNIs and MACs. When MLAG is active, both switches announce this information with the shared anycast IP address.

For active-active configuration, make sure that:

MLAG synchronizes information between the two switches in the MLAG pair; EVPN does not synchronize.

For type-5 routes in an EVPN symmetric configuration with VXLAN active-active mode, Cumulus Linux uses Primary IP Address Advertisement. For information on configuring Primary IP Address Advertisement, see Advertise Primary IP Address.

For information about active-active VTEPs and anycast IP behavior, and for failure scenarios, see VXLAN Active-Active Mode.

Caveats

EVPN Enhancements

This section describes EVPN enhancements.

Define RDs and RTs

When FRR learns about a local VNI and there is no explicit configuration for that VNI in FRR, the route distinguisher (RD), and import and export route targets (RTs) for this VNI are automatically derived. The RD uses RouterId:VNI-Index and the import and export RTs use AS:VNI. For routes that come from a layer 2 VNI (type-2 and type-3), the RD uses the vxlan-local-tunnelip from the layer 2 VNI interface instead of the RouterId (vxlan-local-tunnelip:VNI). The RD and RTs are used in the EVPN route exchange.

The RD disambiguates EVPN routes in different VNIs (as they may have the same MAC and/or IP address) while the RTs describe the VPN membership for the route. The VNI-Index used for the RD is a unique, internally-generated number for a VNI. It only has local significance; on remote switches, its only role is for route disambiguation. This number is used instead of the VNI value itself because this number has to be less than or equal to 65535. In the RT, the AS is always encoded as a 2-byte value to allow room for a large VNI. If the router has a 4-byte AS, only the lower 2 bytes are used. This ensures a unique RT for different VNIs while having the same RT for the same VNI across routers in the same AS.

For eBGP EVPN peering, the peers are in a different AS so using an automatic RT of AS:VNI does not work for route import. Therefore, the import RT is treated as *:VNI to determine which received routes are applicable to a particular VNI. This only applies when the import RT is auto-derived and not configured.

If you do not want RDs and RTs to be derived automatically, you can define them manually. The following example commands are per VNI. You must specify these commands under address-family l2vpn evpn in BGP.

cumulus@switch:~$ net add bgp l2vpn evpn vni 10200 rd 172.16.100.1:20
cumulus@switch:~$ net add bgp l2vpn evpn vni 10200 route-target import 65100:20
cumulus@switch:~$ net add bgp l2vpn evpn advertise-all-vni
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011
switch(config-router)# address-family l2vpn evpn
switch(config-router-af)# vni 10200
switch(config-router-af-vni)# rd 172.16.100.1:20
switch(config-router-af-vni)# route-target import 65100:20
switch(config-router-af-vni)# exit
switch(config-router-af)# advertise-all-vni
switch(config-router-af)# end
switch)# write memory
switch)# exit
cumulus@switch:~$

These commands create the following configuration snippet in the /etc/frr/frr.conf file.

...
address-family l2vpn evpn
  advertise-all-vni
  vni 10200
   rd 172.16.100.1:20
   route-target import 65100:20
...

  • If you delete the RD or RT later, it reverts back to its corresponding default value.
  • Route target auto derivation does not support 4-byte AS numbers; If the router has a 4-byte AS, you must define the RTs manually.

You can configure multiple RT values. In addition, you can configure both the import and export route targets with a single command by using route-target both:

cumulus@switch:~$ net add bgp l2vpn evpn vni 10400 route-target import 100:400
cumulus@switch:~$ net add bgp l2vpn evpn vni 10400 route-target import 100:500
cumulus@switch:~$ net add bgp l2vpn evpn vni 10500 route-target both 65000:500
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011
switch(config-router)# address-family l2vpn evpn
switch(config-router-af)# vni 10400
switch(config-router-af-vni)# route-target import 100:400
switch(config-router-af-vni)# route-target import 100:500
switch(config-router-af-vni)# exit
switch(config-router-af)# vni 10500
switch(config-router-af-vni)# route-target both 65000:500
switch(config-router-af)# end
switch)# write memory
switch)# exit
cumulus@switch:~$

The above commands create the following configuration snippet in the /etc/frr/frr.conf file:

...
address-family l2vpn evpn
  vni 10400
    route-target import 100:400
    route-target import 100:500
  vni 10500
    route-target import 65000:500
    route-target export 65000:500
...

Enable EVPN in an iBGP Environment with an OSPF Underlay

You can use EVPN with an OSPF or static route underlay. This is a more complex configuration than using eBGP. In this case, iBGP advertises EVPN routes directly between VTEPs and the spines are unaware of EVPN or BGP.

The leaf switches peer with each other in a full mesh within the EVPN address family without using route reflectors. The leafs generally peer to their loopback addresses, which are advertised in OSPF. The receiving VTEP imports routes into a specific VNI with a matching route target community.

cumulus@switch:~$ net add bgp autonomous-system 65020
cumulus@switch:~$ net add bgp l2vpn evpn neighbor 10.1.1.2 remote-as internal
cumulus@switch:~$ net add bgp l2vpn evpn neighbor 10.1.1.3 remote-as internal
cumulus@switch:~$ net add bgp l2vpn evpn neighbor 10.1.1.4 remote-as internal
cumulus@switch:~$ net add bgp l2vpn evpn neighbor 10.1.1.2 activate
cumulus@switch:~$ net add bgp l2vpn evpn neighbor 10.1.1.3 activate
cumulus@switch:~$ net add bgp l2vpn evpn neighbor 10.1.1.4 activate
cumulus@switch:~$ net add bgp l2vpn evpn advertise-all-vni
cumulus@switch:~$ net add ospf router-id 10.1.1.1
cumulus@switch:~$ net add loopback lo ospf area 0.0.0.0
cumulus@switch:~$ net add ospf passive-interface lo
cumulus@switch:~$ net add interface swp50 ospf area 0.0.0.0
cumulus@switch:~$ net add interface swp51 ospf area 0.0.0.0
cumulus@switch:~$ net add interface swp50 ospf network point-to-point
cumulus@switch:~$ net add interface swp51 ospf network point-to-point
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65020
switch(config-router)# neighbor 10.1.1.2 remote-as internal
switch(config-router)# neighbor 10.1.1.3 remote-as internal
switch(config-router)# neighbor 10.1.1.4 remote-as internal
switch(config-router)# address-family l2vpn evpn
switch(config-router-af)# neighbor 10.1.1.2 activate
switch(config-router-af)# neighbor 10.1.1.3 activate
switch(config-router-af)# neighbor 10.1.1.4 activate
switch(config-router-af)# advertise-all-vni
switch(config-router-af)# exit
switch(config-router)# exit
switch(config)# router ospf
switch(config-router)# router-id 10.1.1.1
switch(config-router)# passive-interface lo
switch(config-router)# exit
switch(config)# interface lo
switch(config-if)# ip ospf area 0.0.0.0
switch(config-if)# exit
switch(config)# interface swp50
switch(config-if)# ip ospf area 0.0.0.0
switch(config-if)# ospf network point-to-point
switch(config-if)# exit
switch(config)# interface swp51
switch(config-if)# ip ospf area 0.0.0.0
switch(config-if)# ospf network point-to-point
switch(config-if)# end
switch)# write memory
switch)# exit
cumulus@switch:~$

These commands create the following configuration snippet in the /etc/frr/frr.conf file.

...
interface lo
  ip ospf area 0.0.0.0
!
interface swp50
  ip ospf area 0.0.0.0
  ip ospf network point-to-point

interface swp51
  ip ospf area 0.0.0.0
  ip ospf network point-to-point
!
router bgp 65020
  neighbor 10.1.1.2 remote-as internal
  neighbor 10.1.1.3 remote-as internal
  neighbor 10.1.1.4 remote-as internal
  !
  address-family l2vpn evpn
  neighbor 10.1.1.2 activate
  neighbor 10.1.1.3 activate
  neighbor 10.1.1.4 activate
  advertise-all-vni
  exit-address-family
  !
Router ospf
  Ospf router-id 10.1.1.1
  Passive-interface lo
...

ARP and ND Suppression

ARP suppression with EVPN allows a VTEP to suppress ARP flooding over VXLAN tunnels as much as possible. A local proxy handles ARP requests received from locally attached hosts for remote hosts. ARP suppression is the implementation for IPv4; ND suppression is the implementation for IPv6.

ARP/ND suppression is enabled by default on all VNIs in Cumulus Linux to reduce flooding of ARP/ND packets over VXLAN tunnels.

In a centralized routing deployment, you must configure layer 3 interfaces even if the switch is configured only for layer 2 (you are not using VXLAN routing). To avoid unnecessary layer 3 information from being installed, configure the ip forward off or ip6 forward off options as appropriate on the VLANs. See the example configuration below.

The following examples show a configuration using two VXLANs (10100 and 10200) and two VLANs (100 and 200).

cumulus@switch:~$ net add bridge bridge ports vni100,vni200
cumulus@switch:~$ net add bridge bridge vids 100,200
cumulus@switch:~$ net add vxlan vni100 vxlan id 10100
cumulus@switch:~$ net add vxlan vni200 vxlan id 10200
cumulus@switch:~$ net add vxlan vni100 bridge access 100
cumulus@switch:~$ net add vxlan vni200 bridge access 200
cumulus@switch:~$ net add vxlan vni100 vxlan local-tunnelip 10.0.0.1
cumulus@switch:~$ net add vxlan vni200 vxlan local-tunnelip 10.0.0.1
cumulus@switch:~$ net add vlan 100 ip forward off
cumulus@switch:~$ net add vlan 100 ipv6 forward off
cumulus@switch:~$ net add vlan 200 ip forward off
cumulus@switch:~$ net add vlan 200 ipv6 forward off
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-ports vni100 vni200
    bridge-stp on
    bridge-vids 100 200
    bridge-vlan-aware yes

auto vlan100
iface vlan100
    ip6-forward off
    ip-forward off
    vlan-id 100
    vlan-raw-device bridge

auto vlan200
iface vlan200
    ip6-forward off
    ip-forward off
    vlan-id 200
    vlan-raw-device bridge

auto vni100
iface vni100
    bridge-access 100
    vxlan-id 10100
    vxlan-local-tunnelip 10.0.0.1

auto vni200
iface vni200
      bridge-access 200
      vxlan-id 10200
      vxlan-local-tunnelip 10.0.0.1
...

For a bridge in traditional mode, you must edit the bridge configuration in the /etc/network/interfaces file using a text editor:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto bridge1
iface bridge1
    bridge-ports swp3.100 swp4.100 vni100
    ip6-forward off
    ip-forward off
...

When deploying EVPN and VXLAN using a hardware profile other than the default Forwarding Table Profile, ensure that the Linux kernel ARP sysctl settings gc_thresh2 and gc_thresh3 are both set to a value larger than the number of neighbor (ARP/ND) entries anticipated in the deployment. To configure these settings, edit the /etc/sysctl.d/neigh.conf file, then reboot the switch. If your network has more hosts than the values used in the example below, change the sysctl entries accordingly.

Example /etc/sysctl.d/neigh.conf file
cumulus@switch:~$ sudo nano /etc/sysctl.d/neigh.conf
...
net.ipv4.neigh.default.gc_thresh3=14336
net.ipv6.neigh.default.gc_thresh3=16384
net.ipv4.neigh.default.gc_thresh2=7168
net.ipv6.neigh.default.gc_thresh2=8192
...

Keep ARP and ND suppression enabled to reduce flooding of ARP and ND packets over VXLAN tunnels. However, if you need to disable ARP and ND suppression, edit the /etc/network/interfaces file to set bridge-arp-nd-suppress off on the VNI, then run the ifreload -a command:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...

auto vni100
iface vni100
    bridge-access 100
    vxlan-id 10100
    vxlan-local-tunnelip 10.0.0.1
    bridge-arp-nd-suppress off

auto vni200
iface vni200
      bridge-access 200
      vxlan-id 10200
      vxlan-local-tunnelip 10.0.0.1
      bridge-arp-nd-suppress off
...
cumulus@switch:~$ sudo ifreload -a

NVIDIA recommends that you keep ARP and ND suppression enabled on all VXLAN interfaces on the switch. If you must disable suppression for a special use case, you can not disable ARP and ND suppression on some VXLAN interfaces but not others.

Configure Static MAC Addresses

MAC addresses that are intended to be pinned to a particular VTEP can be provisioned on the VTEP as a static bridge FDB entry. EVPN picks up these MAC addresses and advertises them to peers as remote static MACs. You configure static bridge FDB entries for MACs under the bridge configuration:

cumulus@switch:~$ net add bridge post-up bridge fdb add 00:11:22:33:44:55 dev swp1 vlan 101 master static
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

For a bridge in traditional mode, you must edit the bridge configuration in the /etc/network/interfaces file using a text editor:

cumulus@leaf01:~$ sudo nano /etc/network/interfaces
...
auto br101
iface br101
    bridge-ports swp1.101 vni10101
    post-up bridge fdb add 00:11:22:33:44:55 dev swp1.101 master static
...

Edit the /etc/network/interfaces file. For example:

cumulus@leaf01:~$ sudo nano /etc/network/interfaces
...
auto bridge
iface bridge
    bridge-ports swp1 vni10101
    bridge-vids 101
    bridge-vlan-aware yes
    post-up bridge fdb add 00:11:22:33:44:55 dev swp1 vlan 101 master static
...

Filter EVPN Routes

It is common to subdivide the data center into multiple pods with full host mobility within a pod but only do prefix-based routing across pods. You can achieve this by only exchanging EVPN type-5 routes across pods.

The following example commands configure EVPN to advertise type-5 routes:

cumulus@leaf01:~$ net add routing route-map map1 permit 1 match evpn route-type prefix
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# route-map map1 permit 1
leaf01(config)# match evpn route-type prefix
leaf01(config)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

In many situations, it is also desirable to only exchange EVPN routes carrying a particular VXLAN ID. For example, if data centers or pods within a data center only share certain tenants, you can use a route map to control the EVPN routes exchanged based on the VNI.

The following example configures a route map that only advertises EVPN routes from VNI 1000:

cumulus@switch:~$ net add routing route-map map1 permit 1 match evpn vni 1000
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# route-map map1 permit 1
switch(config)# match evpn vni 1000
switch(config)# end
switch# write memory
switch# exit
cumulus@switch:~$

You can only match type-2 and type-5 routes based on VNI.

In a typical EVPN deployment, you reuse SVI IP addresses on VTEPs across multiple racks. However, if you use unique SVI IP addresses across multiple racks and you want the local SVI IP address to be reachable via remote VTEPs, you can enable the advertise-svi-ip option. This option advertises the SVI IP/MAC address as a type-2 route and eliminates the need for any flooding over VXLAN to reach the IP from a remote VTEP/rack.

  • When you enable the advertise-svi-ip option, the anycast IP/MAC address pair is not advertised. Be sure not to enable both the advertise-svi-ip option and the advertise-default-gw option at the same time. (The advertise-default-gw option configures the gateway VTEPs to advertise their IP/MAC address. See Advertising the Default Gateway.
  • If your switch is in an MLAG configuration, refer to Advertise Primary IP Address.

To advertise all SVI IP/MAC addresses on the switch, run these commands:

cumulus@switch:~$ net add bgp l2vpn evpn advertise-svi-ip
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011
switch(config-router)# address-family l2vpn evpn 
switch(config-router-af)# advertise-svi-ip
switch(config-router-af)# end
switch)# write memory
switch)# exit
cumulus@switch:~$

cumulus@switch:~$ sudo cat /etc/frr/frr.conf
...
address-family l2vpn evpn
  advertise-svi-ip
exit-address-family
...

To advertise a specific SVI IP/MAC address, run these commands:

cumulus@switch:~$ net add bgp l2vpn evpn vni 10 advertise-svi-ip
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011
switch(config-router)# address-family l2vpn evpn 
switch(config-router-af)# vni 10
switch(config-router-af-vni)# advertise-svi-ip
switch(config-router-af-vni)# end
switch)# write memory
switch)# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

cumulus@switch:~$ sudo cat /etc/frr/frr.conf
...
address-family l2vpn evpn
  vni 10
  advertise-svi-ip
exit-address-family
...

Extended Mobility

Cumulus Linux supports scenarios where the IP to MAC binding for a host or virtual machine changes across the move. In addition to the simple mobility scenario where a host or virtual machine with a binding of IP1, MAC1 moves from one rack to another, Cumulus Linux supports additional scenarios where a host or virtual machine with a binding of IP1, MAC1 moves and takes on a new binding of IP2, MAC1 or IP1, MAC2. The EVPN protocol mechanism to handle extended mobility continues to use the MAC mobility extended community and is the same as the standard mobility procedures. Extended mobility defines how the sequence number in this attribute is computed when binding changes occur.

Extended mobility not only supports virtual machine moves, but also where one virtual machine shuts down and another is provisioned on a different rack that uses the IP address or the MAC address of the previous virtual machine. For example, in an EVPN deployment with OpenStack, where virtual machines for a tenant are provisioned and shut down very dynamically, a new virtual machine can use the same IP address as an earlier virtual machine but with a different MAC address.

During mobility events, EVPN neighbor management relies on ARP and GARP to learn the new location for hosts and VMs. MAC learning is independent of this and happens in the hardware.

The support for extended mobility is enabled by default and does not require any additional configuration.

You can examine the sequence numbers associated with a host or virtual machine MAC address and IP address with the NCLU net show evpn mac vni <vni> mac <address> command or the vtysh show evpn mac vni <vni> mac <address> command. For example:

cumulus@switch:~$ net show evpn mac vni 10100 mac 00:02:00:00:00:42
MAC: 00:02:00:00:00:42
  Remote VTEP: 10.0.0.2
  Local Seq: 0 Remote Seq: 3
  Neighbors:
    10.1.1.74 Active

cumulus@switch:~$ net show evpn arp vni 10100 ip 10.1.1.74
IP: 10.1.1.74
  Type: local
  State: active
  MAC: 44:39:39:ff:00:24
  Local Seq: 2 Remote Seq: 3

Duplicate Address Detection

Cumulus Linux is able to detect duplicate MAC and IPv4/IPv6 addresses on hosts or virtual machines in a VXLAN-EVPN configuration. The Cumulus Linux switch (VTEP) considers a host MAC or IP address to be duplicate if the address moves across the network more than a certain number of times within a certain number of seconds (five moves within 180 seconds by default). In addition to legitimate host or VM mobility scenarios, address movement can occur when IP addresses are misconfigured on hosts or when packet looping occurs in the network due to faulty configuration or behavior.

Duplicate address detection is enabled by default and triggers when:

By default, when a duplicate address is detected, Cumulus Linux flags the address as a duplicate and generates an error in syslog so that you can troubleshoot the reason and address the fault, then clear the duplicate address flag. No functional action is taken on the address.

If a MAC address is flagged as a duplicate, all IP addresses associated with that MAC are flagged as duplicates.

In an MLAG configuration, MAC mobility detection runs independently on each switch in the MLAG pair. Based on the sequence in which local learning and/or route withdrawal from the remote VTEP occurs, a type-2 route might have its MAC mobility counter incremented only on one of the switches in the MLAG pair. In rare cases, it is possible for neither VTEP to increment the MAC mobility counter for the type-2 prefix.

When Does Duplicate Address Detection Trigger?

The VTEP that sees an address move from remote to local begins the detection process by starting a timer. Each VTEP runs duplicate address detection independently. Detection always starts with the first mobility event from remote to local. If the address is initially remote, the detection count can start with the very first move for the address. If the address is initially local, the detection count starts only with the second or higher move for the address. If an address is undergoing a mobility event between remote VTEPs, duplicate detection is not started.

The following illustration shows VTEP-A, VTEP-B, and VTEP-C in an EVPN configuration. Duplicate address detection triggers on VTEP-A when there is a duplicate MAC address for two hosts attached to VTEP-A and VTEP-B. However, duplicate detection does not trigger on VTEP-A when mobility events occur between two remote VTEPs (VTEP-B and VTEP-C).

Configure Duplicate Address Detection

To change the threshold for MAC and IP address moves, run the net add bgp l2vpn evpn dup-addr-detection max-moves <number-of-events> time <duration> command. You can specify max-moves to be between 2 and 1000 and time to be between 2 and 1800 seconds.

The following example command sets the maximum number of address moves allowed to 10 and the duplicate address detection time interval to 1200 seconds.

cumulus@switch:~$ net add bgp l2vpn evpn dup-addr-detection max-moves 10 time 1200 
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011
switch(config-router)# address-family l2vpn evpn 
switch(config-router-af)# dup-addr-detection max-moves 10 time 1200
switch(config-router-af)# end
switch)# write memory
switch)# exit
cumulus@switch:~$ 

To disable duplicate address detection, see Disable Duplicate Address Detection below.

Example syslog Messages

The following example shows the syslog message that is generated when Cumulus Linux detects a MAC address as a duplicate during a local update:

2018/11/06 18:55:29.463327 ZEBRA: [EC 4043309149] VNI 1001: MAC 00:01:02:03:04:11 detected as duplicate during local update, last VTEP 172.16.0.16

The following example shows the syslog message that is generated when Cumulus Linux detects an IP address as a duplicate during a remote update:

2018/11/09 22:47:15.071381 ZEBRA: [EC 4043309151] VNI 1002: MAC aa:22:aa:aa:aa:aa IP 10.0.0.9 detected as duplicate during remote update, from VTEP 172.16.0.16

Freeze a Detected Duplicate Address

Cumulus Linux provides a freeze option that takes action on a detected duplicate address. You can freeze the address permanently (until you intervene) or for a defined amount of time, after which it is cleared automatically.

When you enable the freeze option and a duplicate address is detected:

To recover from a freeze, shut down the faulty host or VM or fix any other misconfiguration in the network. If the address is frozen permanently, issue the clear command on the VTEP where the address is marked as duplicate. If the address is frozen for a defined period of time, it is cleared automatically after the timer expires (you can clear the duplicate address before the timer expires with the clear command).

If you issue the clear command or the timer expires before you address the fault, duplicate address detection might occur repeatedly.

After you clear a frozen address, if it is present behind a remote VTEP, the kernel and hardware forwarding tables are updated. If the address is locally learned on this VTEP, the address is advertised to remote VTEPs. All VTEPs get the correct address as soon as the host communicates . Silent hosts are learned only after the faulty entries age out, or you intervene and clear the faulty MAC and ARP table entries.

Configure the Freeze Option

To enable Cumulus Linux to freeze detected duplicate addresses, run the net add bgp l2vpn evpn dup-addr-detection freeze <duration>|permanent command. The duration can be any number of seconds between 30 and 3600.

The following example command freezes duplicate addresses for a period of 1000 seconds, after which it is cleared automatically:

cumulus@switch:~$ net add bgp l2vpn evpn dup-addr-detection freeze 1000
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011
switch(config-router)# address-family l2vpn evpn
switch(config-router-af)# dup-addr-detection freeze 1000
switch(config-router-af)# end
switch)# write memory
switch)# exit
cumulus@switch:~$

Set the freeze timer to be three times the duplicate address detection window. For example, if the duplicate address detection window is set to the default of 180 seconds, set the freeze timer to 540 seconds.

The following example command freezes duplicate addresses permanently (until you issue the clear command):

cumulus@switch:~$ net add bgp l2vpn evpn dup-addr-detection freeze permanent
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011
switch(config-router)# address-family l2vpn evpn 
switch(config-router-af)# dup-addr-detection freeze permanent
switch(config-router-af)# end
switch)# write memory
switch)# exit
cumulus@switch:~$

Clear Duplicate Addresses

You can clear a duplicate MAC or IP address (and unfreeze a frozen address). The following example command clears IP address 10.0.0.9 for VNI 101.

cumulus@switch:~$ net clear evpn dup-addr vni 101 ip 10.0.0.9
cumulus@switch:~$ sudo vtysh

switch# clear evpn dup-addr vni 101 ip 10.0.0.9
switch)# exit
cumulus@switch:~$

To clear duplicate addresses for all VNIs, run the following command:

cumulus@switch:~$ net clear evpn dup-addr vni all
cumulus@switch:~$ sudo vtysh

switch# clear evpn dup-addr vni all
switch)# exit
cumulus@switch:~$

In an MLAG configuration, you need to run the clear command on both the MLAG primary and secondary switch.

When you clear a duplicate MAC address, all its associated IP addresses are also cleared. However, you cannot clear an associated IP address if its MAC address is still in a duplicate state.

Disable Duplicate Address Detection

By default, duplicate address detection is enabled and a syslog error is generated when a duplicate address is detected. To disable duplicate address detection, run the following command.

cumulus@switch:~$ net del bgp l2vpn evpn dup-addr-detection
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011
switch(config-router)# address-family l2vpn evpn
switch(config-router-af)# no dup-addr-detection
switch(config-router-af)# end
switch)# write memory
switch)# exit
cumulus@switch:~$

When you disable duplicate address detection, Cumulus Linux clears the configuration and all existing duplicate addresses.

Show Detected Duplicate Address Information

During the duplicate address detection process, you can see the start time and current detection count with the NCLU net show evpn mac vni <vni_id> mac <mac_addr> command or the vtysh show evpn mac vni <vni_id> mac <mac_addr> command. The following command example shows that detection started for MAC address 00:01:02:03:04:11 for VNI 1001 on Tuesday, Nov 6 at 18:55:05 and the number of moves detected is 1.

cumulus@switch:~$ net show evpn mac vni 1001 mac 00:01:02:03:04:11
MAC: 00:01:02:03:04:11
  Intf: hostbond3(15) VLAN: 1001
  Local Seq: 1 Remote Seq: 0
  Duplicate detection started at Tue Nov  6 18:55:05 2018, detection count 1
  Neighbors:
    10.0.1.26 Active

After the duplicate MAC address is cleared, the NCLU net show evpn mac vni <vni_id> mac <mac_addr> command or the vtysh show evpn mac vni <vni_id> mac <mac_addr> command shows:

MAC: 00:01:02:03:04:11
  Remote VTEP: 172.16.0.16
  Local Seq: 13 Remote Seq: 14
  Duplicate, detected at Tue Nov  6 18:55:29 2018
  Neighbors:
    10.0.1.26 Active

To display information for a duplicate IP address, run the NCLU net show evpn arp-cache vni <vni_id> ip <ip_addr> command or the vtysh show evpn arp-cache vni <vni_id> ip <ip_addr> command. The following command example shows information for IP address 10.0.0.9 for VNI 1001.

cumulus@switch:~$ net show evpn arp-cache vni 1001 ip 10.0.0.9
IP: 10.0.0.9
  Type: remote
  State: inactive
  MAC: 00:01:02:03:04:11
  Remote VTEP: 10.0.0.34
  Local Seq: 0 Remote Seq: 14
  Duplicate, detected at Tue Nov  6 18:55:29 2018

To show a list of MAC addresses detected as duplicate for a specific VNI or for all VNIs, run the NCLU net show evpn mac vni <vni-id|all> duplicate command or the vtysh show evpn mac vni <vni-id|all> duplicate command. The following example command shows a list of duplicate MAC addresses for VNI 1001:

cumulus@switch:~$ net show evpn mac vni 1001 duplicate
Number of MACs (local and remote) known for this VNI: 16
MAC               Type   Intf/Remote VTEP      VLAN
aa:bb:cc:dd:ee:ff local  hostbond3             1001  

To show a list of IP addresses detected as duplicate for a specific VNI or for all VNIs, run the NCLU net show evpn arp-cache vni <vni-id|all> duplicate command or the vtysh show evpn arp-cache vni <vni-id|all> duplicate command. The following example command shows a list of duplicate IP addresses for VNI 1001:

cumulus@switch:~$ net show evpn arp-cache vni 1001 duplicate
Number of ARPs (local and remote) known for this VNI: 20
IP                Type   State    MAC                Remote VTEP
10.0.0.8          local  active   aa:11:aa:aa:aa:aa
10.0.0.9          local  active   aa:11:aa:aa:aa:aa
10.10.0.12        remote active   aa:22:aa:aa:aa:aa  172.16.0.16

To show configured duplicate address detection parameters, run the NCLU net show evpn command or the vtysh show evpn command:

cumulus@switch:~$ net show evpn
L2 VNIs: 4
L3 VNIs: 2
Advertise gateway mac-ip: No
Duplicate address detection: Enable
  Detection max-moves 7, time 300
  Detection freeze permanent

Inter-subnet Routing

There are multiple models in EVPN for routing between different subnets (VLANs), also known as inter-VLAN routing. The model you choose depends if every VTEP acts as a layer 3 gateway and performs routing or if only specific VTEPs perform routing, and if routing is performed only at the ingress of the VXLAN tunnel or both the ingress and the egress of the VXLAN tunnel.

Cumulus Linux supports these models:

Distributed routing (asymmetric or symmetric) is commonly deployed with the VTEPs configured with an anycast IP/MAC address for each subnet; each VTEP that has a particular subnet is configured with the same IP/MAC for that subnet. Such a model facilitates easy host/VM mobility as there is no need to change the host/VM configuration when it moves from one VTEP to another.

All routing occurs in the context of a tenant VRF (virtual routing and forwarding). A VRF instance is provisioned for each tenant and the subnets of the tenant are associated with that VRF (the corresponding SVI is attached to the VRF). Inter-subnet routing for each tenant occurs within the context of the VRF for that tenant and is separate from the routing for other tenants.

Centralized Routing

In centralized routing, you configure a specific VTEP to act as the default gateway for all the hosts in a particular subnet throughout the EVPN fabric. It is common to provision a pair of VTEPs in active-active mode as the default gateway using an anycast IP/MAC address for each subnet. You need to configure all subnets on such a gateway VTEP. When a host in one subnet wants to communicate with a host in another subnet, it addresses the packets to the gateway VTEP. The ingress VTEP (to which the source host is attached) bridges the packets to the gateway VTEP over the corresponding VXLAN tunnel. The gateway VTEP performs the routing to the destination host and post-routing, the packet gets bridged to the egress VTEP (to which the destination host is attached). The egress VTEP then bridges the packet on to the destination host.

To enable centralized routing, you must configure the gateway VTEPs to advertise their IP/MAC address. Use the advertise-default-gw command:

cumulus@leaf01:~$ net add bgp autonomous-system 65000
cumulus@leaf01:~$ net add bgp l2vpn evpn advertise-default-gw
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011
switch(config-router)# address-family l2vpn evpn
switch(config-router-af)# advertise-default-gw
switch(config-router-af)# end
switch)# write memory
switch)# exit
cumulus@switch:~$

These commands create the following configuration snippet in the /etc/frr/frr.conf file.

...
router bgp 65000
...
  address-family l2vpn evpn
    advertise-default-gw
  exit-address-family
...

You can deploy centralized routing at the VNI level. Therefore, you can configure the advertise-default-gw command per VNI so that centralized routing is used for some VNIs while distributed routing (described below) is used for other VNIs. This type of configuration is not recommended unless the deployment requires it.

When centralized routing is in use, even if the source host and destination host are attached to the same VTEP, the packets travel to the gateway VTEP to get routed and then come back.

Asymmetric Routing

In distributed asymmetric routing, each VTEP acts as a layer 3 gateway, performing routing for its attached hosts. The routing is called asymmetric because only the ingress VTEP performs routing, the egress VTEP only performs bridging. Asymmetric routing can be achieved with only host routing and does not involve any interconnecting VNIs. However, you must provision each VTEP with all VLANs/VNIs - the subnets between which communication can take place; this is required even if there are no locally-attached hosts for a particular VLAN.

The only additional configuration required to implement asymmetric routing beyond the standard configuration for a layer 2 VTEP described earlier is to ensure that each VTEP has all VLANs (and corresponding VNIs) provisioned on it and the SVI for each such VLAN is configured with an anycast IP/MAC address.

Symmetric Routing

In distributed symmetric routing, each VTEP acts as a layer 3 gateway, performing routing for its attached hosts; however, both the ingress VTEP and egress VTEP route the packets (similar to the traditional routing behavior of routing to a next hop router). In the VXLAN encapsulated packet, the inner destination MAC address is set to the router MAC address of the egress VTEP as an indication that the egress VTEP is the next hop and also needs to perform routing. All routing happens in the context of a tenant (VRF). For a packet received by the ingress VTEP from a locally attached host, the SVI interface corresponding to the VLAN determines the VRF. For a packet received by the egress VTEP over the VXLAN tunnel, the VNI in the packet has to specify the VRF. For symmetric routing, this is a VNI corresponding to the tenant and is different from either the source VNI or the destination VNI. This VNI is referred to as the layer 3 VNI or interconnecting VNI; it has to be provisioned by the operator and is exchanged through the EVPN control plane. To make the distinction clear, the regular VNI, which is used to map a VLAN, is referred to as the layer 2 VNI.

  • There is a one-to-one mapping between a layer 3 VNI and a tenant (VRF).
  • The VRF to layer 3 VNI mapping has to be consistent across all VTEPs. The layer 3 VNI has to be provisioned by the operator.
  • A layer 3 VNI and a layer 2 VNI cannot have the same ID. If the VNI IDs are the same, the layer 2 VNI does not get created.
  • In an MLAG configuration, the SVI used for the layer 3 VNI cannot be part of the bridge. This ensures that traffic tagged with that VLAN ID is not forwarded on the peer link or other trunks.

In an EVPN symmetric routing configuration, when a type-2 (MAC/IP) route is announced, in addition to containing two VNIs (the layer 2 VNI and the layer 3 VNI), the route also contains separate RTs for layer 2 and layer 3. The layer 3 RT associates the route with the tenant VRF. By default, this is auto-derived in a similar way to the layer 2 RT, using the layer 3 VNI instead of the layer 2 VNI; however you can also explicitly configure it.

For EVPN symmetric routing, additional configuration is required:

Optional configuration includes configuring RD and RTs for the tenant VRF and advertising the locally-attached subnets.

Configure a Per-tenant VXLAN Interface

cumulus@leaf01:~$ net add vxlan vni104001 vxlan id 104001
cumulus@leaf01:~$ net add vxlan vni104001 bridge access 4001
cumulus@leaf01:~$ net add vxlan vni104001 vxlan local-tunnelip 10.0.0.11
cumulus@leaf01:~$ net add bridge bridge ports vni104001
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

Edit the /etc/network/interfaces file. For example:

cumulus@leaf01:~$ sudo nano /etc/network/interfaces
...
auto vni104001
iface vni104001
    bridge-access 4001
    vxlan-id 104001
    vxlan-local-tunnelip 10.0.0.11

auto bridge
  iface bridge
    bridge-ports vni104001
    bridge-vlan-aware yes
...

Configure an SVI for the Layer 3 VNI

cumulus@leaf01:~$ net add vlan 4001 vrf turtle
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

Edit the /etc/network/interfaces file. For example:

cumulus@leaf01:~$ sudo nano /etc/network/interfaces
...
auto vlan4001
iface vlan4001
    vlan-id 4001
    vlan-raw-device bridge
    vrf turtle
...

  • Do not add the Layer 3 VNI VLAN IDs to the bridge vids list in the layer 2 bridge configuration.
  • When two VTEPs are operating in VXLAN active-active mode and performing symmetric routing, you need to configure the router MAC corresponding to each layer 3 VNI to ensure both VTEPs use the same MAC address. Specify the address-virtual (MAC address) for the SVI corresponding to the layer 3 VNI. Use the same address on both switches in the MLAG pair. Use the MLAG system MAC address. See Advertise Primary IP Address.

Configure the VRF to Layer 3 VNI Mapping

cumulus@leaf01:~$ net add vrf turtle vni 104001
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

Edit the /etc/frr/frr.conf file. For example:

cumulus@leaf01:~$ sudo nano /etc/frr/frr.conf
...
vrf turtle
  vni 104001
!
...

Configure RD and RTs for the Tenant VRF

If you do not want the RD and RTs (layer 3 RTs) for the tenant VRF to be derived automatically, you can configure them manually by specifying them under the l2vpn evpn address family for that specific VRF.

cumulus@switch:~$ net add bgp vrf tenant1 l2vpn evpn rd 172.16.100.1:20
cumulus@switch:~$ net add bgp vrf tenant1 l2vpn evpn route-target import 65100:20
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011 vrf tenant1
switch(config-router)# address-family l2vpn evpn
switch(config-router-af)# rd 172.16.100.1:20
switch(config-router-af)# route-target import 65100:20
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

These commands create the following configuration snippet in the /etc/frr/frr.conf file:

...
router bgp <as> vrf tenant1
  address-family l2vpn evpn
  rd 172.16.100.1:20
  route-target import 65100:20
...

The tenant VRF RD and RTs are different from the RD and RTs for the layer 2 VNI. See Define RDs and RTs.

Symmetric routing presents a problem in the presence of silent hosts. If the ingress VTEP does not have the destination subnet and the host route is not advertised for the destination host, the ingress VTEP cannot route the packet to its destination. You can overcome this problem by having VTEPs announce the subnet prefixes corresponding to their connected subnets in addition to announcing host routes. These routes are announced as EVPN prefix (type-5) routes.

To advertise locally attached subnets:

  1. Enable advertisement of EVPN prefix (type-5) routes. Refer to Prefix-based Routing - EVPN Type-5 Routes, below.
  2. Ensure that the routes corresponding to the connected subnets are known in the BGP VRF routing table by injecting them using the network command or redistributing them using the redistribute connected command.

This configuration is recommended only if the deployment is known to have silent hosts. It is also recommended that you enable on only one VTEP per subnet, or two for redundancy.

Prefix-based Routing

EVPN in Cumulus Linux supports prefix-based routing using EVPN type-5 (prefix) routes. Type-5 routes (or prefix routes) are primarily used to route to destinations outside of the data center fabric.

EVPN prefix routes carry the layer 3 VNI and router MAC address and follow the symmetric routing model for routing to the destination prefix.

  • When connecting to a WAN edge router to reach destinations outside the data center, deploy specific border/exit leaf switches to originate the type-5 routes.
  • On switches with Spectrum ASICs, centralized routing, symmetric routing, and prefix-based routing only work with the Spectrum A1 chip.
  • If you are using a Broadcom Trident II+ switch as a border/exit leaf, see the Inter-subnet Routing below for a required workaround; the workaround only applies to Trident II+ switches, not Tomahawk or Spectrum.

Install EVPN Type-5 Routes

For a switch to be able to install EVPN type-5 routes into the routing table, you must configure it with the layer 3 VNI related information. This configuration is the same as for symmetric routing. You need to:

  1. Configure a per-tenant VXLAN interface that specifies the layer 3 VNI for the tenant. This VXLAN interface is part of the bridge; router MAC addresses of remote VTEPs are installed over this interface.
  2. Configure an SVI (layer 3 interface) corresponding to the per-tenant VXLAN interface. This is attached to the VRF of the tenant. The remote prefix routes are installed over this SVI.
  3. Specify the mapping of the VRF to layer 3 VNI. This configuration is for the BGP control plane.

Announce EVPN Type-5 Routes

The following configuration is required in the tenant VRF to announce IP prefixes in the BGP RIB as EVPN type-5 routes.

cumulus@switch:~$ net add bgp vrf vrf1 l2vpn evpn advertise ipv4 unicast
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011 vrf vrf1
switch(config-router)# address-family l2vpn evpn
switch(config-router-af)# advertise ipv4 unicast
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

These commands create the following snippet in the /etc/frr/frr.conf file:

...
router bgp 65005 vrf vrf1
  address-family l2vpn evpn
    advertise ipv4 unicast
  exit-address-family
end
...

EVPN Type-5 Routing in Asymmetric Mode

Asymmetric routing is an ideal choice when all VLANs (subnets) are configured on all leaf switches. It simplifies the routing configuration and eliminates the potential need for advertising subnet routes to handle silent hosts. However, most deployments need access to external networks to reach the Internet or global destinations, or to do subnet-based routing between pods or data centers; this requires EVPN type-5 routes.

Cumulus Linux supports EVPN type-5 routes for prefix-based routing in asymmetric configurations within the pod or data center by providing an option to use the layer 3 VNI only for type-5 routes; type-2 routes (host routes) only use the layer 2 VNI.

The following example commands show how to use the layer 3 VNI for type-5 routes only:

cumulus@leaf01:~$ net add vrf turtle vni 104001 prefix-routes-only
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

There is no command to delete the prefix-routes-only option. The net del vrf <vrf> vni <vni> prefix-routes-only command deletes the VNI.

Edit the /etc/frr/frr.conf file. For example:

cumulus@leaf01:~$ sudo nano /etc/frr/frr.conf
...
vrf turtle
  vni 104001 prefix-routes-only
...

Control RIB Routes

By default, when announcing IP prefixes in the BGP RIB as EVPN type-5 routes, all routes in the BGP RIB are picked for advertisement as EVPN type-5 routes. You can use a route map to allow selective advertisement of routes from the BGP RIB as EVPN type-5 routes.

The following commands add a route map filter to IPv4 EVPN type-5 route advertisement:

cumulus@switch:~$ net add bgp vrf turtle l2vpn evpn advertise ipv4 unicast route-map map1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65011 vrf turtle
switch(config-router)# address-family l2vpn evpn
switch(config-router-af)# advertise ipv4 unicast route-map map1
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

Originate Default EVPN Type-5 Routes

Cumulus Linux supports originating EVPN default type-5 routes. The default type-5 route is originated from a border (exit) leaf and advertised to all the other leafs within the pod. Any leaf within the pod follows the default route towards the border leaf for all external traffic (towards the Internet or a different pod).

To originate a default type-5 route in EVPN, you need to execute FRRouting commands. The following shows an example:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 650030 vrf vrf1
switch(config-router)# address-family l2vpn evpn
switch(config-router-af)# default-originate ipv4
switch(config-router-af)# default-originate ipv6
switch(config-router-af)# end
switch# write memory

With Cumulus Linux 3.7 and earlier, in EVPN symmetric routing configurations with VXLAN active-active (MLAG), all EVPN routes are advertised with the anycast IP address (clagd-vxlan-anycast-ip) as the next-hop IP address and the anycast MAC address as the router MAC address. In a failure scenario, this can lead to traffic being forwarded to a leaf switch that does not have the destination routes. Traffic has to traverse the peer link (with additional BGP sessions per VRF).

To prevent sub-optimal routing in Cumulus Linux 4.0 and later, the next hop IP address of the VTEP is conditionally handled depending on the route type: host type-2 (MAC/IP advertisement) or type-5 (IP prefix route).

See EVPN and VXLAN Active-Active mode for information about EVPN and VXLAN active-active mode.

Configure Advertise Primary IP Address

Run the address-virtual <anycast-mac> command under the SVI, where <anycast-mac> is the MLAG system MAC address (clagd-sys-mac). Run these commands on both switches in the MLAG pair.

Run the net add vlan <vlan> address-virtual <anycast-mac> command. For example:

cumulus@leaf01:~$ net add vlan 4001 address-virtual 44:38:39:FF:40:94
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

Edit the /etc/network/interfaces file and add address-virtual <anycast-mac> under the SVI. For example:

cumulus@leaf01:~$ sudo nano /etc/network/interfaces
...
auto vlan4001
iface vlan4001
    address-virtual 44:38:39:FF:40:94
    vlan-id 4001
    vlan-raw-device bridge
    vrf turtle
...

  • In Cumulus Linux 3.7 and earlier, the hwaddress command is used instead of the address-virtual command. If you upgrade from Cumulus Linux 3.7 to 4.0 and have a previous symmetric routing with VXLAN active-active configuration, you must change hwaddress to address-virtual. Either run the NCLU address-virtual <anycast-mac> command or edit the /etc/network/interfaces file.
  • When configuring third party networking devices using MLAG and EVPN for interoperability, you must configure and announce a single shared router MAC value per advertised next hop IP address.

Optional Configuration

If you do not want Cumulus Linux to derive the system IP address automatically, you can provide the system IP address and system MAC address under each BGP VRF instance.

The system MAC address must be the layer 3 SVI MAC address (not the clad-sys-mac).

The following example commands add the system IP address 10.0.0.11 and the system MAC address 44:38:39:ff:00:00:

cumulus@switch:~$ net add vlan 4001 hwaddress 44:38:39:ff:00:00
cumulus@switch:~$ net add bgp vrf vrf1 l2vpn evpn advertise-pip ip 10.0.0.11 mac 44:38:39:ff:00:00  
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65000 vrf vrf1
switch(config)# address-family l2vpn evpn
switch(config)# advertise-pip ip 10.0.0.11 mac 44:38:39:ff:00:00
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

The system IP address and system MAC address you provide take precedence over the addresses that Cumulus Linux derives automatically.

Disable Advertise Primary IP Address

Each switch in the MLAG pair advertises type-5 routes with its own system IP, which creates an additional next hop at the remote VTEPs. In a large multi-tenancy EVPN deployment, where additional resources are a concern, you might prefer to disable this feature.

To disable Advertise Primary IP Address under each tenant VRF BGP instance:

cumulus@leaf01:~$ net del bgp vrf vrf1 l2vpn evpn advertise-pip
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# router bgp 65000 vrf vrf1
switch(config)# address-family l2vpn evpn
switch(config)# no advertise-pip
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

Show Advertise Primary IP Address Information

To show Advertise Primary IP Address parameters, run the NCLU net show bgp l2vpn evpn vni <vni> command or the vtysh show bgp l2vpn evpn vni <vni> command. For example:

cumulus@switch:~$ sudo vtysh
switch# show bgp l2vpn evpn vni 4001
VNI: 4001 (known to the kernel)
 Type: L3
 Tenant VRF: vrf1
 RD: 10.0.0.11:2
 Originator IP: 10.0.0.112 🡨 Anycast IP
 Advertise-gw-macip : n/a
 Advertise-pip: Yes
 System-IP: 10.0.0.11
 System-MAC: 44:38:39:ff:00:00
 Router-MAC: 44:01:02:ff:ff:01
 Import Route Target:
  5586:4002
 Export Route Target:
  5586:4002
switch#

To show EVPN routes with Primary IP Advertisement, run the NCLU net show bgp l2vpn evpn route command or the vtysh show bgp l2vpn evpn route command. For example:

cumulus@switch:~$ sudo vtysh
switch# show bgp l2vpn evpn route
 ...
Route Distinguisher: 10.0.0.11:2
*> [5]:[0]:[24]:[81.6.1.0]
                    10.0.0.11                0             0 5541 i
                    ET:8 RT:5586:4002 Rmac:44:38:39:ff:00:00
 ...
Route Distinguisher: 10.0.0.11:3
*> [2]:[0]:[48]:[00:02:00:00:00:2e]:[32]:[45.0.4.2]
                    10.0.0.11                          32768 i
                    ET:8 RT:5586:1004 RT:5546:4002 Rmac:44:38:39:ff:00:00

To show the learned route from an external router injected as a type-5 route, run the NCLU net show bgp vrf <vrf> ipv4 unicast command or the vtysh show bgp vrf <vrf> ipv4 unicast command. For example:

cumulus@switch:~$ net show bgp vrf <vrf> ipv4 unicast
...
 Network          Next Hop            Metric LocPrf Weight Path
*> 10.0.0.0/8    10.0.0.42                0             0 5541 I

Caveats

VXLAN Decapsulation on Maverick and Broadcom Trident II Switches

On the Broadcom Trident II+ and Maverick-based switch, when a lookup is done after VXLAN decapsulation on the external-facing switch (the exit or border leaf), the switch does not rewrite the MAC addresses or TTL. For through traffic, packets are dropped by the next hop instead of correctly routing from a VXLAN overlay network into a non-VXLAN external network (such as the Internet). This applies to all forms of VXLAN routing (centralized, asymmetric, and symmetric) and affects all traffic from VXLAN overlay hosts that need to be routed after VXLAN decapsulation on an exit or border leaf. This includes traffic destined to external networks (through traffic) and traffic destined to the exit leaf SVI address. To work around this issue, modify the external-facing interface for each VLAN sub-interface on the exit leaf by creating a temporary VNI and associating it with the existing VLAN ID.

Example Workaround

For example, if the expected interface configuration is:

auto swp3.2001
iface swp3.2001
    vrf vrf1
    address 10.0.0.2/24
# where swp3 is the external facing port and swp3.2001 is the VLAN sub-interface

auto bridge
iface bridge
    bridge-vlan-aware yes
    bridge ports vx-4001
    bridge-vids 4001

auto vx-4001
iface vx-4001
    vxlan-id 4001
    <... usual vxlan config ...>
      bridge-access 4001
# where vnid 4001 represents the L3 VNI

auto vlan4001
iface vlan4001
    vlan-id 4001
    vlan-raw-device bridge
    vrf vrf1

Modify the configuration as follows:

auto swp3
iface swp3
    bridge-access 2001
# associate the port (swp3) with bridge 2001

auto bridge
iface bridge
    bridge-vlan-aware yes
    bridge ports swp3 vx-4001 vx-16000000
    bridge-vids 2001
# where vx-4001 is the existing VNI and vx-16000000 is a new temporary VNI
# this is now bridging the port (swp3), the VNI (vx-4001),
# and the new temporary VNI (vx-16000000)
# the bridge VLAN ID is now 2001

auto vlan2001
iface vlan2001
    vlan-id 2001
    vrf vrf1
    address 10.0.0.2/24
    vlan-raw-device bridge
# create a VLAN 2001 with the associated VRF and IP address

auto vx-16000000
iface vx-16000000
    vxlan-id 16000000
    bridge-access 2001
    <... usual vxlan config ...>
# associate the temporary VNI (vx-16000000) with bridge 2001

 auto vx-4001
iface vx-4001
    vxlan-id 4001
    <... usual vxlan config ...>
    bridge-access 4001
# where vnid 4001 represents the L3 VNI

auto vlan4001
iface vlan4001
    vlan-id 4001
    vlan-raw-device bridge
    vrf vrf1

If you use an MLAG pair instead of a single exit/border leaf, add the same temporary VNIs on both switches of the MLAG pair.

Centralized Routing with ARP Suppression Enabled on the Gateway

In an EVPN centralized routing configuration, where the layer 2 network extends beyond VTEPs, (for example, a host with bridges), the gateway MAC address is not refreshed in the network when ARP suppression is enabled on the gateway. To work around this issue, disable ARP suppression on the centralized gateway.

Type-5 Routes and ECMP

For VXLAN type-5 routes, ECMP does not work when the VTEP is directly connected to remote VTEPs. To work around this issue, add an additional device in the VXLAN fabric between the local and remote VTEPs, so that local and remote VTEPs are not directly connected.

Symmetric Routing and the Same SVI IP Address Across Racks

In EVPN symmetric routing, if you use the same SVI IP address across racks; for example, if the SVI IP address for a specific VLAN interface (such as vlan100) is the same on all VTEPs where this SVI is present, be aware of the following:

There are no issues with host-to-host traffic.

EVPN BUM Traffic with PIM-SM

Without EVPN and PIM-SM, HER is the default way to replicate BUM traffic to remote VTEPs, where the ingress VTEP generates as many copies as VTEPs for each overlay BUM packet. This might not be optimal in certain deployments.

The following example shows a EVPN-PIM configuration, where underlay multicast is used to distribute BUM traffic. A multicast distribution tree (MDT) optimizes the flow of overlay BUM in the underlay network.

In the above example, host01 sends an ARP request to resolve host03. leaf01 (in addition to flooding the packet to host02) sends an encapsulated packet over the underlay network, which is forwarded using the MDT to leaf02 and leaf03.

For PIM-SM, type-3 routes do not result in any forwarding entries. Cumulus Linux does not advertise type-3 routes for a layer 2 VNI when BUM mode for that VNI is PIM-SM.

EVPN-PIM is supported on Broadcom Trident3 Trident 2+ switches.

Configure Multicast VXLAN Tunnels

To configure multicast VXLAN tunnels, you need to configure PIM-SM in the underlay:

The configuration steps needed to configure PIM-SM in the underlay are provided in Protocol Independent Multicast - PIM.

In addition to the PIM-SM configuration, you need to run the following commands on each VTEP to provide the layer 2 VNI to MDT mapping.

Run the net add vxlan <interface> vxlan mcastgrp <ip-address> command. For example:

cumulus@switch:~$ net add vxlan vxlan1000111 vxlan mcastgrp 239.1.1.111

Edit the /etc/network/interfaces file and add vxlan-mcastgrp <ip-address> to the interface stanza. For example:

cumulus@switch:~$ sudo vi /etc/network/interfaces
...
auto vxlan1000111
iface vxlan1000111
  vxlan-id 1000111
  vxlan-local-tunnelip 10.0.0.28
  vxlan-mcastgrp 239.1.1.111

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

One multicast group per layer 2 VNI is optimal configuration for underlay bandwidth utilization. However, you can specify the same multicast group for more than one layer 2 VNI.

Example Configuration

The following example shows an EVPN-PIM configuration on the VTEP, where:

cumulus@switch:~$ sudo cat /etc/frr/frr.conf
...
ip pim rp 192.168.0.1
ip pim keep-alive-timer 3600
...
vrf vrf1
 vni 104001
 exit-vrf
!
vrf vrf2
 vni 104002
 exit-vrf
!
interface swp1
 description swp1 > leaf-11's swp3
 ip ospf network point-to-point
 ip pim
!
interface swp2
 description swp2 > leaf-12's swp3
 ip ospf network point-to-point
 ip pim
!
interface swp3
 description swp3 > host-111's swp1
!
interface swp6
 description swp6 > host-112's swp1
!
#auto-generated interface
interface ipmr-lo
 ip pim
!
interface lo
 ip pim
!
router bgp 650000
 bgp router-id 10.0.0.28
 bgp bestpath as-path multipath-relax
 bgp bestpath compare-routerid
 neighbor RR peer-group
 neighbor RR remote-as internal
 neighbor RR advertisement-interval 0
 neighbor RR timers 3 10
 neighbor RR timers connect 5
 neighbor 10.0.0.26 peer-group RR
 neighbor 10.0.0.26 update-source lo
 neighbor 10.0.0.27 peer-group RR
 neighbor 10.0.0.27 update-source lo
 !
 address-family ipv4 unicast
  redistribute connected
  maximum-paths ibgp 16
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor RR activate
  advertise-all-vni
 exit-address-family
!
router ospf
 ospf router-id 10.0.0.28
 network 10.0.0.28/32 area 0.0.0.0
!
line vty
 exec-timeout 0 0
!
end
cumulus@switch:~$ sudo cat /etc/network/interfaces
auto lo
iface lo
    address 10.0.0.28/32
# The primary network interface
auto eth0
iface eth0 inet dhcp

auto swp1
iface swp1
    link-speed 10000
    link-duplex full
    link-autoneg off
    address 10.0.0.28/32

auto swp2
iface swp2
    link-speed 10000
    link-duplex full
    link-autoneg off
    address 10.0.0.28/32

auto swp3
iface swp3
    link-speed 10000
    link-duplex full
    link-autoneg off
    bridge-access 111

auto swp6
iface swp6
    link-speed 10000
    link-duplex full
    link-autoneg off
    bridge-access 112

auto vxlan1000111
iface vxlan1000111
    vxlan-id 1000111
    vxlan-local-tunnelip 10.0.0.28
    bridge-access 111
    vxlan-mcastgrp 239.1.1.111
auto vxlan1000112
iface vxlan1000112
    vxlan-id 1000112
    vxlan-local-tunnelip 10.0.0.28
    bridge-access 112
    vxlan-mcastgrp 239.1.1.112
auto vrf1
iface vrf1
    vrf-table auto
auto vrf2
iface vrf2
    vrf-table auto
auto vxlan104001
iface vxlan104001
    vxlan-id 104001
    vxlan-local-tunnelip 10.0.0.28
    bridge-access 4001
auto vxlan104002
iface vxlan104002
    vxlan-id 104002
    vxlan-local-tunnelip 10.0.0.28
    bridge-access 4002
auto bridge
iface bridge
    bridge-ports swp3 swp6 swp56s0 swp56s1 vxlan1000111 vxlan1000112 vxlan104001 vxlan104002
    bridge-vlan-aware yes
    bridge-vids 111 112 4001 4002
auto vlan111
iface vlan111
    address 10.1.1.11/24
    address 2060:1:1:1::11/64
    vlan-id 111
    vlan-raw-device bridge
    address-virtual 00:00:5e:00:01:01 10.1.1.250/24 2060:1:1:1::250/64
    vrf vrf2
auto vlan112
iface vlan112
    address 50.1.1.11/24
    address 2050:1:1:1::11/64
    vlan-id 112
    vlan-raw-device bridge
    address-virtual 00:00:5e:00:01:01 10.10.1.250/24 2050:1:1:1::250/64
    vrf vrf1
auto vlan4001
iface vlan4001
    vlan-id 4001
    vlan-raw-device bridge
    vrf vrf1
auto vlan4002
iface vlan4002
    vlan-id 4002
    vlan-raw-device bridge
    vrf vrf2

Verify EVPN-PIM

Run the NCLU net show mroute command or the vtysh show ip mroute command to review the multicast route information in FRR. When using EVPN-PIM, every VTEP acts as both source and destination for a VNI-MDT group, therefore, mroute entries on each VTEP should look like this:

cumulus@switch:~$ net show mroute
Source          Group           Proto  Input            Output           TTL  Uptime
*               239.1.1.111     IGMP   swp2             pimreg           1    21:37:36
                                PIM                     ipmr-lo          1    21:37:36
10.0.0.28       239.1.1.111     STAR   lo               ipmr-lo          1    21:36:41
                                PIM                     swp2             1    21:36:41
*               239.1.1.112     IGMP   swp2             pimreg           1    21:37:36
                                PIM                     ipmr-lo          1    21:37:36
10.0.0.28       239.1.1.112     STAR   lo               ipmr-lo          1    21:36:41
                                PIM                     swp2             1    21:36:41

(*,G) entries should show ipmr-lo in the OIL (Outgoing Interface List) and (S,G) entries should show lo as the Source interface or incoming interface and ipmr-lo in the OIL.

Run the ip mroute command to review the multicast route information in the kernel. The kernel information should match the FRR information.

cumulus@switch:~$ ip mroute
(10.0.0.28,239.1.1.112)      Iif: lo     Oifs: swp2   State: resolved
(10.0.0.28,239.1.1.111)      Iif: lo     Oifs: swp2   State: resolved
(0.0.0.0,239.1.1.111)        Iif: swp2   Oifs: pimreg ipmr-lo swp2  State: resolved
(0.0.0.0,239.1.1.112)        Iif: swp2   Oifs: pimreg ipmr-lo swp2  State: resolved

Run the bridge fdb show | grep 00:00:00:00:00:00 command to verify that all zero MAC addresses for every VXLAN device point to the correct multicast group destination.

cumulus@switch:~$ bridge fdb show | grep 00:00:00:00:00:00
00:00:00:00:00:00 dev vxlan1000112 dst 239.1.1.112 self permanent
00:00:00:00:00:00 dev vxlan1000111 dst 239.1.1.111 self permanent

The show ip mroute count command, often used to check multicast packet counts does not update for encapsulated BUM traffic originating or terminating on the VTEPs.

Run the NCLU net show evpn vni <vni> command or the vtysh show evpn vni <vni> command to ensure that your layer 2 VNI has the correct flooding information:

cumulus@switch:~$ net show evpn vni 10
VNI: 10
 Type: L2
 Tenant VRF: default
 VxLAN interface: vni10
 VxLAN ifIndex: 18
 Local VTEP IP: 10.0.0.28
 Mcast group: 239.1.1.112   <<<<<<<
 Remote VTEPs for this VNI:
  10.0.0.26 flood: -
  10.0.0.27 flood: -
 Number of MACs (local and remote) known for this VNI: 9
 Number of ARPs (IPv4 and IPv6, local and remote) known for this VNI: 14
 Advertise-gw-macip: No

Configure EVPN-PIM in VXLAN Active-Active Mode

To configure EVPN-PIM in VXLAN active-active mode, enable PIM on the peer link on each MLAG peer switch (in addition to the configuration described in Configure Multicast VXLAN Tunnels, above).

Run the net add interface <peerlink> pim command. For example:

cumulus@switch:~$ net add interface peerlink.4094 pim
cumulus@switch:~$ net commit
cumulus@switch:~$ net pending

In the vtysh shell, run the following commands:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface peerlink.4094
switch(config-if)# ip pim
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

Configuration Examples

This section shows the following EVPN configuration examples:

The configuration examples are based on the reference topology below:

Layer 2 EVPN with External Routing

The following example configures a network infrastructure that creates a layer 2 extension between racks. Inter-VXLAN routed traffic routes between VXLANs on an external device.

The following images shows traffic flow between tenants. The spines and other devices are omitted for simplicity.

Traffic Flow between server01 and server04
server01 and server04 are in the same VLAN but are located across different leafs.
  1. server01 makes a LACP hash decision and forwards traffic to leaf01.
  2. leaf01 does a layer 2 lookup, has the MAC address for server04, and forwards the packet out VNI10, towards leaf04.
  3. The VXLAN encapsulated frame arrives on leaf04, which does a layer 2 lookup and has the MAC address for server04 in VLAN10.

/etc/network/interfaces

cumulus@leaf01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.1/32
    clagd-vxlan-anycast-ip 10.0.1.1
    vxlan-local-tunnelip 10.10.10.1

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 vni10 vni20
    bridge-vids 10 20  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    vlan-raw-device bridge
    vlan-id 10
    ip-forward off
    ip6-forward off

auto vlan20
iface vlan20
    vlan-raw-device bridge
    vlan-id 20
    ip-forward off
    ip6-forward off

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.2
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf02:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.2/32
    clagd-vxlan-anycast-ip 10.0.1.1
    vxlan-local-tunnelip 10.10.10.2

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 vni10 vni20
    bridge-vids 10 20  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    vlan-raw-device bridge
    vlan-id 10
    ip-forward off
    ip6-forward off

auto vlan20
iface vlan20
    vlan-raw-device bridge
    vlan-id 20
    ip-forward off
    ip6-forward off

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.1
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf03:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.3/32
    clagd-vxlan-anycast-ip 10.0.1.2
    vxlan-local-tunnelip 10.10.10.3

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 vni10 vni20
    bridge-vids 10 20  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    vlan-raw-device bridge
    vlan-id 10
    ip-forward off
    ip6-forward off

auto vlan20
iface vlan20
    vlan-raw-device bridge
    vlan-id 20
    ip-forward off
    ip6-forward off

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.4
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:BB

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf04:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.4/32
    clagd-vxlan-anycast-ip 10.0.1.2
    vxlan-local-tunnelip 10.10.10.4

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 vni10 vni20
    bridge-vids 10 20  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    vlan-raw-device bridge
    vlan-id 10
    ip-forward off
    ip6-forward off

auto vlan20
iface vlan20
    vlan-raw-device bridge
    vlan-id 20
    ip-forward off
    ip6-forward off

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.3
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:BB

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@spine01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.101/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@spine02:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.102/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@spine03:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.103/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@spine04:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.104/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@border01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.63/32
    clagd-vxlan-anycast-ip 10.0.1.254
    vxlan-local-tunnelip 10.10.10.63

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink
    bridge-ports bond3
    bridge-ports vni10 vni20
    bridge-vids 10 20  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    vlan-raw-device bridge
    vlan-id 10
    ip-forward off
    ip6-forward off

auto vlan20
iface vlan20
    vlan-raw-device bridge
    vlan-id 20
    ip-forward off
    ip6-forward off

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.64
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:FF

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 1
    bridge-vids 10 20
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@border02:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.64/32
    clagd-vxlan-anycast-ip 10.0.1.254
    vxlan-local-tunnelip 10.10.10.64

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink
    bridge-ports bond3
    bridge-ports vni10 vni20
    bridge-vids 10 20  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    vlan-raw-device bridge
    vlan-id 10
    ip-forward off
    ip6-forward off

auto vlan20
iface vlan20
    vlan-raw-device bridge
    vlan-id 20
    ip-forward off
    ip6-forward off

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.63
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:FF

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 1
    bridge-vids 10 20
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

/etc/frr/frr.conf

cumulus@leaf01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65101
 bgp router-id 10.10.10.1
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
line vty
cumulus@leaf02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65101
 bgp router-id 10.10.10.2
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
line vty
cumulus@leaf03:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65102
 bgp router-id 10.10.10.3
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
line vty
cumulus@leaf04:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65102
 bgp router-id 10.10.10.4
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
line vty
cumulus@spine01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.101
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@spine02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.102
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@spine03:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.103
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@spine04:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.104
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@border01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65132
 bgp router-id 10.10.10.63
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
line vty
cumulus@border02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65132
 bgp router-id 10.10.10.64
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
line vty

EVPN Centralized Routing

The following example shows an EVPN centralized routing configuration:

The following images shows traffic flow between tenants. The spines and other devices are omitted for simplicity.

Traffic Flow between server01 and server05
server01 and server05 are in a different VLAN and are located across different leafs.
  1. server01 makes a LACP hash decision and forwards traffic to leaf01.
  2. leaf01 does a layer 2 lookup and forwards traffic to server01’s default gateway (border01) out VNI10.
  3. border01 does a layer 3 lookup and routes the packet out VNI20 towards leaf04.
  4. The VXLAN encapsulated frame arrives on leaf04, which does a layer 2 lookup and has the MAC address for server05 in VLAN20.

/etc/network/interfaces

cumulus@leaf01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.1/32
    clagd-vxlan-anycast-ip 10.0.1.1
    vxlan-local-tunnelip 10.10.10.1

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 vni10 vni20
    bridge-vids 10 20  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    vlan-raw-device bridge
    vlan-id 10
    ip-forward off
    ip6-forward off

auto vlan20
iface vlan20
    vlan-raw-device bridge
    vlan-id 20
    ip-forward off
    ip6-forward off

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.2
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf02:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.2/32
    clagd-vxlan-anycast-ip 10.0.1.1
    vxlan-local-tunnelip 10.10.10.2

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 vni10 vni20
    bridge-vids 10 20  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    vlan-raw-device bridge
    vlan-id 10
    ip-forward off
    ip6-forward off

auto vlan20
iface vlan20
    vlan-raw-device bridge
    vlan-id 20
    ip-forward off
    ip6-forward off

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.1
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf03:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.3/32
    clagd-vxlan-anycast-ip 10.0.1.2
    vxlan-local-tunnelip 10.10.10.3

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 vni10 vni20
    bridge-vids 10 20  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    vlan-raw-device bridge
    vlan-id 10
    ip-forward off
    ip6-forward off

auto vlan20
iface vlan20
    vlan-raw-device bridge
    vlan-id 20
    ip-forward off
    ip6-forward off

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.4
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:BB

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf04:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.4/32
    clagd-vxlan-anycast-ip 10.0.1.2
    vxlan-local-tunnelip 10.10.10.4

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 vni10 vni20
    bridge-vids 10 20  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    vlan-raw-device bridge
    vlan-id 10
    ip-forward off
    ip6-forward off

auto vlan20
iface vlan20
    vlan-raw-device bridge
    vlan-id 20
    ip-forward off
    ip6-forward off

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.3
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:BB

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@spine01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.101/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@spine02:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.102/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@spine03:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.103/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@spine04:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.104/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@border01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.63/32
    clagd-vxlan-anycast-ip 10.0.1.254
    vxlan-local-tunnelip 10.10.10.63

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond3 vni10 vni20
    bridge-vids 10 20
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    address 10.1.10.2/24
    address-virtual 00:00:00:00:00:1a 10.1.10.1/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.2/24
    address-virtual 00:00:00:00:00:1a 10.1.20.1/24
    vlan-raw-device bridge
    vlan-id 20

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.64
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:FF

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 1
    bridge-vids 10 20
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@border02:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.64/32
    clagd-vxlan-anycast-ip 10.0.1.254
    vxlan-local-tunnelip 10.10.10.64

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond3 vni10 vni20
    bridge-vids 10 20
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    address 10.1.10.2/24
    address-virtual 00:00:00:00:00:1a 10.1.10.1/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.2/24
    address-virtual 00:00:00:00:00:1a 10.1.20.1/24
    vlan-raw-device bridge
    vlan-id 20

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.63
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:FF

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 1
    bridge-vids 10 20
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

/etc/frr/frr.conf

cumulus@leaf01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65101
 bgp router-id 10.10.10.1
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@leaf02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65101
 bgp router-id 10.10.10.2
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@leaf03:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65102
 bgp router-id 10.10.10.3
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@leaf04:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65102
 bgp router-id 10.10.10.4
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@spine01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.101
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@spine02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.102
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@spine03:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.103
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@spine04:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.104
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@border01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65132
 bgp router-id 10.10.10.63
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
  advertise-default-gw
 exit-address-family
!
line vty
cumulus@border02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65132
 bgp router-id 10.10.10.64
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
  advertise-default-gw
 exit-address-family
!
line vty

EVPN Symmetric Routing

The following example shows an EVPN symmetric routing configuration, where:

The following images shows traffic flow between tenants. The spines and other devices are omitted for simplicity.

Traffic Flow between server01 and server04
server01 and server04 are in the same VRF and the same VLAN but are located across different leafs.
  1. server01 makes a LACP hash decision and forwards traffic to leaf01.
  2. leaf01 does a layer 2 lookup and has the MAC address for server04, it then forwards the packet out VNI10, through leaf04.
  3. The VXLAN encapsulated frame arrives on leaf04, which does a layer 2 lookup and has the MAC address for server04 in VLAN10.
Traffic Flow between server01 and server05
server01 and server05 are in the same VRF, different VLANs, and are located across different leafs.
  1. server01 makes an LACP hash decision to reach the default gateway and forwards traffic to leaf01.
  2. leaf01 does a layer 3 lookup in VRF RED and has a route out VNIRED through leaf04.
  3. The VXLAN encapsulated packet arrives on leaf04, which does a layer 3 lookup in VRF RED and has a route through VLAN20 to server05.
Traffic Flow between server01 and server06
server01 and server06 are in different VRFs, different VLANs, and are located across different leafs.
  1. server01 makes an LACP hash decision to reach the default gateway and forwards traffic to leaf01.
  2. leaf01 does a layer 3 lookup in VRF RED and has a route out VNIRED through border01.
  3. The VXLAN encapsulated packet arrives on border01, which does a layer 3 lookup in VRF RED and has a route through VLAN30 to fw01 (the policy device).
  4. fw01 does a layer 3 lookup (without any VRFs) and has a route in VLAN40, through border02.
  5. border02 does a layer 3 lookup in VRF BLUE and has a route out VNIBLUE, through leaf04.
  6. The VXLAN encapsulated packet arrives on leaf04, which does a layer 3 lookup in VRF BLUE and has a route in VLAN30 to server06.

/etc/network/interfaces

cumulus@leaf01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.1/32
    clagd-vxlan-anycast-ip 10.0.1.1
    vxlan-local-tunnelip 10.10.10.1

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto RED
iface RED
  vrf-table auto

auto BLUE
iface BLUE
  vrf-table auto

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 bond3 vni10 vni20 vni30 vniRED vniBLUE
    bridge-vids 10 20 30  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni30
iface vni30
    bridge-access 30
    vxlan-id 30
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vniRED
iface vniRED
    bridge-access 4001
    vxlan-id 4001
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vniBLUE
iface vniBLUE
    bridge-access 4002
    vxlan-id 4002
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    address 10.1.10.2/24
    address-virtual 00:00:00:00:00:1a 10.1.10.1/24
    vrf RED
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.2/24
    address-virtual 00:00:00:00:00:1a 10.1.20.1/24
    vrf RED
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.2/24
    address-virtual 00:00:00:00:00:1a 10.1.30.1/24
    vrf BLUE
    vlan-raw-device bridge
    vlan-id 30

auto vlan4001
iface vlan4001
    address-virtual 44:38:39:BE:EF:AA
    vrf RED
    vlan-raw-device bridge
    vlan-id 4001

auto vlan4002
iface vlan4002
    address-virtual 44:38:39:BE:EF:AA
    vrf BLUE
    vlan-raw-device bridge
    vlan-id 4002

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.2
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf02:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.2/32
    clagd-vxlan-anycast-ip 10.0.1.1
    vxlan-local-tunnelip 10.10.10.2

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto RED
iface RED
  vrf-table auto

auto BLUE
iface BLUE
  vrf-table auto

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 bond3 vni10 vni20 vni30 vniRED vniBLUE
    bridge-vids 10 20 30  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni30
iface vni30
    bridge-access 30
    vxlan-id 30
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vniRED
iface vniRED
    bridge-access 4001
    vxlan-id 4001
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vniBLUE
iface vniBLUE
    bridge-access 4002
    vxlan-id 4002
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    address 10.1.10.3/24
    address-virtual 00:00:00:00:00:1a 10.1.10.1/24
    vrf RED
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.3/24
    address-virtual 00:00:00:00:00:1a 10.1.20.1/24
    vrf RED
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.3/24
    address-virtual 00:00:00:00:00:1a 10.1.30.1/24
    vrf BLUE
    vlan-raw-device bridge
    vlan-id 30

auto vlan4001
iface vlan4001
    address-virtual 44:38:39:BE:EF:AA
    vrf RED
    vlan-raw-device bridge
    vlan-id 4001

auto vlan4002
iface vlan4002
    address-virtual 44:38:39:BE:EF:AA
    vrf BLUE
    vlan-raw-device bridge
    vlan-id 4002

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.1
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf03:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.3/32
    clagd-vxlan-anycast-ip 10.0.1.2
    vxlan-local-tunnelip 10.10.10.3

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto RED
iface RED
  vrf-table auto

auto BLUE
iface BLUE
  vrf-table auto

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 bond3 vni10 vni20 vni30 vniRED vniBLUE
    bridge-vids 10 20 30  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni30
iface vni30
    bridge-access 30
    vxlan-id 30
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vniRED
iface vniRED
    bridge-access 4001
    vxlan-id 4001
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vniBLUE
iface vniBLUE
    bridge-access 4002
    vxlan-id 4002
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    address 10.1.10.2/24
    address-virtual 00:00:00:00:00:1a 10.1.10.1/24
    vrf RED
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.2/24
    address-virtual 00:00:00:00:00:1a 10.1.20.1/24
    vrf RED
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.2/24
    address-virtual 00:00:00:00:00:1a 10.1.30.1/24
    vrf BLUE
    vlan-raw-device bridge
    vlan-id 30

auto vlan4001
iface vlan4001
    address-virtual 44:38:39:BE:EF:BB
    vrf RED
    vlan-raw-device bridge
    vlan-id 4001

auto vlan4002
iface vlan4002
    address-virtual 44:38:39:BE:EF:BB
    vrf BLUE
    vlan-raw-device bridge
    vlan-id 4002

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.4
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:BB

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf04:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.4/32
    clagd-vxlan-anycast-ip 10.0.1.2
    vxlan-local-tunnelip 10.10.10.4

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto RED
iface RED
    vrf-table auto

auto BLUE
iface BLUE
    vrf-table auto

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 bond3 vni10 vni20 vni30 vniRED vniBLUE
    bridge-vids 10 20 30  
    bridge-vlan-aware yes

auto vni10
iface vni10
    bridge-access 10
    vxlan-id 10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni20
iface vni20
    bridge-access 20
    vxlan-id 20
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vni30
iface vni30
    bridge-access 30
    vxlan-id 30
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vniRED
iface vniRED
    bridge-access 4001
    vxlan-id 4001
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vniBLUE
iface vniBLUE
    bridge-access 4002
    vxlan-id 4002
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan10
iface vlan10
    address 10.1.10.3/24
    address-virtual 00:00:00:00:00:1a 10.1.10.1/24
    vrf RED
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.3/24
    address-virtual 00:00:00:00:00:1a 10.1.20.1/24
    vrf RED
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.3/24
    address-virtual 00:00:00:00:00:1a 10.1.30.1/24
    vrf BLUE
    vlan-raw-device bridge
    vlan-id 30

auto vlan4001
iface vlan4001
    address-virtual 44:38:39:BE:EF:BB
    vrf RED
    vlan-raw-device bridge
    vlan-id 4001

auto vlan4002
iface vlan4002
    address-virtual 44:38:39:BE:EF:BB
    vrf BLUE
    vlan-raw-device bridge
    vlan-id 4002

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.3
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:BB

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@spine01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.101/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@spine02:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.102/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@spine03:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.103/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@spine04:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.104/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

auto swp5
iface swp5
    alias leaf to spine

auto swp6
iface swp6
    alias leaf to spine
cumulus@border01:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.63/32
    clagd-vxlan-anycast-ip 10.0.1.254
    vxlan-local-tunnelip 10.10.10.63

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto RED
iface RED
  vrf-table auto

auto BLUE
iface BLUE
  vrf-table auto

auto bridge
iface bridge
    bridge-ports peerlink bond3 vniRED vniBLUE
    bridge-vids 4001 4002  
    bridge-vlan-aware yes

auto vniRED
iface vniRED
    bridge-access 4001
    vxlan-id 4001
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vniBLUE
iface vniBLUE
    bridge-access 4002
    vxlan-id 4002
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan4001
iface vlan4001
    address-virtual 44:38:39:BE:EF:FF
    vrf RED
    vlan-raw-device bridge
    vlan-id 4001

auto vlan4002
iface vlan4002
    address-virtual 44:38:39:BE:EF:FF
    vrf BLUE
    vlan-raw-device bridge
    vlan-id 4002

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.64
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:FF

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 1
    bridge-vids 10 20 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@border02:~$ cat /etc/network/interfaces

auto lo
iface lo inet loopback
    address 10.10.10.64/32
    clagd-vxlan-anycast-ip 10.0.1.254
    vxlan-local-tunnelip 10.10.10.64

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto RED
iface RED
  vrf-table auto

auto BLUE
iface BLUE
  vrf-table auto

auto bridge
iface bridge
    bridge-ports peerlink bond3 vniRED vniBLUE
    bridge-vids 4001 4002  
    bridge-vlan-aware yes

auto vniRED
iface vniRED
    bridge-access 4001
    vxlan-id 4001
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vniBLUE
iface vniBLUE
    bridge-access 4002
    vxlan-id 4002
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    bridge-learning off
    bridge-arp-nd-suppress on

auto vlan4001
iface vlan4001
    address-virtual 44:38:39:BE:EF:FF
    vrf RED
    vlan-raw-device bridge
    vlan-id 4001

auto vlan4002
iface vlan4002
    address-virtual 44:38:39:BE:EF:FF
    vrf BLUE
    vlan-raw-device bridge
    vlan-id 4002

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp53
iface swp53
    alias leaf to spine

auto swp54
iface swp54
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.63
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:FF

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 1
    bridge-vids 10 20 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

/etc/frr/frr.conf

cumulus@leaf01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
vrf RED
  vni 4001
vrf BLUE
  vni 4002
!
router bgp 65101
 bgp router-id 10.10.10.1
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
line vty
cumulus@leaf02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
vrf RED
  vni 4001
vrf BLUE
  vni 4002
!
router bgp 65101
 bgp router-id 10.10.10.2
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
line vty
cumulus@leaf03:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
vrf RED
  vni 4001
vrf BLUE
  vni 4002
!
router bgp 65102
 bgp router-id 10.10.10.3
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
line vty
cumulus@leaf04:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
vrf RED
  vni 4001
vrf BLUE
  vni 4002
!
router bgp 65102
 bgp router-id 10.10.10.4
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
line vty
cumulus@spine01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.101
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@spine02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.102
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@spine03:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.103
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@spine04:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.104
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 neighbor swp5 interface peer-group underlay
 neighbor swp6 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
 exit-address-family
!
line vty
cumulus@border01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
vrf RED
  vni 4001
vrf BLUE
  vni 4002
!
router bgp 65132
 bgp router-id 10.10.10.63
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
router bgp 65132 vrf RED
 bgp router-id 10.10.10.63
 bgp bestpath as-path multipath-relax
 !
 address-family ipv4 unicast
  redistribute static
 exit-address-family
 !
 address-family l2vpn evpn
  advertise ipv4 unicast
 exit-address-family
!
router bgp 65132 vrf BLUE
 bgp router-id 10.10.10.63
 bgp bestpath as-path multipath-relax
 !
 address-family ipv4 unicast
  redistribute static
 exit-address-family
 !
 address-family l2vpn evpn
  advertise ipv4 unicast
 exit-address-family
!
line vty
cumulus@border02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
vrf RED
  vni 4001
vrf BLUE
  vni 4002
!
router bgp 65132
 bgp router-id 10.10.10.64
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 neighbor swp53 interface peer-group underlay
 neighbor swp54 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
 !
 address-family l2vpn evpn
  neighbor underlay activate
  advertise-all-vni
 exit-address-family
!
router bgp 65132 vrf RED
 bgp router-id 10.10.10.64
 bgp bestpath as-path multipath-relax
 !
 address-family ipv4 unicast
  redistribute static
 exit-address-family
 !
 address-family l2vpn evpn
  advertise ipv4 unicast
 exit-address-family
!
router bgp 65132 vrf BLUE
 bgp router-id 10.10.10.64
 bgp bestpath as-path multipath-relax
 !
 address-family ipv4 unicast
  redistribute static
 exit-address-family
 !
 address-family l2vpn evpn
  advertise ipv4 unicast
 exit-address-family
!
line vty

Troubleshooting

This section provides various commands to help you examine your EVPN configuration and provides troubleshooting tips.

General Linux Commands

You can use various iproute2 commands to examine links, VLAN mappings and the bridge MAC forwarding database known to the Linux kernel. You can also use these commands to examine the neighbor cache and the routing table (for the underlay or for a specific tenant VRF). Some of the key commands are:

A sample output of ip -d link show type vxlan is shown below for one VXLAN interface. Relevant parameters are the VNI value, the state, the local IP address for the VXLAN tunnel, the UDP port number (4789) and the bridge of which the interface is part (bridge in the example below). The output also shows that MAC learning is disabled (off) on the VXLAN interface.

cumulus@leaf01:~$ ip -d link show type vxlan
9: vni100: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master bridge state UNKNOWN mode DEFAULT group default 
    link/ether 72:bc:b4:a3:eb:1e brd ff:ff:ff:ff:ff:ff promiscuity 1
    vxlan id 10100 local 10.0.0.1 srcport 0 0 dstport 4789 nolearning ageing 300
    bridge_slave state forwarding priority 8 cost 100 hairpin off guard off root_block off fastleave off learning off flood on port_id 0x8001 port_no 0x1 designated_port 32769 designated_cost 0 designated_bridge 8000.0:1:0:0:11:0 designated_root 8000.0:1:0:0:11:0 hold_timer    0.00 message_age_timer    0.00 forward_delay_timer    0.00 topology_change_ack 0 config_pending 0 proxy_arp off proxy_arp_wifi off mcast_router 1 mcast_fast_leave off mcast_flood on neigh_suppress on group_fwd_mask 0x0 group_fwd_mask_str 0x0 group_fwd_maskhi 0x0 group_fwd_maskhi_str 0x0 addrgenmode eui64
...

The following example output for the bridge fdb show command shows:

cumulus@leaf01:~$ bridge fdb show
00:02:00:00:00:13 dev swp3 master bridge permanent
00:02:00:00:00:01 dev swp3 vlan 100 master bridge
00:02:00:00:00:02 dev swp4 vlan 100 master bridge
72:bc:b4:a3:eb:1e dev vni100 master bridge permanent
00:02:00:00:00:06 dev vni100 vlan 100 extern_learn master bridge
00:00:00:00:00:00 dev vni100 dst 10.0.0.3 self permanent
00:00:00:00:00:00 dev vni100 dst 10.0.0.4 self permanent
00:00:00:00:00:00 dev vni100 dst 10.0.0.2 self permanent
00:02:00:00:00:06 dev vni100 dst 10.0.0.2 self extern_learn
...

The following example output for the ip neigh show command shows:

cumulus@leaf01:~$ ip neigh show
172.16.120.11 dev vlan100-v0 lladdr 00:02:00:00:00:01 STALE
172.16.120.42 dev vlan100 lladdr 00:02:00:00:00:0e extern_learn REACHABLE
172.16.130.23 dev vlan200 lladdr 00:02:00:00:00:07 extern_learn REACHABLE
172.16.120.11 dev vlan100 lladdr 00:02:00:00:00:01 REACHABLE
...

General BGP Commands

If you use BGP for the underlay routing, run the NCLU net show bgp summary command or the vtysh show bgp summary command to view a summary of the layer 3 fabric connectivity:

cumulus@leaf01:~$ net show bgp summary
show bgp ipv4 unicast summary
=============================
BGP router identifier 10.0.0.1, local AS number 65001 vrf-id 0
BGP table version 9
RIB entries 11, using 1496 bytes of memory
Peers 2, using 42 KiB of memory
Peer groups 1, using 72 bytes of memory

Neighbor        V         AS MsgRcvd MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd
s1(swp49s0)     4      65100      43      49        0    0    0 02:04:00            4
s2(swp49s1)     4      65100      43      49        0    0    0 02:03:59            4
Total number of neighbors 2

show bgp ipv6 unicast summary
=============================
No IPv6 neighbor is configured

show bgp evpn summary
=====================
BGP router identifier 10.0.0.1, local AS number 65001 vrf-id 0
BGP table version 0
RIB entries 15, using 2040 bytes of memory
Peers 2, using 42 KiB of memory
Peer groups 1, using 72 bytes of memory

Neighbor        V         AS MsgRcvd MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd
s1(swp49s0)     4      65100      43      49        0    0    0 02:04:00           30
s2(swp49s1)     4      65100      43      49        0    0    0 02:03:59           30
Total number of neighbors 2

Run the NCLU net show route command or the vtysh show route command to examine the underlay routing and determine how remote VTEPs are reached. The following example shows output from a leaf switch:

cumulus@leaf01:~$ net show route

show ip route
=============
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR,
       > - selected route, * - FIB route

C>* 10.0.0.11/32 is directly connected, lo, 19:48:21
B>* 10.0.0.12/32 [20/0] via fe80::4638:39ff:fe00:54, swp51, 19:48:03
  *                     via fe80::4638:39ff:fe00:25, swp52, 19:48:03
B>* 10.0.0.13/32 [20/0] via fe80::4638:39ff:fe00:54, swp51, 19:48:03
  *                     via fe80::4638:39ff:fe00:25, swp52, 19:48:03
B>* 10.0.0.14/32 [20/0] via fe80::4638:39ff:fe00:54, swp51, 19:48:03
  *                     via fe80::4638:39ff:fe00:25, swp52, 19:48:03
B>* 10.0.0.21/32 [20/0] via fe80::4638:39ff:fe00:54, swp51, 19:48:04
B>* 10.0.0.22/32 [20/0] via fe80::4638:39ff:fe00:25, swp52, 19:48:03
B>* 10.0.0.41/32 [20/0] via fe80::4638:39ff:fe00:54, swp51, 19:48:03
  *                     via fe80::4638:39ff:fe00:25, swp52, 19:48:03
B>* 10.0.0.42/32 [20/0] via fe80::4638:39ff:fe00:54, swp51, 19:48:03
  *                     via fe80::4638:39ff:fe00:25, swp52, 19:48:03
C>* 10.0.0.112/32 is directly connected, lo, 19:48:21
B>* 10.0.0.134/32 [20/0] via fe80::4638:39ff:fe00:54, swp51, 19:48:03
  *                      via fe80::4638:39ff:fe00:25, swp52, 19:48:03
C>* 169.254.1.0/30 is directly connected, peerlink.4094, 19:48:21

show ipv6 route
===============
Codes: K - kernel route, C - connected, S - static, R - RIPng,
       O - OSPFv3, I - IS-IS, B - BGP, N - NHRP, T - Table,
       v - VNC, V - VNC-Direct, A - Babel, D - SHARP, F - PBR,
       > - selected route, * - FIB route
C * fe80::/64 is directly connected, bridge, 19:48:21
C * fe80::/64 is directly connected, peerlink.4094, 19:48:21
C * fe80::/64 is directly connected, swp52, 19:48:21
C>* fe80::/64 is directly connected, swp51, 19:48:21

Run the NCLU net show bridge macs command to view the MAC forwarding database on the switch:

cumulus@leaf01:~$ net show bridge macs
VLAN      Master    Interface    MAC                TunnelDest    State      Flags          LastSeen
--------  --------  -----------  -----------------  ------------  ---------  -------------  ---------------
100       br0       br0          00:00:5e:00:01:01                permanent                 1 day, 03:38:43
100       br0       br0          00:01:00:00:11:00                permanent                 1 day, 03:38:43
100       br0       swp3         00:02:00:00:00:01                                          00:00:26
100       br0       swp4         00:02:00:00:00:02                                          00:00:16
100       br0       vni100       00:02:00:00:00:0a                           extern_learn   1 day, 03:38:20
100       br0       vni100       00:02:00:00:00:0d                           extern_learn   1 day, 03:38:20
100       br0       vni100       00:02:00:00:00:0e                           extern_learn   1 day, 03:38:20
100       br0       vni100       00:02:00:00:00:05                           extern_learn   1 day, 03:38:19
100       br0       vni100       00:02:00:00:00:06                           extern_learn   1 day, 03:38:19
100       br0       vni100       00:02:00:00:00:09                           extern_learn   1 day, 03:38:20
200       br0       br0          00:00:5e:00:01:01                permanent                 1 day, 03:38:42
200       br0       br0          00:01:00:00:11:00                permanent                 1 day, 03:38:43
200       br0       swp5         00:02:00:00:00:03                                          00:00:26
 200       br0       swp6         00:02:00:00:00:04                                         00:00:26
200       br0       vni200       00:02:00:00:00:0b                           extern_learn   1 day, 03:38:20
200       br0       vni200       00:02:00:00:00:0c                           extern_learn   1 day, 03:38:20
200       br0       vni200       00:02:00:00:00:0f                           extern_learn   1 day, 03:38:20
200       br0       vni200       00:02:00:00:00:07                           extern_learn   1 day, 03:38:19
200       br0       vni200       00:02:00:00:00:08                           extern_learn   1 day, 03:38:19
200       br0       vni200       00:02:00:00:00:10                           extern_learn   1 day, 03:38:20
4001      br0       br0          00:01:00:00:11:00                permanent                 1 day, 03:38:42
4001      br0       vni4001      00:01:00:00:12:00                           extern_learn   1 day, 03:38:19
4001      br0       vni4001      00:01:00:00:13:00                           extern_learn   1 day, 03:38:20
4001      br0       vni4001      00:01:00:00:14:00                           extern_learn   1 day, 03:38:20
untagged            br0          00:00:5e:00:01:01                permanent  self           never
untagged            vlan100      00:00:5e:00:01:01                permanent  self           never
untagged            vlan200      00:00:5e:00:01:01                permanent  self           never
...

Show EVPN address-family Peers

Run the NCLU net show bgp l2vpn evpn summary command or the vtysh show bgp l2vpn evpn summary command to see the BGP peers participating in the layer 2 VPN/EVPN address-family and their states. The following example output from a leaf switch shows eBGP peering with two spine switches to exchange EVPN routes; both peering sessions are in the established state.

cumulus@leaf01:~$ net show bgp l2vpn evpn summary
BGP router identifier 10.0.0.1, local AS number 65001 vrf-id 0
BGP table version 0
RIB entries 15, using 2280 bytes of memory
Peers 2, using 39 KiB of memory
Peer groups 1, using 64 bytes of memory
Neighbor        V         AS MsgRcvd MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd
s1(swp1)        4      65100     103     107        0    0    0 1d02h08m           30
s2(swp2)        4      65100     103     107        0    0    0 1d02h08m           30
Total number of neighbors 2

Show EVPN VNIs

Run the NCLU net show bgp l2vpn evpn vni command or the vtysh show bgp l2vpn evpn vni command to display the configured VNIs on a network device participating in BGP EVPN. This command is only relevant on a VTEP. If you have configured symmetric routing, this command displays the special layer 3 VNIs that are configured per tenant VRF.

The following example from a leaf switch shows two layer 2 VNIs (10100 and 10200) as well as a layer 3 VNI (104001). The command output also shows the number of associated MAC and neighbor entries for layer 2 VNIs, and the VXLAN interface and VRF corresponding to each VNI.

cumulus@leaf01:~$ net show evpn vni
VNI        Type  VxLAN IF            # MACs   # ARPs   # Remote VTEPs  Tenant VRF
10200      L2    vni200              8        12       3               vrf1

10100      L2    vni100              8        12       3               vrf1

104001     L3    vni4001             3        3        n/a             vrf1

Run the NCLU net show evpn vni <vni> command or the vtysh show evpn vni <vni> command to examine EVPN information for a specific VNI in detail. The following example output shows details for the layer 2 VNI 10100 as well as for the layer 3 VNI 104001. For the layer 2 VNI, the remote VTEPs that contain that VNI are shown. For the layer 3 VNI, the router MAC and associated layer 2 VNIs are shown. The state of the layer 3 VNI depends on the state of its associated VRF as well as the states of its underlying VXLAN interface and SVI.

cumulus@leaf01:~$ net show evpn vni 10100
VNI: 10100
  Type: L2
  Tenant VRF: vrf1
  VxLAN interface: vni100
  VxLAN ifIndex: 9
  Local VTEP IP: 10.0.0.1
  Remote VTEPs for this VNI:
  10.0.0.2
  10.0.0.4
  10.0.0.3
  Number of MACs (local and remote) known for this VNI: 8
  Number of ARPs (IPv4 and IPv6, local and remote) known for this VNI: 12
  Advertise-gw-macip: No
cumulus@leaf01:~$
cumulus@leaf01:~$ net show evpn vni 104001
VNI: 104001
  Type: L3
  Tenant VRF: vrf1
  Local Vtep Ip: 10.0.0.1
  Vxlan-Intf: vni4001
  SVI-If: vlan4001
  State: Up
  Router MAC: 00:01:00:00:11:00
  L2 VNIs: 10100 10200

Examine Local and Remote MAC Addresses for a VNI

Run the NCLU net show evpn mac vni <vni> command or the vtysh show evpn mac vni <vni> command to examine all local and remote MAC addresses for a VNI. This command is only relevant for a layer 2 VNI:

cumulus@leaf01:~$ net show evpn mac vni 10100
Number of MACs (local and remote) known for this VNI: 8
MAC               Type   Intf/Remote VTEP      VLAN
00:02:00:00:00:0e remote 10.0.0.4
00:02:00:00:00:06 remote 10.0.0.2
00:02:00:00:00:05 remote 10.0.0.2
00:02:00:00:00:02 local  swp4                  100  
00:00:5e:00:01:01 local  vlan100-v0            100  
00:02:00:00:00:09 remote 10.0.0.3
00:01:00:00:11:00 local  vlan100               100  
00:02:00:00:00:01 local  swp3                  100  
00:02:00:00:00:0a remote 10.0.0.3
00:02:00:00:00:0d remote 10.0.0.4

Run the NCLU net show evpn mac vni all command or the vtysh show evpn mac vni all command to examine MAC addresses for all VNIs.

You can examine the details for a specific MAC addresse or query all remote MAC addresses behind a specific VTEP:

cumulus@leaf01:~$ net show evpn mac vni 10100 mac 00:02:00:00:00:02
MAC: 00:02:00:00:00:02
  Intf: swp4(6) VLAN: 100
  Local Seq: 0 Remote Seq: 0
  Neighbors:
    172.16.120.12 Active
cumulus@leaf01:~$ net show evpn mac vni 10100 mac 00:02:00:00:00:05
MAC: 00:02:00:00:00:05
  Remote VTEP: 10.0.0.2
  Neighbors:
    172.16.120.21 
cumulus@leaf01:~$ net show evpn mac vni 10100 vtep 10.0.0.3
VNI 10100
MAC               Type   Intf/Remote VTEP      VLAN
00:02:00:00:00:09 remote 10.0.0.3
00:02:00:00:00:0a remote 10.0.0.3

Examine Local and Remote Neighbors for a VNI

Run the NCLU net show evpn arp-cache vni <vni> command or the vtysh show evpn arp-cache vni <vni> command to examine all local and remote neighbors (ARP entries) for a VNI. This command is only relevant for a layer 2 VNI and the output shows both IPv4 and IPv6 neighbor entries:

cumulus@leaf01:~$ net show evpn arp-cache vni 10100
Number of ARPs (local and remote) known for this VNI: 12
IP                      Type   MAC               Remote VTEP          
172.16.120.11           local  00:02:00:00:00:01
172.16.120.12           local  00:02:00:00:00:02
172.16.120.22           remote 00:02:00:00:00:06 10.0.0.2            
fe80::201:ff:fe00:1100  local  00:01:00:00:11:00
172.16.120.1            local  00:01:00:00:11:00
172.16.120.31           remote 00:02:00:00:00:09 10.0.0.3            
fe80::200:5eff:fe00:101 local  00:00:5e:00:01:01
...

Run the NCLU net show evpn arp-cache vni all command or the vtysh show evpn arp-cache vni all command to examine neighbor entries for all VNIs.

Examine Remote Router MACs

For symmetric routing, run the NCLU net show evpn rmac vni <vni> command or the vtysh show evpn rmac vni <vni> command to examine the router MACs corresponding to all remote VTEPs. This command is only relevant for a layer 3 VNI:

cumulus@leaf01:~$ net show evpn rmac vni 104001
Number of Remote RMACs known for this VNI: 3
MAC               Remote VTEP          
00:01:00:00:14:00 10.0.0.4            
00:01:00:00:12:00 10.0.0.2            
00:01:00:00:13:00 10.0.0.3            
cumulus@leaf01:~$

Run the NCLU net show evpn rmac vni all command or the vtysh show evpn rmac vni all command to examine router MACs for all layer 3 VNIs.

Examine Gateway Next Hops

For symmetric routing, you can run the NCLU net show evpn next-hops vni <vni> command or the vtysh show evpn next-hops vni <vni> command to examine the gateway next hops. This command is only relevant for a layer 3 VNI. In general, the gateway next hop IP addresses correspond to the remote VTEP IP addresses. Remote host and prefix routes are installed sing these next hops:

cumulus@leaf01:~$ net show evpn next-hops vni 104001
Number of NH Neighbors known for this VNI: 3
IP              RMAC             
10.0.0.3       00:01:00:00:13:00
10.0.0.4       00:01:00:00:14:00
10.0.0.2       00:01:00:00:12:00
cumulus@leaf01:~$

Run the NCLU net show evpn next-hops vni all command or the vtysh show evpn next-hops vni all command to examine gateway next hops for all layer 3 VNIs.

You can query a specific next hop; the output displays the remote host and prefix routes through this next hop:

cumulus@leaf01:~$ net show evpn next-hops vni 104001 ip 10.0.0.4
Ip: 10.0.0.4
  RMAC: 00:01:00:00:14:00
  Refcount: 4
  Prefixes:
    172.16.120.41/32
    172.16.120.42/32
    172.16.130.43/32
    172.16.130.44/32
cumulus@leaf01:~$

Show the VRF Routing Table in FRR

Run the net show route vrf <vrf-name> command to examine the VRF routing table. In the context of EVPN, this command is relevant for symmetric routing to verify that remote host and prefix routes are installed in the VRF routing table and point to the appropriate gateway next hop.

cumulus@leaf01:~$ net show route vrf vrf1
show ip route vrf vrf1 
=======================
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, P - PIM, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel,
       > - selected route, * - FIB route

VRF vrf1:
K * 0.0.0.0/0 [255/8192] unreachable (ICMP unreachable), 1d02h42m
C * 172.16.120.0/24 is directly connected, vlan100-v0, 1d02h42m
C>* 172.16.120.0/24 is directly connected, vlan100, 1d02h42m
B>* 172.16.120.21/32 [20/0] via 10.0.0.2, vlan4001 onlink, 1d02h41m
B>* 172.16.120.22/32 [20/0] via 10.0.0.2, vlan4001 onlink, 1d02h41m
B>* 172.16.120.31/32 [20/0] via 10.0.0.3, vlan4001 onlink, 1d02h41m
B>* 172.16.120.32/32 [20/0] via 10.0.0.3, vlan4001 onlink, 1d02h41m
B>* 172.16.120.41/32 [20/0] via 10.0.0.4, vlan4001 onlink, 1d02h41m
...

In the output above, the next hops for these routes are specified by EVPN to be onlink, or reachable over the specified SVI. This is necessary because this interface is not required to have an IP address. Even if the interface is configured with an IP address, the next hop is not on the same subnet as it is usually the IP address of the remote VTEP (part of the underlay IP network).

Show the Global BGP EVPN Routing Table

Run the NCLU net show bgp l2vpn evpn route command or the vtysh show bgp l2vpn evpn route command to display all EVPN routes, both local and remote. The routes displayed here are based on RD as they are across VNIs and VRFs:

cumulus@leaf01:~$ net show bgp l2vpn evpn route 
BGP table version is 0, local router ID is 10.0.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
EVPN type-2 prefix: [2]:[ESI]:[EthTag]:[MAClen]:[MAC]
EVPN type-3 prefix: [3]:[EthTag]:[IPlen]:[OrigIP]
    Network          Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 10.0.0.1:1
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:01]
                     10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:01]:[32]:[172.16.120.11]
                   10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:01]:[128]:[2001:172:16:120::11]
                     10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:02]
                     10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:02]:[32]:[172.16.120.12]
                     10.0.0.1                          32768 i
*> [3]:[0]:[32]:[10.0.0.1]
                     10.0.0.1                          32768 i
Route Distinguisher: 10.0.0.1:2
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:01]
                     10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:01]:[32]:[172.16.130.11]
                     10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:02]
                     10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:02]:[32]:[172.16.130.12]
                     10.0.0.1                          32768 i
*> [3]:[0]:[32]:[10.0.0.1]
                     10.0.0.1                          32768 i
...

You can filter the routing table based on EVPN route type. The available options are shown below:

cumulus@leaf01:~$ net show bgp l2vpn evpn route type 
    macip      :  MAC-IP (Type-2) route
    multicast  :  Multicast
    prefix     :  An IPv4 or IPv6 prefix
cumulus@leaf01:~$

Show a Specific EVPN Route

To drill down on a specific route for more information, run the NCLU net show bgp l2vpn evpn route rd <rd-value> command or the vtysh show bgp l2vpn evpn route rd <rd-value> command. This command displays all EVPN routes with that RD and with the path attribute details for each path. Additional filtering is possible based on route type or by specifying the MAC and/or IP address. The following example shows a specific MAC/IP route. The output shows that this remote host is behind VTEP 10.0.0.4 and is reachable through two paths; one through either spine switch. This example is from a symmetric routing configuration, so the route shows both the layer 2 VNI (10200) and the layer 3 VNI (104001), as well as the EVPN route target attributes corresponding to each and the associated router MAC address.

cumulus@leaf01:~$ net show bgp l2vpn evpn route rd 10.0.0.4:3 mac 00:02:00:00:00:10 ip 172.16.130.44
BGP routing table entry for 10.0.0.4:3:[2]:[0]:[0]:[48]:[00:02:00:00:00:10]:[32]:[172.16.130.44]
Paths: (2 available, best #2)
  Advertised to non peer-group peers:
  s1(swp1) s2(swp2)
  Route [2]:[0]:[0]:[48]:[00:02:00:00:00:10]:[32]:[172.16.130.44] VNI 10200/104001
  65100 65004
    10.0.0.4 from s2(swp2) (172.16.110.2)
      Origin IGP, localpref 100, valid, external
      Extended Community: RT:65004:10200 RT:65004:104001 ET:8 Rmac:00:01:00:00:14:00
      AddPath ID: RX 0, TX 97
      Last update: Sun Dec 17 20:57:24 2017
  Route [2]:[0]:[0]:[48]:[00:02:00:00:00:10]:[32]:[172.16.130.44] VNI 10200/104001
  65100 65004
    10.0.0.4 from s1(swp1) (172.16.110.1)
      Origin IGP, localpref 100, valid, external, bestpath-from-AS 65100, best
      Extended Community: RT:65004:10200 RT:65004:104001 ET:8 Rmac:00:01:00:00:14:00
      AddPath ID: RX 0, TX 71
      Last update: Sun Dec 17 20:57:23 2017

Displayed 2 paths for requested prefix
cumulus@leaf01:~$

  • Only global VNIs are supported. Even though VNI values are exchanged in the type-2 and type-5 routes, the received values are not used when installing the routes into the forwarding plane; the local configuration is used. You must ensure that the VLAN to VNI mappings and the layer 3 VNI assignment for a tenant VRF are uniform throughout the network.
  • If the remote host is dual attached, the next hop for the EVPN route is the anycast IP address of the remote MLAG pair, when MLAG is active.

The following example shows a prefix (type-5) route. Such a route has only the layer 3 VNI and the route target corresponding to this VNI. This route is learned through two paths, one through each spine switch.

cumulus@leaf01:~$ net show bgp l2vpn evpn route rd 172.16.100.2:3 type prefix
EVPN type-2 prefix: [2]:[ESI]:[EthTag]:[MAClen]:[MAC]
EVPN type-3 prefix: [3]:[EthTag]:[IPlen]:[OrigIP]
EVPN type-5 prefix: [5]:[EthTag]:[IPlen]:[IP]
BGP routing table entry for 172.16.100.2:3:[5]:[0]:[30]:[172.16.100.0]
Paths: (2 available, best #2)
  Advertised to non peer-group peers:
  s1(swp1) s2(swp2)
  Route [5]:[0]:[30]:[172.16.100.0] VNI 104001
  65100 65050
    10.0.0.5 from s2(swp2) (172.16.110.2)
      Origin incomplete, localpref 100, valid, external
      Extended Community: RT:65050:104001 ET:8 Rmac:00:01:00:00:01:00
      AddPath ID: RX 0, TX 112
      Last update: Tue Dec 19 00:12:18 2017
  Route [5]:[0]:[30]:[172.16.100.0] VNI 104001
  65100 65050
    10.0.0.5 from s1(swp1) (172.16.110.1)
      Origin incomplete, localpref 100, valid, external, bestpath-from-AS 65100, best
      Extended Community: RT:65050:104001 ET:8 Rmac:00:01:00:00:01:00
      AddPath ID: RX 0, TX 71
      Last update: Tue Dec 19 00:12:17 2017

Displayed 1 prefixes (2 paths) with this RD (of requested type)

Show the per-VNI EVPN Routing Table

Received EVPN routes are maintained in the global EVPN routing table (described above), even if there are no appropriate local VNIs to import them into. For example, a spine switch maintains the global EVPN routing table even though there are no VNIs present on it. When local VNIs are present, received EVPN routes are imported into the per-VNI routing tables based on the route target attributes. You can examine the per-VNI routing table with the net show bgp l2vpn evpn route vni <vni> command:

cumulus@leaf01:~$ net show bgp l2vpn evpn route vni 10110
BGP table version is 8, local router ID is 10.0.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
EVPN type-2 prefix: [2]:[ESI]:[EthTag]:[MAClen]:[MAC]:[IPlen]:[IP]
EVPN type-3 prefix: [3]:[EthTag]:[IPlen]:[OrigIP]
    Network          Next Hop            Metric LocPrf Weight Path
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:07]
                   10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:07]:[32]:[172.16.120.11]
                   10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:07]:[128]:[fe80::202:ff:fe00:7]
                   10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:08]
                   10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:08]:[32]:[172.16.120.12]
                   10.0.0.1                          32768 i
*> [2]:[0]:[0]:[48]:[00:02:00:00:00:08]:[128]:[fe80::202:ff:fe00:8]
                   10.0.0.1                          32768 i
*> [3]:[0]:[32]:[10.0.0.1]
                   10.0.0.1                          32768 i
Displayed 7 prefixes (7 paths)

To display the VNI routing table for all VNIs, run the net show bgp l2vpn evpn route vni all command.

Show the per-VRF BGP Routing Table

For symmetric routing, received type-2 and type-5 routes are imported into the VRF routing table (against the corresponding address-family: IPv4 unicast or IPv6 unicast) based on a match on the route target attributes. Run the NCLU net show bgp vrf <vrf-name> ipv4 unicast command or the net show bgp vrf <vrf-name> ipv6 unicast command to examine the BGP VRF routing table. The equivalent vtysh commands are show bgp vrf <vrf-name> ipv4 unicast and show bgp vrf <vrf-name> ipv6 unicast.

cumulus@leaf01:~$ net show bgp vrf vrf1 ipv4 unicast 
BGP table version is 8, local router ID is 172.16.120.250
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
              i internal, r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete
    Network          Next Hop            Metric LocPrf Weight Path
*  172.16.120.21/32     10.0.0.2                              0 65100 65002 i
*>                  10.0.0.2                              0 65100 65002 i
*  172.16.120.22/32     10.0.0.2                              0 65100 65002 i
*>                  10.0.0.2                              0 65100 65002 i
*  172.16.120.31/32     10.0.0.3                              0 65100 65003 i
*>                  10.0.0.3                              0 65100 65003 i
*  172.16.120.32/32     10.0.0.3                              0 65100 65003 i
*>                  10.0.0.3                              0 65100 65003 i
*  172.16.120.41/32     10.0.0.4                              0 65100 65004 i
*>                  10.0.0.4                              0 65100 65004 i
*  172.16.120.42/32     10.0.0.4                              0 65100 65004 i
*>                  10.0.0.4                              0 65100 65004 i
*  172.16.100.0/24     10.0.0.5                              0 65100 65050 ?
*>                  10.0.0.5                              0 65100 65050 ?
*  172.16.100.0/24     10.0.0.6                              0 65100 65050 ?
*>                  10.0.0.6                              0 65100 65050 ?
Displayed  8 routes and 16 total paths

Support for EVPN Neighbor Discovery (ND) Extended Community

In an EVPN VXLAN deployment with ARP and ND suppression where the VTEPs are only configured for layer 2, EVPN needs to carry additional information for the attached devices so proxy ND can provide the correct information to attached hosts. Without this information, hosts might not be able to configure their default routers or might lose their existing default router information. Cumulus Linux supports the EVPN Neighbor Discovery (ND) Extended Community with a type field value of 0x06, a sub-type field value of 0x08 (ND Extended Community), and a router flag; this enables the switch to determine if a particular IPv6-MAC pair belongs to a host or a router.

The router flag (R-bit) is used in:

When the MAC/IP (type-2) route contains the IPv6-MAC pair and the R-bit is set, the route belongs to a router. If the R-bit is set to zero, the route belongs to a host. If the router is in a local LAN segment, the switch implementing the proxy ND function learns of this information by snooping on neighbor advertisement messages for the associated IPv6 address. This information is then exchanged with other EVPN peers by using the ND extended community in BGP updates.

To show the EVPN arp-cache that gets populated by the neighbor table and see if the IPv6-MAC entry belongs to a router, run either the NCLU net show evpn arp-cache vni <vni> ip <address> command or the vtysh show evpn arp-cache vni <vni> ip <address> command. For example:

cumulus@switch:mgmt-vrf:~$ net show evpn arp-cache vni 101 ip fe80::202:ff:fe00:11
IP: fe80::202:ff:fe00:11
  Type: remote
  State: active
  MAC: 00:02:00:00:00:11
  Remote VTEP: 10.0.0.134
  Flags: Router
  Local Seq: 0 Remote Seq: 0

To show the BGP routing table entry for the IPv6-MAC EVPN route with the ND extended community, run the NCLU net show bgp l2vpn evpn route vni <vni> mac <mac-address> ip <ip-address> command or the vtysh show bgp l2vpn evpn route vni <vni> mac <mac-address> ip <ip-address> command. For example:

cumulus@switch:mgmt-vrf:~$ net show bgp l2vpn evpn route vni 101 mac 00:02:00:00:00:11 ip fe80::202:ff:fe00:11
BGP routing table entry for [2]:[0]:[0]:[48]:[00:02:00:00:00:11]:[128]:[fe80::202:ff:fe00:11]
Paths: (1 available, best #1)
  Not advertised to any peer
  Route [2]:[0]:[0]:[48]:[00:02:00:00:00:11]:[128]:[fe80::202:ff:fe00:11] VNI 101
  Imported from 1.1.1.2:2:[2]:[0]:[0]:[48]:[00:02:00:00:00:11]:[128]:[fe80::202:ff:fe00:11]
   65002
    10.0.0.134 from leaf2(swp53s0) (10.0.0.134)
        Origin IGP, valid, external, bestpath-from-AS 65002, best
        Extended Community: RT:65002:101 ET:8 ND:Router Flag
        AddPath ID: RX 0, TX 18
        Last update: Thu Aug 30 14:12:09 2018

Examine MAC Moves

The first time a MAC moves from behind one VTEP to behind another, BGP associates a MAC Mobilit (MM) extended community attribute of sequence number 1, with the type-2 route for that MAC. From there, each time this MAC moves to a new VTEP, the MM sequence number increments by 1. You can examine the MM sequence number associated with a MAC’s type-2 route with the NCLU net show bgp l2vpn evpn route vni <vni> mac <mac> command or the vtysh show bgp l2vpn evpn route vni <vni> mac <mac> command. The example output below shows the type-2 route for a MAC that has moved three times:

cumulus@switch:~$ net show bgp l2vpn evpn route vni 10109 mac 00:02:22:22:22:02
BGP routing table entry for [2]:[0]:[0]:[48]:[00:02:22:22:22:02]
Paths: (1 available, best #1)
Not advertised to any peer
Route [2]:[0]:[0]:[48]:[00:02:22:22:22:02] VNI 10109
Local
6.0.0.184 from 0.0.0.0 (6.0.0.184)
Origin IGP, localpref 100, weight 32768, valid, sourced, local, bestpath-from-AS Local, best
Extended Community: RT:650184:10109 ET:8 MM:3
AddPath ID: RX 0, TX 10350121
Last update: Tue Feb 14 18:40:37 2017

Displayed 1 paths for requested prefix

Examine Static MAC Addresses

You can identify static or sticky MACs in EVPN by the presence of MM:0, sticky MAC in the Extended Community line of the output from the NCLU net show bgp l2vpn evpn route vni <vni> mac <mac> command or the vtysh show bgp l2vpn evpn route vni <vni> mac <mac> command.

cumulus@switch:~$ net show bgp l2vpn evpn route vni 10101 mac 00:02:00:00:00:01
BGP routing table entry for [2]:[0]:[0]:[48]:[00:02:00:00:00:01]
Paths: (1 available, best #1)
  Not advertised to any peer
  Route [2]:[0]:[0]:[48]:[00:02:00:00:00:01] VNI 10101
  Local
    172.16.130.18 from 0.0.0.0 (172.16.130.18)
      Origin IGP, localpref 100, weight 32768, valid, sourced, local, bestpath-from-AS Local, best
      Extended Community: ET:8 RT:60176:10101 MM:0, sticky MAC
      AddPath ID: RX 0, TX 46
      Last update: Tue Apr 11 21:44:02 2017

Displayed 1 paths for requested prefix

Enable FRR Debug Logs

To troubleshoot EVPN, enable FRR debug logs. The relevant debug options are:

Option
Description
debug zebra vxlan Traces VNI addition and deletion (local and remote) as well as MAC and neighbor addition and deletion (local and remote).
debug zebra kernel Traces actual netlink messages exchanged with the kernel, which includes everything, not just EVPN.
debug bgp updates Traces BGP update exchanges, including all updates. Output is extended to show EVPN specific information.
debug bgp zebra Traces interactions between BGP and zebra for EVPN (and other) routes.

ICMP echo Replies and the ping Command

When you run the ping -I command and specify an interface, you don’t get an ICMP echo reply. However, when you run the ping command without the -I option, everything works as expected.

ping -I command example:

cumulus@switch:default:~:# ping -I swp2 10.0.10.1
PING 10.0.10.1 (10.0.10.1) from 10.0.0.2 swp1.5: 56(84) bytes of data.

ping command example:

cumulus@switch:default:~:# ping 10.0.10.1
PING 10.0.10.1 (10.0.10.1) 56(84) bytes of data.
64 bytes from 10.0.10.1: icmp_req=1 ttl=63 time=4.00 ms
64 bytes from 10.0.10.1: icmp_req=2 ttl=63 time=0.000 ms
64 bytes from 10.0.10.1: icmp_req=3 ttl=63 time=0.000 ms
64 bytes from 10.0.10.1: icmp_req=4 ttl=63 time=0.000 ms
^C
--- 10.0.10.1 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3004ms
rtt min/avg/max/mdev = 0.000/1.000/4.001/1.732 ms

This is expected behavior with Cumulus Linux; when you send an ICMP echo request to an IP address that is not in the same subnet using the ping -I command, Cumulus Linux creates a failed ARP entry for the destination IP address.

For more information, refer to this article.

VXLAN Active-Active Mode

VXLAN active-active mode enables a pair of MLAG switches to act as a single VTEP, providing active-active VXLAN termination for bare metal as well as virtualized workloads.

Terminology

Term
Definition
VTEP The virtual tunnel endpoint. This is an encapsulation and decapsulation point for VXLANs.
active-active VTEP A pair of switches acting as a single VTEP.
ToR The top of rack switch; also referred to as a leaf or access switch.
spine The aggregation switch for multiple leafs. Specifically used when a data center is using a Clos network architecture. Read more about spine-leaf architecture in this white paper.
exit leaf A switch dedicated to peering the Clos network to an outside network; also referred to as a border leaf, service leaf, or edge leaf.
anycast An IP address that is advertised from multiple locations. Anycast enables multiple devices to share the same IP address and effectively load balance traffic across them. With VXLAN, anycast is used to share a VTEP IP address between a pair of MLAG switches.
RIOT Routing in and out of tunnels. A Broadcom feature for routing in and out of tunnels. Allows a VXLAN bridge to have a switch VLAN interface associated with it, and traffic to exit a VXLAN into the layer 3 fabric. Also called VXLAN Routing.
VXLAN routing The industry standard term for the ability to route in and out of a VXLAN. Equivalent to the Broadcom RIOT feature.
clagd-vxlan-anycast-ip The anycast address for the MLAG pair to share and bind to when MLAG is up and running.

Configure VXLAN Active-active Mode

VXLAN active-active mode requires the following underlying technologies to work correctly.

Technology More Information
MLAG Refer to MLAG for more detailed configuration information. Example configurations are provided below.
OSPF or BGP Refer to OSPF or BGP for more detailed configuration information. Example configurations for BGP are provided below.
STP You must enable BPDU filter and BPDU guard in the VXLAN interfaces if STP is enabled in the bridge that is connected to the VXLAN. Example configurations are provided below.

Active-active VTEP Anycast IP Behavior

You must provision each individual switch within an MLAG pair with a virtual IP address in the form of an anycast IP address for VXLAN data-path termination. The VXLAN termination address is an anycast IP address that you configure as a clagd parameter (clagd-vxlan-anycast-ip) under the loopback interface. clagd dynamically adds and removes this address as the loopback interface address as follows:

  1. When the switches boot up, ifupdown2 places all VXLAN interfaces in a PROTO_DOWN state. The configured anycast addresses are not configured yet.
  2. MLAG peering takes place and a successful VXLAN interface consistency check between the switches occurs.
  3. clagd (the daemon responsible for MLAG) adds the anycast address to the loopback interface as a second address. It then changes the local IP address of the VXLAN interface from a unique address to the anycast virtual IP address and puts the interface in an UP state.

For the anycast address to activate, you must configure a VXLAN interface on each switch in the MLAG pair.

Failure Scenario Behaviors

Scenario
Behavior
The peer link goes down. The primary MLAG switch continues to keep all VXLAN interfaces up with the anycast IP address while the secondary switch brings down all VXLAN interfaces and places them in a PROTO_DOWN state. The secondary MLAG switch removes the anycast IP address from the loopback interface.
One of the switches goes down. The other operational switch continues to use the anycast IP address.
clagd is stopped. All VXLAN interfaces are put in a PROTO_DOWN state. The anycast IP address is removed from the loopback interface and the local IP addresses of the VXLAN interfaces are changed from the anycast IP address to unique non-virtual IP addresses.
MLAG peering could not be established between the switches. clagd brings up all the VXLAN interfaces after the reload timer expires with the configured anycast IP address. This allows the VXLAN interface to be up and running on both switches even though peering is not established.
When the peer link goes down but the peer switch is up (the backup link is active). All VXLAN interfaces are put into a PROTO_DOWN state on the secondary switch.
A configuration mismatch between the MLAG switches The VXLAN interface is placed into a PROTO_DOWN state on the secondary switch.

Check VXLAN Interface Configuration Consistency

The active-active configuration for a given VXLAN interface must be consistent between the MLAG switches for correct traffic behavior. MLAG ensures that the configuration consistency is met before bringing up the VXLAN interfaces:

Run the clagctl command to check if any VXLAN switches are in a PROTO_DOWN state.

Configure the Anycast IP Address

With MLAG peering, both switches use an anycast IP address for VXLAN encapsulation and decapsulation. This enables remote VTEPs to learn the host MAC addresses attached to the MLAG switches against one logical VTEP, even though the switches independently encapsulate and decapsulate layer 2 traffic originating from the host. You can configure the anycast address under the loopback interface, as shown below.

auto lo
iface lo inet loopback
  address 10.0.0.11/32
  clagd-vxlan-anycast-ip 10.10.10.20
auto lo
iface lo inet loopback
  address 10.0.0.12/32
  clagd-vxlan-anycast-ip 10.10.10.20

Example VXLAN Active-Active Configuration

The VXLAN interfaces are configured with individual IP addresses, which clagd changes to anycast upon MLAG peering.

FRRouting Configuration

You can configure the layer 3 fabric using BGP or OSPF. The following example uses BGP unnumbered. The MLAG switch configuration for the topology above is:

Layer 3 IP Addressing

The IP address configuration for this example:

auto lo
iface lo inet loopback
  address 10.0.0.21/32

auto eth0
iface eth0 inet dhcp

# downlinks
auto swp1
iface swp1

auto swp2
iface swp2

auto swp3
iface swp3

auto swp4
iface swp4

auto swp29
iface swp29

auto swp30
iface swp30
auto lo
iface lo inet loopback
    address 10.0.0.22/32

auto eth0
iface eth0 inet dhcp

# downlinks
auto swp1
iface swp1

auto swp2
iface swp2

auto swp3
iface swp3

auto swp4
iface swp4

auto swp29
iface swp29

auto swp30
iface swp30
auto lo
iface lo inet loopback
    address 10.0.0.11/32
    clagd-vxlan-anycast-ip 10.10.10.20

auto eth0
iface eth0 inet dhcp

# peerlinks
auto swp49
iface swp49

auto swp50
iface swp50

auto peerlink
iface peerlink
  bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
  address 169.254.1.1/30
  clagd-peer-ip 169.254.1.2
  clagd-backup-ip 10.0.0.12
  clagd-sys-mac 44:38:39:FF:40:94

# Downlinks
auto swp1
iface swp1

auto bond0
iface bond0
    bond-slaves swp1
    clag-id 1

auto bridge
iface bridge
  bridge-vlan-aware yes
  bridge-ports peerlink bond0 vni10 vni20
  bridge-vids 10 20

auto vlan10
iface vlan10

auto vlan20
iface vlan20

auto vni10
iface vni10
  vxlan-id 10
  vxlan-local-tunnelip 10.0.0.11
  bridge-access 10
  mstpctl-bpduguard yes
  mstpctl-portbpdufilter yes

auto vni20
iface vni20
  vxlan-id 20
  vxlan-local-tunnelip 10.0.0.11
  bridge-access 20
  mstpctl-bpduguard yes
  mstpctl-portbpdufilter yes

# uplinks
auto swp51
iface swp51

auto swp52
iface swp52
auto lo
iface lo inet loopback
    address 10.0.0.12/32
  clagd-vxlan-anycast-ip 10.10.10.20

auto eth0
iface eth0 inet dhcp

# peerlinks
auto swp49
iface swp49

auto swp50
iface swp50

auto peerlink
iface peerlink
  bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
  address 169.254.1.2/30
  clagd-peer-ip 169.254.1.1
  clagd-backup-ip 10.0.0.11
  clagd-sys-mac 44:38:39:FF:40:94

# Downlinks
auto swp1
iface swp1

auto bond0
iface bond0
    bond-slaves swp1
    clag-id 1

auto bridge
iface bridge
  bridge-vlan-aware yes
  bridge-ports peerlink bond0 vni10 vni20
  bridge-vids 10 20

auto vlan10
iface vlan10
  
auto vlan20
iface vlan20

auto vni10
iface vni10
  vxlan-id 10
  vxlan-local-tunnelip 10.0.0.12
  bridge-access 10
  mstpctl-bpduguard yes
  mstpctl-portbpdufilter yes

auto vni20
iface vni20
  vxlan-id 20
  vxlan-local-tunnelip 10.0.0.12
  bridge-access 20
  mstpctl-bpduguard yes
  mstpctl-portbpdufilter yes

# uplinks
auto swp51
iface swp51

auto swp52
iface swp52
auto lo
iface lo inet loopback
  address 10.0.0.13/32
  clagd-vxlan-anycast-ip 10.10.10.30

auto eth0
iface eth0 inet dhcp

# peerlinks
auto swp49
iface swp49

auto swp50
iface sw50p

auto peerlink
iface peerlink
  bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
  address 169.254.1.1/30
  clagd-peer-ip 169.254.1.2
  clagd-backup-ip 10.0.0.14
  clagd-sys-mac 44:38:39:FF:40:95

# Downlinks
auto swp1
iface swp1
  
auto bond0
iface bond0
    bond-slaves swp1
    clag-id 1

auto bridge
iface bridge
  bridge-vlan-aware yes
  bridge-ports peerlink bond0 vni10 vni20
  bridge-vids 10 20

auto vlan10
iface vlan10
  
auto vlan20
iface vlan20

auto vni10
iface vni10
  vxlan-id 10
  vxlan-local-tunnelip 10.0.0.13
  bridge-access 10
  mstpctl-bpduguard yes
  mstpctl-portbpdufilter yes

auto vni20
iface vni20
  vxlan-id 20
  vxlan-local-tunnelip 10.0.0.13
  bridge-access 20
  mstpctl-bpduguard yes
  mstpctl-portbpdufilter yes

# uplinks
auto swp51
iface swp51

auto swp52
iface swp52
auto lo
iface lo inet loopback
  address 10.0.0.14/32
  clagd-vxlan-anycast-ip 10.10.10.30

auto eth0
iface eth0 inet dhcp

# peerlinks
auto swp49
iface swp49

auto swp50
iface swp50

auto peerlink
iface peerlink
  bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
  address 169.254.1.2/30
  clagd-peer-ip 169.254.1.1
  clagd-backup-ip 10.0.0.13
  clagd-sys-mac 44:38:39:FF:40:95

# Downlinks
auto swp1
iface swp1
  
auto bond0
iface bond0
    bond-slaves swp1
    clag-id 1

auto bridge
iface bridge
  bridge-vlan-aware yes
  bridge-ports peerlink bond0 vni10 vni20
  bridge-vids 10 20

auto vlan10
iface vlan10
  
auto vlan20
iface vlan20

auto vni10
iface vni10
  vxlan-id 10
  vxlan-local-tunnelip 10.0.0.14
  bridge-access 10
  mstpctl-bpduguard yes
  mstpctl-portbpdufilter yes

auto vni20
iface vni20
  vxlan-id 20
  vxlan-local-tunnelip 10.0.0.14
  bridge-access 20
  mstpctl-bpduguard yes
  mstpctl-portbpdufilter yes
  
# uplinks
auto swp51
iface swp51

auto swp52
iface swp52

Host Configuration

In this example, the servers are running Ubuntu 14.04. A layer2 bond must be mapped from server01 and server03 to the respective switch. In Ubuntu, you use subinterfaces.

auto lo
iface lo inet loopback

auto lo
iface lo inet static
  address 10.0.0.31/32
  
auto eth0
iface eth0 inet dhcp

auto eth1
iface eth1 inet manual
    bond-master bond0

auto eth2
iface eth2 inet manual
    bond-master bond0

auto bond0
iface bond0 inet static
  bond-slaves none
  bond-miimon 100
  bond-min-links 1
  bond-mode 802.3ad
  bond-xmit-hash-policy layer3+4
  bond-lacp-rate 1
  address 172.16.1.101/24

auto bond0.10
iface bond0.10 inet static
  address 172.16.10.101/24
  
auto bond0.20
iface bond0.20 inet static
  address 172.16.20.101/24
auto lo
iface lo inet loopback

auto lo
iface lo inet static
  address 10.0.0.33/32
  
auto eth0
iface eth0 inet dhcp

auto eth1
iface eth1 inet manual
    bond-master bond0

auto eth2
iface eth2 inet manual
    bond-master bond0

auto bond0
iface bond0 inet static
  bond-slaves none
  bond-miimon 100
  bond-min-links 1
  bond-mode 802.3ad
  bond-xmit-hash-policy layer3+4
  bond-lacp-rate 1
  address 172.16.1.103/24

auto bond0.10
iface bond0.10 inet static
  address 172.16.10.103/24
  
auto bond0.20
iface bond0.20 inet static
  address 172.16.20.103/24

Troubleshooting

Run the clagctl command to show MLAG behavior and any inconsistencies that might arise between a MLAG pair.

cumulus@leaf01$ clagctl
The peer is alive
      Our Priority, ID, and Role: 32768 44:38:39:00:00:35 primary
    Peer Priority, ID, and Role: 32768 44:38:39:00:00:36 secondary
          Peer Interface and IP: peerlink.4094 169.254.1.2
                VxLAN Anycast IP: 10.10.10.30
                      Backup IP: 10.0.0.14 (inactive)
                      System MAC: 44:38:39:ff:40:95
CLAG Interfaces
Our Interface      Peer Interface     CLAG Id   Conflicts     Proto-Down Reason
----------------   ----------------   -------   -----------   -----------------
           bond0   bond0              1         -             -
         vxlan20   vxlan20            -         -             -
          vxlan1   vxlan1             -         -             -
         vxlan10   vxlan10            -         -             -

The additions to normal MLAG behavior are:

Output
Explanation
VXLAN Anycast IP: 10.10.10.30 The anycast IP address being shared by the MLAG pair for VTEP termination is in use and is 10.10.10.30.
Conflicts: - There are no conflicts for this MLAG Interface.
Proto-Down Reason: - The VXLAN is up and running (there is no Proto-Down).

In the following example the vxlan-id on VXLAN10 is switched to the wrong vxlan-id. When you run the clagctl command, VXLAN10 is down because this switch is the secondary switch and the peer switch takes control of VXLAN. The reason code is vxlan-single indicating that there is a vxlan-id mis-match on VXLAN10.

cumulus@leaf02$ clagctl
The peer is alive
    Peer Priority, ID, and Role: 32768 44:38:39:00:00:11 primary
      Our Priority, ID, and Role: 32768 44:38:39:00:00:12 secondary
          Peer Interface and IP: peerlink.4094 169.254.1.1
                VxLAN Anycast IP: 10.10.10.20
                      Backup IP: 10.0.0.11 (inactive)
                      System MAC: 44:38:39:ff:40:94
CLAG Interfaces
Our Interface      Peer Interface     CLAG Id   Conflicts      Proto-Down Reason
----------------   ----------------   -------   ------------   -----------------
           bond0   bond0              1         -              -
         vxlan20   vxlan20            -         -              -
          vxlan1   vxlan1             -         -              -
         vxlan10   -                  -         -              vxlan-single

Caveats and Errata

Do not reuse the VLAN for the peer link layer 3 subinterface for any other interface in the system. A high VLAN ID value is recommended. For more information on VLAN ID ranges, refer to the VLAN-aware bridge chapter.

Bonds with Vagrant in Cumulus VX

Bonds (or LACP Etherchannels) fail to work in a Vagrant configuration unless the link is set to promiscuous mode. This is a limitation on virtual topologies only and is not needed on real hardware.

auto swp49
iface swp49
  #for vagrant so bonds work correctly
  post-up ip link set $IFACE promisc on

auto swp50
iface swp50
  #for vagrant so bonds work correctly
  post-up ip link set $IFACE promisc on

For more information on using Cumulus VX and Vagrant, refer to the Cumulus VX documentation.

VXLAN Routing

VXLAN routing, sometimes referred to as inter-VXLAN routing, provides IP routing between VXLAN VNIs in overlay networks. The routing of traffic is based on the inner header or the overlay tenant IP address.

Because VXLAN routing is fundamentally routing, it is most commonly deployed with a control plane, such as Ethernet Virtual Private Network (EVPN). You can also set up static routing for MAC distribution and BUM handling.

This topic describes the platform and hardware considerations for VXLAN routing. For a detailed description of different VXLAN routing models and configuration examples, refer to EVPN.

VXLAN routing supports full layer 3 multi-tenancy; all routing occurs in the context of a VRF. Also, VXLAN routing is supported for dual-attached hosts where the associated VTEPs function in active-active mode.

Supported Platforms

The following ASICs support VXLAN routing:

  • Using ECMP with VXLAN routing is supported only on RIOT-capable Broadcom ASICs (Trident 3, Maverick, Trident 2+) in addition to Tomahawk, Tomahawk+ and Mellanox Spectrum-A1 ASICs.
  • For additional restrictions and considerations for VXLAN routing with EVPN, refer to Ethernet Virtual Private Network - EVPN.

VXLAN Routing Data Plane and Broadcom Switches

Trident II+, Trident3, and Maverick

The Trident II+, Trident3, and Maverick ASICs provide native support for VXLAN routing, also referred to as Routing In and Out of Tunnels (RIOT).

You can specify a VXLAN routing profile in the vxlan_routing_overlay.profile field of the /usr/lib/python2.7/dist-packages/cumulus/__chip_config/bcm/datapath.conf file to control the maximum number of overlay next hops (adjacency entries). The profile is one of the following:

The following shows an example of the VXLAN Routing Profile section of the datapath.conf file where the default profile is enabled.

...
# Specify a VxLan Routing Profile - the profile selected determines the
# maximum number of overlay next hops that can be allocated.
# This is supported only on TridentTwoPlus and Maverick
#
# Profile can be one of {'default', 'mode-1', 'mode-2', 'mode-3', 'disable'}
# default: 15% of the overall nexthops are for overlay.
# mode-1:  25% of the overall nexthops are for overlay.
# mode-2:  50% of the overall nexthops are for overlay.
# mode-3:  80% of the overall nexthops are for overlay.
# disable: VxLan Routing is disabled
#
# By default VxLan Routing is enabled with the default profile.
vxlan_routing_overlay.profile = default

The Trident II+ and Trident3 ASICs support a maximum of 48k underlay next hops.

For any profile you specify, you can allocate a maximum of 2K (2048) VXLAN SVI interfaces.

To disable VXLAN routing on a Trident II+ or Trident3 switch, set the vxlan_routing_overlay.profile field to disable.

Tomahawk and Tomahawk+

The Tomahawk and Tomahawk+ ASICs do not support RIOT natively; you must configure the switch ports for VXLAN routing to use internal loopback (also referred to as internal hyperloop). The internal loopback facilitates the recirculation of packets through the ingress pipeline to achieve VXLAN routing.

For routing into a VXLAN tunnel, the first pass of the ASIC performs routing and routing rewrites of the packet MAC source, destination address, and VLAN, then packets recirculate through the internal hyperloop for VXLAN encapsulation and underlay forwarding on the second pass.

For routing out of a VXLAN tunnel, the first pass performs VXLAN decapsulation, then packets recirculate through the hyperloop for routing on the second pass.

You only need to configure the switch ports that must be in internal loopback mode based on the amount of bandwidth required. No additional configuration is necessary.

To configure one or more switch ports for loopback mode, edit the /etc/cumulus/ports.conf file and change the port speed to loopback. In the example below, swp8 and swp9 are configured for loopback mode:

cumulus@switch:~$ sudo nano /etc/cumulus/ports.conf
...
7=4x10G
8=loopback
9=loopback
10=100G
...

Restart switchd for the changes to take effect.

VXLAN routing with internal loopback is supported only with VLAN-aware bridges; you cannot use a bridge in traditional mode.

Tomahawk+ and 25G Ports for Loopback

For VXLAN routing on a switch with the Tomahawk+ ASIC, if you use 25G ports as the internal loopback, you must configure all four ports in the same port group.

VXLAN Routing Data Plane and Broadcom Trident II Platforms

VXLAN routing is not supported on Trident II switches, and the external hyperloop workaround for RIOT on Trident II switches has been removed in Cumulus Linux 4.0.0. Use native VXLAN routing platforms and EVPN for network virtualization.

VXLAN Routing Data Plane and the Mellanox Spectrum ASIC

There is no special configuration required for VXLAN routing on the Mellanox Spectrum ASIC.

Bridge Layer 2 Protocol Tunneling

A VXLAN connects layer 2 domains across a layer 3 fabric; however, layer 2 protocol packets, such as LLDP, LACP, STP, and CDP are normally terminated at the ingress VTEP. If you want the VXLAN to behave more like a wire or hub, where protocol packets are tunneled instead of being terminated locally, you can enable bridge layer 2 protocol tunneling.

Configuration

To configure bridge layer 2 protocol tunneling for all protocols:

cumulus@switch:~$ net add interface swp1 bridge l2protocol-tunnel all
cumulus@switch:~$ net add interface vni13 bridge l2protocol-tunnel all
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To configure bridge layer 2 protocol tunneling for a specific protocol, such as LACP:

cumulus@switch:~$ net add interface swp1 bridge l2protocol-tunnel lacp
cumulus@switch:~$ net add interface vni13 bridge l2protocol-tunnel lacp
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

You must enable layer 2 protocol tunneling on the VXLAN link also so that the packets get bridged and correctly forwarded.

The above commands create the following configuration in the /etc/network/interfaces file:

auto swp1
iface swp1
    bridge-access 10
    bridge-l2protocol-tunnel lacp

auto swp2
iface swp2

auto swp3
iface swp3

auto swp4
iface swp4

...

interface vni13
    bridge-access 13
    bridge-l2protocol-tunnel all
    bridge-learning off
    mstpctl-bpduguard yes
    mstpctl-portbpdufilter yes
    vxlan-id 13
    vxlan-local-tunnelip 10.0.0.4

LLDP Example

Here is another example configuration for Link Layer Discovery Protocol. You can verify the configuration with lldpcli.

cumulus@switch:~$ sudo lldpcli show neighbors
-------------------------------------------------------------------------------
LLDP neighbors:
-------------------------------------------------------------------------------
Interface: swp23, via LLDP, RID: 13, TIme: 0 day, 00:58:20
  Chassis:
    ChassisID: mac e4:1d:2d:f7:d5:52
    SysName: H1
    MgmtIP: 10.0.2.207
    MgmtIP: fe80::e61d:2dff:fef7:d552
    Capability: Bridge, off
    Capability: Router, on
  Port:
    PortID: ifname swp14
    PortDesc: swp14
    TTL: 120
    PMD autoneg: support: yes, enabled: yes
      Adv: 1000Base-T, HD: no, FD: yes
      MAU oper type: 40GbaseCR4 - 40GBASE-R PCS/PMA over 4 lane shielded copper balanced cable
...

LACP Example

H2 bond0:
Bonding Mode: IEEE 802.3ad Dynamic link aggregation
Transmit Hash Policy: layer 3+4(1)

802.3ad: info
LACP rate: fast
Min links: 1
Aggregator selection policy (ad_select): stable
System priority: 65535
System MAC address: cc:37:ab:e7:b5:7e
Active Aggregator Info:
    Aggregator ID: 1
    Number of ports: 2

Slave Interface: eth0
...
details partner lacp pdu:
    system priority: 65535
    system MAC address: 44:38:39:00:a4:95
...
Slave Interface: eth1
...
details partner lacp pdu:
    system priority: 65535
    system MAC address: 44:38:39:00:a4:95

Pseudo-wire Example

In this example, there are only 2 VTEPs in the VXLAN. VTEP1 and VTEP2 point to each other as the only remote VTEP.

The bridge on each VTEP is configured in 802.1ad mode.

The host interface is an 802.1Q VLAN trunk.

The bridge-l2protocol-tunnel is set to all.

The VTEP host-facing port is in access mode, and the PVID is mapped to the VNI.

Notes

Use caution when enabling bridge layer 2 protocol tunneling. Keep the following issues in mind:

Static VXLAN Tunnels

In VXLAN-based networks, there are a range of complexities and challenges in determining the destination virtual tunnel endpoints (VTEPs) for any given VXLAN. At scale, solutions such as EVPN try to address these complexities, however, they also have their own complexities.

Static VXLAN tunnels serve to connect two VTEPs in a given environment. Static VXLAN tunnels are the simplest deployment mechanism for small scale environments and are interoperable with other vendors that adhere to VXLAN standards. Because you simply map which VTEPs are in a particular VNI, you can avoid the tedious process of defining connections to every VLAN on every other VTEP on every other rack.

Requirements

Static VXLAN tunnels are supported only on switches that use the Mellanox Spectrum ASICs or the Broadcom Tomahawk, Trident II+, Trident II, and Trident3 ASICs.

For a basic VXLAN configuration, make sure that:

Example Configuration

The following topology is used in this chapter. Each IP address corresponds to the loopback address of the switch.

Configure Static VXLAN Tunnels

To configure static VXLAN tunnels, do the following on each leaf:

For example, to configure static VXLAN tunnels on the four leafs in the topology shown above:

Run the following commands on leaf01:

cumulus@leaf01:~$ net add loopback lo ip address 10.0.0.11/32
cumulus@leaf01:~$ net add vxlan vni-10 vxlan id 10
cumulus@leaf01:~$ net add vxlan vni-10 bridge learning on
cumulus@leaf01:~$ net add vxlan vni-10 vxlan local-tunnelip 10.0.0.11
cumulus@leaf01:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.12
cumulus@leaf01:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.13
cumulus@leaf01:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.14
cumulus@leaf01:~$ net add vxlan vni-10 bridge access 10
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

Run these commands on leaf02, leaf03, and leaf04:

leaf02

cumulus@leaf02:~$ net add loopback lo ip address 10.0.0.12/32
cumulus@leaf02:~$ net add vxlan vni-10 vxlan id 10
cumulus@leaf02:~$ net add vxlan vni-10 bridge learning on
cumulus@leaf02:~$ net add vxlan vni-10 vxlan local-tunnelip 10.0.0.12
cumulus@leaf02:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.11
cumulus@leaf02:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.13
cumulus@leaf02:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.14
cumulus@leaf02:~$ net add vxlan vni-10 bridge access 10
cumulus@leaf02:~$ net pending
cumulus@leaf02:~$ net commit

leaf03

cumulus@leaf03:~$ net add loopback lo ip address 10.0.0.13/32
cumulus@leaf03:~$ net add vxlan vni-10 vxlan id 10
cumulus@leaf03:~$ net add vxlan vni-10 bridge learning on
cumulus@leaf03:~$ net add vxlan vni-10 vxlan local-tunnelip 10.0.0.13
cumulus@leaf03:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.11
cumulus@leaf03:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.12
cumulus@leaf03:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.14
cumulus@leaf03:~$ net add vxlan vni-10 bridge access 10
cumulus@leaf03:~$ net pending
cumulus@leaf03:~$ net commit

leaf04

cumulus@leaf04:~$ net add loopback lo ip address 10.0.0.14/32
cumulus@leaf04:~$ net add vxlan vni-10 vxlan id 10
cumulus@leaf04:~$ net add vxlan vni-10 bridge learning on
cumulus@leaf04:~$ net add vxlan vni-10 vxlan local-tunnelip 10.0.0.14
cumulus@leaf04:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.11
cumulus@leaf04:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.12
cumulus@leaf04:~$ net add vxlan vni-10 vxlan remoteip 10.0.0.13
cumulus@leaf04:~$ net add vxlan vni-10 bridge access 10
cumulus@leaf04:~$ net pending
cumulus@leaf04:~$ net commit

Configure leaf01 by editing the /etc/network/interfaces file as follows:

# The loopback network interface
auto lo
iface lo inet loopback
    address 10.0.0.11/32

# The primary network interface
auto eth0
iface eth0 inet dhcp

auto swp1
iface swp1

auto swp2
iface swp2

auto bridge
iface bridge
    bridge-ports vni-10
    bridge-vids 10
    bridge-vlan-aware yes

auto vni-10
iface vni-10
    bridge-access 10
    mstpctl-bpduguard yes
    mstpctl-portbpdufilter yes
    vxlan-id 10
    vxlan-local-tunnelip 10.0.0.11
    vxlan-remoteip 10.0.0.12
    vxlan-remoteip 10.0.0.13
    vxlan-remoteip 10.0.0.14
    bridge-learning on

Configure leaf02, leaf03, and leaf04 as follows:

leaf02

# The loopback network interface
auto lo
iface lo inet loopback
    address 10.0.0.12/32

# The primary network interface
auto eth0
iface eth0 inet dhcp

auto swp1
iface swp1

auto swp2
iface swp2

auto bridge
iface bridge
    bridge-ports vni-10
    bridge-vids 10
    bridge-vlan-aware yes

auto vni-10
iface vni-10
    bridge-access 10
    mstpctl-bpduguard yes
    mstpctl-portbpdufilter yes
    vxlan-id 10
    vxlan-local-tunnelip 10.0.0.12
    vxlan-remoteip 10.0.0.11
    vxlan-remoteip 10.0.0.13
    vxlan-remoteip 10.0.0.14
    bridge-learning on

leaf03

# The loopback network interface
auto lo
iface lo inet loopback
   address 10.0.0.13/32

# The primary network interface
auto eth0
iface eth0 inet dhcp

auto swp1
iface swp1

auto swp2
iface swp2

auto bridge
iface bridge
   bridge-ports vni-10
   bridge-vids 10
   bridge-vlan-aware yes

auto vni-10
iface vni-10
   bridge-access 10
   mstpctl-bpduguard yes
   mstpctl-portbpdufilter yes
   vxlan-id 10
   vxlan-local-tunnelip 10.0.0.13
   vxlan-remoteip 10.0.0.11
   vxlan-remoteip 10.0.0.12
   vxlan-remoteip 10.0.0.14
   bridge-learning on

leaf04

# The loopback network interface
auto lo
iface lo inet loopback
    address 10.0.0.14/32

# The primary network interface
auto eth0
iface eth0 inet dhcp

auto swp1
iface swp1

auto swp2
iface swp2

auto bridge
iface bridge
    bridge-ports vni-10
    bridge-vids 10
    bridge-vlan-aware yes

auto vni-10
iface vni-10
    bridge-access 10
    mstpctl-bpduguard yes
    mstpctl-portbpdufilter yes
    vxlan-id 10
    vxlan-local-tunnelip 10.0.0.14
    vxlan-remoteip 10.0.0.11
    vxlan-remoteip 10.0.0.12
    vxlan-remoteip 10.0.0.13
    bridge-learning on

Verify the Configuration

After you configure all the leaf switches, run the following command to check for replication entries:

cumulus@leaf01:~$ sudo bridge fdb show | grep 00:00:00:00:00:00
00:00:00:00:00:00 dev vni-10 dst 10.0.0.14 self permanent
00:00:00:00:00:00 dev vni-10 dst 10.0.0.12 self permanent
00:00:00:00:00:00 dev vni-10 dst 10.0.0.13 self permanent

In Cumulus Linux 4.0 and later, bridge learning is disabled and ARP suppression is enabled by default. You can change the default behavior to set bridge learning on and ARP suppression off for all VNIs by creating a policy file called bridge.json in the /etc/network/ifupdown2/policy.d/ directory. For example:

cumulus@leaf01:~$ sudo cat /etc/network/ifupdown2/policy.d/bridge.json
{
    "bridge": {
        "module_globals": {
            "bridge_vxlan_port_learning" : "on",
            "bridge-vxlan-arp-nd-suppress" : "off"
        }
    }
}

After you create the file, run ifreload -a to load the new configuration.

VXLAN Scale

On Broadcom Trident II and Tomahawk switches running Cumulus Linux, there is a limit to the number of VXLANs you can configure simultaneously. The limit most often given is 2000 VXLANs, but you might want to get more specific and know exactly the limit for your specific design.

While this limitation does apply to Trident II+, Trident3, or Maverick ASICs, Cumulus Linux supports the same number of VXLANs on these ASICs as it does for Trident II or Tomahawk ASICs.

Mellanox Spectrum ASICs do not have a limitation on the number of VXLANs that they can support.

The limit is a physical to virtual mapping where a switch can hold 15000 mappings in hardware before you encounter hash collisions. There is also an upper limit of around 3000 VLANs you can configure before you hit the reserved range (Cumulus Linux uses 3000-3999 by default). Cumulus Linux typically uses a soft number because the math is unique to each environment. An internal VLAN is consumed by each layer 3 port, subinterface, traditional bridge, and the VLAN-aware bridge. Therefore, the number of configurable VLANs is:

(total configurable 802.1q VLANs) - (reserved VLANS) - (physical or logical interfaces) =

4094-999-eth0-loopback = 3093 by default (without any other configuration)

The equation for the number of configurable VXLANs looks like this:

(number of trunks) * (VXLAN/VLANs per trunk) = 15000 - (Linux logical and physical interfaces)

For example, on a 10Gb switch with 48 * 10 G ports and 6 * 40G uplinks, you can calculate for X, the amount of configurable VXLANs:

48 * X = 15000 - (48 downlinks + 6 uplinks + 1 loopback + 1 eth0 + 1 bridge)

48 * X = 14943

X = 311 VXLANs

Similarly, you can apply this logic to a 32 port 100G switch where 16 ports are broken up to 4 * 25 Gbps ports, for a total of 64 * 25 Gbps ports:

64 * X = 15000 - (64 downlinks + 16 uplinks + 1 loopback + 1 eth0 + 1 bridge)

64 * X = 14917

X = 233 VXLANs

However, not all ports are trunks for all VXLANs (or at least not all the time). It is much more common for subsets of ports to be used for different VXLANs. For example, a 10G (48 * 10G + 6 * 40G uplinks) can have the following configuration:

Ports Trunks
swp1-20 100 VXLAN/VLANs
swp21-30 100 VXLAN/VLANs
swp31-48 X VXLAN/VLANs

The equation now looks like this:

20 swps * 100 VXLANs + 10 swps * 100 VXLANs + 18 swps * X VXLANs + (48 downlinks + 6 uplinks + loopback + 1 eth0 + 1 bridge) = 15000

20 swps * 100 VXLANs + 10 swps * 100 VXLANs + 18 swps * X VXLANs = 14943

18 * X = 11943

663 = VXLANS (still configurable) for a total of 863

VXLAN Tunnel DSCP Operations

Cumulus Linux provides configuration options to control DSCP operations during VXLAN encapsulation and decapsulation, specifically for solutions that require end-to-end quality of service, such as RDMA over Converged Ethernet.

The configuration options propagate explicit congestion notification (ECN) between the underlay and overlay and are based on RFC 6040, which describes how to construct the IP header of an ECN field on both ingress to and egress from an IP-in-IP tunnel.

VXLAN Tunnel DSCP operations are supported on Mellanox Spectrum switches only.

Configure DSCP Operations

You can set the following DSCP operations by editing the /etc/cumulus/switchd.conf file. After you modify /etc/cumulus/switchd.conf file, you must restart switchd for the changes to take effect; run the cumulus@switch:~$ sudo systemctl restart switchd.service command.

Option Description
vxlan.def_encap_dscp_action Sets the VXLAN outer DSCP action during encapsulation. You can specify one of the following options:
- copy (if the inner packet is IP)
- set (to a specific value)
- derive (from the switch priority).
The default setting is derive.
vxlan.def_encap_dscp_value If the vxlan.def_encap_dscp_action option is set, you must specify a value.
xlan.def_decap_dscp_action Sets the VXLAN decapsulation DSCP/COS action. You can specify one of the following options:
- copy (if the inner packet is IP)
- preserve (the inner DSCP is unchanged)
- derive (from the switch priority)

The following example shows that the VXLAN outer DSCP action during encapsulation is set with a value of 16.

cumulus@switch:~$ sudo nano /etc/cumulus/switchd.conf
...
# default vxlan outer dscp action during encap
# {copy | set | derive}
# copy: only if inner packet is IP
# set: to specific value
# derive: from switch priority
vxlan.def_encap_dscp_action = set

# default vxlan encap dscp value, only applicable if action is 'set'
vxlan.def_encap_dscp_value = 16

# default vxlan decap dscp/cos action
# {copy | preserve | derive}
# copy: only if inner packet is IP
# preserve: inner dscp unchanged
# derive: from switch priority
#vxlan.def_decap_dscp_action = derive
...

You can also set the DSCP operations from the command line. Use the echo command to change the settings in the /etc/cumulus/switchd.conf file. For example, to change the encapsulation action to copy:

cumulus@switch:~$ echo "copy" > /cumulus/switchd/config/vxlan/def_encap_dscp_action

To change the VXLAN outer DSCP action during encapsulation to set with a value of 32:

cumulus@switch:~$ echo "32" > /cumulus/switchd/config/vxlan/def_encap_dscp_value
cumulus@switch:~$ echo "set" > /cumulus/switchd/config/vxlan/def_encap_dscp_action

Caveats and Errata

Cumulus Linux supports only the default global settings. Per-VXLAN and per-tunnel granularity are not supported.

Hybrid Cloud Connectivity with QinQ and VXLANs

QinQ is an amendment to the IEEE 802.1Q specification that provides the capability for multiple VLAN tags to be inserted into a single Ethernet frame.

QinQ with VXLAN is typically used by a service provider who offers multi-tenant layer 2 connectivity between different customer data centers (private clouds) and also needs to connect those data centers to public cloud providers. Public clouds often has a mandatory QinQ handoff interface, where the outer tag is for the customer and the inner tag is for the service.

In Cumulus Linux, you map QinQ packets to VXLANs through:

QinQ is available on switches with the following ASICs:

You must disable ARP/ND suppression on VXLAN bridges when using QinQ.

Configure Single Tag Translation

Single tag translation adheres to the traditional QinQ service model. The customer-facing interface is a QinQ access port with the outer S-tag being the PVID, representing the customer. The S-tag is translated to a VXLAN VNI. The inner C-tag, which represents the service, is transparent to the provider. The public cloud handoff interface is a QinQ trunk where packets on the wire carry both the S-tag and the C-tag.

Single tag translation works with both VLAN-aware bridge mode and traditional bridge mode. However, single tag translation with VLAN-aware bridge mode is more scalable.

An example configuration in VLAN-aware bridge mode looks like this:

You configure two switches: one at the service provider edge that faces the customer (the switch on the left above), and one on the public cloud handoff edge (the switch on the right above).

To correctly interoperate, all edges must support QinQ with VXLANs.

Configure the Public Cloud-facing Switch

For the switch facing the public cloud:

To configure the public cloud-facing switch:

cumulus@switch:~$ net add vxlan vni-1000 vxlan id 1000
cumulus@switch:~$ net add vxlan vni-1000 vxlan local-tunnelip 10.0.0.1
cumulus@switch:~$ net add vxlan vni-1000 bridge access 100
cumulus@switch:~$ net add vxlan vni-3000 vxlan id 3000
cumulus@switch:~$ net add vxlan vni-3000 vxlan local-tunnelip 10.0.0.1
cumulus@switch:~$ net add vxlan vni-3000 bridge access 200
cumulus@switch:~$ net add bridge bridge vlan-protocol 802.1ad
cumulus@switch:~$ net add bridge bridge ports swp3,vni-1000,vni-3000
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file to add the following configuration:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto vni-1000
iface vni-1000
    bridge-access 100
    vxlan-id 1000
    vxlan-local-tunnelip 10.0.0.1

auto vni-3000
iface vni-3000
    bridge-access 200
    vxlan-id 3000
    vxlan-local-tunnelip 10.0.0.1

auto bridge
iface bridge
    bridge-ports swp3 vni-1000 vni-3000
    bridge-vids 100 200
    bridge-vlan-aware yes
    bridge-vlan-protocol 802.1ad
...

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

Configure the Customer-facing Edge Switch

For the switch facing the customer:

To configure the customer-facing switch:

cumulus@switch:~$ net add interface swp3 bridge access 100
cumulus@switch:~$ net add interface swp4 bridge access 200
cumulus@switch:~$ net add vxlan vni-1000 vxlan id 1000
cumulus@switch:~$ net add vxlan vni-1000 vxlan local-tunnelip 10.0.0.1
cumulus@switch:~$ net add vxlan vni-1000 bridge access 100
cumulus@switch:~$ net add vxlan vni-3000 vxlan id 3000
cumulus@switch:~$ net add vxlan vni-3000 vxlan local-tunnelip 10.0.0.1
cumulus@switch:~$ net add vxlan vni-3000 bridge access 200
cumulus@switch:~$ net add bridge bridge ports swp3,swp4,vni-1000,vni-3000
cumulus@switch:~$ net add bridge bridge vlan-protocol 802.1ad
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file to add the following configuration:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto vni-1000
iface vni-1000
    bridge-access 100
    vxlan-id 1000
    vxlan-local-tunnelip 10.0.0.1

auto vni-3000
iface vni-3000
    bridge-access 200
    vxlan-id 3000
    vxlan-local-tunnelip 10.0.0.1

auto swp3
iface swp3
    bridge-access 100

auto swp4
iface swp4
    bridge-access 200

auto bridge
iface bridge
    bridge-ports swp3 swp4 vni-1000 vni-3000
    bridge-vids 100 200
    bridge-vlan-aware yes
    bridge-vlan-protocol 802.1ad
...

View the Configuration

In the output below, customer A is on VLAN 100 (S-TAG) and customer B is on VLAN 200 (S-TAG).

To check the public cloud-facing switch, run the net show bridge vlan command:

cumulus@switch:~$ net show bridge vlan

Interface      VLAN  Flags                  VNI
-----------  ------  ---------------------  -----
swp3             1   PVID, Egress Untagged
               100
               200
vni-1000       100   PVID, Egress Untagged   1000
vni-3000       200   PVID, Egress Untagged   3000

To check the customer-facing switch, use net show bridge vlan:

cumulus@switch:~$ net show bridge vlan
Interface      VLAN  Flags                  VNI
-----------  ------  ---------------------  -----
swp3            100  PVID, Egress Untagged
swp4            200  PVID, Egress Untagged
vni-1000        100  PVID, Egress Untagged  1000
vni-3000        200  PVID, Egress Untagged  3000

To verify that the bridge is configured for QinQ, run ip -d link show bridge and look for vlan_protocol 802.1ad in the output:

cumulus@switch:~$ sudo ip -d link show bridge
287: bridge: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default
    link/ether 06:a2:ae:de:e3:43 brd ff:ff:ff:ff:ff:ff promiscuity 0
    bridge forward_delay 1500 hello_time 200 max_age 2000 ageing_time 30000 stp_state 2 priority 32768 vlan_filtering 1 vlan_protocol 802.1ad bridge_id 8000.6:a2:ae:de:e3:43 designated_root 8000.6:a2:ae:de:e3:43 root_port 0 root_path_cost 0 topology_change 0 topology_change_detected 0 hello_timer    0.00 tcn_timer    0.00 topology_change_timer    0.00 gc_timer   64.29 vlan_default_pvid 1 vlan_stats_enabled 1 group_fwd_mask 0 group_address 01:80:c2:00:00:08 mcast_snooping 0 mcast_router 1 mcast_query_use_ifaddr 0 mcast_querier 0 mcast_hash_elasticity 4096 mcast_hash_max 4096 mcast_last_member_count 2 mcast_startup_query_count 2 mcast_last_member_interval 100 mcast_membership_interval 26000 mcast_querier_interval 25500 mcast_query_interval 12500 mcast_query_response_interval 1000 mcast_startup_query_interval 3125 mcast_stats_enabled 1 mcast_igmp_version 2 mcast_mld_version 1 nf_call_iptables 0 nf_call_ip6tables 0 nf_call_arptables 0 addrgenmode eui64

Example Configuration in Traditional Bridge Mode

An example configuration for single tag translation in traditional bridge mode on a leaf switch is shown below.

Example /etc/network/interfaces File
auto swp3.11
iface swp3.11
    vlan-protocol 802.1ad

auto vxlan1000101
iface vxlan1000101
    vxlan-id 1000101
    vxlan-local-tunnelip 10.0.0.13

auto br11
iface br11
    bridge-ports swp3.11 vxlan1000101

Configure Double Tag Translation

Double tag translation involves a bridge with double-tagged member interfaces, where a combination of the C-tag and S-tag map to a VNI. You create the configuration only at the edge facing the public cloud. The VXLAN configuration at the customer-facing edge doesn’t need to change.

The double tag is always a cloud connection. The customer-facing edge is either single-tagged or untagged. At the public cloud handoff point, the VNI maps to double VLAN tags, with the S-tag indicating the customer and the C-tag indicating the service.

The configuration in Cumulus Linux uses the outer tag for the customer and the inner tag for the service.

You configure a double-tagged interface by stacking the VLANs in the following manner: <port>.<outer tag>.<inner tag>. For example, consider swp1.100.10: the outer tag is VLAN 100, which represents the customer, and the inner tag is VLAN 10, which represents the service.

The outer tag or TPID (tagged protocol identifier) needs the vlan_protocol to be specified. It can be either 802.1Q or 802.1ad. If 802.1ad is used, it must be specified on the lower VLAN device, such as swp3.100 in the example below.

Double tag translation only works with bridges in traditional mode (not VLAN-aware mode).

An example configuration:

To configure the switch for double tag translation using the above example, edit the /etc/network/interfaces file in a text editor and add the following:

auto swp3.100
iface swp3.100
    vlan_protocol 802.1ad

auto swp3.100.10
iface swp3.100.10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes

auto vni1000
iface vni1000
    vxlan-local-tunnelip  10.0.0.1
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes
    vxlan-id 1000

auto custA-10-azr
iface custA-10-azr
    bridge-ports swp3.100.10 vni1000
    bridge-vlan-aware no

To check the configuration, run the brctl show command:

cumulus@switch:~$ sudo brctl show
bridge name     bridge id               STP enabled     interfaces
custA-10-azr    8000.00020000004b       yes             swp3.100.10
                                                        vni1000
custB-20-azr    8000.00020000004b       yes             swp3.200.20
                                                        vni3000

If the bridge is not VXLAN-enabled, the configuration looks like this:

auto swp5.100
iface swp5.100
    vlan-protocol 802.1ad

auto swp5.100.10
iface swp5.100.10
    mstpctl-portbpdufilter yes
    mstpctl-bpduguard yes

auto br10
iface br10
    bridge-ports swp3.10  swp4  swp5.100.10
    bridge-vlan-aware no

Caveats and Errata

Feature Limitations

Long Interface Names

The Linux kernel limits interface names to 15 characters in length. For QinQ interfaces, you can reach this limit easily.

To work around this issue, create two VLANs as nested VLAN raw devices, one for the outer tag and one for the inner tag. For example, you cannot create an interface called swp50s0.1001.101 because it contains 16 characters. Instead, edit the /etc/network/interfaces file to create VLANs with IDs 1001 and 101. For example:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto vlan1001
iface vlan1001
      vlan-id 1001
       vlan-raw-device swp50s0
       vlan-protocol 802.1ad

auto vlan1001-101
iface vlan1001-101
       vlan-id 101
       vlan-raw-device vlan1001

auto bridge101
iface bridge101
    bridge-ports vlan1001-101 vxlan1000101
...

Layer 3

This section describes layer 3 configuration. Read this section to understand routing protocols and learn how to configure routing on the Cumulus Linux switch.

Routing

This chapter discusses routing on switches running Cumulus Linux.

Manage Static Routes

Static routes are added to the FRRouting routing table and then the kernel routing table.

To add static routes:

cumulus@switch:~$ net add routing route 203.0.113.0/24 198.51.100.2
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# ip route 203.0.113.0/24 198.51.100.2
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
!
ip route 203.0.113.0/24 198.51.100.2
!
...

To delete a static route:

cumulus@switch:~$ net del routing route 203.0.113.0/24 198.51.100.2
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# no ip route 203.0.113.0/24 198.51.100.2
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

To view static routes, run the NCLU net show route static command or the vtysh show ip route command. For example:

cumulus@switch:~$ net show route static 
RIB entry for static
====================
Codes: K - kernel route, C - connected, S - static, R - RIP,
        O - OSPF, I - IS-IS, B - BGP, P - PIM, T - Table,
        > - selected route, * - FIB route
 S>* 203.0.113.0/24 [1/0] via 198.51.100.2, swp3

Static Multicast Routes

To add a static multicast route (mroute):

cumulus@switch:~$ net add routing mroute 230.0.0.0/24
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# ip mroute 203.0.0.0/24
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
!
ip mroute 230.0.0.0/24
!
...

To delete an mroute:

cumulus@switch:~$ net del routing mroute 230.0.0.0/24
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# no ip mroute 203.0.0.0/24
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

To view mroutes, run the following command from the vtysh shell:

cumulus@switch:~$ sudo vtysh
switch# show ip rpf 230.0.0.0
Routing entry for 230.0.0.0/24 using Multicast RIB
  Known via "static", distance 1, metric 0, best
  * directly connected, swp31s0

Static Routing via ip route

You can also create a static route by adding the route to a switch port configuration. For example:

cumulus@switch:~$ net add interface swp3 ip address 198.51.100.1/24
cumulus@switch:~$ net add interface swp3 post-up routing route add 203.0.113.0/24 via 198.51.100.2
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface swp3
switch(config-if)# post-up ip route 203.0.113.0/24 198.51.100.2
switch(config-if)# exit
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/network/interfaces file. For example:

...
auto swp3
iface swp3
    address 198.51.100.1/24
    post-up ip route add 203.0.113.0/24 via 198.51.100.2
...

The ip route command allows you to manipulate the kernel routing table directly from the Linux shell. See man ip(8) for details. FRRouting monitors the kernel routing table changes and updates its own routing table accordingly.

To display the routing table:

cumulus@switch:~$ ip route show
default via 10.0.1.2 dev eth0
10.0.1.0/24 dev eth0  proto kernel  scope link  src 10.0.1.52
192.0.2.0/24 dev swp1  proto kernel  scope link  src 192.0.2.12
192.0.2.10/24 via 192.0.2.1 dev swp1  proto zebra  metric 20
192.0.2.20/24  proto zebra  metric 20
     nexthop via 192.0.2.1  dev swp1 weight 1
     nexthop via 192.0.2.2  dev swp2 weight 1
192.0.2.30/24 via 192.0.2.1 dev swp1  proto zebra  metric 20
192.0.2.40/24 dev swp2  proto kernel  scope link  src 192.0.2.42
192.0.2.50/24 via 192.0.2.2 dev swp2  proto zebra  metric 20
192.0.2.60/24 via 192.0.2.2 dev swp2  proto zebra  metric 20
192.0.2.70/24  proto zebra  metric 30
     nexthop via 192.0.2.1  dev swp1 weight 1
     nexthop via 192.0.2.2  dev swp2 weight 1
198.51.100.0/24 dev swp3  proto kernel  scope link  src 198.51.100.1
198.51.100.10/24 dev swp4  proto kernel  scope link  src 198.51.100.11
198.51.100.20/24 dev br0  proto kernel  scope link  src 198.51.100.21

Apply a Route Map for Route Updates

To apply a route map to filter route updates from Zebra into the Linux kernel:

cumulus@switch:~$ net add routing protocol static route-map myroutemap
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# ip protocol static route-map myroutemap
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
!
ip protocol static route-map myroutemap
!
...

Configure a Gateway or Default Route

Consider creating a gateway or default route on each switch for traffic destined outside the switch’s subnet or local network. All such traffic passes through the gateway, which is a host on the same network that routes packets to their destination beyond the local network.

In the following example, you create a default route in the routing table 0.0.0.0/0, which indicates any IP address can be sent to the gateway, which is another switch with the IP address 10.1.0.1.

cumulus@switch:~$ net add routing route 0.0.0.0/0 10.1.0.1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# ip route 0.0.0.0/0 10.1.0.1
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
!
ip route 0.0.0.0/0 10.1.0.1
!
...

Supported Route Table Entries

Cumulus Linux (via switchd)advertises the maximum number of route table entries that are supported on a given switch architecture, including:

In addition, switches on the Tomahawk, Trident II, Trident II+, and Trident3 platforms are configured to manage route table entries using Algorithm Longest Prefix Match (ALPM). In ALPM mode, the hardware can store significantly more route entries.

You can use cl-resource-query to determine the current table sizes on a given switch.

Forwarding Table Profiles

On Mellanox Spectrum and some Broadcom ASICs, you can configure the allocation of forwarding table resources and mechanisms. Cumulus Linux provides a number of generalized profiles for the platforms described below. These profiles work only with layer 2 and layer 3 unicast forwarding.

Cumulus Linux defines these profiles as default, l 2-heavy, v4-lpm-heavy and v6-lpm-heavy. Choose the profile that best suits your network architecture and specify the profile name for the forwarding_table.profile variable in the /etc/cumulus/datapath/traffic.conf file.

cumulus@switch:~$ cat /etc/cumulus/datapath/traffic.conf | grep forwarding_table -B 4
# Manage shared forwarding table allocations
# Valid profiles -
# default, l2-heavy, v4-lpm-heavy, v6-lpm-heavy
#
forwarding_table.profile = default

After you specify a different profile, restart switchd for the change to take effect. You can see the forwarding table profile when you run cl-resource-query.

Broadcom ASICs other than Maverick, Tomahawk/Tomahawk+, Trident II, Trident II+, and Trident3 support only the default profile.

For Broadcom ASICs, the maximum number of IP multicast entries is 8k.

Number of Supported Route Entries By Platform

The following tables list the number of MAC addresses, layer 3 neighbors, and LPM routes validated for each forwarding table profile for the various supported platforms. If you do not specify any profiles as described above, the default values are the ones that the switch will use.

The values in the following tables reflect results from testing on the different platforms that support Cumulus Linux, which might differ from published manufacturer specifications.

Mellanox Spectrum Switches

Profile
MAC Addresses
L3 Neighbors
Longest Prefix Match (LPM)
default 40k 32k (IPv4) and 16k (IPv6) 64k (IPv4) and 28k (IPv6-long)
l2-heavy 88k 48k (IPv4) and 40k (IPv6) 8k (IPv4) and 8k (IPv6-long)
l2-heavy-1 180K 8k (IPv4) and 8k (IPv6) 8k (IPv4) and 8k (IPv6-long)
v4-lpm-heavy 8k 8k (IPv4) and 16k (IPv6) 80k (IPv4) and 16k (IPv6-long)
v4-lpm-heavy-1 8k 8k (IPv4) and 2k (IPv6) 176k (IPv4) and 2k (IPv6-long)
v6-lpm-heavy 40k 8k (IPv4) and 40k (IPv6) 8k (IPv4) and 32k (IPv6-long) and 32K (IPv6/64)
lpm-balanced 8k 8k (IPv4) and 8k (IPv6) 60k (IPv4) and 60k (IPv6-long)

Broadcom Tomahawk/Tomahawk+ Switches

Profile MAC Addresses L3 Neighbors Longest Prefix Match (LPM)
default 40k 40k 64k (IPv4) or 8k (IPv6-long)
l2-heavy 72k 72k 8k (IPv4) or 2k (IPv6-long)
v4-lpm-heavy, v6-lpm-heavy 8k 8k 128k (IPv4) or 20k (IPv6-long)

Broadcom Trident II/Trident II+/Trident3 Switches

Profile MAC Addresses L3 Neighbors Longest Prefix Match (LPM)
default 32k 16k 128k (IPv4) or 20k (IPv6-long)
l2-heavy 160k 96k 8k (IPv4) or 2k (IPv6-long)
v4-lpm-heavy, v6-lpm-heavy 32k 16k 128k (IPv4) or 20k (IPv6-long)

Broadcom Helix4 Switches

Helix4 switches do not have profiles.

MAC Addresses L3 Neighbors Longest Prefix Match (LPM)
24k 12k 7.8k (IPv4) or 2k (IPv6-long)

For Broadcom switches, IPv4 and IPv6 entries are not carved in separate spaces so it is not possible to define explicit numbers in the L3 Neighbors column of the tables shown above. An IPv6 entry takes up twice the space of an IPv4 entry.

TCAM Resource Profiles for Spectrum Switches

On the Mellanox Spectrum ASIC, you can configure TCAM resource allocation, which is shared between IP multicast forwarding entries and ACL tables. Cumulus Linux provides a number of general profiles for this platform: default, ipmc-heavy and acl-heavy. Choose the profile that best suits your network architecture and specify that profile name in the tcam_resource.profile variable in the /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf file.

cumulus@switch:~$ cat /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf | grep -B3 "tcam_resource"
#TCAM resource forwarding profile

    1. Valid profiles -
    2. default, ipmc-heavy, acl-heavy, ipmc-max
       tcam_resource.profile = default

After you specify a different profile, restart switchd for the change to take effect.

When nonatomic updates are enabled (acl.non_atomic_update_mode is set to TRUE in the /etc/cumulus/switchd.conf file), the maximum number of mroute and ACL entries for each profile are:

Profile Mroute Entries ACL Entries
default 1000 500 (IPv6) or 1000 (IPv4)
ipmc-heavy 8500 1000 (IPv6) or 1500 (IPv4)
acl-heavy 450 2000 (IPv6) or 3500 (IPv4)
ipmc-max 13000 1000 (IPv6) or 2000 (IPv4)

When nonatomic updates are disabled (acl.non_atomic_update_mode is set to FALSE in the /etc/cumulus/switchd.conf file), the maximum number of mroute and ACL entries for each profile are:

Profile Mroute Entries ACL Entries
default 1000 250 (IPv6) or 500 (IPv4)
ipmc-heavy 8500 500 (IPv6) or 750 (IPv4)
acl-heavy 450 1000 (IPv6) or 1750 (IPv4)
ipmc-max 13000 500 (IPv6) or 1000 (IPv4)

Route Entry Takes Precedence Over Neighbor Entry

On Broadcom switches with Cumulus Linux 4.0 and later, when there is a /32 IPv4 or /128 IPv6 route and the same prefix is also a neighbor entry in the linux kernel, the route entry takes precedence over the neighbor entry in the forwarding lookup. To change this behavior, update the route_preferred_over_neigh variable to FALSE in the /etc/cumulus/switchd.conf file.

Caveats and Errata

Do Not Delete Routes through Linux Shell

Do not use the Linux shell to delete static routes added via FRRouting (with vtysh commands). Delete the routes with the vtysh commands; otherwise FRRouting might not be able to clean up its internal state completely, which can result in incorrect routing.

Using NCLU Commands to Delete Routing Configuration

When you use NCLU commands to delete routing (FRR) configuration, such as static routes or route map rules (multiples of which can exist in a configuration), commit ten or fewer delete commands at a time to avoid commit failures.

Add IPv6 Default Route with src Address on eth0 Fails without Adding Delay

Attempting to install an IPv6 default route on eth0 with a source address fails at reboot or when running ifup on eth0.

The first execution of ifup -dv returns this warning and does not install the route:

cumulus@switch:~$ sudo ifup -dv eth0
warning: eth0: post-up cmd '/sbin/ip route add default via 2001:620:5ca1:160::1 /
src 2001:620:5ca1:160::45 dev eth0' failed (RTNETLINK answers: Invalid argument)<<<<<<<<<<

Running ifup a second time on eth0 successfully installs the route.

To work around this issue, either add a two second delay or exclude the src parameter to the ip route add that causes the need for the delay:

cumulus@switch:~$ net add interface eth0 ipv6 address 2001:620:5ca1:160::45/64 post-up /bin/sleep 2s
cumulus@switch:~$ net add interface eth0 post-up /sbin/ip route add default via 2001:620:5ca1:160::1 src 2001:620:5ca11:160::45 dev eth0
cumulus@switch:~$ net add interface eth0 post-up /sbin/ip route add default via 2001:620:5ca1:160::1 dev eth0
cumulus@switch:~$ ifdown eth0
Stopping NTP server: ntpd.
Starting NTP server: ntpd.
cumulus@switch:~$ ip -6 r s
cumulus@switch:~$ ifup eth0
Stopping NTP server: ntpd.
Starting NTP server: ntpd.
cumulus@switch:~$ ip -6 r s
2001:620:5ca1:160::/64 dev eth0  proto kernel  metric 256
fe80::/64 dev eth0  proto kernel  metric 256
default via 2001:620:5ca1:160::1 dev eth0  metric 1024

Use the Same Neighbor Cache Aging Timer for IPv4 and IPv6

Cumulus Linux does not support different neighbor cache aging timer settings for IPv4 and IPv6.

For example, see the two settings for neigh.default.base_reachable_time_ms in /etc/sysctl.d/neigh.conf:

cumulus@switch:~$ sudo cat /etc/sysctl.d/neigh.conf

...

net.ipv4.neigh.default.base_reachable_time_ms=1080000
net.ipv6.neigh.default.base_reachable_time_ms=1080000

...

Introduction to Routing Protocols

A routing protocol dynamically computes reachability between various end points. This enables communication to work around link and node failures, and additions and withdrawals of various addresses.

IP routing protocols are typically distributed; an instance of the routing protocol runs on each of the routers in a network.

Cumulus Linux does not support running multiple instances of the same protocol on a router.

Distributed routing protocols compute reachability between end points by disseminating relevant information and running a routing algorithm to determine the routes to each end station. To scale the amount of information that needs to be exchanged, routes are computed on address prefixes rather than on every end point address.

Configure Routing Protocols

A routing protocol needs to know three pieces of information, at a minimum:

Most routing protocols use the concept of a router ID to identify a node. Different routing protocols answer the last two questions differently.

The way they answer these questions affects the network design and thereby configuration. For example, in a link-state protocol such as OSPF (see Open Shortest Path First - OSPF) or IS-IS, complete local information (links and attached address prefixes) about a node is disseminated to every other node in the network. Since the state that a node has to keep grows rapidly in such a case, link-state protocols typically limit the number of nodes that communicate this way. They allow for bigger networks to be built by breaking up a network into a set of smaller subnetworks (which are called areas or levels) and by advertising summarized information about an area to other areas.

Protocol Tuning

Most protocols provide certain tunable parameters that are specific to convergence during changes.

Wikipedia defines convergence as the “state of a set of routers that have the same topological information about the network in which they operate. " It is imperative that the routers in a network have the same topological state for the proper functioning of a network. Without this, traffic can be blackholed and unable to reach its destination. It is normal for different routers to have differing topological states during changes, but this difference should vanish as the routers exchange information about the change and recompute the forwarding paths. Different protocols converge at different speeds in the presence of changes.

A key factor that governs how quickly a routing protocol converges is the time it takes to detect the change. For example, how quickly can a routing protocol be expected to act when there is a link failure. Routing protocols classify changes into two kinds: hard changes such as link failures and soft changes such as a peer dying silently. They are classified differently because protocols provide different mechanisms for dealing with these failures.

It is important to configure the protocols to be notified immediately on link changes. This is also true when a node goes down, causing all of its links to go down.

Even if a link does not fail, a routing peer can crash. This causes that router to delete the routes it has computed or worse, it makes that router impervious to changes in the network, causing it to go out of sync with the other routers in the network because it no longer shares the same topological information as its peers.

The most common way to detect a protocol peer dying is to detect the absence of a heartbeat. All routing protocols send a heartbeat (or hello) packet periodically. When a node does not see a consecutive set of these hello packets from a peer, it declares its peer dead and informs other routers in the network about this. The period of each heartbeat and the number of heartbeats that need to be missed before a peer is declared dead are two popular configurable parameters.

If you configure these timers very low, the network can quickly descend into instability under stressful conditions when a router is not able to keep sending the heartbeats quickly as it is busy computing routing state; or the traffic is so much that the hellos get lost. Alternately, configuring the timers to very high values also causes blackholing of communication because it takes much longer to detect peer failures. Usually, the default values initialized within each protocol are good enough for most networks. Do not adjust these settings.

Network Topology

In computer networks, topology refers to the structure of interconnecting various nodes. Some commonly used topologies in networks are star, hub and spoke, leaf and spine, and broadcast.

Clos Topologies

In the vast majority of modern data centers, Clos or fat tree topology is very popular. This topology is shown in the figure below. It is also commonly referred to as leaf-spine topology.

This topology allows you to build networks of varying size using nodes of different port counts and/or by increasing the tiers. The picture above is a three-tiered Clos network. We number the tiers from the bottom to the top. In the illustration above, the lowermost layer is called tier 1 and the topmost tier is called tier 3.

The number of end stations (such as servers) that can be attached to such a network is determined by a very simple mathematical formula.

In a 2-tier network, if each node is made up of m ports, then the total number of end stations that can be connected is m^2/2. In more general terms, if tier-1 nodes are m-port nodes and tier-2 nodes are n-port nodes, then the total number of end stations that can be connected are (m*n)/2. In a three tier network, where tier-3 nodes are o-port nodes, the total number of end stations that can be connected are (m*n*o)/2^(number of tiers-1).

In many data centers, it is typical to connect 40 servers to a top-of-rack (ToR) switch. The ToRs are all connected via a set of spine switches. If a ToR switch has 64 ports, then after hooking up 40 ports to the servers, the remaining 24 ports can be hooked up to 24 spine switches of the same link speed or to a smaller number of higher link speed switches. For example, if the servers are all hooked up as 10GE links, then the ToRs can connect to the spine switches via 40G links. So, instead of connecting to 24 spine switches with 10G links, the ToRs can connect to 6 spine switches with each link being 40G. If the spine switches are also 64-port switches, then the total number of end stations that can be connected is 2560 (40*64) stations.

In a three tier network of 64-port switches, the total number of servers that can be connected are (40*64*64)/2^(3-1) = 40960. As you can see, this kind of topology can serve quite a large network with three tiers.

Over-subscribed and Non-blocking Configurations

In the above example, the network is over-subscribed; that is, 400G of bandwidth from end stations (40 servers * 10GE links) is serviced by only 240G of inter-rack bandwidth. The over-subscription ratio is 0.6 (240/400).

This can lead to congestion in the network and hot spots. Instead, if network operators connected 32 servers per rack, then 32 ports are left to be connected to spine switches. Now, the network is said to be rearrangably non-blocking. Now any server in a rack can talk to any other server in any other rack without necessarily blocking traffic between other servers.

In such a network, the total number of servers that can be connected are (64*64)/2 = 2048. Similarly, a three-tier version of the same can serve up to (64*64*64)/4 = 65536 servers.

Contain the Failure Domain

Traditional data centers were built using just two spine switches. This means that if one of those switches fails, the network bandwidth is cut in half, thereby greatly increasing network congestion and adversely affecting many applications. To avoid this problem, vendors typically try and make the spine switches resilient to failures by providing such features as dual control line cards and attempting to make the software highly available. In many cases, HA is among the top two or three causes of software failure (and thereby switch failure).

To support a fairly large network with just two spine switches also means that these switches have a large port count. This can make the switches quite expensive. If the number of spine switches were to be merely doubled, the effect of a single switch failure is halved. With 8 spine switches, the effect of a single switch failure only causes a 12 percent reduction in available bandwidth. So, in modern data centers, people build networks with anywhere from 4 to 32 spine switches.

Load Balancing

In a Clos network, traffic is load balanced across the multiple links using equal cost multi-pathing (ECMP).

Routing algorithms compute shortest paths between two end stations where shortest is typically the lowest path cost. Each link is assigned a metric or cost. By default, a link’s cost is a function of the link speed. The higher the link speed, the lower its cost. A 10G link has a higher cost than a 40G or 100G link, but a lower cost than a 1G link. The link cost is a measure of its traffic carrying capacity.

In the modern data center, the links between tiers of the network are homogeneous; they have the same characteristics (same speed and therefore link cost) as the other links. As a result, the first hop router can pick any of the spine switches to forward a packet to its destination (assuming that there is no link failure between the spine and the destination switch). Most routing protocols recognize that there are multiple equal-cost paths to a destination and enable any of them to be selected for a given traffic flow.

FRRouting Overview

Cumulus Linux uses FRRouting to provide the routing protocols for dynamic routing and supports the following routing protocols:

Architecture

The FRRouting suite consists of various protocol-specific daemons and a protocol-independent daemon called zebra. Each of the protocol-specific daemons are responsible for running the relevant protocol and building the routing table based on the information exchanged.

It is not uncommon to have more than one protocol daemon running at the same time. For example, at the edge of an enterprise, protocols internal to an enterprise (called IGP for Interior Gateway Protocol) such as OSPF text or RIP run alongside the protocols that connect an enterprise to the rest of the world (called EGP or Exterior Gateway Protocol) such as BGP text.

About zebra

zebra is the daemon that resolves the routes provided by multiple protocols (including the static routes you specify) and programs these routes in the Linux kernel via netlink (in Linux). The FRRouting documentation defines zebra as the IP routing manager for FRRouting that “provides kernel routing table updates, interface lookups, and redistribution of routes between different routing protocols.”

Configuring FRRouting

This section discusses FRRouting configuration.

Configure FRRouting

FRRouting does not start by default in Cumulus Linux. Before you run FRRouting, make sure you have enabled the relevant daemons that you intend to use (bgpd, ospfd, ospf6d or pimd) in the /etc/frr/daemons file.

NVIDIA has not tested RIP, RIPv6, IS-IS and Babel.

The zebra daemon is enabled by default. You can enable the other daemons according to how you plan to route your network.

Before you start FRRouting, edit the /etc/frr/daemons file to enable each daemon you want to use. For example, to enable BGP, set bgpd to yes:

...
bgpd=yes
ospfd=no
ospf6d=no
ripd=no
ripngd=no
isisd=no
fabricd=no
pimd=no
ldpd=no
nhrpd=no
eigrpd=no
babeld=no
sharpd=no
pbrd=no
vrrpd=no
...

Enable and Start FRRouting

After you enable the appropriate daemons, enable and start the FRRouting service:

cumulus@switch:~$ sudo systemctl enable frr.service
cumulus@switch:~$ sudo systemctl start frr.service

All the routing protocol daemons (bgpd, ospfd, ospf6d, ripd, ripngd, isisd and pimd) are dependent on zebra. When you start FFRouting, systemd determines whether zebra is running; if zebra is not running, systemd starts zebra, then starts the dependent service, such as bgpd.

In general, if you restart a service, its dependent services are also restarted. For example, running systemctl restart frr.service restarts any of the routing protocol daemons that are enabled and running.

For more information on the systemctl command and changing the state of daemons, read Services and Daemons in Cumulus Linux.

Integrated Configurations

By default in Cumulus Linux, FRRouting saves all daemon configurations in a single integrated configuration file, frr.conf.

You can disable this mode by running the following command in the vtysh FRRouting CLI:

cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# no service integrated-vtysh-config

To reenable integrated configuration file mode, run:

switch(config)# service integrated-vtysh-config

If you disable integrated configuration mode, FRRouting saves each daemon-specific configuration file in a separate file. At a minimum for a daemon to start, that daemon must be enabled and its daemon-specific configuration file must be present, even if that file is empty.

To save the current configuration:

switch# write memory
Building Configuration...
Integrated configuration saved to /etc/frr/frr.conf
[OK]
switch# exit
cumulus@switch:~$

You can use write file instead of write memory.

When integrated configuration mode is disabled, the output looks like this:

switch# write memory
Building Configuration...
Configuration saved to /etc/frr/zebra.conf
Configuration saved to /etc/frr/bgpd.conf
[OK]

Restore the Default Configuration

If you need to restore the FRRouting configuration to the default running configuration, delete the frr.conf file and restart the frr service.

Back up frr.conf (or any configuration files you want to remove) before proceeding.

  1. Confirm that service integrated-vtysh-config is enabled:
cumulus@switch:~$ net show configuration | grep integrated
service integrated-vtysh-config  
  1. Remove /etc/frr/frr.conf:
cumulus@switch:~$ sudo rm /etc/frr/frr.conf

If integrated configuration file mode is disabled, remove all the configuration files (such as zebra.conf or ospf6d.conf) instead of frr.conf.

  1. Restart FRR with this command:

    cumulus@switch:~$ sudo systemctl restart frr.service

    Restarting FRR restarts all the routing protocol daemons that are enabled and running.

Interface IP Addresses and VRFs

FRRouting inherits the IP addresses and any associated routing tables for the network interfaces from the /etc/network/interfaces file. This is the recommended way to define the addresses; do not create interfaces using FRRouting. For more information, see Configure IP Addresses and Virtual Routing and Forwarding - VRF.

FRRouting vtysh Modal CLI

FRRouting provides a command-line interface (CLI) called vtysh for configuring and displaying protocol state. To start the CLI, run the sudo vtysh command:

cumulus@switch:~$ sudo vtysh

Hello, this is FRRouting (version 0.99.23.1+cl3u2).
Copyright 1996-2005 Kunihiro Ishiguro, et al.

switch#

vtysh provides a Cisco-like modal CLI and many of the commands are similar to Cisco IOS commands. There are different modes to the CLI and certain commands are only available within a specific mode. Configuration is available with the configure terminal command:

switch# configure terminal
switch(config)#

The prompt displays the current CLI mode. For example, when the interface-specific commands are invoked, the prompt changes to:

switch(config)# interface swp1
switch(config-if)#

When the routing protocol specific commands are invoked, the prompt changes to:

switch(config)# router ospf
switch(config-router)#

? displays the list of available top-level commands:

switch(config-if)# ?
  bandwidth    Set bandwidth informational parameter
  description  Interface specific description
  end          End current mode and change to enable mode
  exit         Exit current mode and down to previous mode
  ip           IP Information
  ipv6         IPv6 Information
  isis         IS-IS commands
  link-detect  Enable link detection on interface
  list         Print command list
  mpls-te      MPLS-TE specific commands
  multicast    Set multicast flag to interface
  no           Negate a command or set its defaults
  ptm-enable   Enable neighbor check with specified topology
  quit         Exit current mode and down to previous mode
  shutdown     Shutdown the selected interface

?-based completion is also available to see the parameters that a command takes:

switch(config-if)# bandwidth ?
<1-10000000>  Bandwidth in kilobits
switch(config-if)# ip ?
address  Set the IP address of an interface
irdp     Alter ICMP Router discovery preference this interface
ospf     OSPF interface commands
rip      Routing Information Protocol
router   IP router interface commands

To search for specific vtysh commands so that you can identify the correct syntax to use, run the sudo vtysh -c 'find <term>' command. For example, to show only commands that include mlag:

cumulus@leaf01:mgmt:~$ sudo vtysh -c 'find mlag'
  (view)  show ip pim [mlag] vrf all interface [detail|WORD] [json]
  (view)  show ip pim [vrf NAME] interface [mlag] [detail|WORD] [json]
  (view)  show ip pim [vrf NAME] mlag upstream [A.B.C.D [A.B.C.D]] [json]
  (view)  show ip pim mlag summary [json]
  (view)  show ip pim vrf all mlag upstream [json]
  (view)  show zebra mlag
  (enable)  [no$no] debug zebra mlag
  (enable)  debug pim mlag
  (enable)  no debug pim mlag
  (enable)  test zebra mlag <none$none|primary$primary|secondary$secondary>
  (enable)  show ip pim [mlag] vrf all interface [detail|WORD] [json]
  (enable)  show ip pim [vrf NAME] interface [mlag] [detail|WORD] [json]
  (enable)  show ip pim [vrf NAME] mlag upstream [A.B.C.D [A.B.C.D]] [json]
  (enable)  show ip pim mlag summary [json]
  (enable)  show ip pim vrf all mlag upstream [json]
  (enable)  show zebra mlag
  (config)  [no$no] debug zebra mlag
  (config)  debug pim mlag
  (config)  ip pim mlag INTERFACE role [primary|secondary] state [up|down] addr A.B.C.D
  (config)  no debug pim mlag
  (config)  no ip pim mlag

Displaying state can be done at any level, including the top level. For example, to see the routing table as seen by zebra:

switch# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, T - Table,
       > - selected route, * - FIB route
B>* 0.0.0.0/0 [20/0] via fe80::4638:39ff:fe00:c, swp29, 00:11:57
  *                  via fe80::4638:39ff:fe00:52, swp30, 00:11:57
B>* 10.0.0.1/32 [20/0] via fe80::4638:39ff:fe00:c, swp29, 00:11:57
  *                    via fe80::4638:39ff:fe00:52, swp30, 00:11:57
B>* 10.0.0.11/32 [20/0] via fe80::4638:39ff:fe00:5b, swp1, 00:11:57
B>* 10.0.0.12/32 [20/0] via fe80::4638:39ff:fe00:2e, swp2, 00:11:58
B>* 10.0.0.13/32 [20/0] via fe80::4638:39ff:fe00:57, swp3, 00:11:59
B>* 10.0.0.14/32 [20/0] via fe80::4638:39ff:fe00:43, swp4, 00:11:59
C>* 10.0.0.21/32 is directly connected, lo
B>* 10.0.0.51/32 [20/0] via fe80::4638:39ff:fe00:c, swp29, 00:11:57
  *                     via fe80::4638:39ff:fe00:52, swp30, 00:11:57
B>* 172.16.1.0/24 [20/0] via fe80::4638:39ff:fe00:5b, swp1, 00:11:57
  *                      via fe80::4638:39ff:fe00:2e, swp2, 00:11:57
B>* 172.16.3.0/24 [20/0] via fe80::4638:39ff:fe00:57, swp3, 00:11:59
  *                      via fe80::4638:39ff:fe00:43, swp4, 00:11:59

To run the same command at a config level, prepend do to it:

switch(config-router)# do show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, T - Table,
       > - selected route, * - FIB route
B>* 0.0.0.0/0 [20/0] via fe80::4638:39ff:fe00:c, swp29, 00:05:17
  *                  via fe80::4638:39ff:fe00:52, swp30, 00:05:17
B>* 10.0.0.1/32 [20/0] via fe80::4638:39ff:fe00:c, swp29, 00:05:17
  *                    via fe80::4638:39ff:fe00:52, swp30, 00:05:17
B>* 10.0.0.11/32 [20/0] via fe80::4638:39ff:fe00:5b, swp1, 00:05:17
B>* 10.0.0.12/32 [20/0] via fe80::4638:39ff:fe00:2e, swp2, 00:05:18
B>* 10.0.0.13/32 [20/0] via fe80::4638:39ff:fe00:57, swp3, 00:05:18
B>* 10.0.0.14/32 [20/0] via fe80::4638:39ff:fe00:43, swp4, 00:05:18
C>* 10.0.0.21/32 is directly connected, lo
B>* 10.0.0.51/32 [20/0] via fe80::4638:39ff:fe00:c, swp29, 00:05:17
  *                     via fe80::4638:39ff:fe00:52, swp30, 00:05:17
B>* 172.16.1.0/24 [20/0] via fe80::4638:39ff:fe00:5b, swp1, 00:05:17
  *                      via fe80::4638:39ff:fe00:2e, swp2, 00:05:17
B>* 172.16.3.0/24 [20/0] via fe80::4638:39ff:fe00:57, swp3, 00:05:18
  *                      via fe80::4638:39ff:fe00:43, swp4, 00:05:18

To run single commands with vtysh, use the -c option of vtysh:

cumulus@switch:~$ sudo vtysh -c 'sh ip route'
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, A - Babel,
       > - selected route, * - FIB route

K>* 0.0.0.0/0 via 192.168.0.2, eth0
C>* 192.0.2.11/24 is directly connected, swp1
C>* 192.0.2.12/24 is directly connected, swp2
B>* 203.0.113.30/24 [200/0] via 192.0.2.2, swp1, 11:05:10
B>* 203.0.113.31/24 [200/0] via 192.0.2.2, swp1, 11:05:10
B>* 203.0.113.32/24 [200/0] via 192.0.2.2, swp1, 11:05:10
C>* 127.0.0.0/8 is directly connected, lo
C>* 192.168.0.0/24 is directly connected, eth0

To run a command multiple levels down:

cumulus@switch:~$ sudo vtysh -c 'configure terminal' -c 'router ospf' -c 'area 0.0.0.1 range 10.10.10.0/24'

Notice that the commands also take a partial command name (for example, sh ip route) as long as the partial command name is not aliased:

cumulus@switch:~$ sudo vtysh -c 'sh ip r'
% Ambiguous command.

To disable a command or feature in FRRouting, prepend the command with no. For example:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf
switch(config-router)# no area 0.0.0.1 range 10.10.10.0/24
switch(config-router)# exit
switch(config)# exit
switch# write mem
switch# exit
cumulus@switch:~$

To view the current state of the configuration, run the show running-config command:

Example command
switch# show running-config
Building configuration...

Current configuration:
!
username cumulus nopassword
!
service integrated-vtysh-config
!
vrf mgmt
!
interface lo
  link-detect
!
interface swp1
  ipv6 nd ra-interval 10
  link-detect
!
interface swp2
  ipv6 nd ra-interval 10
  link-detect
!
interface swp3
  ipv6 nd ra-interval 10
  link-detect
!
interface swp4
  ipv6 nd ra-interval 10
  link-detect
!
interface swp29
  ipv6 nd ra-interval 10
  link-detect
!
interface swp30
  ipv6 nd ra-interval 10
  link-detect
!
interface swp31
  link-detect
!
interface swp32
  link-detect
!
interface vagrant
  link-detect
!
interface eth0 vrf mgmt
  ipv6 nd suppress-ra
  link-detect
!
interface mgmt vrf mgmt
  link-detect
!
router bgp 65020
  bgp router-id 10.0.0.21
  bgp bestpath as-path multipath-relax
  bgp bestpath compare-routerid
  neighbor fabric peer-group
  neighbor fabric remote-as external
  neighbor fabric description Internal Fabric Network
  neighbor fabric capability extended-nexthop
  neighbor swp1 interface peer-group fabric
  neighbor swp2 interface peer-group fabric
  neighbor swp3 interface peer-group fabric
  neighbor swp4 interface peer-group fabric
  neighbor swp29 interface peer-group fabric
  neighbor swp30 interface peer-group fabric
  !
  address-family ipv4 unicast
  network 10.0.0.21/32
  neighbor fabric activate
  neighbor fabric prefix-list dc-spine in
  neighbor fabric prefix-list dc-spine out
  exit-address-family
!
ip prefix-list dc-spine seq 10 permit 0.0.0.0/0
ip prefix-list dc-spine seq 20 permit 10.0.0.0/24 le 32
ip prefix-list dc-spine seq 30 permit 172.16.1.0/24
ip prefix-list dc-spine seq 40 permit 172.16.2.0/24
ip prefix-list dc-spine seq 50 permit 172.16.3.0/24
ip prefix-list dc-spine seq 60 permit 172.16.4.0/24
ip prefix-list dc-spine seq 500 deny any
!
ip forwarding
ipv6 forwarding
!
line vty
!
end

If you try to configure a routing protocol that has not been started, vtysh silently ignores those commands.

If you do not want to use a modal CLI to configure FRRouting, you can use a suite of Cumulus Linux-specific commands instead.

Reload the FRRouting Configuration

If you make a change to your routing configuration, you need to reload FRRouting so your changes take place. FRRouting reload enables you to apply only the modifications you make to your FRRouting configuration, synchronizing its running state with the configuration in /etc/frr/frr.conf. This is useful for optimizing FRRouting automation in your environment or to apply changes made at runtime.

FRRouting reload only applies to an integrated service configuration, where your FRRouting configuration is stored in a single frr.conf file instead of one configuration file per FRRouting daemon (like zebra or bgpd).

To reload your FRRouting configuration after you modify /etc/frr/frr.conf, run:

cumulus@switch:~$ sudo systemctl reload frr.service

Examine the running configuration and verify that it matches the configuration in /etc/frr/frr.conf:

cumulus@switch:~$ net show configuration

If the running configuration is not what you expect, submit a support request and supply the following information:

FRR Logging

By default, Cumulus Linux configures FFR with syslog severity level 6 (informational). Log output is written to the /var/log/frr/frr.log file.

To write debug messages to the log file, you must run the log syslog debug command to configure FRR with syslog severity 7 (debug); otherwise, when you issue a debug command such as, debug bgp neighbor-events, no output is sent to /var/log/frr/frr.log. However, when you manually define a log target with the log file /var/log/frr/debug.log command, FRR automatically defaults to severity 7 (debug) logging and the output is logged to /var/log/frr/debug.log.

Caveats

Duplicate Hostnames

If you change the hostname, either with NCLU or with the hostname command in vtysh, the switch can have two hostnames in the FRR configuration. For example:

Spine01# configure terminal
Spine01(config)# hostname Spine01-1
Spine01-1(config)# do sh run
Building configuration...
Current configuration:
!
frr version 4.0+cl3u1
frr defaults datacenter
hostname Spine01
hostname Spine01-1
...

Accidentally configuring the same numbered BGP neighbor using both the neighbor x.x.x.x and neighbor swp# interface commands results in two neighbor entries being present for the same IP address in the configuration and operationally. To correct this issue, update the configuration and restart the FRR service.

Comparing NCLU and vtysh Commands

Using NCLU is the recommended way to configure routing in Cumulus Linux; however, you can use the vtysh modal CLI.

The following table shows the FRRouting commands and the equivalent Cumulus Linux NCLU commands.

Action NCLU Commands FRRouting Commands
Display the routing table
cumulus@switch:~$ net show route
switch# show ip route
Create a new neighbor
cumulus@switch:~$ net add bgp autonomous-system 65002
cumulus@switch:~$ net add bgp neighbor 14.0.0.22
switch(config)# router bgp 65002
switch(config-router)# neighbor 14.0.0.22
Redistribute routing information from static route entries into RIP tables
cumulus@switch:~$ net add bgp redistribute static
switch(config)# router bgp 65002
switch(config-router)# redistribute static
Define a static route
cumulus@switch:~$ net add routing route 155.1.2.20/24 bridge 45
switch(config)# ip route 155.1.2.20/24 bridge 45
Configure an IPv6 address
cumulus@switch:~$ net add interface swp3 ipv6 address 3002:2123:1234:1abc::21/64
switch(config)# int swp3
switch(config-if)# ipv6 address 3002:2123:1234:1abc::21/64
Enable topology checking (PTM)
cumulus@switch:~$ net add routing ptm-enable
switch(config)# ptm-enable
Configure MTU in IPv6 network discovery for an interface
cumulus@switch:~$ sudo cl-ra interface swp3 set mtu 9000
switch(config)# int swp3
switch(config-if)# ipv6 nd mtu 9000
Set the OSPF interface priority
cumulus@switch:~$ net add interface swp3 ospf6 priority 120
switch(config)# int swp3
switch(config-if)# ip ospf6 priority 120
Configure timing for OSPF SPF calculations
cumulus@switch:~$ net add ospf6 timers throttle spf 40 50 60
switch(config)# router ospf6
switch(config-ospf6)# timer throttle spf 40 50 60
Configure the OSPF Hello packet interval in number of seconds for an interface
cumulus@switch:~$ net add interface swp4 ospf6 hello-interval 60
switch(config)# int swp4
switch(config-if)# ipv6 ospf6 hello-interval 60
Display BGP information
cumulus@switch:~$ net show bgp summary
switch# show ip bgp summary
Display OSPF debugging status
cumulus@switch:~$ net show debugs
switch# show debugging ospf
Show information about the interfaces on the switch
cumulus@switch:~$ net show interface
switch# show interface
To quickly check important information, such as IP address, VRF, and operational status, in easy to read tabular format:
switch# show interface brief

Address Resolution Protocol - ARP

Address Resolution Protocol (ARP) is a communication protocol used for discovering the link layer address, such as a MAC address, associated with a given network layer address. ARP is defined by RFC 826. The Cumulus Linux ARP implementation differs from standard Debian Linux ARP behavior in a few ways because Cumulus Linux is an operating system for routers/switches rather than servers.

Standard Debian ARP Behavior and the Tunable ARP Parameters

Debian has these five tunable ARP parameters:

These parameters are described in the Linux documentation, but snippets for each parameter description are included in the table below and are highlighted in italics.

In a standard Debian installation, all of these ARP parameters are set to 0, leaving the router as wide open and unrestricted as possible. These settings are based on the assertion made long ago that Linux IP addresses are a property of the device, not a property of an individual interface. Therefore, an ARP request or reply could be sent on one interface containing an address residing on a different interface. While this unrestricted behavior makes sense for a server, it is not the normal behavior of a router. Routers expect the MAC/IP address mappings supplied by ARP to match the physical topology, with the IP addresses matching the interfaces on which they reside. With these tunable ARP parameters, Cumulus Linux is able to specify the behavior to match the expectations of a router.

ARP Tunable Parameter Settings in Cumulus Linux

The ARP tunable parameters are set to the following values by default in Cumulus Linux.

Parameter Default Setting Type Description
arp_accept 0 BOOL Defines the behavior for gratuitous ARP frames when the IP address is not already in the ARP table:
  • 0: Do not create new entries in the ARP table.
  • 1: Create new entries in the ARP table.

You can set arp_accept on an individual interface which differs from the rest of the switch (see below).
arp_announce 2 INT Defines different restriction levels for announcing the local source IP address from IP packets in ARP requests that send on an interface:
  • 0: Use any local address configured on any interface.
  • 1: Avoid local addresses that are not in the target subnet for this interface. You can use this mode when target hosts reachable through this interface require the source IP address in ARP requests to be part of their logical network configured on the receiving interface. When Cumulus Linux generates the request, it checks all subnets that include the target IP address and preserves the source address if it is from such a subnet. If there is no such subnet, Cumulus Linux selects the source address according to the rules for level 2.
  • 2: Always use the best local address for this target. In this mode, Cumulus Linux ignores the source address in the IP packet and tries to select the local address preferred for talks with the target host. To select the local address, Cumulus Linux looks for primary IP addresses on all the subnets on the outgoing interface that include the target IP address. If there is no suitable local address, Cumulus Linux selects the first local address on the outgoing interface or on all other interfaces, so that it receives a reply for the request regardless of the announced source IP address.
The default Debian behavior (arp_announce is 0) sends gratuitous ARPs or ARP requests using any local source IP address and does not limit the IP source of the ARP packet to an address residing on the interface that sends the packet.

Routers expect a different relationship between the IP address and the physical network. Adjoining routers look for MAC and IP addresses to reach a next hop residing on a connecting interface for transiting traffic. By setting the arp_announce parameter to 2, Cumulus Linux uses the best local address for each ARP request, preferring the primary addresses on the interface that sends the ARP.
arp_filter 0 BOOL
  • 0: The kernel can respond to ARP requests with addresses from other interfaces to increase the chance of successful communication. The complete host on Linux (not specific interfaces) owns the IP addresses. For more complex configurations, such as load balancing, this behavior can cause problems.
  • 1: Allows you to have multiple network interfaces on the same subnet and to answer the ARPs for each interface based on whether the kernel routes a packet from the ARPd IP address out of that interface (you must use source based routing).
arp_filter for the interface is on if at least one of conf/{all,interface}/arp_filter is TRUE, it is off otherwise.

Cumulus Linux uses the default Debian Linux arp_filter setting of 0.
The switch uses arp_filter when multiple interfaces reside in the same subnet and allows certain interfaces to respond to ARP requests. For OSPF with IP unnumbered interfaces, multiple interfaces appear in the same subnet and contain the same address. If you use multiple interfaces between a pair of routers and set arp_filter to 1, forwarding can fail.

The arp_filter parameter allows a response on any interface in the subnet, where the arp_ignore setting (below) limits cross-interface ARP behavior.
arp_ignore 1 INT Defines different modes for sending replies in response to received ARP requests that resolve local target IP addresses:
  • 0: Reply for any local target IP address on any interface.
  • 1: Reply only if the target IP address is the local address on the incoming interface.
  • 2: Reply only if the target IP address is the local address on the incoming interface and the sender IP address is part of same subnet on this interface.
  • 3: Do not reply for local addresses with scope host; the switch replies only for global and link addresses.
  • 4-7: Reserved.
  • 8: Do not reply for all local addresses.
The switch uses the maximum value from conf/{all,interface}/arp_ignore when the {interface} receives the ARP request.

The default arp_ignore setting of 1 allows the device to reply to an ARP request for any IP address on any interface. While this matches the expectation that an IP address belongs to the device, not an interface, it can cause some unexpected behavior on a router.

For example, if arp_ignore is 0 and the switch receives an ARP request on one interface for the IP address residing on a different interface, the switch responds with an ARP reply even if the interface of the target address is down. This can cause traffic loss because the switch does not know if it can reach the next hops and results in troubleshooting challenges for failure conditions.

If you set arp_ignore to 2, the switch only replies to ARP requests if the target IP address is a local address and both the sender and target IP addresses are part of the same subnet on the incoming interface. The router does not create stale neighbor entries when a peer device sends an ARP request from a source IP address that is not on the connected subnet. Eventually, the switch sends ARP requests to the host to try to keep the entry fresh. If the host responds, the switch now has reachable neighbor entries for hosts that are not on the connected subnet.
arp_notify 1 BOOL Defines the mode to notify address and device changes.
  • 0: Do nothing.
  • 1: Generate gratuitous ARP requests when the device comes up or the hardware address changes.
The default Debian arp_notify setting is to remain silent when an interface comes up or the hardware address changes. Because Cumulus Linux often acts as a next hop for several end hosts, it notifies attached devices when an interface comes up or the address changes, which speeds up new information convergence and provides the most rapid support for changes.

Change Tunable ARP Parameters

You can change the ARP parameter settings in several places, including:

The ARP parameter changes in Cumulus Linux use the default file locations.

The all and default locations sound similar, with the exception of which interfaces are impacted, but they operate in significantly different ways. The all location can potentially change the value for all interfaces running IP, both now and in the future. The reason for this uncertainty is that the all value is applied to each parameter using either MAX or OR logic between the all and any port-specific settings, as the following table shows:

ARP Parameter Condition
arp_accept OR
arp_announce MAX
arp_filter OR
arp_ignore MAX
arp_notify MAX

For example, if you set the /proc/sys/net/conf/all/arp_ignore value to 1 and the /proc/sys/net/conf/swp1/arp_ignore value to 0 to try to disable it on a per-port basis, interface swp1 still uses the value of 1; the port-specific setting does not override the global all setting. Instead, the MAX value between the all value and port-specific value defines the actual behavior.

The default location /proc/sys/net/ipv4/conf/default/arp* defines the values for all future IP interfaces. Changing the default setting of an ARP parameter does not impact interfaces that already contain an IP address. If changes are being made to a running system that already has IP addresses assigned to it, port-specific settings should be used instead.

In Cumulus Linux, the value of the default parameter is copied to every port-specific location, excluding those that already have an IP address assigned. Therefore, there is no complicated logic between the default setting and the port-specific setting like there is when using the all location. This makes the application of particular port-specific policies much simpler and more deterministic.

To determine the current ARP parameter settings for each of the locations, run the following commands:

cumulus@switch:~$ sudo grep . /proc/sys/net/ipv4/conf/all/arp*
/proc/sys/net/ipv4/conf/all/arp_accept:0
/proc/sys/net/ipv4/conf/all/arp_announce:0
/proc/sys/net/ipv4/conf/all/arp_filter:0
/proc/sys/net/ipv4/conf/all/arp_ignore:0
/proc/sys/net/ipv4/conf/all/arp_notify:1
cumulus@switch:~$ sudo grep . /proc/sys/net/ipv4/conf/default/arp*
/proc/sys/net/ipv4/conf/default/arp_accept:0
/proc/sys/net/ipv4/conf/default/arp_announce:2
/proc/sys/net/ipv4/conf/default/arp_filter:0
/proc/sys/net/ipv4/conf/default/arp_ignore:1
/proc/sys/net/ipv4/conf/default/arp_notify:1
cumulus@switch:~$ sudo grep . /proc/sys/net/ipv4/conf/swp1/arp*
/proc/sys/net/ipv4/conf/swp1/arp_accept:0
/proc/sys/net/ipv4/conf/swp1/arp_announce:2
/proc/sys/net/ipv4/conf/swp1/arp_filter:0
/proc/sys/net/ipv4/conf/swp1/arp_ignore:1
/proc/sys/net/ipv4/conf/swp1/arp_notify:1

Cumulus Linux implements this change at boot time using the arp.conf file in the following location:

cumulus@switch:~$ cat /etc/sysctl.d/arp.conf
net.ipv4.conf.default.arp_announce = 2
net.ipv4.conf.default.arp_notify = 1
net.ipv4.conf.default.arp_ignore=1

Change Port-specific ARP Parameters

To configure port-specific ARP parameters in a running device, run the following command:

cumulus@switch:~$ sudo sh -c "echo 0 > /proc/sys/net/ipv4/conf/swp1/arp_ignore"
cumulus@switch:~$ sudo grep . /proc/sys/net/ipv4/conf/swp1/arp*
/proc/sys/net/ipv4/conf/swp1/arp_accept:0
/proc/sys/net/ipv4/conf/swp1/arp_announce:2
/proc/sys/net/ipv4/conf/swp1/arp_filter:0
/proc/sys/net/ipv4/conf/swp1/arp_ignore:0
/proc/sys/net/ipv4/conf/swp1/arp_notify:1

To make the change persist through reboots, edit the /etc/sysctl.d/arp.conf file and add your port-specific ARP setting.

Configure Proxy ARP

When you enable proxy ARP, if the switch receives an ARP request for which it has a route to the destination IP address, the switch sends a proxy ARP reply that contains its own MAC address. The host that sent the ARP request then sends its packets to the switch and the switch forwards the packets to the intended host.

Proxy ARP works with IPv4 only; ARP is an IPv4-only protocol.

To enable proxy ARP:

The following example commands enable proxy ARP on swp1.

cumulus@switch:~$ net add interface swp1 post-up "echo 1 > /proc/sys/net/ipv4/conf/swp1/proxy_arp"
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file to set /proc/sys/net/ipv4/conf/<interface>/proxy_arp to 1 in the interface stanza. The following example configuration enables proxy ARP on swp1.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto swp1
iface swp1
    post-up echo 1 > /proc/sys/net/ipv4/conf/swp1/proxy_arp
...

Run the ifreload -a command to reload the configuration:

cumulus@switch:~$ sudo ifreload -a

If you are running two interfaces in the same broadcast domain (typically seen when using VRR, which creates a -v0 interface in the same broadcast domain), set /proc/sys/net/ipv4/conf/<INTERFACE>/medium_id to 2 on both the base SVI interface and the -v0 interface so that only one of the two interfaces replies when getting an ARP request. This prevents the v0 interface from proxy replying on behalf of the SVI (and the SVI from proxy replying on behalf of the v0 interface). You can only prevent duplicate replies when the ARP request is for the SVI or the v0 interface directly.

cumulus@switch:~$ net add interface swp1 post-up "echo 2 > /proc/sys/net/ipv4/conf/swp1/medium_id"
cumulus@switch:~$ net add interface swp1-v0 post-up "echo 1 > /proc/sys/net/ipv4/conf/swp1-v0/proxy_arp"
cumulus@switch:~$ net add interface swp1-v0 post-up "echo 2 > /proc/sys/net/ipv4/conf/swp1-v0/medium_id"
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file. For example:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto swp1
iface swp1
    post-up echo 1 > /proc/sys/net/ipv4/conf/swp1/proxy_arp
    post-up echo 2 > /proc/sys/net/ipv4/conf/swp1/medium_id

auto swp1-v0
iface swp1-v0
    post-up echo 1 > /proc/sys/net/ipv4/conf/swp1-v0/proxy_arp
    post-up echo 2 > /proc/sys/net/ipv4/conf/swp1-v0/medium_id
...

Run the ifreload -a command to reload the configuration:

cumulus@switch:~$ sudo ifreload -a

If you are running proxy ARP on a VRR interface, add a post-up line to the VRR interface stanza similar to the following. For example, if vlan100 is the VRR interface for the configuration above:

cumulus@switch:~$ net add vlan 100 post-up "echo 1 > /proc/sys/net/ipv4/conf/swp1/proxy_arp"
cumulus@switch:~$ net add vlan 100 post-up "echo 1 > /proc/sys/net/ipv4/conf/swp1-v0/proxy_arp"
cumulus@switch:~$ net add vlan 100 post-up "echo 2 > /proc/sys/net/ipv4/conf/swp1/medium_id" 
cumulus@switch:~$ net add vlan 100 post-up "echo 2 > /proc/sys/net/ipv4/conf/swp1-v0/medium_id"
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file. For example:

cumulus@switch:~$ sudo nano /etc/networks/interfaces
...
auto vlan100
iface vlan100
    post-up echo 1 > /proc/sys/net/ipv4/conf/swp1-v0/proxy_arp
    post-up echo 1 > /proc/sys/net/ipv4/conf/swp1/proxy_arp
    post-up echo 2 > /proc/sys/net/ipv4/conf/swp1-v0/medium_id
    post-up echo 2 > /proc/sys/net/ipv4/conf/swp1/medium_id
    vlan-id 100
...

Run the ifreload -a command to reload the configuration:

cumulus@switch:~$ sudo ifreload -a

Duplicate Address Detection (Windows Hosts)

In centralized VXLAN environments, where ARP/ND suppression is enabled and SVIs exist on the leaf switches but are not assigned an address within the subnet, problems with the Duplicate Address Detection process on Microsoft Windows hosts can occur. For example, in a pure layer 2 scenario or with SVIs that have the ip-forward option set to off, the IP address is not assigned to the SVI. The neighmgrd service selects a source IP address for an ARP probe based on the subnet match on the neighbor IP address. Because the SVI on which this neighbor is learned does not contiain an IP address, the subnet match fails. This results in neighmgrd using UNSPEC (0.0.0.0 for IPv4) as the source IP address in the ARP probe.

To work around this issue, run the neighmgrctl setsrcipv4 <ipaddress> command to specify a non-0.0.0.0 address for the source; for example:

cumulus@switch:~$ neighmgrctl setsrcipv4 10.1.0.2

The configuration above takes effect immediately but does not persist if you reboot the switch. To make the changes apply persistently:

  1. Create a new file called /etc/cumulus/neighmgr.conf and add the setsrcipv4 <ipaddress> option; for example:

    cumulus@switch:~$  sudo nano /etc/cumulus/neighmgr.conf
    
    [main]
    setsrcipv4: 10.1.0.2
    
  2. Restart the neighmgrd service:

    cumulus@switch:~$ sudo systemctl restart neighmgrd
    

Configure ARP Timers

Cumulus Linux does not interact directly with end systems as much as end systems interact with each another. Therefore, after ARP places a neighbor into a reachable state, if Cumulus Linux does not interact with the client again for a long enough period of time, the neighbor can move into a stale state. To keep neighbors in the reachable state, Cumulus Linux includes a background process (/usr/bin/neighmgrd). The background process can track neighbors that move into a stale, delay, or probe state, and attempt to refresh their state before removing them from the Linux kernel and from hardware forwarding. If you want the neighmgrd process to add a neighbor if the sender IP address in the ARP packet is in one of the SVI’s subnets, create the /etc/cumulus/neighmgr.conf file and add the subnet_checks=1 parameter under the [snooper] header. By default, the subnet_checks option is set to 0 (disabled) so that neighmgrd allows out-of-network neighbors to be processed from SVIs.

The ARP refresh timer defaults to 1080 seconds (18 minutes).

cumulus@leaf02:mgmt:~$ sudo nano /etc/cumulus/neighmgr.conf
[snooper]
subnet_checks=1

Open Shortest Path First - OSPF

OSPF maintains the view of the network topology conceptually as a directed graph. Each router represents a vertex in the graph. Each link between neighboring routers represents a unidirectional edge and has an associated weight (called cost) that is either automatically derived from its bandwidth or administratively assigned. Using the weighted topology graph, each router computes a shortest path tree (SPT) with itself as the root, and applies the results to build its forwarding table. The computation is generally referred to as SPF computation and the resultant tree as the SPF tree.

An LSA (link-state advertisement) is the fundamental piece of information that OSPF routers exchange with each other. It seeds the graph building process on the node and triggers SPF computation. LSAs originated by a node are distributed to all the other nodes in the network through a mechanism called flooding. Flooding is done hop-by-hop. OSPF ensures reliability by using link state acknowledgement packets. The set of LSAs in a router’s memory is termed link-state database (LSDB) and is a representation of the network graph. OSPF ensures a consistent view of the LSDB on each node in the network in a distributed fashion, which is key to the protocol’s correctness.

This topic describes OSPFv2, which is a link-state routing protocol for IPv4. For IPv6 commands, refer to Open Shortest Path First v3 - OSPFv3.

Scalability and Areas

The OSPF protocol advocates hierarchy as a divide and conquer approach to achieve high scale. You can divide the topology into areas, resulting in a two-level hierarchy. Area 0 (or 0.0.0.0), called the backbone area, is the top level of the hierarchy. Packets traveling from one non-zero area to another must go through the backbone area. For example, you can divide the leaf-spine topology into the following areas:

  • Routers R3, R4, R5, R6 are area border routers (ABRs). These routers have links to multiple areas and perform a set of specialized tasks, such as SPF computation per area and summarization of routes across areas.
  • Most of the LSAs have an area-level flooding scope. These include router LSA, network LSA, and summary LSA.
  • Where ABRs do not connect to multiple non-zero areas, you can use the same area address.

Configure OSPFv2

Before you configure OSPF, you need to identify:

To configure OSPF, you specify the router ID, IP subnet prefix, and area address. All the interfaces on the router whose IP address matches the network subnet are put into the specified area. The OSPF process starts bringing up peering adjacency on those interfaces. It also advertises the interface IP addresses formatted into LSAs (of various types) to the neighbors for proper reachability.

If you do not want to bring up OSPF adjacency on certain interfaces, you can configure the interfaces as passive interfaces. For example, in a data center topology, the host-facing interfaces do not need to run OSPF, however, the corresponding IP addresses still need to be advertised to neighbors.

The subnets can be as inclusive as possible to cover the highest number of interfaces on the router that run OSPF.

The example commands below perform the following configuration:

When you commit a change that configures a new routing service such as OSPF, the FRR daemon restarts and might interrupt network operations for other configured routing services.

cumulus@switch:~$ net add ospf router-id 0.0.0.1
cumulus@switch:~$ net add ospf network 10.0.0.0/16 area 0.0.0.0
cumulus@switch:~$ net add ospf network 192.0.2.0/16 area 0.0.0.1
cumulus@switch:~$ net add ospf passive-interface swp10
cumulus@switch:~$ net add ospf passive-interface swp11
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Instead of configuring the IP subnet prefix with an area address per network with the net add ospf network command, you can configure OSPF per interface with the net add interface command. However, you cannot use both configuration methods at the same time. Here is an example of configuring OSPF per interface:

cumulus@switch:~$ net add interface swp1 ospf area 0.0.0.0 

You can use the net add ospf passive-interface default command to set all interfaces as passive and the net del ospf passive-interface <interface> command to selectively bring up protocol adjacency only on certain interfaces:

cumulus@switch:~$ net add ospf passive-interface default
cumulus@switch:~$ net del ospf passive-interface swp1

To redistribute protocol routes, run the net add ospf redistribute <connected|bgp|zebra> command. Redistribution loads the database unnecessarily with type-5 LSAs. Only use this method to generate real external prefixes (type-5 LSAs). For example:

cumulus@switch:~$ net add ospf redistribute connected
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
  1. Enable the ospf daemon, then start the FRRouting service. See Configuring FRRouting.

  2. From the vtysh shell, configure OSPF.

    cumulus@switch:~$ sudo vtysh
    
    switch# configure terminal
    switch(config)# router ospf
    switch(config-router)# router-id 0.0.0.1
    switch(config-router)# network 10.0.0.0/16 area 0.0.0.0
    switch(config-router)# network 192.0.2.0/16 area 0.0.0.1
    switch(config-router)# passive-interface swp10
    switch(config-router)# passive-interface swp11
    switch(config-router)# exit
    switch(config)# exit
    switch# write memory
    switch# exit
    cumulus@switch:~$
    

Instead of configuring the IP subnet prefix and area address per network with the router ospf network command, you can configure OSPF per interface with the interface command. However, you cannot use both configuration methods at the same time. Here is an example of configuring OSPF per interface:

cumulus@switch:~$ sudo vtysh

switch# configure terminal switch(config)# interface swp1 switch(config-if)# ip ospf area 0.0.0.0 switch(config-if)# end switch# write memory switch# exit cumulus@switch:~$

You can use the passive-interface default command to set all interfaces as passive and selectively bring up protocol adjacency only on certain interfaces:

switch(config)# router ospf
switch(config-router)# passive-interface default
switch(config-router)# no passive-interface swp1

To redistribute protocol routes, run the redistribute <connected|bgp|zebra> command. Redistribution loads the database unnecessarily with type-5 LSAs. Only use this method to generate real external prefixes (type-5 LSAs). For example:

switch(config)# router ospf
switch(config-router)# redistribute connected

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router ospf
router-id 0.0.0.1
network 10.0.0.0/30 area 0.0.0.0
network 192.0.2.0/16 area 0.0.0.1
passive-interface swp10
passive-interface swp11
...

Define Custom OSPF Parameters on Interfaces

You can define additional custom parameters for OSPF per interface, such as the network type (point-to-point or broadcast) and the interval between hello packets that OSPF sends on the interface.

Configure the interface as point-to-point unless you intend to use the Ethernet media as a LAN with multiple connected routers. Point-to-point has the additional advantage of a simplified adjacency state machine; there is no need for DR/BDR election and LSA reflection. See RFC5309 for a more information.

The following command example sets the network type to point-to-point and the hello interval to 5 seconds. The hello interval can be any value between 1 and 65535 seconds.

cumulus@switch:~$ net add interface swp1 ospf network point-to-point
cumulus@switch:~$ net add interface swp1 ospf hello-interval 5
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface swp1
switch(config-if)# ospf network point-to-point
switch(config-if)# ospf network hello-interval 5
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example

...
interface swp1
 ip ospf area 0.0.0.1
 ip ospf hello-interval 5
 ip ospf network point-to-point
...

SPF Timer Defaults

OSPF uses the following default timers to prevent consecutive SPFs from overburdening the CPU:

The following example commands change the number of milliseconds from the initial event until SPF runs to 80, the number of milliseconds between consecutive SPF runs to 100, and the maximum number of milliseconds between SPFs to 6000.

cumulus@switch:~$ net add ospf timers throttle spf 80 100 6000 
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf
switch(config-router)# timers throttle spf 80 100 6000
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router ospf
 router-id 0.0.0.1
 timers throttle spf 80 100 6000
...

Configure MD5 Authentication

To configure MD5 authentication on the switch, you need to create a key and a key ID, then enable MD5 authentication. The key ID must be a value between 1 and 255 that represents the key used to create the message digest. This value must be consistent across all routers on a link. The key must be a value with an upper range of 16 characters (longer strings are truncated) that represents the actual message digest.

The following example commands create key ID 1 with the key thisisthekey and enable MD5 authentication on swp1.

cumulus@switch:~$ net add interface swp1 ospf message-digest-key 1 md5 thisisthekey
cumulus@switch:~$ net add interface swp1 ospf authentication message-digest
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

You can remove existing MD5 authentication hashes with the net del command. For example, net del interface swp1 ospf message-digest-key 1 md5 thisisthekey

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface swp1
switch(config-if)# ip ospf authentication message-digest
switch(config-if)# ip ospf message-digest-key 1 md5 thisisthekey
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

You can remove existing MD5 authentication hashes with the no ip ospf message-digest-key command. For example, no ip ospf message-digest-key 1 md5 thisisthekey

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
interface swp1
 ip ospf authentication message-digest
 ip ospf message-digest-key 1 md5 thisisthekey
 ...

Summarization

By default, an ABR creates a summary (type-3) LSA for each route in an area and advertises it in adjacent areas. Prefix range configuration optimizes this behavior by creating and advertising one summary LSA for multiple routes.

The following example commands create a summary route for all the routes in the range 30.0.0.0/8 in area 0.0.0.1:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf
switch(config-router)# area 0.0.0.1 range 30.0.0.0/8
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

The vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router ospf
 router-id 0.0.0.1
 area 0.0.0.1 range 30.0.0.0/8
 ...

Make sure you configure the summary towards the backbone. The backbone receives summarized routes and injects them to other areas already summarized.

Summarization can cause non-optimal forwarding of packets during failures:

The ABRs in the right non-zero area summarize the host prefixes as 10.1.0.0/16.

When the link between R5 and R10 fails, R5 sends a worse metric for the summary route (the metric for the summary route is the maximum of the metrics of intra-area routes that are covered by the summary route). The metric for 10.1.2.0/24 increases at R5 as the path is R5-R9-R6-R10). As a result, other backbone routers shift traffic destined to 10.1.0.0/16 towards R6. This breaks ECMP and is an under-utilization of network capacity for traffic destined to 10.1.1.0/24.

Stub Areas

External routes are the routes redistributed into OSPF from another protocol. They have an AS-wide flooding scope. In many cases, external link states make up a large percentage of the LSDB. Stub areas reduce the link-state database size by not flooding AS-external LSAs.

To configure a stub area:

cumulus@switch:~$ net add ospf area 0.0.0.1 stub
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf
switch(config-router)# area 0.0.0.1 stub
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router ospf
 router-id 0.0.0.1
 area 0.0.0.1 stub
...

Stub areas still receive information about networks that belong to other areas of the same OSPF domain. If summarization is not configured (or is not comprehensive), the information can be overwhelming for the nodes. Totally stubby areas address this issue. Routers in totally stubby areas keep information about routing within their area in their LSDB.

To configure a totally stubby area:

cumulus@switch:~$ net add ospf area 0.0.0.1 stub no-summary
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf
switch(config-router)# area 0.0.0.1 stub no-summary
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router ospf
 router-id 0.0.0.1
 area 0.0.0.1 stub no-summary
...

Here is a brief summary of the area type differences:

Type Behavior
Normal non-zero area LSA types 1, 2, 3, 4 area-scoped, type 5 externals, inter-area routes summarized
Stub area LSA types 1, 2, 3, 4 area-scoped, no type 5 externals, inter-area routes summarized
Totally stubby area LSA types 1, 2 area-scoped, default summary, no type 3, 4, 5 LSA types allowed

Multiple ospfd Instances

The ospfd daemon can have up to five independent processes, where each OSPF instance has its own routing table isolated from the others. Each instance must have an ID (any value between 1 and 65535).

Multiple ospfd instances (processes) are supported with:

  • The default VRF.
  • OSPFv2 only.

To configure multi-instance OSPF:

  1. Edit the /etc/frr/daemons file to add ospfd_instances to the ospfd line. Specify an instance ID for each separate instance. For example, the following configuration enables two ospfd instances, 11 and 22:

    cumulus@switch:~$ cat /etc/frr/daemons
    ...
    bgpd=no
    ospfd=yes ospfd_instances="11 22"
    ospf6d=no
    ripd=no
    ...
    
  2. Restart FRR with this command:

    cumulus@switch:~$ sudo systemctl restart frr.service

    Restarting FRR restarts all the routing protocol daemons that are enabled and running.

  3. Assign and enable an OSPF interface for each instance:

cumulus@switch:~$ net add interface swp1 ospf instance-id 11
cumulus@switch:~$ net add interface swp1 ospf area 0.0.0.0
cumulus@switch:~$ net add ospf router-id 1.1.1.1
cumulus@switch:~$ net add interface swp2 ospf instance-id 22
cumulus@switch:~$ net add interface swp2 ospf area 0.0.0.0
cumulus@switch:~$ net add ospf router-id 1.1.1.1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface swp1
switch(config-if)#  ip ospf 11 area 0.0.0.0
switch(config-if)# router ospf 11
switch(config-router)# ospf router-id 0.0.0.1
...
switch(config)# interface swp2
switch(config-if)#  ip ospf 22 area 0.0.0.0
switch(config-if)# router ospf 22
switch(config-router)# ospf router-id 0.0.0.1
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

To confirm that all the OSPF instances are running:

cumulus@switch:~$ ps -ax | grep ospf
21135 ?        S<s    0:00 /usr/lib/frr/ospfd --daemon -A 127.0.0.1 -n 11
21139 ?        S<s    0:00 /usr/lib/frr/ospfd --daemon -A 127.0.0.1 -n 22
21160 ?        S<s    0:01 /usr/lib/frr/watchfrr -adz -r /usr/sbin/servicebBfrrbBrestartbB%s -s /usr/sbin/servicebBquaggabBstartbB%s -k /usr/sbin/servicebBfrrbBstopbB%s -b bB -t 30 zebra ospfd-11 ospfd-22 pimd
22021 pts/3    S+     0:00 grep ospf

You can use the redistribute ospf option with the instance ID in your frr.conf file to route between the instances. For example:

cumulus@switch:~$ cat /etc/frr/frr.conf
hostname zebra
log file /var/log/frr/zebra.log
username cumulus nopassword
!
service integrated-vtysh-config
!
...
!
router ospf 11
  ospf router-id 0.0.0.1
!
router ospf 22
  ospf router-id 0.0.0.1
  redistribute ospf 11
!
...

If you disable the integrated FRRouting configuration, you must create a separate ospfd configuration file for each instance. The ospfd.conf file must include the instance ID in the file name. For example, create /etc/frr/ospfd-11.conf and /etc/frr/ospfd-22.conf.

cumulus@switch:~$ cat /etc/frr/ospfd-11.conf 
!
hostname zebra
log file /var/log/frr/zebra.log
username cumulus nopassword
!
service integrated-vtysh-config
!
interface eth0
  ipv6 nd suppress-ra
  link-detect
!
interface lo
  link-detect
!
interface swp1
  ip ospf 11 area 0.0.0.0
  link-detect
!
interface swp2
  ip ospf 22 area 0.0.0.0
  link-detect
!
interface swp45
  link-detect
!
interface swp46
  link-detect
...
!
router ospf 11
  ospf router-id 0.0.0.1
!
router ospf 22
  ospf router-id 0.0.0.1
!
ip forwarding
ipv6 forwarding
!
line vty
!

Auto-cost Reference Bandwidth

When you set the auto-cost reference bandwidth, Cumulus Linux dynamically calculates the OSPF interface cost to cater for higher speed links. The default value is 100000 for 100Gbps link speed. The cost of interfaces with link speeds lower than 100Gbps is higher.

To avoid routing loops, set the bandwidth to a consistent value across all OSPF routers.

The following example commands configure the auto-cost reference bandwidth for 90Gbps link speed:

cumulus@switch:~$ net add ospf auto-cost reference-bandwidth 90000
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf
switch(config-router)# auto-cost reference-bandwidth 90000
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router ospf
 router-id 0.0.0.1
 auto-cost reference-bandwidth 90000
...

Unnumbered Interfaces

Unnumbered interfaces are interfaces without unique IP addresses. In OSPFv2, configuring unnumbered interfaces reduces the links between routers into pure topological elements, which simplifies network configuration and reconfiguration. In addition, the routing database contains only the real networks, so the memory footprint is reduced and SPF is faster.

Unnumbered is supported with point-to-point interfaces only.

To configure an unnumbered interface, take the IP address of another interface (called the anchor) and use that as the IP address of the unnumbered interface:

Configure the unnumbered interface:

cumulus@switch:~$ net add loopback lo ip address 192.0.2.1/32
cumulus@switch:~$ net add interface swp1 ip address 192.0.2.1/32
cumulus@switch:~$ net add interface swp2 ip address 192.0.2.1/32

Enable OSPF on the unnumbered interface:

cumulus@switch:~$ net add interface swp1 ospf area 0.0.0.1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
  1. Edit the /etc/network/interfaces file to configure the unnumbered interface:

    cumulus@switch:~$ sudo nano /etc/network/interfaces
    ...
    auto lo
    iface lo inet loopback
    address 192.0.2.1/32
    
    auto swp1
    iface swp1
      address 192.0.2.1/32
    
    auto swp2
    iface swp2
      address 192.0.2.1/32
    ...
    
  2. Run the ifreload -a command to load the new configuration:

    cumulus@switch:~$ ifreload -a
    
  3. From the vtysh shell, enable OSPF on an unnumbered interface:

    cumulus@switch:~$ sudo vtysh
    
    switch# configure terminal
    switch(config)# interface swp1
    switch(config-if)# ip ospf area 0.0.0.1
    switch(config-if)# end
    switch# write memory
    switch# exit
    cumulus@switch:~$
    

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
interface swp1
 ip ospf area 0.0.0.0
...

Apply a Route Map for Route Updates

You can apply a route map to filter route updates from Zebra into the Linux kernel.

The following example commands apply the route map called map1:

cumulus@switch:~$ net add routing protocol ospf route-map map1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following example commands apply the route map called map1:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# ip protocol ospf route-map map1
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$ 

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router ospf
  ospf router-id 0.0.0.1
  ...
!
ip protocol ospf route-map map1
!
...

To apply a route map to redistributed routes:

The following example commands apply the route map called map1 to redistributed routes:

cumulus@switch:~$ net add ospf redistribute connected route-map map1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following example commands apply the route map called map1 to redistributed routes:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# redistribute connected route-map map1
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router ospf
 ospf router-id 0.0.0.1
 redistribute connected route-map map1
...

ECMP

During SPF computation for an area, if OSPF finds multiple paths with equal cost, all those paths are used for forwarding. For example, in the reference topology diagram above, R8 uses both R3 and R4 as next hops to reach a destination attached to R9.

Topology Changes and OSPF Reconvergence

Topology changes usually occur due to router node maintenance or failure, or link maintenance or failure.

For maintenance events, you can raise the OSPF administrative weight of the links to ensure that all traffic is diverted from the link or the node (referred to as costing out). The speed of reconvergence does not matter. Changing the OSPF cost causes LSAs to be reissued, but the links remain in service during the SPF computation process of all routers in the network.

For failure events, traffic might be lost during reconvergence (until SPF on all nodes computes an alternative path around the failed link or node to each of the destinations). The reconvergence depends on layer 1 failure detection capabilities and the DeadInterval OSPF timer.

Example configuration for router maintenance:

cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# router ospf
switch(config-router)# max-metric router-lsa administrative
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

Example configuration for link maintenance:

cumulus@switch:~$ net add interface swp1 ospf cost 65535
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# interface swp1
switch(config-if)# ospf cost 65535
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

Troubleshooting

Cumulus Linux provides the following troubleshooting commands for OSPF:

The following example shows the net show route ospf command output:

cumulus@switch:~$ net show route ospf
RIB entry for ospf
==================
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR,
       > - selected route, * - FIB route
O   10.0.0.11/32 [110/0] is directly connected, lo, 00:06:31
O>* 10.0.0.12/32 [110/200] via 10.1.0.0, swp51, 00:06:11
  *                        via 10.1.0.2, swp52, 00:06:11
O>* 10.0.0.13/32 [110/200] via 10.1.0.0, swp51, 00:06:11
  *                        via 10.1.0.2, swp52, 00:06:11
O>* 10.0.0.14/32 [110/200] via 10.1.0.0, swp51, 00:06:11
  *                        via 10.1.0.2, swp52, 00:06:11
O>* 10.0.0.21/32 [110/100] via 10.1.0.0, swp51, 00:06:21
O>* 10.0.0.22/32 [110/100] via 10.1.0.2, swp52, 00:06:21
O   10.1.0.0/31 [110/100] is directly connected, swp51, 00:06:31
O   10.1.0.2/31 [110/100] is directly connected, swp52, 00:06:31
O>* 10.1.0.4/31 [110/200] via 10.1.0.0, swp51, 00:06:21
O>* 10.1.0.6/31 [110/200] via 10.1.0.2, swp52, 00:06:21
O>* 10.1.0.8/31 [110/200] via 10.1.0.0, swp51, 00:06:21
O>* 10.1.0.10/31 [110/200] via 10.1.0.2, swp52, 00:06:21
O>* 10.1.0.12/31 [110/200] via 10.1.0.0, swp51, 00:06:21
O>* 10.1.0.14/31 [110/200] via 10.1.0.2, swp52, 00:06:21
O   172.16.1.0/24 [110/10] is directly connected, br0, 00:06:31
O>* 172.16.2.0/24 [110/210] via 10.1.0.0, swp51, 00:06:11
  *                         via 10.1.0.2, swp52, 00:06:11
O>* 172.16.3.0/24 [110/210] via 10.1.0.0, swp51, 00:06:11
  *                         via 10.1.0.2, swp52, 00:06:11
O>* 172.16.4.0/24 [110/210] via 10.1.0.0, swp51, 00:06:11
  *                         via 10.1.0.2, swp52, 00:06:11

For a list all of the OSPF debug options, refer to Debugging OSPF.

Open Shortest Path First v3 - OSPFv3

OSPFv3 is a revised version of OSPFv2 and supports the IPv6 address family. Refer to Open Shortest Path First - OSPF for a discussion on the basic concepts, which remain the same between the two versions.

OSPFv3 has changed the formatting in some of the packets and LSAs to support IPv6 and to improve the protocol behavior. OSPFv3 defines a new LSA, called intra-area prefix LSA, to separate the advertisement of stub networks attached to a router from the router LSA. It is a clear separation of node topology from prefix reachability and lends itself well to an optimized SPF computation.

IETF has defined extensions to OSPFv3 to support multiple address families (both IPv6 and IPv4). FRR does not currently support multiple address families.

Configure OSPFv3

To configure OSPFv3, you need to specify the router ID and map interfaces to areas. The following commands provide examples.

When you commit a change that configures a new routing service such as OSPF, the FRR daemon restarts and might interrupt network operations for other configured routing services.

cumulus@switch:~$ net add ospf6 router-id 0.0.0.1
cumulus@switch:~$ net add ospf6 interface swp1 area 0.0.0.0
cumulus@switch:~$ net add ospf6 interface swp2 area 0.0.0.1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
  1. Enable the ospf6 daemon, then start the FRRouting service. See Configuring FRRouting.

  2. From the vtysh shell, configure OSPFv3:

    cumulus@switch:~$ sudo vtysh
    
    switch# configure terminal
    switch(config)# router ospf6
    switch(config-ospf6)# router-id 0.0.0.1
    switch(config-ospf6)# interface swp1 area 0.0.0.0
    switch(config-ospf6)# interface swp2 area 0.0.0.1
    switch(config-ospf6)#exit
    switch(config)#exit
    switch# write memory
    switch# exit
    cumulus@switch:~$
    

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router ospf6
 ospf6 router-id 0.0.0.1
 interface swp1 area 0.0.0.0
 interface swp2 area 0.0.0.1
...

Define Custom OSPFv3 Parameters

You can define additional custom parameters for OSPFv3, such as such as the network type (point-to-point or broadcast) and the interval between hello packets that OSPF sends.

The following command example sets the network type to point-to-point and the hello interval to 5 seconds. The hello interval can be any value between 1 and 65535 seconds.

cumulus@switch:~$ net add interface swp1 ospf6 network point-to-point
cumulus@switch:~$ net add interface swp1 ospf6 hello-interval 5
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface swp1
switch(config-if)# ipv6 ospf6 network point-to-point
switch(config-if)# ipv6 ospf6 hello-interval 5
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
interface swp1
 ipv6 ospf6 hello-interval 5
 ipv6 ospf6 network point-to-point
...

Unlike OSPFv2, OSPFv3 intrinsically supports unnumbered interfaces. Forwarding to the next hop router is done entirely using IPv6 link local addresses. You do not need to configure any global IPv6 address to interfaces between routers.

Configure the OSPFv3 Area

You can use different areas to control routing. You can:

The following section provides command examples.

The following example command removes the 3:3::/64 route from the routing table. Without a route in the table, any destinations in that network are not reachable.

cumulus@switch:~$ net add ospf6 area 0.0.0.0 range 3:3::/64 not-advertise
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following example command creates a summary route for all the routes in the range 2001::/64:

cumulus@switch:~$ net add ospf6 area 0.0.0.0 range 2001::/64 advertise
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

You can also configure the cost for a summary route, which is used to determine the shortest paths to the destination. The value for cost must be between 0 and 16777215.

cumulus@switch:~$ net add ospf6 area 0.0.0.0 range 2001::/64 cost 160
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following example command removes the 3:3::/64 route from the routing table. Without a route in the table, any destinations in that network are not reachable.

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf6
switch(config-ospf6)# area 0.0.0.0 range 3:3::/64 not-advertise
switch(config-ospf6)# end
switch# write memory
switch# exit
cumulus@switch:~

The following example command creates a summary route for all the routes in the range 2001::/64:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf6
switch(config-ospf6)# area 0.0.0.0 range 2001::/64 advertise
switch(config-ospf6)# end
switch# write memory
switch# exit
cumulus@switch:~$

You can also configure the cost for a summary route, which is used to determine the shortest paths to the destination. The value for cost must be between 0 and 16777215.

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf6
switch(config-ospf6)# area 0.0.0.0 range 2001::/64 cost 160
switch(config-ospf6)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router ospf6
  area 0.0.0.0 range 3:3::/64 not-advertise
  area 0.0.0.0 range 2001::/64 advertise
  area 0.0.0.0 range 2001::/64 cost 160
...

Configure the OSPFv3 Distance

Cumulus Linux provides several commands to change the administrative distance for OSPF routes.

This example command sets the distance for an entire group of routes, rather than a specific route.

cumulus@switch:~$ net add ospf6 distance 254
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

This example command changes the OSPF administrative distance to 150 for internal routes and 220 for external routes:

cumulus@switch:~$ net add ospf6 distance ospf6 intra-area 150 inter-area 150 external 220
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

This example command changes the OSPF administrative distance to 150 for internal routes to a subnet or network inside the same area as the router:

cumulus@switch:~$ net add ospf6 distance ospf6 intra-area 150
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

This example command changes the OSPF administrative distance to 150 for internal routes to a subnet in an area of which the router is not a part:

cumulus@switch:~$ net add ospf6 distance ospf6 inter-area 150
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

This example command sets the distance for an entire group of routes, rather than a specific route.

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf6
switch(config-ospf6)# distance 254
switch(config-ospf6)# end
switch# write memory
switch# exit
cumulus@switch:~$

This example command changes the OSPF administrative distance to 150 for internal routes and 220 for external routes:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf6
switch(config-ospf6)# distance ospf6 intra-area 150 inter-area 150 external 220
switch(config-ospf6)# end
switch# write memory
switch# exit
cumulus@switch:~$

This example command changes the OSPF administrative distance to 150 for internal routes to a subnet or network inside the same area as the router:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf6
switch(config-ospf6)# distance ospf6 intra-area 150
switch(config-ospf6)# end
switch# write memory
switch# exit
cumulus@switch:~$

This example command changes the OSPF administrative distance to 150 for internal routes to a subnet in an area of which the router is not a part:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf6
switch(config-ospf6)# distance ospf6 inter-area 150
switch(config-ospf6)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration to the /etc/frr/frr.conf file. For example:

...
router ospf6
  distance ospf6 intra-area 150 inter-area 150 external 220
...

Configure OSPFv3 Interfaces

You can configure an interface, a bond interface, or a VLAN with an existing advertise prefix list. The prefix list defines the outbound route filter.

The following example command configures interface swp3s1 with the IPv6 advertise prefix list named filter:

cumulus@switch:~$ net add interface swp3s1 ospf6 advertise prefix-list filter
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

You can also configure the cost for a particular interface, bond interface, or VLAN. The following example command configures the cost for swp2.

cumulus@switch:~$ net add interface swp2 ospf6 cost 1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following example command configures interface swp3s1 with the IPv6 advertise prefix-list named filter.

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface swp3s1
switch(config-if)# ipv6 ospf advertise prefix-list filter
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

You can also configure the cost for a particular interface, bond interface, or VLAN. The following example command configures the cost for swp2.

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface swp2
switch(config-if)# ipv6 ospf cost 1
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
interface swp2
  ipv6 ospf6 cost 1
...

Troubleshooting

Cumulus Linux provides troubleshooting commands for OSPFv3:

For example:

cumulus@switch:~$ net show ospf6 neighbor
Neighbor ID     Pri    DeadTime    State/IfState         Duration I/F[State]
10.0.0.21         1    00:00:37     Full/DROther         00:11:32 swp51[PointToPoint]
10.0.0.22         1    00:00:37     Full/DROther         00:11:32 swp52[PointToPoint]

Run the net show ospf6 help command to show available NCLU command options.

For a list of all the OSPF debug options, refer to Debugging OSPF.

Border Gateway Protocol - BGP

BGP is the routing protocol that runs the Internet. It manages how packets get routed from network to network by exchanging routing and reachability information.

BGP is an increasingly popular protocol for use in the data center as it lends itself well to the rich interconnections in a Clos topology. RFC 7938 provides further details about using BGP in the data center.

How does BGP Work?

BGP directs packets between autonomous systems (AS), which are a set of routers under a common administration. Each router maintains a routing table that controls how packets are forwarded. The BGP process on the router generates information in the routing table based on information coming from other routers and from information in the BGP routing information base (RIB). The RIB is a database that stores routes and continually updates the routing table as changes occur.

Autonomous System

Because BGP was originally designed to peer between independently managed enterprises and service providers, each such enterprise is treated as an autonomous system responsible for a set of network addresses. Each such autonomous system is given a unique number called an autonomous system number (ASN). ASNs are handed out by a central authority (ICANN); however, ASNs between 64512 and 65535 are reserved for private use. Using BGP within the data center relies on either using this number space or using the single ASN you own.

The ASN is central to how BGP builds a forwarding topology. A BGP route advertisement carries with it not only the ASN of the originator, but also the list of ASNs that this route advertisement passes through. When forwarding a route advertisement, a BGP speaker adds itself to this list. This list of ASNs is called the AS path. BGP uses the AS path to detect and avoid loops.

ASNs were originally 16-bit numbers, but were later modified to be 32-bit. FRRouting supports both 16-bit and 32-bit ASNs, but many implementations still run with 16-bit ASNs.

In a VRF-lite deployment (where multiple independent routing tables work simultaneously on the same switch), Cumulus Linux supports multiple ASNs. Multiple ASNs are not supported in deployments that use EVPN or VRF route leaking.

Auto BGP

In a two-tier leaf and spine environment, you can use auto BGP to generate 32-bit ASNs automatically so that you don’t have to think about which numbers to allocate. Auto BGP helps build optimal ASN configurations in your data center to avoid suboptimal routing and path hunting, which occurs when you assign the wrong spine ASNs. Auto BGP makes no changes to standard BGP behavior or configuration.

Auto BGP assigns private ASNs in the range 4200000000 through 4294967294. This is the private space defined in RFC 6996. Each leaf is assigned a random and unique value in the range 4200000001 through 4294967294. Each spine is assigned 4200000000; the first number in the range. For information about configuring auto BGP, refer to Basic BGP Configuration.

  • Use auto BGP in new deployments to avoid conflicting ASNs in an existing configuration.
  • It is not necessary to use auto BGP across all switches in your configuration. For example, you can use auto BGP to configure one switch but allocate ASNs manually to other switches.
  • Auto BGP is intended for use in two-tier spine and leaf networks. Using auto BGP in three-tier networks with superspines might result in incorrect ASN assignments.
  • The leaf keyword generates the ASN based on a hash of the switch MAC address. The ASN assigned might change after a switch replacement.
  • You can configure auto BGP with NCLU only.

eBGP and iBGP

When BGP is used to peer between autonomous systems, the peering is referred to as external BGP or eBGP. When BGP is used within an autonomous system, the peering used is referred to as internal BGP or iBGP. eBGP peers have different ASNs while iBGP peers have the same ASN.

The heart of the protocol is the same when used as eBGP or iBGP but there is a key difference in the protocol behavior between eBGP and iBGP. To prevent loops, an iBGP speaker does not forward routing information learned from one iBGP peer to another iBGP peer. eBGP prevents loops using the AS_Path attribute.

All iBGP speakers need to be peered with each other in a full mesh. In a large network, this requirement can quickly become unscalable. The most popular method to scale iBGP networks is to introduce a route reflector.

BGP Path Selection

BGP is a path-vector routing algorithm that does not rely on a single routing metric to determine the lowest cost route, unlike interior gateway protocols (IGPs) like OSPF.

The BGP path selection algorithm looks at multiple factors to determine exactly which path is best. BGP multipath is enabled by default in Cumulus Linux so that multiple equal cost routes can be installed in the routing table but only a single route is advertised to BGP peers.

The order of the BGP algorithm process is as follows:

Cumulus Linux provides the reason it selects one path over another in NCLU net show bgp and vtysh show ip bgp command output for a specific prefix.

When BGP multipath is in use, if multiple paths are equal, BGP still selects a single best path to advertise to peers. This path is indicated as best with the reason, although multiple paths might be installed into the routing table.

BGP Unnumbered

Historically, peers connect over IPv4 and TCP port 179, and after they establish a session, they exchange prefixes. When a BGP peer advertises an IPv4 prefix, it must include an IPv4 next hop address, which is usually the address of the advertising router. This requires that each BGP peer has an IPv4 address, which in a large network can consume a lot of address space, requiring a separate IP address for each peer-facing interface.

The BGP unnumbered standard, specified in RFC 5549, uses extended next hop encoding (ENHE) and no longer requires an IPv4 prefix to be advertised along with an IPv4 next hop. This means that you can set up BGP peering between your Cumulus Linux switches and exchange IPv4 prefixes without having to configure an IPv4 address on each switch; the interfaces that BGP uses are unnumbered.

The next hop address for each prefix is an IPv6 link-local address, which is assigned automatically to each interface. Using the IPv6 link-local address as a next hop instead of an IPv4 unicast address, BGP unnumbered saves you from having to configure IPv4 addresses on each interface.

When you use BGP unnumbered, BGP learns the prefixes, calculates the routes and installs them in IPv4 AFI to IPv6 AFI format. ENHE in Cumulus Linux does not install routes into the kernel in IPv4 prefix to IPv6 next hop format. For link-local peerings enabled by dynamically learning the other end’s link-local address using IPv6 neighbor discovery router advertisements, an IPv6 next hop is converted into an IPv4 link-local address and a static neighbor entry is installed for this IPv4 link-local address with the MAC address derived from the link-local address of the other end.

  • If an IPv4 /30 or /31 IP address is assigned to the interface, IPv4 peering is used over IPv6 link-local peering.
  • BGP unnumbered only works with two switches at a time, as it is designed to work with point-to-point links.
  • The IPv6 implementation on the peering device uses the MAC address as the interface ID when assigning the IPv6 link-local address, as suggested by RFC 4291.
  • Every router or end host must have an IPv4 address to complete a traceroute of IPv4 addresses. In this case, the IPv4 address used is that of the loopback device. Even if extended next-hop encoding (ENHE) is not used in the data center, link addresses are not typically advertised because they take up valuable FIB resources and also expose an additional attack vector for intruders to use to either break in or engage in DDOS attacks. Assigning an IP address to the loopback device is essential.

Basic BGP Configuration

This section describes how to configure BGP using either BGP numbered or BGP unnumbered. With BGP unnumbered, you can set up BGP peering between your Cumulus Linux switches and exchange IPv4 prefixes without having to configure an IPv4 address on each switch.

BGP unnumbered simplifies configuration and is recommended for data center deployments.

BGP Numbered

To configure BGP numbered on a BGP node, you need to:

When you commit a change that configures a new routing service such as BGP, the FRR daemon restarts and might interrupt network operations for other configured routing services.

  1. Identify the BGP node by assigning an ASN.

    • To assign an ASN manually:

      cumulus@leaf01:~$ net add bgp autonomous-system 65101
      
    • To use auto BGP to assign an ASN automatically on the leaf:

      cumulus@leaf01:~$ net add bgp auto leaf
      

      The auto BGP leaf keyword is only used to configure the ASN. The configuration files and net show commands display the AS number.

  2. Assign the router ID.

    cumulus@leaf01:~$ net add bgp router-id 10.10.10.1
    
  3. Specify the BGP neighbor to which you want to distribute routing information.

    cumulus@leaf01:~$ net add bgp neighbor 169.254.10.101 remote-as external
    

    For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. The IPv4 address family is enabled by default and the activate command is not required for IPv4 route exchange.

    cumulus@leaf01:~$ net add bgp neighbor 2001:db8:0002::0a00:0002 remote-as external
    cumulus@leaf01:~$ net add bgp ipv6 unicast neighbor 2001:db8:0002::0a00:0002 activate
    

    For BGP to advertise IPv4 prefixes with IPv6 next hops, see Advertise IPv4 Prefixes with IPv6 Next Hops.

  4. Specify which prefixes to originate:

    cumulus@leaf01:~$ net add bgp ipv4 unicast network 10.10.10.1/32
    cumulus@leaf01:~$ net add bgp ipv4 unicast network 10.1.10.0/24
    cumulus@leaf01:~$ net pending
    cumulus@leaf01:~$ net commit
    

    IPv6 prefix example:

    cumulus@leaf01:~$ net add bgp ipv6 unicast network 2001:db8::1/128
    cumulus@leaf01:~$ net pending
    cumulus@leaf01:~$ net commit
    
  1. Identify the BGP node by assigning an ASN.

    • To assign an ASN manually:

      cumulus@spine01:~$ net add bgp autonomous-system 65199
      
    • To use auto BGP to assign an ASN automatically on the spine:

      cumulus@spine01:~$ net add bgp auto spine
      

      The auto BGP spine keyword is only used to configure the ASN. The configuration files and net show commands display the AS number.

  2. Assign the router ID.

    cumulus@spine01:~$ net add bgp router-id 10.10.10.101
    
  3. Specify the BGP neighbor to which you want to distribute routing information.

    cumulus@spine01:~$ net add bgp neighbor 169.254.10.1 remote-as external
    

    For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. The IPv4 address family is enabled by default and the activate command is not required for IPv4 route exchange.

    cumulus@spine01:~$ net add bgp neighbor 2001:db8:0002::0a00:1 remote-as external
    cumulus@spine01:~$ net add bgp ipv6 unicast neighbor 2001:db8:0002::0a00:1 activate
    

    For BGP to advertise IPv4 prefixes with IPv6 next hops, see Advertise IPv4 Prefixes with IPv6 Next Hops.

  4. Specify which prefixes to originate:

    cumulus@spine01:~$ net add bgp ipv4 unicast network 10.10.10.101/32
    cumulus@spine01:~$ net pending
    cumulus@spine01:~$ net commit
    

    IPv6 prefix example:

    cumulus@spine01:~$ net add bgp ipv6 unicast network 2001:db8::101/128
    cumulus@spine01:~$ net pending
    cumulus@spine01:~$ net commit
    
  1. Enable the bgpd daemon as described in Configuring FRRouting.

  2. Identify the BGP node by assigning an ASN and the router ID:

    cumulus@leaf01:~$ sudo vtysh
    

    leaf01# configure terminal leaf01(config)# router bgp 65101 leaf01(config-router)# bgp router-id 10.10.10.1

  3. Specify where to distribute routing information:

    leaf01(config-router)# neighbor 169.254.10.101 remote-as external
    

    For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. The IPv4 address family is enabled by default and the activate command is not required for IPv4 route exchange.

    leaf01(config-router)# neighbor 2001:db8:0002::0a00:1 remote-as external
    leaf01(config-router)# address-family ipv6 unicast
    leaf01(config-router-af)# neighbor 2001:db8:0002::0a00:1 activate
    

    For BGP to advertise IPv4 prefixes with IPv6 next hops, see Advertise IPv4 Prefixes with IPv6 Next Hops.

  4. Specify which prefixes to originate:

    leaf01(config-router)# address-family ipv4
    leaf01(config-router-af)# network 10.10.10.1/32
    leaf01(config-router-af)# network 10.1.10.0/24
    leaf01(config-router-af)# end
    leaf01# write memory
    leaf01# exit
    cumulus@leaf01:~$
    

    IPv6 prefix example:

    leaf01(config-router)# address-family ipv6
    leaf01(config-router-af)# network 2001:db8::1/128
    leaf01(config-router-af)# end
    leaf01# write memory
    leaf01# exit
    cumulus@leaf01:~$
    
  1. Enable the bgpd daemon as described in Configuring FRRouting.

  2. Identify the BGP node by assigning an ASN and the router ID:

    cumulus@spine01:~$ sudo vtysh
    

    spine01# configure terminal spine01(config)# router bgp 65199 spine01(config-router)# bgp router-id 10.10.10.101

  3. Specify where to distribute routing information:

    spine01(config-router)# neighbor 169.254.10.1 remote-as external
    

    For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. The IPv4 address family is enabled by default and the activate command is not required for IPv4 route exchange.

    spine01(config-router)# neighbor 2001:db8:0002::0a00:0002 remote-as external
    spine01(config-router)# address-family ipv6 unicast
    spine01(config-router-af)# neighbor 2001:db8:0002::0a00:0002 activate
    

    For BGP to advertise IPv4 prefixes with IPv6 next hops, see Advertise IPv4 Prefixes with IPv6 Next Hops.

  4. Specify which prefixes to originate:

    spine01(config-router)# address-family ipv4
    spine01(config-router-af)# network 10.10.10.101/32
    spine01(config-router-af)# end
    spine01# write memory
    spine01# exit
    cumulus@spine01:~$
    

    IPv6 prefixes:

    spine01(config-router)# address-family ipv4
    spine01(config-router-af)# network 2001:db8::101/128
    spine01(config-router-af)# end
    spine01# write memory
    spine01# exit
    cumulus@spine01:~$
    

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

cumulus@leaf01:~$  sudo cat /etc/frr/frr.conf
...
router bgp 65101
 bgp router-id 10.10.10.1
 neighbor 169.254.10.101 remote-as external
 !
 address-family ipv4 unicast
  network 10.10.10.1/32
  network 10.1.10.0/24
 exit-address-family
...
cumulus@spine01:~$  sudo cat /etc/frr/frr.conf
...
router bgp 65199
 bgp router-id 10.10.10.101
 neighbor 169.254.10.1 remote-as external
 !
 address-family ipv4 unicast
  network 10.10.10.101/32
 exit-address-family
...

When using auto BGP, there are no references to leaf or spine in the configurations. Auto BGP determines the ASN for the system and configures it using standard vtysh commands.

BGP Unnumbered

The following example commands show a basic BGP unnumbered configuration for two switches, leaf01 and spine01, which are eBGP peers.

The only difference between a BGP unnumbered configuration and the BGP numbered configuration shown above is that the BGP neighbor is specified as an interface (insead of an IP address). The interface between the two peers does not need to have an IP address configured on each side.

When you commit a change that configures a new routing service such as BGP, the FRR daemon restarts and might interrupt network operations for other configured routing services.

cumulus@leaf01:~$ net add bgp autonomous-system 65101
cumulus@leaf01:~$ net add bgp router-id 10.10.10.1
cumulus@leaf01:~$ net add bgp neighbor swp51 remote-as external
cumulus@leaf01:~$ net add bgp ipv4 unicast network 10.10.10.1/32
cumulus@leaf01:~$ net add bgp ipv4 unicast network 10.1.10.0/24
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. The IPv4 address family is enabled by default and the activate command is not required for IPv4 route exchange.

cumulus@leaf01:~$ net add bgp autonomous-system 65101
cumulus@leaf01:~$ net add bgp router-id 10.10.10.1
cumulus@leaf01:~$ net add bgp neighbor swp51 remote-as external
cumulus@leaf01:~$ net add bgp ipv6 unicast neighbor swp51 activate
cumulus@leaf01:~$ net add bgp ipv6 unicast network 2001:db8::1/128
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@spine01:~$ net add bgp autonomous-system 65199
cumulus@spine01:~$ net add bgp router-id 10.10.10.101
cumulus@spine01:~$ net add bgp neighbor swp1 remote-as external
cumulus@spine01:~$ net add bgp ipv4 unicast network 10.10.10.101/32
cumulus@spine01:~$ net pending
cumulus@spine01:~$ net commit

For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. The IPv4 address family is enabled by default and the activate command is not required for IPv4 route exchange.

cumulus@spine01:~$ net add bgp autonomous-system 65199
cumulus@spine01:~$ net add bgp router-id 10.10.10.101
cumulus@spine01:~$ net add bgp neighbor swp1 remote-as external
cumulus@spine01:~$ net add bgp ipv6 unicast neighbor swp1 activate
cumulus@spine01:~$ net add bgp ipv6 unicast network 2001:db8::101/128
cumulus@spine01:~$ net pending
cumulus@spine01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal leaf01(config)# router bgp 65101 leaf01(config-router)# bgp router-id 10.10.10.1 leaf01(config-router)# neighbor swp1 remote-as external leaf01(config-router)# address-family ipv4 leaf01(config-router-af)# network 10.10.10.1/32 leaf01(config-router-af)# network 10.1.10.0/24 leaf01(config-router-af)# end leaf01# write memory leaf01# exit cumulus@leaf01:~$

For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. The IPv4 address family is enabled by default and the activate command is not required for IPv4 route exchange.

cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# bgp router-id 10.10.10.1
leaf01(config-router)# neighbor swp51 remote-as external
leaf01(config-router)# address-family ipv6 unicast
leaf01(config-router-af)# neighbor swp51 activate
leaf01(config-router-af)# network 2001:db8::1/128
leaf01(config-router-af)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$
cumulus@spine01:~$ sudo vtysh

spine01# configure terminal spine01(config)# router bgp 65199 spine01(config-router)# bgp router-id 10.10.10.101 spine01(config-router)# neighbor swp1 remote-as external spine01(config-router)# address-family ipv4 spine01(config-router-af)# network 10.10.10.101/32 spine01(config-router-af)# end spine01# write memory spine01# exit cumulus@spine01:~$

For BGP to advertise IPv6 prefixes, you need to run an additional command to activate the BGP neighbor under the IPv6 address family. The IPv4 address family is enabled by default and the activate command is not required for IPv4 route exchange.

cumulus@spine01:~$ sudo vtysh

spine01# configure terminal
spine01(config)# router bgp 65199
spine01(config-router)# bgp router-id 10.10.10.101
spine01(config-router)# neighbor swp1 remote-as external
spine01(config-router)# address-family ipv6 unicast
spine01(config-router-af)# neighbor swp1 activate
spine01(config-router-af)# network 2001:db8::101/128
spine01(config-router-af)# end
spine01# write memory
spine01# exit
cumulus@spine01:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

cumulus@leaf01:~$  sudo cat /etc/frr/frr.conf
...
router bgp 65101
 bgp router-id 10.10.10.1
 neighbor swp51 interface
 neighbor swp51 remote-as external
 !
 address-family ipv4 unicast
  network 10.10.10.1/32
  network 10.1.10.0/24
 exit-address-family
...
cumulus@spine01:~$  sudo cat /etc/frr/frr.conf
...
router bgp 65199
 bgp router-id 10.10.10.101
 neighbor swp1 interface
 neighbor swp1 remote-as external
 !
 address-family ipv4 unicast
  network 10.10.10.101/32
 exit-address-family
...

Optional BGP Configuration

This section describes optional configuration. The steps provided in this section assume that you already configured basic BGP as described in Basic BGP Configuration.

Peer Groups

Instead of specifying properties of each individual peer, you can define one or more peer groups and associate all the attributes common to that peer session to a peer group. A peer needs to be attached to a peer group only once, when it then inherits all address families activated for that peer group.

If the peer you want to add to a group already exists in the BGP configuration, delete it first, than add it to the peer group.

The following example commands create a peer group called SPINE that includes two external peers.

cumulus@leaf01:~$ net add bgp neighbor SPINE peer-group
cumulus@leaf01:~$ net add bgp neighbor SPINE remote-as external
cumulus@leaf01:~$ net add bgp neighbor 169.254.10.101 peer-group SPINE
cumulus@leaf01:~$ net add bgp neighbor 169.254.10.102 peer-group SPINE
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# neighbor SPINE peer-group
leaf01(config-router)# neighbor SPINE remote-as external
leaf01(config-router)# neighbor 169.254.10.101 peer-group SPINE
leaf01(config-router)# neighbor 169.254.10.102 peer-group SPINE
leaf01(config-router)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

For an unnumbered configuration, you can use a single command to configure a neighbor and attach it to a peer group.

cumulus@leaf01:~$ net add bgp neighbor swp51 interface peer-group SPINE
leaf01(config-router)# neighbor swp51 interface peer-group SPINE

BGP Dynamic Neighbors

BGP dynamic neighbor provides BGP peering to a group of remote neighbors within a specified range of IPv4 or IPv6 addresses for a BGP peer group. You can configure each range as a subnet IP address.

You configure dynamic neighbors using the bgp listen range <ip-address> peer-group <group> command. After you configure the dynamic neighbors, a BGP speaker can listen for, and form peer relationships with, any neighbor that is in the IP address range and is mapped to a peer group.

The following example commands create the peer group SPINE and configure BGP peering to remote neighbors within the address range 169.254.10.0/24.

cumulus@leaf01:~$ net add bgp neighbor SPINE peer-group
cumulus@leaf01:~$ net add bgp neighbor SPINE remote-as external
cumulus@leaf01:~$ net add bgp listen range 169.254.10.0/24 peer-group SPINE
cumulus@leaf01:~$ net add bgp listen limit 5
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

The net add bgp listen limit command limits the number of dynamic peers. The default value is 100.

cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# bgp listen range 169.254.10.0/24 peer-group SPINE
leaf01(config-router)# bgp listen limit 5
leaf01(config-router)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

The bgp listen limit command limits the number of dynamic peers. The default value is 100.

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

router bgp 65101
  neighbor SPINE peer-group
  neighbor SPINE remote-as external
  bgp listen limit 5
  bgp listen range 169.254.10.0/24 peer-group SPINE

eBGP Multihop

The eBGP multihop option lets you use BGP to exchange routes with an external peer that is more than one hop away.

To establish a connection between two eBGP peers that are not directly connected:

cumulus@leaf01:~$ net add bgp neighbor 10.10.10.101 remote-as external
cumulus@leaf01:~$ net add bgp neighbor 10.10.10.101 ebgp-multihop
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# neighbor 10.10.10.101 remote-as external
leaf01(config-router)# neighbor 10.10.10.101 ebgp-multihop
leaf01(config)# exit
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

BGP TTL Security Hop Count

You can use the TTL security hop count option to prevent attacks against eBGP, such as denial of service (DoS) attacks. By default, BGP messages are sent to eBGP neighbors with an IP time-to-live (TTL) of 1, which requires the peer to be directly connected, otherwise, the packets expire along the way. (You can adjust the TTL with the eBGP multihop option.) An attacker can easily adjust the TTL of packets so that they appear to be originating from a peer that is directly connected.

The BGP TTL security hops option inverts the direction in which the TTL is counted. Instead of accepting only packets with a TTL set to 1, only BGP messages with a TTL greater than or equal to 255 minus the specified hop count are accepted.

When TTL security is in use, eBGP multihop is no longer needed.

The following command example sets the TTL security hop count value to 200:

cumulus@leaf01:~$ net add bgp neighbor swp51 ttl-security hops 200
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# neighbor swp51 ttl-security hops 200
leaf01(config-router)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65101
  ...
  neighbor swp51 ttl-security hops 200
...

  • When you configure ttl-security hops on a peer group instead of a specific neighbor, FRR does not add it to either the running configuration or to the /etc/frr/frr.conf file. To work around this issue, add ttl-security hops to individual neighbors instead of the peer group.
  • Enabling ttl-security hops does not program the hardware with relevant information. Frames are forwarded to the CPU and are dropped. Use the net add acl command to explicitly add the relevant entry to hardware. For more information about ACLs, see Netfilter - ACLs.

MD5-enabled BGP Neighbors

You can authenticate your BGP peer connection to prevent interference with your routing tables.

To enable MD5 authentication for BGP peers, set the same password on each peer.

The following example commands set the password mypassword on BGP peers leaf01 and spine01:

cumulus@leaf01:~$ net add bgp neighbor swp51 password mypassword
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@spine01:~$ net add bgp neighbor swp1 password mypassword
cumulus@spine01:~$ net pending
cumulus@spine01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal leaf01(config)# router bgp 65101 leaf01(config-router)# neighbor swp51 password mypassword leaf01(config-router)# exit leaf01(config)# exit leaf01# write memory leaf01# exit cumulus@leaf01:~$

cumulus@spine01:~$ sudo vtysh

spine01# configure terminal spine01(config)# router bgp 65199 spine01(config-router)# neighbor swp1 password mypassword spine01(config-router)# end spine01# write memory spine01# exit cumulus@spine01:~$

You can confirm the configuration with the NCLU command net show bgp neighbor <neighbor> or with the vtysh command show ip bgp neighbor <neighbor>.

net show bgp neighbor <neighbor> example

The following example shows that a session with the peer is established and that authentication is enabled. The output shows Peer Authentication Enabled towards the end.

cumulus@spine01:~$ net show bgp neighbor swp1
BGP neighbor on swp1: fe80::2294:15ff:fe02:7bbf, remote AS 65101, local AS 65199, external link
Hostname: leaf01
  BGP version 4, remote router ID 10.10.10.1, local router ID 10.10.10.101
  BGP state = Established, up for 00:00:39
  Last read 00:00:00, Last write 00:00:00
  Hold time is 9, keepalive interval is 3 seconds
  Neighbor capabilities:
    4 Byte AS: advertised and received
    AddPath:
      IPv4 Unicast: RX advertised IPv4 Unicast and received
    Route refresh: advertised and received(old & new)
    Address Family IPv4 Unicast: advertised and received
    Hostname Capability: advertised (name: spine01,domain name: n/a) received (name: leaf01,domain name: n/a)
    Graceful Restart Capability: advertised and received
      Remote Restart timer is 120 seconds
      Address families by peer:
        none
  Graceful restart information:
    End-of-RIB send: IPv4 Unicast
    End-of-RIB received: IPv4 Unicast
  Message statistics:
    Inq depth is 0
    Outq depth is 0
                         Sent       Rcvd
    Opens:                  2          2
    Notifications:          0          2
    Updates:              424        369
    Keepalives:           633        633
    Route Refresh:          0          0
    Capability:             0          0
    Total:               1059       1006
  Minimum time between advertisement runs is 0 seconds
  For address family: IPv4 Unicast
  Update group 1, subgroup 1
  Packet Queue length 0
  Community attribute sent to this neighbor(all)
  3 accepted prefixes
  Connections established 2; dropped 1
  Last reset 00:02:37,   Notification received (Cease/Other Configuration Change)
Local host: fe80::7c41:fff:fe93:b711, Local port: 45586
Foreign host: fe80::2294:15ff:fe02:7bbf, Foreign port: 179
Nexthop: 10.10.10.101
Nexthop global: fe80::7c41:fff:fe93:b711
Nexthop local: fe80::7c41:fff:fe93:b711
BGP connection: shared network
BGP Connect Retry Timer in Seconds: 10
Peer Authentication Enabled
Read thread: on  Write thread: on  FD used: 27

The MD5 password configured against a BGP listen-range peer group (used to accept and create dynamic BGP neighbors) is not enforced; connections are accepted from peers that do not specify a password.

Remove Private ASNs

If you use private ASNs in the data center, any routes you send out to the internet contain your private ASNs. You can remove all the private ASNs from routes to a specific neighbor.

The following example command removes private ASNs from routes sent to the neighbor on swp51 (an unnumbered interface):

cumulus@switch:~$ net add bgp neighbor swp51 remove-private-AS

You can replace the private ASNs with your public ASN with the following command:

cumulus@switch:~$ net add bgp neighbor swp51 remove-private-AS replace-AS

ECMP

BGP supports equal-cost multipathing (ECMP). If a BGP node hears a certain prefix from multiple peers, it has all the information necessary to program the routing table and forward traffic for that prefix through all of these peers. BGP typically chooses one best path for each prefix and installs that route in the forwarding table.

In Cumulus Linux, the BGP multipath option is enabled by default with the maximum number of paths set to 64 so that the switch can install multiple equal-cost BGP paths to the forwarding table and load balance traffic across multiple links. You can change the number of paths allowed, according to your needs.

The example commands change the maximum number of paths to 120. You can set a value between 1 and 256. 1 disables the BGP multipath option.

cumulus@switch:~$ net add bgp maximum-paths 120
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65101
switch(config-router)# address-family ipv4
switch(config-router-af)# maximum-paths 120
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the address-family stanza of the /etc/frr/frr.conf file. For example:

...
!
address-family ipv4 unicast
 network 10.1.10.0/24
 network 10.10.10.1/32
 maximum-paths 120
exit-address-family
...

When BGP multipath is enabled, only BGP routes from the same AS are load balanced. If the routes go across several different AS neighbors, even if the AS path length is the same, they are not load balanced. To be able to load balance between multiple paths received from different AS neighbors, you need to set the bestpath as-path multipath-relax option.

cumulus@switch:~$ net add bgp bestpath as-path multipath-relax
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65101
switch(config-router)# bgp bestpath as-path multipath-relax
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65101
  bgp router-id 10.0.0.1
  bgp bestpath as-path multipath-relax
...

When you disable the bestpath as-path multipath-relax option, EVPN type-5 routes do not use the updated configuration. Type-5 routes continue to use all available ECMP paths in the underlay fabric, regardless of ASN.

RFC 5549 defines the method used for BGP to advertise IPv4 prefixes with IPv6 next hops. The RFC does not make a distinction between whether the IPv6 peering and next hop values should be global unicast addresses (GUA) or link-local addresses. Cumulus Linux supports advertising IPv4 prefixes with IPv6 global unicast and link-local next hop addresses, with either unnumbered or numbered BGP.

When BGP peering uses IPv6 global addresses and IPv4 prefixes are being advertised and installed, IPv6 route advertisements are used to derive the MAC address of the peer so that FRR can create an IPv4 route with a link-local IPv4 next hop address (defined by RFC 3927). This is required to install the route into the kernel. These route advertisement settings are configured automatically when FRR receives an update from a BGP peer using IPv6 global addresses that contain an IPv4 prefix with an IPv6 next hop, and the enhanced-next hop capability has been negotiated.

To enable advertisement of IPv4 prefixes with IPv6 next hops over global IPv6 peerings, add the extended-nexthop capability to the global IPv6 neighbor statements on each end of the BGP sessions.

cumulus@switch:~$ net add bgp neighbor 2001:db8:0002::0a00:0002 capability extended-nexthop
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65101
switch(config-router)# neighbor 2001:db8:0002::0a00:0002 capability extended-nexthop
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65101
  ...
  neighbor 2001:db8:0002::0a00:0002 capability extended-nexthop
...

Ensure that the IPv6 peers are activated under the IPv4 unicast address family; otherwise, all peers are activated in the IPv4 unicast address family by default. If no bgp default ipv4-unicast is configured, you need to explicitly activate the IPv6 neighbor under the IPv4 unicast address family as shown below:

cumulus@switch:~$ net add bgp neighbor 2001:db8:0002::0a00:0002 capability extended-nexthop
cumulus@switch:~$ net add bgp ipv4 unicast neighbor 2001:db8:0002::0a00:0002 activate
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65101
switch(config-router)# neighbor 2001:db8:0002::0a00:0002 capability extended-nexthop
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# neighbor 2001:db8:0002::0a00:0002 activate
switch(config-router-af)# end
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65101
router-id 10.10.10.1
no bgp default ipv4-unicast
neighbor 2001:db8:0002::0a00:0002 remote-as external
neighbor 2001:db8:0002::0a00:0002 capability extended-nexthop
!
address-family ipv4 unicast
  neighbor 2001:db8:0002::0a00:0002 activate
exit-address-family
...

Neighbor Maximum Prefixes

To protect against an internal network connectivity disruption caused by BGP, you can control how many route announcements (prefixes) can be received from a BGP neighbor.

The following example commands set the maximum number of prefixes allowed from the BGP neighbor on swp51 to 3000:

cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65001
leaf01(config-router)# neighbor swp51 maximum-prefix 3000
leaf01(config-router)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

Aggregate Addresses

To minimize the size of the routing table and save bandwidth, you can aggregate a range of networks in your routing table into a single prefix.

The following example command aggregates a range of addresses, such as 10.1.1.0/24, 10.1.2.0/24, 10.1.3.0/24 into the single prefix 10.1.0.0/16.

cumulus@switch:~$ net add bgp aggregate-address 10.1.0.0/16
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The summary-only option ensures that longer-prefixes inside the aggregate address are suppressed before sending BGP updates:

cumulus@switch:~$ net add bgp aggregate-address 10.1.0.0/16 summary-only
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

BGP add-path

Cumulus Linux supports both BGP add-path RX and BGP add-path TX.

BGP add-path RX

BGP add-path RX allows BGP to receive multiple paths for the same prefix. A path identifier is used so that additional paths do not override previously advertised paths. BGP add-path RX is enabled by default; no additional configuration is required.

To view the existing capabilities, run the NCLU command net show bgp neighbor or the vtysh command show ip bgp neighbors. The existing capabilities are listed in the subsection Add Path, below Neighbor capabilities.

The following example output shows that additional BGP paths can be sent and received and that the BGP neighbor on swp51 supports both.

cumulus@leaf01:~$ net show bgp neighbor
BGP neighbor on swp51: fe80::7c41:fff:fe93:b711, remote AS 65199, local AS 65101, external link
Hostname: spine01
  BGP version 4, remote router ID 10.10.10.101, local router ID 10.10.10.1
  BGP state = Established, up for 1d12h39m
  Last read 00:00:03, Last write 00:00:01
  Hold time is 9, keepalive interval is 3 seconds
  Neighbor capabilities:
    4 Byte AS: advertised and received
    AddPath:
      IPv4 Unicast: RX advertised IPv4 Unicast and received
    Extended nexthop: advertised and received
      Address families by peer:
                   IPv4 Unicast
    Route refresh: advertised and received(old & new)
    Address Family IPv4 Unicast: advertised and received
    Hostname Capability: advertised (name: leaf01,domain name: n/a) received (name: spine01,domain name: n/a)
    Graceful Restart Capability: advertised and received
...

To view the current additional paths, run the NCLU command net show bgp <prefix> or the vtysh command show ip bgp <prefix>. The example output shows an additional path that has been added by the TX node for receiving. Each path has a unique AddPath ID.

cumulus@leaf01:mgmt:~$ net show bgp 10.10.10.9
BGP routing table entry for 10.10.10.9/32
Paths: (2 available, best #1, table Default-IP-Routing-Table)
  Advertised to non peer-group peers:
  spine01(swp51) spine02(swp52)
  65020 65012
    fe80::4638:39ff:fe00:5c from spine01(swp51) (10.10.10.12)
    (fe80::4638:39ff:fe00:5c) (used)
      Origin incomplete, localpref 100, valid, external, multipath, bestpath-from-AS 65020, best (Older Path)
      AddPath ID: RX 0, TX 6
      Last update: Wed Nov 16 22:47:00 2016
  65020 65012
    fe80::4638:39ff:fe00:2b from spine02(swp52) (10.10.10.12)
    (fe80::4638:39ff:fe00:2b) (used)
      Origin incomplete, localpref 100, valid, external, multipath
      AddPath ID: RX 0, TX 3
      Last update: Fri Oct  2 03:56:33 2020

BGP add-path TX

BGP add-path TX enables BGP to advertise more than just the best path for a prefix. Cumulus Linux includes two options:

The following example commands configure leaf01 to advertise the best path learned from each AS to the BGP neighbor on swp50:

cumulus@leaf01:~$ net add bgp autonomous-system 65101
cumulus@leaf01:~$ net add bgp neighbor swp50 addpath-tx-bestpath-per-AS
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# neighbor swp50 addpath-tx-bestpath-per-AS
leaf01(config-router)#

The following example commands configure leaf01 to advertise all paths learned from each AS to the BGP neighbor on swp50:

cumulus@leaf01:~$ net add bgp autonomous-system 65101
cumulus@leaf01:~$ net add bgp neighbor swp50 addpath-tx-all-paths
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# neighbor swp50 addpath-tx-all-paths
leaf01(config-router)#

The following example configuration shows how BGP add-path TX is used to advertise the best path learned from each AS.

In this configuration:
  • Every leaf and every spine has a different ASN
  • eBGP is configured between:
    • leaf01 and spine01, spine02
    • leaf03 and spine01, spine02
    • leaf01 and leaf02 (leaf02 only has a single peer, which is leaf01)
  • leaf01 is configured to advertise the best path learned from each AS to BGP neighbor leaf02
  • leaf03 generates a loopback IP address (10.10.10.3/32) into BGP with a network statement

When you run the net show bgp 10.10.10.3/32 command on leaf02, the command output shows the leaf03 loopback IP address and that two BGP paths are learned, both from leaf01:

cumulus@leaf02:mgmt:~$ net show bgp 10.10.10.3/32
BGP routing table entry for 10.10.10.3/32
Paths: (2 available, best #2, table default)
       Advertised to non peer-group peers:
       leaf01(swp50)
  65101 65199 65103
    fe80::4638:39ff:fe00:13 from leaf01(swp50) (10.10.10.1)
    (fe80::4638:39ff:fe00:13) (used)
      Origin IGP, valid, external
      AddPath ID: RX 4, TX-All 0 TX-Best-Per-AS 0
      Last update: Thu Oct 15 18:31:46 2020
  65101 65198 65103
    fe80::4638:39ff:fe00:13 from leaf01(swp50) (10.10.10.1)
    (fe80::4638:39ff:fe00:13) (used)
      Origin IGP, valid, external, bestpath-from-AS 65101, best (Nothing left to compare)
      AddPath ID: RX 3, TX-All 0 TX-Best-Per-AS 0
      Last update: Thu Oct 15 18:31:46 2020

BGP Timers

BGP includes several timers that you can configure.

Keepalive Interval and Hold Time

By default, BGP exchanges periodic keepalive messages to measure and ensure that a peer is still alive and functioning. If a keepalive or update message is not received from the peer within the hold time, the peer is declared down and all routes received by this peer are withdrawn from the local BGP table. By default, the keepalive interval is set to 3 seconds and the hold time is set to 9 seconds. To decrease CPU load, especially in the presence of a lot of neighbors, you can increase the values of these timers or disable the exchange of keepalives entirely. When manually configuring new values, the keepalive interval can be less than or equal to one third of the hold time, but cannot be less than 1 second. Setting the keepalive and hold time values to 0 disables the exchange of keepalives.

The following example commands set the keepalive interval to 10 seconds and the hold time to 30 seconds.

cumulus@leaf01:~$ net add bgp neighbor swp51 timers 10 30
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp
leaf01(config-router)# neighbor swp51 timers 10 30
leaf01(config-router)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65101
  ...
  neighbor swp51 timers 10 30
...

Reconnect Interval

By default, the BGP process attempts to connect to a peer after a failure (or on startup) every 10 seconds. You can change this value to suit your needs.

The following example commands set the reconnect value to 30 seconds:

cumulus@leaf01:~$ net add bgp neighbor swp51 timers connect 30
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp
leaf01(config-router)# neighbor swp51 timers connect 30
leaf01(config-router)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65101
  ...
  neighbor swp51 timers connect 30
...

After making a new best path decision for a prefix, BGP can optionally insert a delay before advertising the new results to a peer. This delay is used to rate limit the amount of changes advertised to downstream peers and lowers processing requirements by slowing down convergence. By default, this interval is set to 0 seconds for both eBGP and iBGP sessions, which allows for very fast convergence. For more information about the advertisement interval, see this IETF draft.

The following example commands set the advertisement interval to 5 seconds:

cumulus@leaf01:~$ net add bgp neighbor swp51 advertisement-interval 5
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp
leaf01(config-router)# neighbor swp51 advertisement-interval 5
leaf01(config-router)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65101
  ...
  neighbor swp51 advertisement-interval 5
...

Route Reflectors

iBGP rules state that a route learned from an iBGP peer can not be sent to another iBGP peer. In a data center spine and leaf network using iBGP, this prevents a spine from sending a route learned from a leaf to any other leaf. As a workaround, BGP introduced the concept of a route reflector that selectively ignores this rule so that when an iBGP speaker is configured as a route reflector, it can send iBGP learned routes to other iBGP peers.

In the following example, spine01 is acting as a route reflector. The leaf switches, leaf01, leaf02 and leaf03 are route reflector clients. Any route that spine01 learns from a route reflector client is sent to other route reflector clients.

To configure the BGP node as a route reflector for a BGP peer, set the neighbor route-reflector-client option. The following example sets spine01 shown in the illustration above to be a route reflector for leaf01 (on swp1), which is a route reflector client. No configuration is required on the client.

cumulus@spine01:~$ net add bgp neighbor swp1 route-reflector-client
cumulus@spine01:~$ net pending
cumulus@spine01:~$ net commit
cumulus@spine01:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65199
switch(config-router)# address-family ipv4
switch(config-router-af)# neighbor swp1 route-reflector-client
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@spine01:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65199
 bgp router-id 10.10.10.101
 neighbor swp51 remote-as external
 !
 address-family ipv4 unicast
  network 10.10.10.101/32
  neighbor swp51 route-reflector-client
 exit-address-family
...

When configuring BGP for IPv6, you must run the route-reflector-client command after the activate command; otherwise, the route-reflector-client command is ignored.

Administrative Distance

Cumulus Linux uses the administrative distance to choose which routing protocol to use when two different protocols provide route information for the same destination. The smaller the distance, the more reliable the protocol. For example, if the switch receives a route from OSPF with an administrative distance of 110 and the same route from BGP with an administrative distance of 100, the switch chooses BGP.

Set the administrative distance with vtysh commands.

The following example commands set the administrative distance for routes from 10.10.10.101 to 100:

cumulus@spine01:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65101
switch(config-router)# distance 100 10.10.10.101/32
switch(config-router)# end
switch# write memory
switch# exit
cumulus@spine01:~$

The following example commands set the administrative distance for routes external to the AS to 150, routes internal to the AS to 110, and local routes to 100:

cumulus@spine01:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65101
switch(config-router)# distance bgp 150 110 100
switch(config-router)# end
switch# write memory
switch# exit
cumulus@spine01:~$

Graceful BGP Shutdown

To reduce packet loss during planned maintenance of a router or link, you can configure graceful BGP shutdown, which forces traffic to route around the BGP node:

To enable graceful shutdown:

cumulus@leaf01:~$ net add bgp graceful-shutdown
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

To disable graceful shutdown:

cumulus@leaf01:~$ net del bgp graceful-shutdown
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit

To enable graceful shutdown:

cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# bgp graceful-shutdown
leaf01(config-router)# end
leaf01# write memory
leaf01# exit
cumulus@v:~$

To disable graceful shutdown:

cumulus@leaf01:~$ sudo vtysh

leaf01# configure terminal
leaf01(config)# router bgp 65101
leaf01(config-router)# no bgp graceful-shutdown
leaf01(config-router)# end
leaf01# write memory
leaf01# exit
cumulus@leaf01:~$

When configured, the graceful-shutdown community is added to all inbound and outbound routes from eBGP peers and the local-pref for that route is set to 0 (refer to RFC8326). To see the configuration, run the NCLU command net show bgp <route> or the vtysh command show ip bgp <route>. For example:

cumulus@switch:~$ net show bgp 10.10.10.0/24
BGP routing table entry for 10.10.10.0/24
Paths: (2 available, best #1, table Default-IP-Routing-Table)
  Advertised to non peer-group peers:
  bottom0(10.10.10.2)
  30 20
    10.10.10.2 (metric 10) from top1(10.10.10.2) (10.10.10.2)
      Origin IGP, localpref 100, valid, internal, bestpath-from-AS 30, best
      Community: 99:1
      AddPath ID: RX 0, TX 52
      Last update: Mon Sep 18 17:01:18 2017

  20
    10.10.10.3 from bottom0(10.10.10.32) (10.10.10.10)
      Origin IGP, metric 0, localpref 0, valid, external, bestpath-from-AS 20
      Community: 99:1 graceful-shutdown
      AddPath ID: RX 0, TX 2
      Last update: Mon Sep 18 17:01:18 2017

Enable Read-only Mode

As BGP peers are established and updates are received, prefixes might be installed in the RIB and advertised to BGP peers even though the information from all peers is not yet received and processed. Depending on the timing of the updates, prefixes might be installed and propagated through BGP, and then immediately withdrawn and replaced with new routing information. Read-only mode minimizes this BGP route churn in both the local RIB and with BGP peers.

Enable read-only mode to reduce CPU and network usage when restarting the BGP process. Because intermediate best paths are possible for the same prefix as peers get established and start receiving updates at different times, read-only mode is particularly useful in topologies where BGP learns a prefix from many peers and the network has a high number of prefixes.

While in read-only mode, BGP does not run best-path or generate any updates to its peers.

To enable read-only mode, you set the max-delay timer and, optionally, the establish-wait timer. Read-only mode begins as soon as the first peer reaches its established state and the max-delay timer starts, and continues until either of the following two conditions are met:

The default value for max-delay is 0, which disables read-only mode. The update delay and establish wait can be any value between 0 and 3600 seconds. The establish-wait setting is optional; however, if specified, it must be shorter than the max-delay.

The following example commands enable read-only mode by setting the max-delay timer to 300 seconds and the establish-wait timer to 90 seconds.

cumulus@switch:~$ net add bgp update-delay 300 90
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp
switch(config-router)# update-delay 300 90
switch(config-router)# end
switch# write memory
switch# switch
cumulus@switch:~$

To show information about the state of the update delay, run the NCLU command net show bgp summary or the vtysh command show ip bgp summary.

Route Maps for Route Updates

You can apply route maps in BGP in one of two ways:

In NCLU, you can only set the community number in a route map. You cannot set other community options such as no-export, no-advertise, or additive. This is a known limitation in network-docopt, which NCLU uses to parse commands.

Filter Routes from BGP into Zebra

You can apply a route map on route updates from BGP to Zebra. All the applicable match operations are allowed, such as match on prefix, next hop, communities, and so on. Set operations are limited to metric and next hop only. Applying a route map on route updates from BGP to Zebra does not affect the BGP internal RIB.

Both IPv4 and IPv6 address families are supported. Route maps work on multi-paths; however, the metric setting is based on the best path only.

The following example command applies a route map called routemap1 to filter route updates from BGP into Zebra:

cumulus@switch:~$ net add bgp table-map routemap1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp
switch(config-router)# table-map routemap1
switch(config-router)# end
switch# write memory
switch# switch
cumulus@switch:~$

Filter Routes from Zebra into the Linux Kernel

The following example commands apply a route map called routemap1 to filter route updates from Zebra into the Linux kernel:

cumulus@switch:~$ net add routing protocol bgp route-map routemap1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp
switch(config-router)# bgp route-map routemap1
switch(config-router)# end
switch# write memory
switch# switch
cumulus@switch:~$

BGP Community Lists

You can use community lists to define a BGP community to tag one or more routes. You can then use the communities to apply a route policy on either egress or ingress.

The BGP community list can be either standard or expanded. The standard BGP community list is a pair of values (such as 100:100) that can be tagged on a specific prefix and advertised to other neighbors or applied on route ingress. Or, it can be one of four BGP default communities:

An expanded BGP community list takes a regular expression of communities and matches the listed communities.

When the neighbor receives the prefix, it examines the community value and takes action accordingly, such as permitting or denying the community member in the routing policy.

Here is an example of a standard community list filter:

cumulus@switch:~$ net add routing community-list standard COMMUNITY1 permit 100:100

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# bgp community-list standard COMMUNITY1 permit 100:100
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

You can apply the community list to a route map to define the routing policy:

cumulus@switch:~$ net add bgp table-map ROUTE-MAP1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65101
switch(config-router)# table-map ROUTE-MAP1
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

Configuration Example

This section shows a BGP configuration example based on the reference topology. The example configures BGP unnumbered on all leafs and spines and uses the peer group underlay. MLAG is configured leaf01 and leaf02, and on leaf03 and leaf04.

/etc/network/interfaces

cumulus@leaf01:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.1/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 bond3
    bridge-vids 10 20 30
    bridge-vlan-aware yes

auto vlan10
iface vlan10
    address 10.1.10.2/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.2/24
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.2/24
    vlan-raw-device bridge
    vlan-id 30

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.2
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf02:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.2/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 bond3
    bridge-vids 10 20 30
    bridge-vlan-aware yes

auto vlan10
iface vlan10
    address 10.1.10.3/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.3/24
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.3/24
    vlan-raw-device bridge
    vlan-id 30

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.1
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:AA

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf03:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.3/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 bond3
    bridge-vids 10 20 30
    bridge-vlan-aware yes

auto vlan10
iface vlan10
    address 10.1.10.2/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.2/24
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.2/24
    vlan-raw-device bridge
    vlan-id 30

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.4
    clagd-peer-ip linklocal
    clagd-priority 1000
    clagd-sys-mac 44:38:39:BE:EF:BB

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@leaf04:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.4/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto bridge
iface bridge
    bridge-ports peerlink bond1 bond2 bond3
    bridge-vids 10 20 30
    bridge-vlan-aware yes

auto vlan10
iface vlan10
    address 10.1.10.3/24
    vlan-raw-device bridge
    vlan-id 10

auto vlan20
iface vlan20
    address 10.1.20.3/24
    vlan-raw-device bridge
    vlan-id 20

auto vlan30
iface vlan30
    address 10.1.30.3/24
    vlan-raw-device bridge
    vlan-id 30

auto swp51
iface swp51
    alias leaf to spine

auto swp52
iface swp52
    alias leaf to spine

auto swp49
iface swp49
    alias peerlink

auto swp50
iface swp50
    alias peerlink

auto peerlink
iface peerlink
    bond-slaves swp49 swp50

auto peerlink.4094
iface peerlink.4094
    clagd-backup-ip 10.10.10.3
    clagd-peer-ip linklocal
    clagd-priority 32768
    clagd-sys-mac 44:38:39:BE:EF:BB

auto swp1
iface swp1
    alias bond member of bond1
    mtu 9000

auto bond1
iface bond1
    alias bond1 on swp1
    mtu 9000
    clag-id 1
    bridge-access 10
    bond-slaves swp1
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp2
iface swp2
    alias bond member of bond2
    mtu 9000

auto bond2
iface bond2
    alias bond2 on swp2
    mtu 9000
    clag-id 2
    bridge-access 20
    bond-slaves swp2
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes

auto swp3
iface swp3
    alias bond member of bond3
    mtu 9000

auto bond3
iface bond3
    alias bond3 on swp3
    mtu 9000
    clag-id 3
    bridge-access 30
    bond-slaves swp3
    bond-lacp-bypass-allow yes
    mstpctl-bpduguard yes
    mstpctl-portadminedge yes
cumulus@spine01:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.101/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine
cumulus@spine02:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback
    address 10.10.10.102/32

auto mgmt
iface mgmt
    vrf-table auto
    address 127.0.0.1/8
    address ::1/128

auto eth0
iface eth0 inet dhcp
    vrf mgmt

auto swp1
iface swp1
    alias leaf to spine

auto swp2
iface swp2
    alias leaf to spine

auto swp3
iface swp3
    alias leaf to spine

auto swp4
iface swp4
    alias leaf to spine

/etc/frr/frr.conf

cumulus@leaf01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65101
 bgp router-id 10.10.10.1
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
!
line vty
cumulus@leaf02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65101
 bgp router-id 10.10.10.2
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
!
line vty
cumulus@leaf03:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65102
 bgp router-id 10.10.10.3
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
!
line vty
cumulus@leaf04:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65102
 bgp router-id 10.10.10.4
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor peerlink.4094 interface remote-as internal
 neighbor swp51 interface peer-group underlay
 neighbor swp52 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
!
line vty
cumulus@spine01:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.101
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
!
line vty
cumulus@spine02:~$ cat /etc/frr/frr.conf
...
log syslog informational
!
router bgp 65199
 bgp router-id 10.10.10.102
 bgp bestpath as-path multipath-relax
 neighbor underlay peer-group
 neighbor underlay remote-as external
 neighbor swp1 interface peer-group underlay
 neighbor swp2 interface peer-group underlay
 neighbor swp3 interface peer-group underlay
 neighbor swp4 interface peer-group underlay
 !
 address-family ipv4 unicast
  redistribute connected
 exit-address-family
!
line vty

Troubleshooting

Use the following commands to troubleshoot BGP.

Basic Troubleshooting Commands

The following example commands run on a BGP unnumbered configuration and show IPv6 next hops or the interface name for any IPv4 prefix.

To show a summary of the BGP configuration on the switch, run the NCLU net show bgp summary command or the vtysh show ip bgp summary command. For example:

cumulus@switch:~$ net show bgp summary
how bgp ipv4 unicast summary
=============================
BGP router identifier 10.10.10.1, local AS number 65101 vrf-id 0
BGP table version 88
RIB entries 25, using 4800 bytes of memory
Peers 5, using 106 KiB of memory
Peer groups 1, using 64 bytes of memory

Neighbor              V         AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd
spine01(swp51)        4      65199     31122     31194        0    0    0 1d01h44m            7
spine02(swp52)        4      65199     31060     31151        0    0    0 01:47:13            7
spine03(swp53)        4      65199     31150     31207        0    0    0 01:48:31            7
spine04(swp54)        4      65199     31042     31098        0    0    0 01:46:57            7
leaf02(peerlink.4094) 4      65101     30919     30913        0    0    0 01:47:43           12

Total number of neighbors 5


show bgp ipv6 unicast summary
=============================
% No BGP neighbors found

To determine if the sessions above are iBGP or eBGP sessions, look at the ASNs.

To view the routing table as defined by BGP, run the NCLU net show bgp ipv4 unicast command or the vtysh show ip bgp command. For example:

cumulus@leaf01:~$ net show bgp ipv4 unicast
GP table version is 88, local router ID is 10.10.10.1, vrf id 0
Default local pref 100, local AS 65101
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
* i10.0.1.1/32      peerlink.4094            0    100      0 ?
*>                  0.0.0.0                  0         32768 ?
*= 10.0.1.2/32      swp54                                  0 65199 65102 ?
*=                  swp52                                  0 65199 65102 ?
* i                 peerlink.4094                 100      0 65199 65102 ?
*=                  swp53                                  0 65199 65102 ?
*>                  swp51                                  0 65199 65102 ?
*= 10.0.1.254/32    swp54                                  0 65199 65132 ?
*=                  swp52                                  0 65199 65132 ?
* i                 peerlink.4094                 100      0 65199 65132 ?
*=                  swp53                                  0 65199 65132 ?
*>                  swp51                                  0 65199 65132 ?
*> 10.10.10.1/32    0.0.0.0                  0         32768 ?
*>i10.10.10.2/32    peerlink.4094            0    100      0 ?
*= 10.10.10.3/32    swp54                                  0 65199 65102 ?
*=                  swp52                                  0 65199 65102 ?
* i                 peerlink.4094                 100      0 65199 65102 ?
*=                  swp53                                  0 65199 65102 ?
*>                  swp51                                  0 65199 65102 ?
...

Displayed  13 routes and 42 total paths

To show a more detailed breakdown of a specific neighbor, run the NCLU net show bgp neighbor <neighbor> command or the vtysh show ip bgp neighbor <neighbor> command:

cumulus@switch:~$ net show bgp neighbor swp51
GP neighbor on swp51: fe80::7c41:fff:fe93:b711, remote AS 65199, local AS 65101, external link
Hostname: spine01
 Member of peer-group underlay for session parameters
  BGP version 4, remote router ID 10.10.10.101, local router ID 10.10.10.1
  BGP state = Established, up for 1d01h47m
  Last read 00:00:00, Last write 00:00:00
  Hold time is 9, keepalive interval is 3 seconds
  Neighbor capabilities:
    4 Byte AS: advertised and received
    AddPath:
      IPv4 Unicast: RX advertised IPv4 Unicast and received
    Extended nexthop: advertised and received
      Address families by peer:
                   IPv4 Unicast
    Route refresh: advertised and received(old & new)
    Address Family IPv4 Unicast: advertised and received
    Hostname Capability: advertised (name: leaf01,domain name: n/a) received (name: spine01,domain name: n/a)
    Graceful Restart Capability: advertised
  Graceful restart information:
    Local GR Mode: Helper*
    Remote GR Mode: Disable
    R bit: False
    Timers:
      Configured Restart Time(sec): 120
      Received Restart Time(sec): 0
  Message statistics:
    Inq depth is 0
    Outq depth is 0
                         Sent       Rcvd
    Opens:                  2          1
    Notifications:          0          0
    Updates:              309        237
    Keepalives:         30942      30943
    Route Refresh:          0          0
    Capability:             0          0
    Total:              31253      31181
  Minimum time between advertisement runs is 0 seconds

 For address family: IPv4 Unicast
  underlay peer-group member
  Update group 2, subgroup 2
  Packet Queue length 0
  Community attribute sent to this neighbor(all)
  7 accepted prefixes

  Connections established 1; dropped 0
  Last reset 1d01h47m,  No AFI/SAFI activated for peer
Local host: fe80::2294:15ff:fe02:7bbf, Local port: 179
Foreign host: fe80::7c41:fff:fe93:b711, Foreign port: 45548
Nexthop: 10.10.10.1
Nexthop global: fe80::2294:15ff:fe02:7bbf
Nexthop local: fe80::2294:15ff:fe02:7bbf
BGP connection: shared network
BGP Connect Retry Timer in Seconds: 10
Read thread: on  Write thread: on  FD used: 30

To see details of a specific route, such as from where it is received and where it is sent, run the NCLU net show bgp <route> command or the vtysh show ip bgp <route> command.

cumulus@switch:~$ net show bgp 10.10.10.3/32
GP routing table entry for 10.10.10.3/32
Paths: (5 available, best #5, table default)
  Advertised to non peer-group peers:
  spine01(swp51) spine02(swp52) spine03(swp53) spine04(swp54) leaf02(peerlink.4094)
  65199 65102
    fe80::8e24:2bff:fe79:7d46 from spine04(swp54) (10.10.10.104)
    (fe80::8e24:2bff:fe79:7d46) (used)
      Origin incomplete, valid, external, multipath
      Last update: Wed Oct  7 13:13:13 2020
  65199 65102
    fe80::841:43ff:fe27:caf from spine02(swp52) (10.10.10.102)
    (fe80::841:43ff:fe27:caf) (used)
      Origin incomplete, valid, external, multipath
      Last update: Wed Oct  7 13:13:14 2020
  65199 65102
    fe80::90b1:7aff:fe00:3121 from leaf02(peerlink.4094) (10.10.10.2)
      Origin incomplete, localpref 100, valid, internal
      Last update: Wed Oct  7 13:13:08 2020
  65199 65102
    fe80::48e7:fbff:fee9:5bcf from spine03(swp53) (10.10.10.103)
    (fe80::48e7:fbff:fee9:5bcf) (used)
      Origin incomplete, valid, external, multipath
      Last update: Wed Oct  7 13:13:13 2020
  65199 65102
    fe80::7c41:fff:fe93:b711 from spine01(swp51) (10.10.10.101)
    (fe80::7c41:fff:fe93:b711) (used)
      Origin incomplete, valid, external, multipath, bestpath-from-AS 65199, best (Older Path)
      Last update: Wed Oct  7 13:13:13 2020

Troubleshoot BGP Unnumbered

To verify that FRR learned the neighboring link-local IPv6 address through the IPv6 neighbor discovery router advertisements on a given interface, run the NCLU net show interface <interface> command or the vtysh show interface <interface> command.

If ipv6 nd suppress-ra is not enabled on both ends of the interface, Neighbor address(s): has the other end’s link-local address (the address that BGP uses when BGP is enabled on that interface).

IPv6 route advertisements (RAs) are automatically enabled on an interface with IPv6 addresses. The no ipv6 nd suppress-ra command is not needed for BGP unnumbered.

cumulus@switch:~$ net show interface swp51
    Name   MAC                Speed  MTU   Mode
--  -----  -----------------  -----  ----  -------
UP  swp51  10:d8:68:d4:a6:81  1G     9216  Default

Alias
-----
leaf to spine

cl-netstat counters
-------------------
RX_OK  RX_ERR  RX_DRP  RX_OVR  TX_OK  TX_ERR  TX_DRP  TX_OVR
-----  ------  ------  ------  -----  ------  ------  ------
 1874       0       0       0   1252       0       0       0

LLDP Details
------------
LocalPort  RemotePort(RemoteHost)
---------  ----------------------
swp51      swp1(spine01)

Routing
-------
  Interface swp51 is up, line protocol is up
  Link ups:       0    last: (never)
  Link downs:     0    last: (never)
  PTM status: disabled
  vrf: default
  OS Description: leaf to spine
  index 8 metric 0 mtu 9216 speed 1000
  flags: <UP,BROADCAST,RUNNING,MULTICAST>
  Type: Ethernet
  HWaddr: 10:d8:68:d4:a6:81
  inet6 fe80::12d8:68ff:fed4:a681/64
  Interface Type Other
  protodown: off
  ND advertised reachable time is 0 milliseconds
  ND advertised retransmit interval is 0 milliseconds
  ND advertised hop-count limit is 64 hops
  ND router advertisements sent: 217 rcvd: 216
  ND router advertisements are sent every 10 seconds
  ND router advertisements lifetime tracks ra-interval
  ND router advertisement default router preference is medium
  Hosts use stateless autoconfig for addresses.
  Neighbor address(s):
  inet6 fe80::f208:5fff:fe12:cc8c/128

Troubleshoot IPv4 Prefixes Learned with IPv6 Next Hops

To show IPv4 prefixes learned with IPv6 next hops, run the following commands.

The following examples show an IPv4 prefix learned from a BGP peer over an IPv6 session using IPv6 global addresses, but where the next hop installed by BGP is a link-local IPv6 address. This occurs when the session is directly between peers and both link-local and global IPv6 addresses are included as next hops in the BGP update for the prefix. If both global and link-local next hops exist, BGP prefers the link-local address for route installation.

cumulus@spine01:mgmt:~$ net show bgp ipv4 unicast summary
BGP router identifier 10.10.10.101, local AS number 65199 vrf-id 0
BGP table version 3
RIB entries 3, using 576 bytes of memory
Peers 1, using 21 KiB of memory

Neighbor                   V      AS   MsgRcvd   MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd
leaf01(2001:db8:2::a00:1) 4     65101       22        22        0    0    0  00:01:00           0

Total number of neighbors 1
cumulus@spine01:mgmt:~$ net show bgp ipv4 unicast
BGP table version is 3, local router ID is 10.10.10.101, vrf id 0
Default local pref 100, local AS 65199
Status codes:  s suppressed, d damped, h history, * valid, > best, = multipath,
               i internal, r RIB-failure, S Stale, R Removed
Nexthop codes: @NNN nexthop's vrf id, < announce-nh-self
Origin codes:  i - IGP, e - EGP, ? - incomplete

   Network          Next Hop                Metric LocPrf Weight Path
   10.10.10.101/32   fe80::a00:27ff:fea6:b9fe      0     0   32768 i

Displayed  1 routes and 1 total paths
cumulus@spine01:~$ net show bgp ipv4 unicast 10.10.10.101/32
BGP routing table entry for 10.10.10.101/32
Paths: (1 available, best #1, table default)
  Advertised to non peer-group peers:
  Leaf01(2001:db8:0002::0a00:1)
  3
    2001:db8:0002::0a00:1 from Leaf01(2001:db8:0002::0a00:1) (10.10.10.101)
    (fe80::a00:27ff:fea6:b9fe) (used)
      Origin IGP, metric 0, valid, external, bestpath-from-AS 3, best (First path received)
      AddPath ID: RX 0, TX 3
      Last update: Mon Oct 22 08:09:22 2018

The example output below shows the results of installing the route in the FRR RIB as well as the kernel FIB. Note that the next hop used for installation in the FRR RIB is the link-local IPv6 address, but then it is converted into an IPv4 link-local address as required for installation into the kernel FIB.

cumulus@spine01:~$ net show route 10.10.10.101/32
RIB entry for 10.10.10.101/32
===========================
Routing entry for 10.10.10.101/32
  Known via "bgp", distance 20, metric 0, best
  Last update 2d17h05m ago
  * fe80::a00:27ff:fea6:b9fe, via swp1

FIB entry for 10.10.10.101/32
===========================
10.10.10.101/32 via 169.254.10.101 dev swp1 proto bgp metric 20 onlink

If an IPv4 prefix is learned with only an IPv6 global next hop address (for example, when the route is learned through a route reflector), the command output shows the IPv6 global address as the next hop value and shows that it is learned recursively through the link-local address of the route reflector. When a global IPv6 address is used as a next hop for route installation in the FRR RIB, it is still converted into an IPv4 link-local address for installation into the kernel.

cumulus@leaf01:~$ net show bgp ipv4 unicast summary
BGP router identifier 10.10.10.1, local AS number 65101 vrf-id 0
BGP table version 1
RIB entries 1, using 152 bytes of memory
Peers 1, using 19 KiB of memory

Neighbor             V AS MsgRcvd  MsgSent  TblVer  InQ  OutQ  Up/Down  State/PfxRcd
Spine01(2001:db8:0002::0a00:2) 4 1   74       68         0     0     0     00:00:45      1

Total number of neighbors 1
cumulus@leaf01:~$ net show bgp ipv4 unicast
  BGP table version is 1, local router ID is 10.10.10.1
  Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
                i internal, r RIB-failure, S Stale, R Removed
  Origin codes: i - IGP, e - EGP, ? - incomplete

Network          Next Hop    Metric LocPrf Weight Path
*>i10.1.10.0/24 2001:2:2::4       0    100      0    i

Displayed 1 routes and 1 total paths
cumulus@leaf01:~$ net show bgp ipv4 unicast 10.10.10.101/32
BGP routing table entry for 10.10.10.101/32
Paths: (1 available, best #1, table default)
  Not advertised to any peer
  Local
  2001:2:2::4 from Spine01(2001:1:1::1) (10.10.10.104)
    Origin IGP, metric 0, localpref 100, valid, internal, bestpath-from-AS Local, best (First path received)
    Originator: 10.0.0.14, Cluster list: 10.10.10.111
    AddPath ID: RX 0, TX 5
    Last update: Mon Oct 22 14:25:30 2018
cumulus@leaf01:~$ net show route 10.10.10.1/32
RIB entry for 10.10.10.1/32
===========================
Routing entry for 10.10.10.1/32
  Known via "bgp", distance 200, metric 0, best
  Last update 00:01:13 ago
  2001:2:2::4 (recursive)
  * fe80::a00:27ff:fe5a:84ae, via swp1

FIB entry for 10.10.10.1/32
===========================
10.10.10.1/32 via 169.254.10.101 dev swp1 proto bgp metric 20 onlink

To have only IPv6 global addresses used for route installation into the FRR RIB, you must add an additional route map to the neighbor or peer group statement in the appropriate address family. When the route map command set ipv6 next-hop prefer-global is applied to a neighbor, if both a link-local and global IPv6 address are in the BGP update for a prefix, the IPv6 global address is preferred for route installation.

With this additional configuration, the output in the FRR RIB changes in the direct neighbor case as shown below:

router bgp 65101
  bgp router-id 10.10.10.1
  neighbor 2001:db8:2::a00:1 remote-as internal
  neighbor 2001:db8:2::a00:1 capability extended-nexthop
  !
  address-family ipv4 unicast
  neighbor 2001:db8:2::a00:1 route-map GLOBAL in
  exit-address-family
!
route-map GLOBAL permit 20
  set ipv6 next-hop prefer-global
!

The resulting FRR RIB output is as follows:

cumulus@leaf01:~$ net show route
Codes: K - kernel route, C - connected, S - static, R - RIP,
    O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
    T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
    F - PBR,
    > - selected route, * - FIB route

B 0.0.0.0/0 [200/0] via 2001:2:2::4, swp2, 00:01:00
K 0.0.0.0/0 [0/0] via 10.0.2.2, eth0, 1d02h29m
C>* 10.0.0.9/32 is directly connected, lo, 5d18h32m
C>* 10.0.2.0/24 is directly connected, eth0, 03:51:31
B>* 172.16.4.0/24 [200/0] via 2001:2:2::4, swp2, 00:01:00ß
C>* 172.16.10.0/24 is directly connected, swp3, 5d18h32m

When the route is learned through a route reflector, it appears like this:

router bgp 65101
  bgp router-id 10.10.10.1
  neighbor 2001:db8:2::a00:2 remote-as internal
  neighbor 2001:db8:2::a00:2 capability extended-nexthop
  !
  address-family ipv6 unicast
  neighbor 2001:db8:2::a00:2 activate
  neighbor 2001:db8:2::a00:2 route-map GLOBAL in
  exit-address-family
!
route-map GLOBAL permit 10
  set ipv6 next-hop prefer-global
cumulus@leaf01:~$ net show route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR,
       > - selected route, * - FIB route

B   0.0.0.0/0 [200/0] via 2001:2:2::4, 00:00:01
K   0.0.0.0/0 [0/0] via 10.0.2.2, eth0, 3d00h26m
C>* 10.0.0.8/32 is directly connected, lo, 3d00h26m
C>* 10.0.2.0/24 is directly connected, eth0, 03:39:18
C>* 172.16.3.0/24 is directly connected, swp2, 3d00h26m
B>  172.16.4.0/24 [200/0] via 2001:2:2::4 (recursive), 00:00:01
  *                         via 2001:1:1::1, swp1, 00:00:01
C>* 172.16.10.0/24 is directly connected, swp3, 3d00h26m

Check BGP Timer Settings

To check BGP timers, such as the BGP keepalive interval, hold time, and advertisement interval, run the NCLU net show bgp neighbor <peer> command or the vtysh show ip bgp neighbor <peer> command. For example:

cumulus@leaf01:~$ net show bgp neighbor swp51
GP neighbor on swp51: fe80::f208:5fff:fe12:cc8c, remote AS 65199, local AS 65101, external link
Hostname: spine01
 Member of peer-group underlay for session parameters
  BGP version 4, remote router ID 10.10.10.101, local router ID 10.10.10.1
  BGP state = Established, up for 06:50:58
  Last read 00:00:03, Last write 00:00:03
  Hold time is 9, keepalive interval is 3 seconds
  Neighbor capabilities:
    4 Byte AS: advertised and received
    AddPath:
      IPv4 Unicast: RX advertised IPv4 Unicast and received
    Extended nexthop: advertised and received
      Address families by peer:
                   IPv4 Unicast
    Route refresh: advertised and received(old & new)
    Address Family IPv4 Unicast: advertised and received
    Hostname Capability: advertised (name: leaf01,domain name: n/a) received (name: spine01,domain name: n/a)
    Graceful Restart Capability: advertised and received
      Remote Restart timer is 120 seconds
      Address families by peer:
        none
  Graceful restart information:
    End-of-RIB send: IPv4 Unicast
    End-of-RIB received: IPv4 Unicast
    Local GR Mode: Helper*
    Remote GR Mode: Helper
    R bit: True
    Timers:
      Configured Restart Time(sec): 120
      Received Restart Time(sec): 120
    IPv4 Unicast:
      F bit: False
      End-of-RIB sent: Yes
      End-of-RIB sent after update: No
      End-of-RIB received: Yes
      Timers:
        Configured Stale Path Time(sec): 360
  Message statistics:
    Inq depth is 0
    Outq depth is 0
                         Sent       Rcvd
    Opens:                  2          1
    Notifications:          0          0
    Updates:               54         59
    Keepalives:          8219       8219
    Route Refresh:          0          0
    Capability:             0          0
    Total:               8275       8279
  Minimum time between advertisement runs is 0 seconds

Neighbor State Change Log

Cumulus Linux records the changes that a neighbor goes through in syslog and in the /var/log/frr/frr.log file. For example:

020-10-05T15:51:32.621773-07:00 leaf01 bgpd[10104]: %NOTIFICATION: sent to neighbor peerlink.4094 6/7 (Cease/Connection collision resolution) 0 bytes
2020-10-05T15:51:32.623023-07:00 leaf01 bgpd[10104]: %ADJCHANGE: neighbor peerlink.4094(leaf02) in vrf default Up
2020-10-05T15:51:32.623156-07:00 leaf01 bgpd[10104]: %NOTIFICATION: sent to neighbor peerlink.4094 6/7 (Cease/Connection collision resolution) 0 bytes
2020-10-05T15:51:32.623496-07:00 leaf01 bgpd[10104]: %ADJCHANGE: neighbor peerlink.4094(leaf02) in vrf default Down No AFI/SAFI activated for peer
2020-10-05T15:51:33.040332-07:00 leaf01 bgpd[10104]: [EC 33554454] swp53 [Error] bgp_read_packet error: Connection reset by peer
2020-10-05T15:51:33.279468-07:00 leaf01 bgpd[10104]: [EC 33554454] swp52 [Error] bgp_read_packet error: Connection reset by peer
2020-10-05T15:51:33.339487-07:00 leaf01 bgpd[10104]: %ADJCHANGE: neighbor swp54(spine04) in vrf default Up
2020-10-05T15:51:33.340893-07:00 leaf01 bgpd[10104]: %ADJCHANGE: neighbor swp53(spine03) in vrf default Up
2020-10-05T15:51:33.341648-07:00 leaf01 bgpd[10104]: %ADJCHANGE: neighbor swp52(spine02) in vrf default Up
2020-10-05T15:51:33.342369-07:00 leaf01 bgpd[10104]: %ADJCHANGE: neighbor swp51(spine01) in vrf default Up
2020-10-05T15:51:33.627958-07:00 leaf01 bgpd[10104]: %ADJCHANGE: neighbor peerlink.4094(leaf02) in vrf default Up

Policy-based Routing

Typical routing systems and protocols forward traffic based on the destination address in the packet, which is used to look up an entry in a routing table. However, sometimes the traffic on your network requires a more hands-on approach. You might need to forward a packet based on the source address, the packet size, or other information in the packet header.

Policy-based routing (PBR) lets you make routing decisions based on filters that change the routing behavior of specific traffic so that you can override the routing table and influence where the traffic goes. For example, you can use PBR to help you reach the best bandwidth utilization for business-critical applications, isolate traffic for inspection or analysis, or manually load balance outbound traffic.

Policy-based routing is applied to incoming packets. All packets received on a PBR-enabled interface pass through enhanced packet filters that determine rules and specify where to forward the packets.

  • You can create a maximum of 255 PBR match rules and 256 next hop groups (this is the ECMP limit).
  • You can apply only one PBR policy per input interface.
  • You can match on source and destination IP address only.
  • PBR is not supported for VXLAN tunneling.
  • PBR is not supported on management interfaces, such as eth0.
  • A PBR rule cannot contain both IPv4 and IPv6 addresses.

Configure PBR

A PBR policy contains one or more policy maps. Each policy map:

To use PBR in Cumulus Linux, you define a PBR policy and apply it to the ingress interface (the interface must already have an IP address assigned). Traffic is matched against the match rules in sequential order and forwarded according to the set rule in the first match. Traffic that does not match any rule is passed onto the normal destination based routing mechanism.

For Tomahawk and Tomahawk+ platforms, you must configure the switch to operate in non-atomic mode, which offers better scaling as all TCAM resources are used to actively impact traffic. Add the line acl.non_atomic_update_mode = TRUE to the /etc/cumulus/switchd.conf file.

To configure a PBR policy:

When you commit a change that configures a new routing service such as PBR, the FRR daemon restarts and might interrupt network operations for other configured routing services.

  1. Configure the policy map. The example commands below configure a policy map called map1 with sequence number 1, that matches on destination address 10.1.2.0/24 and source address 10.1.4.1/24.

    If the IP address in the rule is 0.0.0.0/0 or ::/0, any IP address is a match. You cannot mix IPv4 and IPv6 addresses in a rule.

    cumulus@switch:~$ net add pbr-map map1 seq 1 match dst-ip 10.1.2.0/24
    cumulus@switch:~$ net add pbr-map map1 seq 1 match src-ip 10.1.4.1/24
    
  2. Either apply a next hop or a next hop group to the policy map. The example command below applies the next hop 192.168.0.31 on the output interface swp2 and VRF rocket to the map1 policy map. The output interface and VRF are optional, however, you must specify the VRF you want to use for resolution if the next hop is not in the default VRF.

    cumulus@switch:~$ net add pbr-map map1 seq 1 set nexthop 192.168.0.31 swp2 nexthop-vrf rocket
    

    To apply a next hop group (for ECMP) to the policy map, first create the next hop group, then apply the group to the policy map. The example commands below create a next hop group called group1 that contains the next hop 192.168.0.21 on output interface swp1 and VRF rocket, and the next hop 192.168.0.22, then applies the next hop group group1 to the map1 policy map.

    The output interface and VRF are optional. However, you must specify the VRF if the next hop is not in the default VRF.

    cumulus@switch:~$ net add nexthop-group group1 nexthop 192.168.0.21 swp1 nexthop-vrf rocket
    cumulus@switch:~$ net add nexthop-group group1 nexthop 192.168.0.22
    cumulus@switch:~$ net add pbr-map map1 seq 1 set nexthop-group group1
    
  3. Assign the PBR policy to an ingress interface. The example command below assigns the PBR policy map1 to interface swp51:

    cumulus@switch:~$ net add interface swp51 pbr-policy map1
    cumulus@switch:~$ net pending
    cumulus@switch:~$ net commit
    

You can only set one policy per interface.

  1. Enable the pbrd service in the /etc/frr/daemons file:

    cumulus@leaf01:~$ sudo nano /etc/frr/daemons
    ...
    bgpd=yes
    ospfd=no
    ospf6d=no
    ripd=no
    ripngd=no
    isisd=no
    fabricd=no
    pimd=no
    ldpd=no
    nhrpd=no
    eigrpd=no
    babeld=no
    sharpd=no
    pbrd=yes
    ...
    
  2. Restart FRR with this command:

cumulus@switch:~$ sudo systemctl restart frr.service

Restarting FRR restarts all the routing protocol daemons that are enabled and running.

  1. Configure the policy map. The example commands below configure a policy map called map1 with sequence number 1, that matches on destination address 10.1.2.0/24 and source address 10.1.4.1/24.

    cumulus@switch:~$ sudo vtysh
    
    switch# configure terminal
    switch(config)# pbr-map map1 seq 1 
    switch(config-pbr-map)# match dst-ip 10.1.2.0/24
    switch(config-pbr-map)# match src-ip 10.1.4.1/24 
    

    If the IP address in the rule is 0.0.0.0/0 or ::/0, any IP address is a match. You cannot mix IPv4 and IPv6 addresses in a rule.

  2. Either apply a next hop or a next hop group to the policy map. The example command below applies the next hop 192.168.0.31 on the output interface swp2 and VRF rocket to the map1 policy map. The output interface and VRF are optional, however, you must specify the VRF you want to use for resolution if the next hop is not in the default VRF.

    switch(config-pbr-map)# set nexthop 192.168.0.31 swp2 nexthop-vrf rocket
    switch(config-pbr-map)# exit
    switch(config)#
    

    To apply a next hop group (for ECMP) to the policy map, first create the next hop group, then apply the group to the policy map. The example commands below create a next hop group called group1 that contains the next hop 192.168.0.21 on output interface swp1 and VRF rocket, and the next hop 192.168.0.22, then applies the next hop group group1 to the map1 policy map.

    The output interface and VRF are optional. However, you must specify the VRF if the next hop is not in the default VRF.

    switch(config)# nexthop-group group1
    switch(config-nh-group)# nexthop 192.168.0.21 swp1 nexthop-vrf rocket
    switch(config-nh-group)# nexthop 192.168.0.22
    switch(config-nh-group)# exit
    switch(config)# pbr-map map1 seq 1
    switch(config-pbr-map)# set nexthop-group group1
    switch(config-pbr-map)# exit
    switch(config)#
    
  3. Assign the PBR policy to an ingress interface. The example command below assigns the PBR policy map1 to interface swp51:

    switch(config)# interface swp51
    switch(config-if)# pbr-policy map1
    switch(config-if)# end
    switch# write memory
    switch# exit
    cumulus@switch:~$
    

You can only set one policy per interface.

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
interface swp51
 pbr-policy map1
...
nexthop-group group1
 nexthop 192.168.0.21 swp1 nexthop-vrf rocket
 nexthop 192.168.0.22
...
pbr-map map1 seq 1
 match dst-ip 10.1.2.0/24
 match src-ip 0.0.0.0/0
 set nexthop nexthop-group group1
...

Configuration Example

In the following example, the PBR-enabled switch has a PBR policy to route all traffic from the Internet to a server that performs anti-DDOS. The traffic returns to the PBR-enabled switch after being cleaned and is then passed onto the regular destination based routing mechanism.

The configuration for the example above is:

cumulus@switch:~$ net add pbr-map map1 seq 1 match src-ip 0.0.0.0/0
cumulus@switch:~$ net add pbr-map map1 seq 1 set nexthop 192.168.0.32
cumulus@switch:~$ net add interface swp51 pbr-policy map1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# pbr-map map1 seq 1 
switch(config-pbr-map)# match src-ip 0.0.0.0/0
switch(config-pbr-map)# set nexthop 192.168.0.32
switch(config-pbr-map)# exit
switch(config)# interface swp51
switch(config-if)# pbr-policy map1
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
interface swp51
 pbr-policy map1
...
pbr-map map1 seq 1
 match src-ip 0.0.0.0/0
 set nexthop 192.168.0.32
...

Review Your Configuration

Use the following commands to see the configured PBR policies.

To see the policies applied to all interfaces on the switch, run the NCLU net show pbr interface command or the vtysh show pbr interface command. For example:

cumulus@switch:~$ net show pbr interface
swp55s3(67) with pbr-policy map1

To see the policies applied to a specific interface on the switch, add the interface name at the end of the command; for example, net show pbr interface swp51 (or show pbr interface swp51 in vtysh).

To see information about all policies, including mapped table and rule numbers, run the NCLU net show pbr map command or the vtysh show pbr map command. If the rule is not set, you see a reason why.

cumulus@switch:~$ net show pbr map
 pbr-map map1 valid: 1
  Seq: 700 rule: 999 Installed: 1(1) Reason: Valid
      SRC Match: 10.0.0.1/32
  nexthop 192.168.0.32
      Installed: 1(1) Tableid: 10003
  Seq: 701 rule: 1000 Installed: 1(2) Reason: Valid
      SRC Match: 90.70.0.1/32
  nexthop 192.168.0.32
      Installed: 1(1) Tableid: 10004

To see information about a specific policy, what it matches, and with which interface it is associated, add the map name at the end of the command; for example, net show pbr map map1 (or show pbr map map1 in vtysh).

To see information about all next hop groups, run the NCLU net show pbr nexthop-group command or the vtysh show pbr nexthop-group command.

cumulus@switch:~$ net show pbr nexthop-group
Nexthop-Group: map1701 Table: 10004 Valid: 1 Installed: 1
Valid: 1 nexthop 10.1.1.2
Nexthop-Group: map1700 Table: 10003 Valid: 1 Installed: 1
Valid: 1 nexthop 10.1.1.2
Nexthop-Group: group1 Table: 10000 Valid: 1 Installed: 1
Valid: 1 nexthop 192.168.10.0 bond1
Valid: 1 nexthop 192.168.10.2
Valid: 1 nexthop 192.168.10.3 vlan70
Nexthop-Group: group2 Table: 10001 Valid: 1 Installed: 1
Valid: 1 nexthop 192.168.8.1
Valid: 1 nexthop 192.168.8.2
Valid: 1 nexthop 192.168.8.3

To see information about a specific next hop group, add the group name at the end of the command; for example, net show pbr nexthop-group group1 (or show pbr nexthop-group group1 in vtysh).

A new Linux routing table ID is used for each next hop and next hop group.

Modifying Existing PBR Rules

When you want to change or extend an existing PBR rule, you must first delete the conditions in the rule, then add the rule back with the modification or addition.

The example below shows an existing configuration.

cumulus@switch:~$ net show pbr map
Seq: 4 rule: 303 Installed: 1(10) Reason: Valid
    SRC Match: 10.1.4.1/24
    DST Match: 10.1.2.0/24
 nexthop 192.168.0.21
    Installed: 1(1) Tableid: 10009

The NCLU commands for the above configuration are:

cumulus@switch:~$ net add pbr-map pbr-policy seq 4 match src-ip 10.1.4.1/24
cumulus@switch:~$ net add pbr-map pbr-policy seq 4 match dst-ip 10.1.2.0/24
cumulus@switch:~$ net add pbr-map pbr-policy seq 4 set nexthop 192.168.0.21

To change the source IP match from 10.1.4.1/24 to 10.1.4.2/24, you must delete the existing sequence by explicitly specifying the match/set condition. For example:

cumulus@switch:~$ net del pbr-map pbr-policy seq 4 match src-ip 10.1.4.1/24
cumulus@switch:~$ net del pbr-map pbr-policy seq 4 match dst-ip 10.1.2.0/24
cumulus@switch:~$ net del pbr-map pbr-policy seq 4 set nexthop 192.168.0.21
cumulus@switch:~$ net commit

Add the new rule with the following NCLU commands:

cumulus@switch:~$ net add pbr-map pbr-policy seq 4 match src-ip 10.1.4.2/24
cumulus@switch:~$ net add pbr-map pbr-policy seq 4 match dst-ip 10.1.2.0/24
cumulus@switch:~$ net add pbr-map pbr-policy seq 4 set nexthop 192.168.0.21
cumulus@switch:~$ net commit

Run the net show pbr map command to verify that the rule has the updated source IP match:

cumulus@switch:~$ net show pbr map
Seq: 4 rule: 303 Installed: 1(10) Reason: Valid
     SRC Match: 10.1.4.2/24
     DST Match: 10.1.2.0/24
   nexthop 192.168.0.21
     Installed: 1(1) Tableid: 10012

Run the ip rule show command to verify the entry in the kernel:

cumulus@switch:~$ ip rule show

303:	from 10.1.4.1/24 to 10.1.4.2 iif swp16 lookup 10012

Run the following command to verify switchd:

cumulus@switch:~$ sudo cat /cumulus/switchd/run/iprule/show | grep 303 -A 1
303: from 10.1.4.1/24 to 10.1.4.2 iif swp16 lookup 10012
     [hwstatus: unit: 0, installed: yes, route-present: yes, resolved: yes, nh-valid: yes, nh-type: nh, ecmp/rif: 0x1, action: route,  hitcount: 0]

The example below shows an existing configuration, where only one source IP match is configured:

Seq: 3 rule: 302 Installed: 1(9) Reason: Valid
	SRC Match: 10.1.4.1/24
nexthop 192.168.0.21
	Installed: 1(1) Tableid: 10008

The NCLU commands for the above configuration are:

net add pbr-map pbr-policy seq 3 match src-ip 10.1.4.1/24
net add pbr-map pbr-policy seq 3 set nexthop 192.168.0.21

To add a destination IP match to the rule, you must delete the existing rule sequence:

net del pbr-map pbr-policy seq 3 match src-ip 10.1.4.1/24
net del pbr-map pbr-policy seq 3 set nexthop 192.168.0.21
net commit

Add back the source IP match and nexthop condition, and add the new destination IP match (dst-ip 10.1.2.0/24):

net add pbr-map pbr-policy seq 3 match src-ip 10.1.4.1/24
net add pbr-map pbr-policy seq 3 match dst-ip 10.1.2.0/24
net add pbr-map pbr-policy seq 3 set nexthop 192.168.0.21
net commit

Run the net show pbr map command to verify the update:

Seq: 3 rule: 302 Installed: 1(9) Reason: Valid
    SRC Match: 10.1.4.1/24
    DST Match: 10.1.2.0/24
   nexthop 192.168.0.21
    Installed: 1(1) Tableid: 10013

Run the ip rule show command to verify the entry in the kernel:

302:   from 10.1.4.1/24 to 10.1.2.0 iif swp16 lookup 10013

Run the following command to verify switchd:

cumulus@mlx-2400-91:~$ cat /cumulus/switchd/run/iprule/show | grep 302 -A 1
302: from 10.1.4.1/24 to 10.1.2.0 iif swp16 lookup 10013
     [hwstatus: unit: 0, installed: yes, route-present: yes, resolved: yes, nh-valid: yes, nh-type: nh, ecmp/rif: 0x1, action: route,  hitcount: 0]

Delete PBR Rules and Policies

You can delete a PBR rule, a next hop group, or a policy. The following commands provide examples.

Use caution when deleting PBR rules and next hop groups, as you might create an incorrect configuration for the PBR policy.

The following examples show how to delete a PBR rule match:

cumulus@switch:~$ net del pbr-map map1 seq 1 match dst-ip 10.1.2.0/24
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following examples show how to delete a next hop from a group:

cumulus@switch:~$ net del nexthop-group group1 nexthop 192.168.0.32 swp1 nexthop-vrf rocket
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following examples show how to delete a next hop group:

cumulus@switch:~$ net del nexthop-group group1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following examples show how to delete a PBR policy so that the PBR interface is no longer receiving PBR traffic:

cumulus@switch:~$ net del interface swp3 pbr-policy map1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following examples show how to delete a PBR rule:

cumulus@switch:~$ net del pbr-map map1 seq 1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following examples show how to delete a PBR rule match:

cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# pbr-map map1 seq 1
switch(config-pbr-map)# no match dst-ip 10.1.2.0/24
switch(config-pbr-map)# end
switch# write memory
switch# exit
cumulus@switch:~$

The following examples show how to delete a next hop from a group:

cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# nexthop-group group1
switch(config-nh-group)# no nexthop 192.168.0.32 swp1 nexthop-vrf rocket
switch(config-nh-group)# end
switch# write memory
switch# exit
cumulus@switch:~$

The following examples show how to delete a next hop group:

cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# no set nexthop-group group1
switch(config)# end
switch# write memory
switch# exit
cumulus@switch:~$

The following examples show how to delete a PBR policy so that the PBR interface is no longer receiving PBR traffic:

cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# interface swp51
switch(config-if)# no pbr-policy map1
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

The following examples show how to delete a PBR rule:

cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# no pbr-map map1 seq 1
switch(config)# end
switch# write memory
switch# exit
cumulus@switch:~$

If a PBR rule has multiple conditions (for example, a source IP match and a destination IP match), but you only want to delete one condition, you have to delete all conditions first, then re-add the ones you want to keep.

The example below shows an existing configuration that has a source IP match and a destination IP match.

Seq: 6 rule: 305 Installed: 1(12) Reason: Valid
   SRC Match: 10.1.4.1/24
   DST Match: 10.1.2.0/24
   nexthop 192.168.0.21
   Installed: 1(1) Tableid: 10011

The NCLU commands for the above configuration are:

net add pbr-map pbr-policy seq 6 match src-ip 10.1.4.1/24
net add pbr-map pbr-policy seq 6 match dst-ip 10.1.2.0/24
net add pbr-map pbr-policy seq 6 set nexthop 192.168.0.21

To remove the destination IP match, you must first delete all existing conditions defined under this sequence:

net del pbr-map pbr-policy seq 6 match src-ip 10.1.4.1/24
net del pbr-map pbr-policy seq 6 match dst-ip 10.1.2.0/24
net del pbr-map pbr-policy seq 6 set nexthop 192.168.0.21
net commit

Then, add back the conditions you want to keep:

net add pbr-map pbr-policy seq 6 match src-ip 10.1.4.1/24
net add pbr-map pbr-policy seq 6 set nexthop 192.168.0.21
net commit

Bidirectional Forwarding Detection - BFD

Bidirectional Forwarding Detection (BFD) provides low overhead and rapid detection of failures in the paths between two network devices. It provides a unified mechanism for link detection over all media and protocol layers. Use BFD to detect failures for IPv4 and IPv6 single or multihop paths between any two network devices, including unidirectional path failure detection.

Cumulus Linux does not support:

  • BFD demand mode
  • Dynamic BFD timer negotiation on an existing session. Any change to the timer values takes effect only when the session goes down and comes back up.

BFD Multihop Routed Paths

BFD multihop sessions are built over arbitrary paths between two systems, which results in some complexity that does not exist for single hop sessions. Here are some best practices for using multihop paths:

Configure BFD

You can configure BFD by either using FRRouting (with NCLU or vtysh commands) or by specifying the configuration in the PTM `topology.dot` file. However, the topology file has some limitations:

Use FRRouting to register multihop peers with PTM and BFD as well as to monitor the connectivity to the remote BGP multihop peer. FRRouting can dynamically register and unregister both IPv4 and IPv6 peers with BFD when the BFD-enabled peer connectivity is established or de-established. Also, you can configure BFD parameters for each BGP or OSPF peer.

The BFD parameter configured in the topology file is given higher precedence over the client-configured BFD parameters for a BFD session that has been created by both the topology file and FRRouting.

BFD requires an IP address for any interface on which it is configured. The neighbor IP address for a single hop BFD session must be in the ARP table before BFD can start sending control packets.

When you configure BFD, you can set the following parameters for both IPv4 and IPv6 sessions. If you do not set these parameters, the default values are used.

BFD in BGP

When you configure BFD in BGP, neighbors are registered and deregistered with PTM dynamically.

To configure BFD in BGP, run the following commands.

You can configure BFD for a peer group or for an individual neighbor.

The following example configures BFD for swp1 and uses the default intervals.

cumulus@switch:~$ net add bgp neighbor swp1 bfd
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following example configures BFD for the peer group fabric and sets the interval multiplier to 4, the minimum interval between received BFD control packets to 400, and the minimum interval for sending BFD control packets to 400.

cumulus@switch:~$ net add bgp neighbor fabric bfd 4 400 400
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following example configures BFD for swp1 and uses the default intervals:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65000
switch(config-router)# neighbor swp1 bfd
switch(config-router)# exit
switch(config)# exit
switch# write mem
switch# exit
cumulus@switch:~$

The following example configures BFD for the peer group fabric and sets the interval multiplier to 4, the minimum interval between received BFD control packets to 400, and the minimum interval for sending BFD control packets to 400.

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65000
switch(config-router)# neighbor fabric bfd 4 400 400
switch(config-router)# exit
switch(config)# exit
switch# write mem
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65000
neighbor fabric bfd 4 400 400
...

To see neighbor information in BGP, including BFD status, run the NCLU net show bgp neighbor <interface> command or the vtysh show ip bgp neighbor <interface> command. For example:

cumulus@switch:~$ net show bgp neighbor swp1
...
BFD: Type: single hop
  Detect Mul: 3, Min Rx interval: 300, Min Tx interval: 300
  Status: Down, Last update: 0:00:00:08
...

BFD in OSPF

When you enable or disable BFD in OSPF, neighbors are registered and de-registered dynamically with PTM. When BFD is enabled on the interface, a neighbor is registered with BFD when two-way adjacency is established and deregistered when adjacency goes down. The BFD configuration is per interface and any IPv4 and IPv6 neighbors discovered on that interface inherit the configuration.

To configure BFD in OSPF, run the following commands.

The following example configures BFD in OSPFv3 for interface swp1 and sets interval multiplier to 4, the minimum interval between received BFD control packets to 400, and the minimum interval for sending BFD control packets to 400.

cumulus@switch:~$ net add interface swp1 ospf6 bfd 4 400 400
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The following example configures BFD in OSPFv3 for interface swp1 and sets interval multiplier to 4, the minimum interval between received BFD control packets to 400, and the minimum interval for sending BFD control packets to 400.

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface swp1
switch(config-if)# ipv6 ospf6 bfd 4 400 400
switch(config-if)# exit
switch(config)# exit
switch# write mem
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
interface swp1
  ipv6 ospf6 bfd 4 400 400
  ...

You can run different commands to show neighbor information in OSPF, including BFD status.

cumulus@switch:~$ net show ospf6 interface swp2s0
swp2s0 is up, type BROADCAST
  Interface ID: 4
  Internet Address:
    inet : 11.0.0.21/30
    inet6: fe80::4638:39ff:fe00:6c8e/64
  Instance ID 0, Interface MTU 1500 (autodetect: 1500)
  MTU mismatch detection: enabled
  Area ID 0.0.0.0, Cost 10
  State PointToPoint, Transmit Delay 1 sec, Priority 1
  Timer intervals configured:
    Hello 10, Dead 40, Retransmit 5
  DR: 0.0.0.0 BDR: 0.0.0.0
  Number of I/F scoped LSAs is 2
    0 Pending LSAs for LSUpdate in Time 00:00:00 [thread off]
    0 Pending LSAs for LSAck in Time 00:00:00 [thread off]
  BFD: Detect Mul: 3, Min Rx interval: 300, Min Tx interval: 300
cumulus@switch:~$ net show ospf6 neighbor detail
  Neighbor 0.0.0.4%swp2s0
    Area 0.0.0.0 via interface swp2s0 (ifindex 4)
    His IfIndex: 3 Link-local address: fe80::202:ff:fe00:a
    State Full for a duration of 02:32:33
    His choice of DR/BDR 0.0.0.0/0.0.0.0, Priority 1
    DbDesc status: Slave SeqNum: 0x76000000
    Summary-List: 0 LSAs
    Request-List: 0 LSAs
    Retrans-List: 0 LSAs
    0 Pending LSAs for DbDesc in Time 00:00:00 [thread off]
    0 Pending LSAs for LSReq in Time 00:00:00 [thread off]
    0 Pending LSAs for LSUpdate in Time 00:00:00 [thread off]
    0 Pending LSAs for LSAck in Time 00:00:00 [thread off]
    BFD: Type: single hop
      Detect Mul: 3, Min Rx interval: 300, Min Tx interval: 300
      Status: Up, Last update: 0:00:00:20

Scripts

ptmd executes scripts at /etc/ptm.d/bfd-sess-down when BFD sessions go down and /etc/ptm.d/bfd-sess-up when BFD sessions goes up. Modify these default scripts as needed.

Echo Function

Cumulus Linux supports the echo function for IPv4 single hops only, and with the asynchronous operating mode only (Cumulus Linux does not support demand mode).

Use the echo function to test the forwarding path on a remote system. To enable the echo function, set echoSupport to 1 in the topology file.

After the echo packets are looped by the remote system, the BFD control packets can be sent at a much lower rate. You configure this lower rate by setting the slowMinTx parameter in the topology file to a non-zero value in milliseconds.

You can use more aggressive detection times for echo packets because the round-trip time is reduced; echo packets access the forwarding path. You can configure the detection interval by setting the echoMinRx parameter in the topology file. The minimum setting is 50 milliseconds. After configured, BFD control packets are sent out at this required minimum echo Rx interval. This indicates to the peer that the local system can loop back the echo packets. Echo packets are transmitted if the peer supports receiving echo packets.

About the Echo Packet

BFD echo packets are encapsulated into UDP packets over destination and source UDP port number 3785. The BFD echo packet format is vendor-specific and has not been defined in the RFC. BFD echo packets that originate from Cumulus Linux are 8 bytes long and have the following format:

0 1 2 3
Version Length Reserved Reserved
My Discriminator

Where:

Transmit and Receive Echo Packets

BFD echo packets are transmitted for a BFD session only when the peer has advertised a non-zero value for the required minimum echo Rx interval (the echoMinRx setting) in the BFD control packet when the BFD session starts. The transmit rate of the echo packets is based on the peer advertised echo receive value in the control packet.

BFD echo packets are looped back to the originating node for a BFD session only if locally the echoMinRx and echoSupport are configured to a non-zero values.

Echo Function Parameters

You configure the echo function by setting the following parameters in the topology file at the global, template and port level:

Troubleshooting

To troubleshoot BFD, run the NCLU net show bfd sessions or net show bfd sessions detail command.

cumulus@switch:~$ net show bfd sessions detail

----------------------------------------------------------------------------------------
port  peer                 state  local  type       diag  det   tx_timeout  rx_timeout  
                                                          mult
----------------------------------------------------------------------------------------
swp1  fe80::202:ff:fe00:1  Up     N/A    singlehop  N/A   3     300         900
swp1  3101:abc:bcad::2     Up     N/A    singlehop  N/A   3     300         900

#continuation of output
---------------------------------------------------------------------
echo        echo        max      rx_ctrl  tx_ctrl  rx_echo  tx_echo
tx_timeout  rx_timeout  hop_cnt
---------------------------------------------------------------------
0           0           N/A      187172   185986   0        0
0           0           N/A      501      533      0        0

You can also run the Linux ptmctl -b command.

Equal Cost Multipath Load Sharing - Hardware ECMP

Cumulus Linux supports hardware-based equal cost multipath (ECMP) load sharing. ECMP is enabled by default in Cumulus Linux. Load sharing occurs automatically for all routes with multiple next hops installed. ECMP load sharing supports both IPv4 and IPv6 routes.

Equal Cost Routing

ECMP operates only on equal cost routes in the Linux routing table.

In this example, the 10.1.1.0/24 route has two possible next hops that have been installed in the routing table:

cumulus@switch:~$ ip route show 10.1.1.0/24
10.1.1.0/24  proto zebra  metric 20
  nexthop via 192.168.1.1 dev swp1 weight 1 onlink
  nexthop via 192.168.2.1 dev swp2 weight 1 onlink

For routes to be considered equal they must:

In Cumulus Linux, the BGP maximum-paths setting is enabled, so multiple routes are installed by default. See ECMP under BGP for more information.

ECMP Hashing

When multiple routes are installed in the routing table, a hash is used to determine which path a packet follows.

Cumulus Linux hashes on the following fields:

Further, on switches with Spectrum ASICs, Cumulus Linux hashes on these additional fields:

For TCP/UDP frames, Cumulus Linux also hashes on:

To prevent out of order packets, ECMP hashing is done on a per-flow basis; all packets with the same source and destination IP addresses and the same source and destination ports always hash to the same next hop. ECMP hashing does not keep a record of flow states.

ECMP hashing does not keep a record of packets that have hashed to each next hop and does not guarantee that traffic sent to each next hop is equal.

Use cl-ecmpcalc to Determine the Hash Result

Because the hash is deterministic and always provides the same result for the same input, you can query the hardware and determine the hash result of a given input. This is useful when determining exactly which path a flow takes through a network.

On Cumulus Linux, use the cl-ecmpcalc command to determine a hardware hash result.

To use cl-ecmpcalc, all fields that are used in the hash must be provided. This includes ingress interface, layer 3 source IP, layer 3 destination IP, layer 4 source port, and layer 4 destination port.

cumulus@switch:~$ sudo cl-ecmpcalc -i swp1 -s 10.0.0.1 -d 10.0.0.1 -p tcp --sport 20000 --dport 80
ecmpcalc: will query hardware
swp3

If any field is omitted, cl-ecmpcalc fails.

cumulus@switch:~$ sudo cl-ecmpcalc -i swp1 -s 10.0.0.1 -d 10.0.0.1 -p tcp
ecmpcalc: will query hardware
usage: cl-ecmpcalc [-h] [-v] [-p PROTOCOL] [-s SRC] [--sport SPORT] [-d DST]
                   [--dport DPORT] [--vid VID] [-i IN_INTERFACE]
                   [--sportid SPORTID] [--smodid SMODID] [-o OUT_INTERFACE]
                   [--dportid DPORTID] [--dmodid DMODID] [--hardware]
                   [--nohardware] [-hs HASHSEED]
                   [-hf HASHFIELDS [HASHFIELDS ...]]
                   [--hashfunction {crc16-ccitt,crc16-bisync}] [-e EGRESS]
                   [-c MCOUNT]
cl-ecmpcalc: error: --sport and --dport required for TCP and UDP frames

cl-ecmpcalc Limitations

cl-ecmpcalc can only take input interfaces that can be converted to a single physical port in the port tab file, such as the physical switch ports (swp). Virtual interfaces like bridges, bonds, and subinterfaces are not supported.

cl-ecmpcalc is supported only on switches with the Mellanox Spectrum and the Broadcom Maverick, Tomahawk, Trident II, Trident II+ and Trident3 chipsets.

ECMP Hash Buckets

When multiple routes are installed in the routing table, each route is assigned to an ECMP bucket. When the ECMP hash is executed the result of the hash determines which bucket gets used.

In the following example, four next hops exist. Three different flows are hashed to different hash buckets. Each next hop is assigned to a unique hash bucket.

Add a Next Hop

When a next hop is added, a new hash bucket is created. The assignment of next hops to hash buckets, as well as the hash result, might change when additional next hops are added.

A new next hop is added and a new hash bucket is created. As a result, the hash and hash bucket assignment changes, causing the existing flows to be sent to different next hops.

Remove a Next Hop

When a next hop is removed, the remaining hash bucket assignments might change, again, potentially changing the next hop selected for an existing flow.

A next hop fails and the next hop and hash bucket are removed. The remaining next hops might be reassigned.

In most cases, the modification of hash buckets has no impact on traffic flows as traffic is being forwarded to a single end host. In deployments where multiple end hosts are using the same IP address (anycast), resilient hashing must be used.

Configure a Hash Seed to Avoid Hash Polarization

It is useful to have a unique hash seed for each switch. This helps avoid hash polarization, a type of network congestion that occurs when multiple data flows try to reach a switch using the same switch ports.

The hash seed is set by the ecmp_hash_seed parameter in the /etc/cumulus/datapath/traffic.conf file. It is an integer with a value from 0 to 4294967295. If you do not specify a value, switchd creates a randomly generated seed instead.

For example, to set the hash seed to 50, run the following commands:

cumulus@switch:~$ net add forwarding ecmp hash-seed 50
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit /etc/cumulus/datapath/traffic.conf file. For example:

cumulus@switch:~$ sudo nano /etc/cumulus/datapath/traffic.conf
...
#Specify the hash seed for Equal cost multipath entries
ecmp_hash_seed = 50
...

Restart the switchd service:

cumulus@switch:~$ sudo systemctl restart switchd.service

ECMP Custom Hashing

Custom hashing is supported on Mellanox switches.

You can configure the set of fields used to hash upon during ECMP load balancing. For example, if you do not want to use source or destination port numbers in the hash calculation, you can disable the source port and destination port fields.

You can enable/disable the following fields:

You can also enable/disable these Inner header fields:

To configure custom hashing, edit the /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf file:

  1. To enable custom hashing, uncomment the hash_config.enable = true line.

  2. To enable a field, set the field to true. To disable a field, set the field to false.

  3. Restart the switchd service:

    cumulus@switch:~$ sudo systemctl restart switchd.service
    

The following shows an example datapath.conf file:

cumulus@switch:~$ sudo nano /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf
...
# HASH config for ECMP to enable custom fields
# Fields will be applicable for ECMP hash
# calculation
#Note: Hash seed can be configured in traffic.conf
#/etc/cumulus/datapath/traffic.conf
#
# Uncomment to enable custom fields configured below
hash_config.enable = true

#symmetric hash will get disabled
#if sip/dip or sport/dport are not enabled in pair
#hash Fields available ( assign true to enable)
#ip protocol
hash_config.ip_prot = true
#source ip
hash_config.sip = true
#destination ip
hash_config.dip = true
#source port
hash_config.sport = false
#destination port
hash_config.dport = false
#ipv6 flow label
hash_config.ip6_label = true
#ingress interface
hash_config.ing_intf = false

#inner fields for  IPv4-over-IPv6 and IPv6-over-IPv6
hash_config.inner_ip_prot = false
hash_config.inner_sip = false
hash_config.inner_dip = false
hash_config.inner_sport = false
hash_config.inner_dport = false
hash_config.inner_ip6_label = false
# Hash config end #
...

Symmetric hashing is enabled by default on Mellanox switches. Make sure that the settings for the source IP (hash_config.sip) and destination IP (hash_config.dip) fields match, and that the settings for the source port (hash_config.sport) and destination port (hash_config.dport) fields match; otherwise symmetric hashing is disabled automatically. You can disable symmetric hashing manually in the /etc/cumulus/datapath/traffic.conf file by setting symmetric_hash_enable = FALSE.

Resilient Hashing

In Cumulus Linux, when a next hop fails or is removed from an ECMP pool, the hashing or hash bucket assignment can change. For deployments where there is a need for flows to always use the same next hop, like TCP anycast deployments, this can create session failures.

Resilient hashing is an alternate mechanism for managing ECMP groups. The ECMP hash performed with resilient hashing is exactly the same as the default hashing mode. Only the method in which next hops are assigned to hash buckets differs — they’re assigned to buckets by hashing their header fields and using the resulting hash to index into the table of 2^n hash buckets. Since all packets in a given flow have the same header hash value, they all use the same flow bucket.

Resilient hashing supports both IPv4 and IPv6 routes.

Resilient hashing behaves slightly differently depending upon whether you are running Cumulus Linux on a switch with a Broadcom ASIC or Mellanox ASIC. The differences are described below.

Resilient hashing is not enabled by default. See below for steps on configuring it.

Resilient Hashing on Broadcom Switches

Resilient hashing is supported only on switches with the Broadcom Tomahawk, Trident II, Trident II+, and Trident3 ASICs. You can run net show system to determine the ASIC.

The Broadcom ASIC assigns packets to hash buckets and assigns hash buckets to next hops as follows:

Resilient Hashing on Mellanox Switches

A Mellanox switch has two unique options for configuring resilient hashing, both of which you configure in the /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf​ file. The recommended values for these options depend largely on the desired outcome for a specific network implementation — the number and duration of flows, and the importance of keeping these flows pinned without interruption.

Note that when you configure these options, a new next hop might not get populated for a long time.

The Mellanox Spectrum ASIC assigns packets to hash buckets and assigns hash buckets to next hops as follows. It also runs a background thread that monitors and may migrate buckets between next hops to rebalance the load.

As a result, any flow may be migrated to any next hop, depending on flow activity and load balance conditions; over time, the flow may get pinned, which is the default setting and behavior.

Resilient Hash Buckets

When resilient hashing is configured, a fixed number of buckets are defined. Next hops are then assigned in round robin fashion to each of those buckets. In this example, 12 buckets are created and four next hops are assigned.

Remove Next Hops

Unlike default ECMP hashing, when a next hop needs to be removed, the number of hash buckets does not change.

With 12 buckets assigned and four next hops, instead of reducing the number of buckets - which would impact flows to known good hosts - the remaining next hops replace the failed next hop.

After the failed next hop is removed, the remaining next hops are installed as replacements. This prevents impact to any flows that hash to working next hops.

Add Next Hops

Resilient hashing does not prevent possible impact to existing flows when new next hops are added. Due to the fact there are a fixed number of buckets, a new next hop requires reassigning next hops to buckets.

As a result, some flows may hash to new next hops, which can impact anycast deployments.

Configure Resilient Hashing

Resilient hashing is not enabled by default. When resilient hashing is enabled, 65,536 buckets are created to be shared among all ECMP groups. An ECMP group is a list of unique next hops that are referenced by multiple ECMP routes.

An ECMP route counts as a single route with multiple next hops. The following example is considered to be a single ECMP route:

cumulus@switch:~$ ip route show 10.1.1.0/24
10.1.1.0/24  proto zebra  metric 20
  nexthop via 192.168.1.1 dev swp1 weight 1 onlink
  nexthop via 192.168.2.1 dev swp2 weight 1 onlink

All ECMP routes must use the same number of buckets (the number of buckets cannot be configured per ECMP route).

The number of buckets can be configured as 64, 128, 256, 512 or 1024; the default is 128:

Number of Hash Buckets Number of Supported ECMP Groups
64 1024
128 512
256 256
512 128
1024 64

Mellanox switches with the Spectrum ASIC do not support 128 or 256 hash buckets. The default number of hash buckets is 64.

A larger number of ECMP buckets reduces the impact on adding new next hops to an ECMP route. However, the system supports fewer ECMP routes. If the maximum number of ECMP routes have been installed, new ECMP routes log an error and are not installed.

To enable resilient hashing, edit /etc/cumulus/datapath/traffic.conf:

  1. Enable resilient hashing:

    # Enable resilient hashing
    resilient_hash_enable = TRUE
    
  2. (Optional) Edit the number of hash buckets:

    # Resilient hashing flowset entries per ECMP group
    # Valid values - 64, 128, 256, 512, 1024
    resilient_hash_entries_ecmp = 256
    
  3. Restart the switchd service:

    cumulus@switch:~$ sudo systemctl restart switchd.service
    

Caveats and Errata

IPv6 Route Replacement

When the next hop information for an IPv6 prefix changes (for example, when ECMP paths are added or deleted, or when the next hop IP address, interface, or tunnel changes), FRR deletes the existing route to that prefix from the kernel and then adds a new route with all the relevant new information. Because of this process, resilient hashing might not be maintained for IPv6 flows in certain situations.

To work around this issue, you can enable the IPv6 route replacement option.

Be aware that for certain configurations, the IPv6 route replacement option can lead to incorrect forwarding decisions and lost traffic. For example, it is possible for a destination to have next hops with a gateway value with the outbound interface or just the outbound interface itself, without a gateway address defined. If both types of next hops for the same destination exist, route replacement does not operate correctly; Cumulus Linux adds an additional route entry and next hop but does not delete the previous route entry and next hop.

To enable the IPv6 route replacement option:

  1. In the /etc/frr/daemons file, add the configuration option --v6-rr-semantics to the zebra daemon definition. For example:

    cumulus@switch:~$ sudo nano /etc/frr/daemons
    ...
    vtysh_enable=yes
    zebra_options=" -M snmp -A 127.0.0.1 --v6-rr-semantics -s 90000000"
    bgpd_options=" -M snmp  -A 127.0.0.1"
    ospfd_options=" -M snmp -A 127.0.0.1"
    ...
    
  2. Restart FRR with this command:

    cumulus@switch:~$ sudo systemctl restart frr.service

    Restarting FRR restarts all the routing protocol daemons that are enabled and running.

To verify that the IPv6 route replacement option is enabled, run the systemctl status frr command:

cumulus@switch:~$ systemctl status frr

● frr.service - FRRouting
  Loaded: loaded (/lib/systemd/system/frr.service; enabled; vendor preset: enabled)
  Active: active (running) since Mon 2020-02-03 20:02:33 UTC; 3min 8s ago
    Docs: https://frrouting.readthedocs.io/en/latest/setup.html
  Process: 4675 ExecStart=/usr/lib/frr/frrinit.sh start (code=exited, status=0/SUCCESS)
  Memory: 14.4M
  CGroup: /system.slice/frr.service
          ├─4685 /usr/lib/frr/watchfrr -d zebra bgpd staticd
          ├─4701 /usr/lib/frr/zebra -d -M snmp -A 127.0.0.1 --v6-rr-semantics -s 90000000
          ├─4705 /usr/lib/frr/bgpd -d -M snmp -A 127.0.0.1
          └─4711 /usr/lib/frr/staticd -d -A 127.0.0.1

Redistribute Neighbor

Redistribute neighbor provides a mechanism for IP subnets to span racks without forcing the end hosts to run a routing protocol.

The fundamental premise behind redistribute neighbor is to announce individual host /32 routes in the routed fabric. Other hosts on the fabric can then use this new path to access the hosts in the fabric. If multiple equal-cost paths (ECMP) are available, traffic can load balance across the available paths natively.

The challenge is to accurately compile and update this list of reachable hosts or neighbors. Luckily, existing commonly-deployed protocols are available to solve this problem. Hosts use ARP to resolve MAC addresses when sending to an IPv4 address. A host then builds an ARP cache table of known MAC addresses: IPv4 tuples as they receive or respond to ARP requests.

In the case of a leaf switch, where the default gateway is deployed for hosts within the rack, the ARP cache table contains a list of all hosts that have ARP’d for their default gateway. In many scenarios, this table contains all the layer 3 information that is needed. This is where redistribute neighbor comes in, as it is a mechanism of formatting and syncing this table into the routing protocol.

Redistribute neighbor is distributed as python-rdnbrd.

The current release of redistribute neighbor:

  • Supports IPv4 only.
  • Does not support VRFs.
  • Supports a maximum of 1024 interfaces. Using more than 1024 interfaces might crash the rdnbrd service.

Target Use Cases and Best Practices

Redistribute neighbor is typically used in these configurations:

Follow these guidelines:

How It Works

Redistribute neighbor works as follows:

  1. The leaf/ToR switches learn about connected hosts when the host sends an ARP request or ARP reply.
  2. An entry for the host is added to the kernel neighbor table of each leaf switch.
  3. The redistribute neighbor daemon, rdnbrd, monitors the kernel neighbor table and creates a /32 route for each neighbor entry. This /32 route is created in kernel table 10.
  4. FRRouting is configured to import routes from kernel table 10.
  5. A route-map controls which routes from table 10 are imported.
  6. In FRRouting these routes are imported as table routes.
  7. BGP, OSPF and so on, are then configured to redistribute the table 10 routes.

Example Configuration

The following example configuration is based on the reference topology. Other configurations are possible, based on the use cases outlined above. Here is a diagram of the topology:

Configure the Leafs

The following steps demonstrate how to configure leaf01, but you can follow the same steps on any of the leafs.

  1. Configure the host facing ports using the same IP address on both host-facing interfaces as well as a /32 prefix. In this case, swp1 and swp2 are configured as they are the ports facing server01 and server02:

    cumulus@leaf01:~$ net add loopback lo ip address 10.0.0.11/32
    cumulus@leaf01:~$ net add interface swp1-2 ip address 10.0.0.11/32
    cumulus@leaf01:~$ net pending
    cumulus@leaf01:~$ net commit
    
  2. Enable the daemon so it starts at bootup, then start the daemon:

    cumulus@leaf01:~$ sudo systemctl enable rdnbrd.service
    cumulus@leaf01:~$ sudo systemctl restart rdnbrd.service
    
  3. Configure routing:

    1. Define a route-map that matches on the host-facing interfaces:

      cumulus@leaf01:~$ net add routing route-map REDIST_NEIGHBOR permit 10 match interface swp1
      cumulus@leaf01:~$ net add routing route-map REDIST_NEIGHBOR permit 20 match interface swp2
      
    2. Import routing table 10 and apply the route-map:

      cumulus@leaf01:~$ net add routing import-table 10 route-map REDIST_NEIGHBOR
      
    3. Redistribute the imported table routes in into the appropriate routing protocol.

      BGP:

      cumulus@leaf01:~$ net add bgp autonomous-system 65001
      cumulus@leaf01:~$ net add bgp ipv4 unicast redistribute table 10
      

      OSPF:

      cumulus@leaf01:~$ net add ospf redistribute table 1
      
  4. Save the configuration by committing your changes.

    cumulus@leaf01:~$ net pending
    cumulus@leaf01:~$ net commit
    
  1. Edit the /etc/network/interfaces file to configure the host facing ports, using the same IP address on both host-facing interfaces as well as a /32 prefix. In this case, swp1 and swp2 are configured as they are the ports facing server01 and server02:

    cumulus@leaf01:~$ sudo nano /etc/network/interfaces
    
    auto lo
    iface lo inet loopback
        address 10.0.0.11/32
    
    auto swp1
    iface swp1
        address 10.0.0.11/32
    
    auto swp2
    iface swp2
        address 10.0.0.11/32
    ...
    
  2. Enable the daemon so it starts at bootup, then start the daemon:

    cumulus@leaf01:~$ sudo systemctl enable rdnbrd.service
    cumulus@leaf01:~$ sudo systemctl restart rdnbrd.service
    
  3. Configure routing:

    1. Add the table as routes into the local routing table:

      cumulus@leaf01:~$ sudo vtysh
      
      leaf01# configure terminal
      leaf01(config)# ip import-table 10
      
    2. Define a route-map that matches on the host-facing interface:

      leaf01(config)# route-map REDIST_NEIGHBOR permit 10
      leaf01(config-route-map)# match interface swp1
      leaf01(config-route-map)# route-map REDIST_NEIGHBOR permit 20
      leaf01(config-route-map)# match interface swp2
      
    3. Apply that route-map to routes imported into table:

      leaf01(config)# ip protocol table route-map REDIST_NEIGHBOR
      
    4. Redistribute the imported table routes in into the appropriate routing protocol.

      BGP:

      leaf01(config)# router bgp 65001
      leaf01(config-router)# address-family ipv4 unicast
      leaf01(config-router-af)# redistribute table 10
      leaf01(config-router-af)# exit
      leaf01(config-router)# exit
      leaf01(config)# exit
      leaf01# write memory
      leaf01# exit
      cumulus@leaf01:~$
      

      OSPF:

      leaf01(config)# router ospf
      leaf01(config-router)# redistribute table 10
      leaf01(config-router)# exit
      leaf01(config)# exit
      leaf01# write memory
      leaf01# exit
      cumulus@leaf01:~$
      

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. The following example uses OSPF as the routing protocol:

frr defaults datacenter
ip import-table 10 route-map REDIST_NEIGHBOR
username cumulus nopassword
!
service integrated-vtysh-config
!
log syslog informational
!
router bgp 65001
 !
 address-family ipv4 unicast
  redistribute table 10
 exit-address-family
!
route-map REDIST_NEIGHBOR permit 10
 match interface swp1
!
route-map REDIST_NEIGHBOR permit 20
 match interface swp2
!
router ospf
 redistribute table 10
!
line vty
!

Configure the Hosts

There are a few possible host configurations that range in complexity. This document only covers the basic use case: dual-connected Linux hosts with static IP addresses assigned.

Configure a Dual-connected Host

Configure a host with the same /32 IP address on its loopback (lo) and uplinks (in this example, eth1 and eth2). This is done so both leaf switches advertise the same /32 regardless of the interface. Cumulus Linux relies on ECMP to load balance across the interfaces southbound, and an equal cost static route (see the configuration below) for load balancing northbound.

The loopback hosts the primary service IP address(es) and to which you can bind services.

Configure the loopback and physical interfaces. Referring back to the topology diagram, server01 is connected to leaf01 via eth1 and to leaf02 via eth2. You should note:

Install ifplugd

Additionally, install and use ifplugd. ifplugd modifies the behavior of the Linux routing table when an interface undergoes a link transition (carrier up/down). The Linux kernel by default leaves routes up even when the physical interface is unavailable (NO-CARRIER).

After you install ifplugd, edit /etc/default/ifplugd as follows, where eth1 and eth2 are the interface names that your host uses to connect to the leaves.

user@server01:$ sudo nano /etc/default/ifplugd
INTERFACES="eth1 eth2"
HOTPLUG_INTERFACES=""
ARGS="-q -f -u10 -d10 -w -I"
SUSPEND_ACTION="stop"

For full instructions on installing ifplugd on Ubuntu, follow this guide.

Known Limitations

TCAM Route Scale

This feature adds each ARP entry as a /32 host route into the routing table of all switches within a summarization domain. Take care to keep the number of hosts minus fabric routes under the TCAM size of the switch.

Possible Uneven Traffic Distribution

Linux uses source layer 3 addresses only to do load balancing on most older distributions.

Silent Hosts Never Receive Traffic

Freshly provisioned hosts that have never sent traffic may not ARP for their default gateways. The post-up ARPing in /etc/network/interfaces on the host should take care of this. If the host does not ARP, then rdnbrd on the leaf cannot learn about the host.

Unsupported with EVPN

Redistribute neighbor is unsupported when the BGP EVPN Address Family is enabled. Enabling both redistribute neighbor and EVPN will lead to unreachable IPv4 ARP and IPv6 neighbor entries.

Troubleshooting

How do I determine if rdnbrd (the redistribute neighbor daemon) is running?

Run the systemctl status rdnbrd.service command:

cumulus@leaf01:~$ systemctl status rdnbrd.service 
* rdnbrd.service - Cumulus Linux Redistribute Neighbor Service
 Loaded: loaded (/lib/systemd/system/rdnbrd.service; enabled)
 Active: active (running) since Wed 2016-05-04 18:29:03 UTC; 1h 13min ago
 Main PID: 1501 (python)
 CGroup: /system.slice/rdnbrd.service
 `-1501 /usr/bin/python /usr/sbin/rdnbrd -d

How do I change the default configuration of rdnbrd?

Edit the /etc/rdnbrd.conf file, then run systemctl restart rdnbrd.service:

cumulus@leaf01:~$ sudo nano /etc/rdnbrd.conf 
# syslog logging level CRITICAL, ERROR, WARNING, INFO, or DEBUG
loglevel = INFO

# TX an ARP request to known hosts every keepalive seconds
keepalive = 1

# If a host does not send an ARP reply for holdtime consider the host down
holdtime = 3

# Install /32 routes for each host into this table
route_table = 10

# Uncomment to enable ARP debugs on specific interfaces.
# Note that ARP debugs can be very chatty.
# debug_arp = swp1 swp2 swp3 br1
# If we already know the MAC for a host, unicast the ARP request. This is
# unusual for ARP (why ARP if you know the destination MAC) but we will be
# using ARP as a keepalive mechanism and do not want to broadcast so many ARPs
# if we do not have to. If a host cannot handle a unicasted ARP request, set
#
# Unicasting ARP requests is common practice (in some scenarios) for other
# networking operating systems so it is unlikely that you will need to set
# this to False.
unicast_arp_requests = True
cumulus@leaf01:~$ sudo systemctl restart rdnbrd.service

What is table 10? Why was table 10 chosen?

The Linux kernel supports multiple routing tables and can utilize 0 through 255 as table IDs; however tables 0, 253, 254 and 255 are reserved, and 1 is usually the first one utilized. Therefore, rdnbrd only allows you to specify 2-252. Cumulus Linux uses table ID 10, however you can set the ID to any value between 2-252. You can see all the tables specified here:

cumulus@leaf01:~$ cat /etc/iproute2/rt_tables
#
# reserved values
#
255 local
254 main
253 default
0 unspec
#
# local
#
#1  inr.ruhep

For more information, refer to Linux route tables or you can read the Ubuntu man pages for ip route.

How do I determine that the /32 redistribute neighbor routes are being advertised to my neighbor?

For BGP, run the NCLU net show bgp neighbor <interface> advertise-routes command or the vtysh show ip bgp neighbor swp51 advertised-routes command. For example:

cumulus@leaf01:~$ net show bgp neighbor swp51 advertise-routes
BGP table version is 5, local router ID is 10.0.0.11
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
              i internal, r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete

    Network         Next Hop            Metric LocPrf Weight Path
*> 10.0.0.11/32     0.0.0.0                  0         32768 i
*> 10.0.0.12/32     ::                                     0 65020 65012 i
*> 10.0.0.21/32     ::                                     0 65020 i
*> 10.0.0.22/32     ::                                     0 65020 i

Total number of prefixes 4

How do I verify that the kernel routing table is being correctly populated?

Use the following workflow to verify that the kernel routing table isbeing populated correctly and that routes are being correctly imported/advertised:

  1. Verify that ARP neighbor entries are being populated into the Kernel routing table 10.

    cumulus@leaf01:~$ ip route show table 10
    10.0.1.101 dev swp1 scope link
    

    If these routes are not being generated, verify the following that the rdnbrd daemon is running and check the /etc/rdnbrd.conf file to verify the correct table number is used.

  2. Verify that routes are being imported into FRRouting from the kernel routing table 10.

    cumulus@leaf01:~$ sudo vtysh
    leaf01# show ip route table
    Codes: K - kernel route, C - connected, S - static, R - RIP,
           O - OSPF, I - IS-IS, B - BGP, A - Babel, T - Table,
           > - selected route, * - FIB route
    T[10]>* 10.0.1.101/32 [19/0] is directly connected, swp1, 01:25:29
    

    Both the > and * should be present so that table 10 routes are installed as preferred into the routing table. If the routes are not being installed, verify the imported distance of the locally imported kernel routes with the ip import 10 distance X command (where X is not less than the administrative distance of the routing protocol). If the distance is too low, routes learned from the protocol might overwrite the locally imported routes. Also, verify that the routes are in the kernel routing table.

  3. Confirm that routes are in the BGP/OSPF database and are being advertised.

    leaf01# show ip bgp
    

Virtual Routing and Forwarding - VRF

Cumulus Linux provides virtual routing and forwarding (VRF) to allow for the presence of multiple independent routing tables working simultaneously on the same router or switch. This permits multiple network paths without the need for multiple switches. Think of this feature as VLAN for layer 3, but unlike VLANs, there is no field in the IP header carrying it. Other implementations call this feature VRF-Lite.

The primary use cases for VRF in a data center are similar to VLANs at layer 2: using common physical infrastructure to carry multiple isolated traffic streams for multi-tenant environments, where these streams are allowed to cross over only at configured boundary points, typically firewalls or IDS. You can also use it to burst traffic from private clouds to enterprise networks where the burst point is at layer 3. Or you can use it in an OpenStack deployment.

VRF is fully supported in the Linux kernel, so it has the following characteristics:

Cumulus Linux supports up to 255 VRFs on a switch.

Configure VRF

Each routing table is called a VRF table, and has its own table ID.

To configure VRF, you associate each subset of interfaces to a VRF routing table and configure an instance of the routing protocol (BGP or OSPFv2) for each routing table.Configuring a VRF is similar to configuring other network interfaces. Keep in mind the following:

To configure a VRF, run the following commands:

The following example commands configure a VRF called rocket with a table ID that is automatically assigned:

cumulus@switch:~$ net add vrf rocket vrf-table auto
cumulus@switch:~$ net add interface swp1 vrf rocket
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file. The following example configures a VRF called rocket with a table ID that is automatically assigned.

...
auto swp1
iface swp1
  vrf rocket

auto rocket
iface rocket
  vrf-table auto
...

To load the new configuration, run ifreload -a:

cumulus@switch:~$ sudo ifreload -a

Specify a Table ID

Instead of having Cumulus Linux assign a table ID for the VRF table, you can specify your own table ID in the configuration. The table ID to name mapping is saved in /etc/iproute2/rt_tables.d/ for name-based references. Instead of using the auto option as shown above, specify the table ID. For example:

cumulus@switch:~$ net add vrf rocket vrf-table 1016
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file:

...
auto swp1
iface swp1
  vrf rocket

auto rocket
iface rocket
  vrf-table 1016
...

To load the new configuration, run ifreload -a:

cumulus@switch:~$ sudo ifreload -a

The table ID must be in the range of 1001 to 1255, which is reserved in Cumulus Linux for VRF table IDs.

Bring a VRF Up After You Run ifdown

If you take down a VRF using ifdown, you need to run one of the following commands to bring the VRF back up:

For example:

cumulus@switch:~$ sudo ifdown rocket
cumulus@switch:~$ sudo ifup --with-depends rocket

Use the vrf Command

Run the vrf command to show information about VRF tables not available in other Linux commands, such as iproute.

To show a list of VRF tables, run the vrf list command:

cumulus@switch:~$ vrf list

VRF              Table
---------------- -----
rocket            1016

To show a list of processes and PIDs associated with a specific VRF table, run the ip vrf pids <vrf-name> command. For example:

cumulus@switch:~$ ip vrf pids rocket

VRF: rocket
-----------------------
dhclient           2508
sshd               2659
bash               2681
su                 2702
bash               2720
vrf                2829

To determine which VRF table is associated with a particular PID, run the ip vrf identify <pid> command. For example:

cumulus@switch:~$ ip vrf identify 2829
rocket

IPv4 and IPv6 Commands in a VRF Context

You can execute non-VRF-specific Linux commands and perform other tasks against a given VRF table. This typically applies to single-use commands started from a login shell, as they affect only AF_INET and AF_INET6 sockets opened by the command that gets executed; it has no impact on netlink sockets, associated with the ip command.

To execute such a command against a VRF table, run ip vrf exec <vrf-name> <command>. For example, to SSH from the switch to a device accessible through VRF rocket:

cumulus@switch:~$ sudo ip vrf exec rocket ssh user@host

Services in VRFs

For services that need to run against a specific VRF, Cumulus Linux uses systemd instances, where the instance is the VRF. In general, you start a service within a VRF with the systemctl start <service>@<vrf-name> command. For example, to run the dhcpd service in the turtle VRF:

cumulus@switch:~$ sudo systemctl start dhcpd@turtle

In most cases, the instance running in the default VRF needs to be stopped before a VRF instance can start. This is because the instance running in the default VRF owns the port across all VRFs (it is VRF global). Cumulus Linux stops systemd-based services when the VRF is deleted and starts them when the VRF is created (when you restart networking or run an ifdown/ifup sequence). Refer to the management VRF chapter for details.

The following services work with VRF instances:

There are cases where systemd instances do not work; you must use a service-specific configuration option instead. For example, to configure rsyslogd to send messages to remote systems over a VRF:

action(type="omfwd" Target="hostname or ip here" Device="mgmt" Port=514
Protocol="udp")

VRF Route Leaking

The most common use case for VRF is to use multiple independent routing and forwarding tables; however, there are situations where destinations in one VRF must be reachable (leaked) from another VRF. For example, to make a service (such as a firewall) available to multiple VRFs or to enable routing to external networks (or the Internet) for multiple VRFs, where the external network itself is reachable through a specific VRF.

Cumulus Linux supports dynamic VRF route leaking. Static route leaking is not supported.

VRF route leaking uses BGP to replicate the leaked routes across VRFs. However, Cumulus Linux cannot replicate the host routes for neighbors local to a switch where the leak is configured. To discover all directly connected neighbors in the source VRF of a leaked route, enable the vrf_route_leak_enable_dynamic option in the /etc/cumulus/switchd.conf file. These routes are then replicated into the target or destination VRF as specified in the leaked route.

The vrf_route_leak_enable_dynamic option makes certain inter-VRF traffic ASIC accelerated. Enable this option if you are experiencing slow performance.

Configure Route Leaking

For route leaking, a destination VRF is interested in the routes of a source VRF. As routes come and go in the source VRF, they are dynamically leaked to the destination VRF through BGP. If the routes in the source VRF are learned through BGP, no additional configuration is necessary. If the routes in the source VRF are learned through OSPF, or if they are statically configured or directly-connected networks have to be reached, the routes need to be first redistributed into BGP (in the source VRF) for them to be leaked.

You can also use route leaking to reach remote destinations as well as directly connected destinations in another VRF. Multiple VRFs can import routes from a single source VRF and a VRF can import routes from multiple source VRFs. This is typically used when a single VRF provides connectivity to external networks or a shared service for many other VRFs. The routes that are leaked dynamically across VRFs can be controlled using a route-map.

Because route leaking happens through BGP, the underlying mechanism relies on the BGP constructs of the Route Distinguisher (RD) and Route Targets (RTs). However, you do not need to configure these parameters; they are automatically derived when you enable route leaking between a pair of VRFs.

When you use route leaking:

In the following example commands, routes in the BGP routing table of VRF rocket are dynamically leaked into VRF turtle.

cumulus@switch:~$ net add bgp vrf turtle ipv4 unicast import vrf rocket
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65001 vrf turtle
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# import vrf rocket
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65001 vrf turtle
 !
 address-family ipv4 unicast
  import vrf rocket
...

Exclude Certain Prefixes

You can exclude certain prefixes from being imported. The prefixes must be configured in a route map.

The following example configures a route map to match the source protocol BGP and imports the routes from VRF turtle to VRF rocket. For the imported routes, the community is set to 11:11 in VRF rocket.

cumulus@switch:~$ net add bgp vrf rocket ipv4 unicast import vrf turtle
cumulus@switch:~$ net add routing route-map turtle-to-rocket-IPV4 permit 10
cumulus@switch:~$ net add routing route-map turtle-to-rocket-IPV4 permit 10 match source-protocol bgp
cumulus@switch:~$ net add routing route-map turtle-to-rocket-IPV4 permit 10 set community 11:11
cumulus@switch:~$ net add bgp vrf rocket ipv4 unicast import vrf route-map turtle-to-rocket-IPV4
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65001 vrf rocket
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# import vrf turtle
switch(config-router-af)# route-map turtle-to-rocket-IPV4 permit 10
switch(config-route-map)# match source-protocol bgp
switch(config-route-map)# set community 11:11
switch(config-route-map)# exit
switch(config)# router bgp 65001 vrf rocket
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# import vrf route-map turtle-to-rocket-IPv4
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

Verify Route Leaking Configuration

To check the status of VRF route leaking, run the NCLU net show bgp vrf <vrf-name> ipv4|ipv6 unicast route-leak command or the vtysh show ip bgp vrf <vrf-name> ipv4|ipv6 unicast route-leak command. For example:

cumulus@switch:~$ net show bgp vrf turtle ipv4 unicast route-leak
This VRF is importing IPv4 Unicast routes from the following VRFs:
  rocket
Import RT(s): 0.0.0.0:3
This VRF is exporting IPv4 Unicast routes to the following VRFs:
  rocket
RD: 10.1.1.1:2
Export RT: 10.1.1.1:2

The following example commands show all routes in VRF turtle, including routes leaked from VRF rocket:

cumulus@switch:~$ net show route vrf turtle
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, P - PIM, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
       F - PBR,
       > - selected route, * - FIB route

VRF turtle:
K * 0.0.0.0/0 [255/8192] unreachable (ICMP unreachable), 6d07h01m
C>* 10.1.1.1/32 is directly connected, turtle, 6d07h01m
B>* 10.0.100.1/32 [200/0] is directly connected, rocket(vrf rocket), 6d05h10m
B>* 10.0.200.0/24 [20/0] via 10.10.2.2, swp1.11, 5d05h10m
B>* 10.0.300.0/24 [200/0] via 10.20.2.2, swp1.21(vrf rocket), 5d05h10m
C>* 10.10.2.0/30 is directly connected, swp1.11, 6d07h01m
C>* 10.10.3.0/30 is directly connected, swp2.11, 6d07h01m
C>* 10.10.4.0/30 is directly connected, swp3.11, 6d07h01m
B>* 10.20.2.0/30 [200/0] is directly connected, swp1.21(vrf rocket), 6d05h10m

Delete Route Leaking Configuration

To remove route leaking configuration, run the following commands. These commands ensure that all leaked routes are removed and routes are no longer leaked from the specified source VRF.

The following example commands delete leaked routes from VRF rocket to VRF turtle:

cumulus@switch:~$ net del bgp vrf turtle ipv4 unicast import vrf rocket
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65001 vrf turtle
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# no import vrf rocket
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

Do not use the kernel commands; they are no longer supported and might cause issues when used with VRF route leaking in FRR.

FRRouting Operation in a VRF

In Cumulus Linux, BGP, OSPFv2 and static routing (IPv4 and IPv6) are supported within a VRF context. Various FRRouting routing constructs, such as routing tables, nexthops, router-id, and related processing are also VRF-aware.

FRRouting learns of VRFs provisioned on the system as well as interface attachment to a VRF through notifications from the kernel.

You can assign switch ports to each VRF table with an interface-level configuration, and BGP instances can be assigned to the table with a BGP router-level command.

Because BGP is VRF-aware, per-VRF neighbors, both iBGP and eBGP, as well as numbered and unnumbered interfaces are supported. Non-interface-based VRF neighbors are bound to the VRF, which is how you can have overlapping address spaces in different VRFs. Each VRF can have its own parameters, such as address families and redistribution. Incoming connections rely on the Linux kernel for VRF-global sockets. BGP neighbors can be tracked using BFD, both for single and multiple hops. You can configure multiple BGP instances, associating each with a VRF.

A VRF-aware OSPFv2 configuration also supports numbered and unnumbered interfaces. Supported layer 3 interfaces include SVIs, sub-interfaces and physical interfaces. The VRF supports types 1 through 5 (ABR/ASBR - external LSAs) and types 9 through 11 (opaque LSAs) link state advertisements, redistributing other routing protocols, connected and static routes, and route maps. As with BGP, you can track OSPF neighbors with BFD.

Cumulus Linux does not support multiple VRFs in multi-instance OSPF.

VRFs are provisioned using NCLU. VRFs can be pre-provisioned in FRRouting too, but they become active only when configured with NCLU.

Example VRF Configuration in BGP

cumulus@switch:~$ net add bgp vrf vrf1012 autonomous-system 64900
cumulus@switch:~$ net add bgp vrf vrf1012 router-id 6.0.2.7
cumulus@switch:~$ net add bgp vrf vrf1012 neighbor ISL peer-group
cumulus@switch:~$ net add bgp vrf vrf1012 neighbor ISLv6 peer-group
cumulus@switch:~$ net add bgp vrf vrf1012 neighbor swp1.2 interface v6only peer-group ISLv6
cumulus@switch:~$ net add bgp vrf vrf1012 neighbor swp1.2 remote-as external
cumulus@switch:~$ net add bgp vrf vrf1012 neighbor swp3.2 interface v6only peer-group ISLv6
cumulus@switch:~$ net add bgp vrf vrf1012 neighbor swp3.2 remote-as external
cumulus@switch:~$ net add bgp vrf vrf1012 neighbor 169.254.2.18 remote-as external
cumulus@switch:~$ net add bgp vrf vrf1012 neighbor 169.254.2.18 peer-group ISL
cumulus@switch:~$ net add bgp vrf vrf1012 ipv4 unicast network 20.7.2.0/24
cumulus@switch:~$ net add bgp vrf vrf1012 ipv4 unicast neighbor ISL activate
cumulus@switch:~$ net add bgp vrf vrf1012 neighbor ISL route-map ALLOW_BR2 out
cumulus@switch:~$ net add bgp vrf vrf1012 ipv6 unicast network 2003:7:2::/125
cumulus@switch:~$ net add bgp vrf vrf1012 ipv6 unicast neighbor ISLv6 activate
cumulus@switch:~$ net add bgp vrf vrf1012 neighbor ISLv6 route-map ALLOW_BR2_v6 out
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65001 vrf vrf1012
switch(config-router)# bgp router-id 6.0.2.7
switch(config-router)# no bgp default ipv4-unicast
switch(config-router)# neighbor ISL peer-group
switch(config-router)# neighbor ISLv6 peer-group
switch(config-router)# neighbor swp1.2 interface v6only peer-group ISLv6
switch(config-router)# neighbor swp1.2 remote-as external
switch(config-router)# neighbor swp3.2 interface v6only peer-group ISLv6
switch(config-router)# neighbor swp3.2 remote-as external
switch(config-router)# neighbor 169.254.2.18 remote-as external
switch(config-router)# neighbor 169.254.2.18 peer-group ISL
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# network 20.7.2.0/24
switch(config-router-af)# neighbor ISL activate
switch(config-router-af)# neighbor ISL route-map ALLOW_BR2 out
switch(config-router-af)# exit
switch(config-router)# address-family ipv6 unicast
switch(config-router-af)# network 2003:7:2::/125
switch(config-router-af)# neighbor ISLv6 activate
switch(config-router-af)# neighbor ISLv6 route-map ALLOW_BR2_v6 out
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 64900 vrf vrf1012
  bgp router-id 6.0.2.7
  no bgp default ipv4-unicast
  neighbor ISL peer-group
  neighbor ISLv6 peer-group
  neighbor swp1.2 interface v6only peer-group ISLv6
  neighbor swp1.2 remote-as external
  neighbor swp3.2 interface v6only peer-group ISLv6
  neighbor swp3.2 remote-as external
  neighbor 169.254.2.18 remote-as external
  neighbor 169.254.2.18 peer-group ISL
  !
  address-family ipv4 unicast
    network 20.7.2.0/24
    neighbor ISL activate
    neighbor ISL route-map ALLOW_BR2 out
  exit-address-family
  !
  address-family ipv6 unicast
    network 2003:7:2::/125
    neighbor ISLv6 activate
    neighbor ISLv6 route-map ALLOW_BR2_v6 out
  exit-address-family
...

Example VRF Configuration in OSPF

cumulus@switch:~$ net add ospf vrf vrf1 
cumulus@switch:~$ net add ospf vrf vrf1 router-id 4.4.4.4
cumulus@switch:~$ net add ospf vrf vrf1 log-adjacency-changes detail
cumulus@switch:~$ net add ospf vrf vrf1 network 10.0.0.0/24 area 0.0.0.1
cumulus@switch:~$ net add ospf vrf vrf1 network 9.9.0.0/16 area 0.0.0.0
cumulus@switch:~$ net add ospf vrf vrf1 redistribute connected
cumulus@switch:~$ net add ospf vrf vrf1 redistribute bgp
cumulus@switch:~$ net add interface swp1 ospf network point-to-point
cumulus@switch:~$ net add interface swp2 ospf network point-to-point
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router ospf vrf vrf1
switch(config-router)# ospf router-id 4.4.4.4
switch(config-router)# log-adjacency-changes detail
switch(config-router)# redistribute connected
switch(config-router)# redistribute bgp
switch(config-router)# network 9.9.0.0/16 area 0.0.0.0
switch(config-router)# network 10.0.0.0/24 area 0.0.0.1
switch(config-router)# exit
switch(config)# interface swp1
switch(config-if)# ip address 192.0.2.1/32
switch(config-if)# ip ospf network point-to-point
switch(config-if)# exit
switch(config)# interface swp2
switch(config-if)# ip address 192.0.2.1/32
switch(config-if)# ip ospf network point-to-point
switch(config-if)# exit
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
interface swp1
  ip address 192.0.2.1/32
  ip ospf network point-to-point
!
interface swp2
  ip address 192.0.2.1/32
  ip ospf network point-to-point
!
router ospf vrf vrf1
  ospf router-id 4.4.4.4
  log-adjacency-changes detail
  redistribute connected
  redistribute bgp
  network 9.9.0.0/16 area 0.0.0.0
  network 10.0.0.0/24 area 0.0.0.1
...

Show VRF Information

To show VRF information, you can use NCLU, vtysh, or Linux commands.

To show the routes in a VRF, run the net show route vrf <vrf-name> command. For example:

cumulus@switch:~$ net show route vrf rocket
RIB entry for rocket
=================
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, T - Table,
       > - selected route, * - FIB route

C>* 169.254.2.8/30 is directly connected, swp1.2
C>* 169.254.2.12/30 is directly connected, swp2.2
C>* 169.254.2.16/30 is directly connected, swp3.2

To show the BGP summary for a VRF, run the net show bgp vrf <vrf-name> summary command. For example:

cumulus@switch:~$ net show bgp vrf rocket summary
BGP router identifier 6.0.2.7, local AS number 64900 vrf-id 14
BGP table version 0
RIB entries 1, using 120 bytes of memory
Peers 6, using 97 KiB of memory
Peer groups 2, using 112 bytes of memory

Neighbor         V  AS   MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
s3(169.254.2.18)
                 4 65000  102039  102040        0    0    0 3d13h03m        0
s1(169.254.2.10)
                 4 65000  102039  102040        0    0    0 3d13h03m        0
s2(169.254.2.14)
                 4 65000  102039  102040        0    0    0 3d13h03m        0

Total number of neighbors 3

To show BGP (IPv4) routes in a VRF, run the net show bgp vrf <vrf-name> command. For example::

cumulus@switch:~$ net show bgp vrf vrf1012
BGP table version is 0, local router ID is 6.0.2.7
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
              i internal, r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete

  Network          Next Hop            Metric LocPrf Weight Path
  20.7.2.0/24      0.0.0.0                  0         32768 i

Total number of prefixes 1

To show BGP IPv6 routes in the VRF, you need to run the vtysh show bgp vrf <vrf-name> command.

To show the OSPF VRFs, run the net show ospf vrf all command. For example:

cumulus@switch:~$ net show ospf vrf all
Name                                  Id         RouterId  
Default-IP-Routing-Table              0          6.0.0.7
vrf1012                               45         9.9.12.7
vrf1013                               52         9.9.13.7
vrf1014                               59         9.9.14.7
vrf1015                               65535      0.0.0.0      <- OSPF instance not active, pre-provisioned config.
vrf1016                               65535      0.0.0.0

Total number of OSPF VRFs: 6

To show all the OSPF routes in a VRF, run the net show ospf vrf <vrf-name> route command. For example:

cumulus@switch:~$ net show ospf vrf vrf1012 route
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, P - PIM, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel,
       > - selected route, * - FIB route

VRF vrf1012:
O>* 6.0.0.1/32 [110/210] via 200.254.2.10, swp2s0.2, 00:13:30
    *                    via 200.254.2.14, swp2s1.2, 00:13:30
    *                    via 200.254.2.18, swp2s2.2, 00:13:30
O>* 6.0.0.2/32 [110/210] via 200.254.2.10, swp2s0.2, 00:13:30
    *                    via 200.254.2.14, swp2s1.2, 00:13:30
    *                    via 200.254.2.18, swp2s2.2, 00:13:30
O>* 9.9.12.5/32 [110/20] via 200.254.2.10, swp2s0.2, 00:13:29
    *                    via 200.254.2.14, swp2s1.2, 00:13:29
    *                    via 200.254.2.18, swp2s2.2, 00:13:29

To show which interfaces are in a VRF (either BGP or OSPF), run the net show vrf list command. For example:

cumulus@switch:~$ net show vrf list
VRF: mgmt
--------------------
eth0              UP     a0:00:00:00:00:11 <BROADCAST,MULTICAST,UP,LOWER_UP>

VRF: turtle
--------------------
vlan13@bridge     UP     44:38:39:00:00:03 <BROADCAST,MULTICAST,UP,LOWER_UP>
vlan13-v0@vlan13  UP     44:39:39:ff:00:13 <BROADCAST,MULTICAST,UP,LOWER_UP>
vlan24@bridge     UP     44:38:39:00:00:03 <BROADCAST,MULTICAST,UP,LOWER_UP>  
vlan24-v0@vlan24  UP     44:39:39:ff:00:24 <BROADCAST,MULTICAST,UP,LOWER_UP>
vlan4001@bridge   UP     44:39:39:ff:40:94 <BROADCAST,MULTICAST,UP,LOWER_UP>

To show the interfaces for a specific VRF, run the net show vrf list <vrf-name> command. For xample:

cumulus@switch:~$ net show vrf list turtle
VRF: turtle
--------------------
vlan13@bridge     UP      44:38:39:00:00:03 <BROADCAST,MULTICAST,UP,LOWER_UP> 
vlan13-v0@vlan13  UP      44:39:39:ff:00:13 <BROADCAST,MULTICAST,UP,LOWER_UP> 
vlan24@bridge     UP      44:38:39:00:00:03 <BROADCAST,MULTICAST,UP,LOWER_UP> 
vlan24-v0@vlan24  UP      44:39:39:ff:00:24 <BROADCAST,MULTICAST,UP,LOWER_UP> 
vlan4001@bridge   UP      44:39:39:ff:40:94 <BROADCAST,MULTICAST,UP,LOWER_UP>

You can only specify one VRF with the net show vrf list <vrf-name> command. For example, net show vrf list mgmt turtle is an invalid command.

To show the VNIs for the interfaces in a VRF, run the net show vrf vni command. For example:

cumulus@switch:~$ net show vrf vni 
VRF         VNI     VxLAN IF    L3-SVI    State  Rmac 
turtle      104001  vxlan4001   vlan4001  Up     44:39:39:ff:40:94

To see the VNIs for the interfaces in a VRF in JSON format, run the net show vrf vni json command. For example:

cumulus@switch:~$ net show vrf vni json
{
  "vrfs":[
    {
      "vrf":"turtle",
      "vni":104001,
      "vxlanIntf":"vxlan4001",
      "sviIntf":"vlan4001",
      "state":"Up",
      "routerMac":"44:39:39:ff:40:94"
    }
  ]
}

To show all VRFs learned by FRRouting from the kernel, run the show vrf command. The table ID shows the corresponding routing table in the kernel.

cumulus@switch:~$ sudo vtysh

switch# show vrf
vrf vrf1012 id 14 table 1012
vrf vrf1013 id 21 table 1013
vrf vrf1014 id 28 table 1014

To show the VRFs configured in BGP (including the default VRF), run the show bgp vrfs command. A non-zero ID is a VRF that has also been provisioned (defined in the /etc/network/interfaces file).

cumulus@switch:~$ sudo vtysh

switch# show bgp vrfs
Type  Id     RouterId          #PeersCfg  #PeersEstb  Name
DFLT  0      6.0.0.7                  0           0  Default
 VRF  14     6.0.2.7                   6           6  vrf1012
 VRF  21     6.0.3.7                   6           6  vrf1013
 VRF  28     6.0.4.7                   6           6  vrf1014

Total number of VRFs (including default): 4

To show interfaces known to FRRouting and attached to a specific VRF, run the show interface vrf <vrf-name> command. For example:

cumulus@switch:~$ sudo vtysh

switch# show interface vrf vrf1012
Interface br2 is up, line protocol is down
  PTM status: disabled
  vrf: vrf1012
  index 13 metric 0 mtu 1500
  flags: <UP,BROADCAST,MULTICAST>
  inet 20.7.2.1/24

  inet6 fe80::202:ff:fe00:a/64
  ND advertised reachable time is 0 milliseconds
  ND advertised retransmit interval is 0 milliseconds
  ND router advertisements are sent every 600 seconds
  ND router advertisements lifetime tracks ra-interval
  ND router advertisement default router preference is medium
  Hosts use stateless autoconfig for addresses.

To show VRFs configured in OSPF, run the show ip ospf vrfs command. For example:

cumulus@switch:~$ sudo vtysh

switch# show ip ospf vrfs
Name                            Id     RouterId
Default-IP-Routing-Table        0      0.0.0.0
rocket                          57     0.0.0.10
turtle                          58     0.0.0.20
Total number of OSPF VRFs (including default): 3

To show all OSPF routes in a VRF, run the show ip ospf vrf all route command. For example:

cumulus@switch:~$ sudo vtysh

switch# show ip ospf vrf all route 
============ OSPF network routing table ============
N    7.0.0.0/24            [10] area: 0.0.0.0
                           directly attached to swp2

============ OSPF router routing table =============

============ OSPF external routing table ===========

============ OSPF network routing table ============
N    8.0.0.0/24            [10] area: 0.0.0.0
                           directly attached to swp1

============ OSPF router routing table =============

============ OSPF external routing table ===========

To see the routing table for each VRF, use the show ip route vrf all command. The OSPF route is denoted in the row that starts with O.

cumulus@switch:~$ sudo vtysh

switch# show ip route vrf all
Codes: K - kernel route, C - connected, S - static, R - RIP,
       O - OSPF, I - IS-IS, B - BGP, P - PIM, E - EIGRP, N - NHRP,
       T - Table, v - VNC, V - VNC-Direct, A - Babel,
       > - selected route, * - FIB route
VRF turtle:
K>* 0.0.0.0/0 [0/8192] unreachable (ICMP unreachable)
O   7.0.0.0/24 [110/10] is directly connected, swp2, 00:28:35
C>* 7.0.0.0/24 is directly connected, swp2
C>* 7.0.0.5/32 is directly connected, turtle
C>* 7.0.0.100/32 is directly connected, turtle
C>* 50.1.1.0/24 is directly connected, swp31s1
VRF rocket:
K>* 0.0.0.0/0 [0/8192] unreachable (ICMP unreachable)
O
8.0.0.0/24 [110/10]
is directly connected, swp1, 00:23:26
C>* 8.0.0.0/24 is directly connected, swp1
C>* 8.0.0.5/32 is directly connected, rocket
C>* 8.0.0.100/32 is directly connected, rocket
C>* 50.0.1.0/24 is directly connected, swp31s0

To list all VRFs, and include the VRF ID and table ID, run the ip -d link show type vrf command. For example:

cumulus@switch:~$ ip -d link show type vrf
14: vrf1012: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether 46:96:c7:64:4d:fa brd ff:ff:ff:ff:ff:ff promiscuity 0
    vrf table 1012 addrgenmode eui64
21: vrf1013: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether 7a:8a:29:0f:5e:52 brd ff:ff:ff:ff:ff:ff promiscuity 0
    vrf table 1013 addrgenmode eui64
28: vrf1014: <NOARP,MASTER,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether e6:8c:4d:fc:eb:b1 brd ff:ff:ff:ff:ff:ff promiscuity 0
    vrf table 1014 addrgenmode eui64

To show the interfaces attached to a specific VRF, run the ip -d link show vrf <vrf-name> command. For example:

cumulus@switch:~$ ip -d link show vrf vrf1012
8: swp1.2@swp1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vrf1012 state UP mode DEFAULT group default
    link/ether 00:02:00:00:00:07 brd ff:ff:ff:ff:ff:ff promiscuity 0
    vlan protocol 802.1Q id 2 <REORDER_HDR>
    vrf_slave addrgenmode eui64
9: swp2.2@swp2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vrf1012 state UP mode DEFAULT group default
    link/ether 00:02:00:00:00:08 brd ff:ff:ff:ff:ff:ff promiscuity
    vlan protocol 802.1Q id 2 <REORDER_HDR>
    vrf_slave addrgenmode eui64
10: swp3.2@swp3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vrf1012 state UP mode DEFAULT group default
    link/ether 00:02:00:00:00:09 brd ff:ff:ff:ff:ff:ff promiscuity 0
    vlan protocol 802.1Q id 2 <REORDER_HDR>
    vrf_slave addrgenmode eui64
11: swp4.2@swp4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vrf1012 state UP mode DEFAULT group default
    link/ether 00:02:00:00:00:0a brd ff:ff:ff:ff:ff:ff promiscuity 0
    vlan protocol 802.1Q id 2 <REORDER_HDR>
    vrf_slave addrgenmode eui64
12: swp5.2@swp5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master vrf1012 state UP mode DEFAULT group default
    link/ether 00:02:00:00:00:0b brd ff:ff:ff:ff:ff:ff promiscuity 0
    vlan protocol 802.1Q id 2 <REORDER_HDR>
    vrf_slave addrgenmode eui64
13: br2: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue master vrf1012 state DOWN mode DEFAULT group default
    link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff promiscuity 0
    bridge forward_delay 100 hello_time 200 max_age 2000 ageing_time 30000 stp_state 0 priority 32768
    vlan_filtering 0 vlan_protocol 802.1Q bridge_id 8000.0:0:0:0:0:0 designated_root 8000.0:0:0:0:0:0
    root_port 0 root_path_cost 0 topology_change 0 topology_change_detected 0 hello_timer    0.00
    tcn_timer    0.00 topology_change_timer    0.00 gc_timer  202.23 vlan_default_pvid 1 group_fwd_mask 0
    group_address 01:80:c2:00:00:00 mcast_snooping 1 mcast_router 1 mcast_query_use_ifaddr 0 mcast_querier 0
    mcast_hash_elasticity 4096 mcast_hash_max 4096 mcast_last_member_count 2 mcast_startup_query_count 2
    mcast_last_member_interval 100 mcast_membership_interval 26000 mcast_querier_interval 25500
    mcast_query_interval 12500 mcast_query_response_interval 1000 mcast_startup_query_interval 3125 
    nf_call_iptables 0 nf_call_ip6tables 0 nf_call_arptables 0
    vrf_slave addrgenmode eui64

To show IPv4 routes in a VRF, run the ip route show table <vrf-name> command. For example:

cumulus@switch:~$ ip route show table vrf1012
unreachable default  metric 240
broadcast 20.7.2.0 dev br2  proto kernel  scope link  src 20.7.2.1 dead linkdown
20.7.2.0/24 dev br2  proto kernel  scope link  src 20.7.2.1 dead linkdown
local 20.7.2.1 dev br2  proto kernel  scope host  src 20.7.2.1
broadcast 20.7.2.255 dev br2  proto kernel  scope link  src 20.7.2.1 dead linkdown
broadcast 169.254.2.8 dev swp1.2  proto kernel  scope link  src 169.254.2.9
169.254.2.8/30 dev swp1.2  proto kernel  scope link  src 169.254.2.9
local 169.254.2.9 dev swp1.2  proto kernel  scope host  src 169.254.2.9
broadcast 169.254.2.11 dev swp1.2  proto kernel  scope link  src 169.254.2.9
broadcast 169.254.2.12 dev swp2.2  proto kernel  scope link  src 169.254.2.13
169.254.2.12/30 dev swp2.2  proto kernel  scope link  src 169.254.2.13
local 169.254.2.13 dev swp2.2  proto kernel  scope host  src 169.254.2.13
broadcast 169.254.2.15 dev swp2.2  proto kernel  scope link  src 169.254.2.13
broadcast 169.254.2.16 dev swp3.2  proto kernel  scope link  src 169.254.2.17
169.254.2.16/30 dev swp3.2  proto kernel  scope link  src 169.254.2.17
local 169.254.2.17 dev swp3.2  proto kernel  scope host  src 169.254.2.17
broadcast 169.254.2.19 dev swp3.2  proto kernel  scope link  src 169.254.2.17

To show IPv6 routes in a VRF, run the ip -6 route show table <vrf-name> command. For example:

cumulus@switch:~$ ip -6 route show table vrf1012
local fe80:: dev lo  proto none  metric 0  pref medium
local fe80:: dev lo  proto none  metric 0  pref medium
local fe80:: dev lo  proto none  metric 0  pref medium
local fe80:: dev lo  proto none  metric 0  pref medium
local fe80::202:ff:fe00:7 dev lo  proto none  metric 0  pref medium
local fe80::202:ff:fe00:8 dev lo  proto none  metric 0  pref medium
local fe80::202:ff:fe00:9 dev lo  proto none  metric 0  pref medium
local fe80::202:ff:fe00:a dev lo  proto none  metric 0  pref medium
fe80::/64 dev br2  proto kernel  metric 256 dead linkdown  pref medium
fe80::/64 dev swp1.2  proto kernel  metric 256  pref medium
fe80::/64 dev swp2.2  proto kernel  metric 256  pref medium
fe80::/64 dev swp3.2  proto kernel  metric 256  pref medium
ff00::/8 dev br2  metric 256 dead linkdown  pref medium
ff00::/8 dev swp1.2  metric 256  pref medium
ff00::/8 dev swp2.2  metric 256  pref medium
ff00::/8 dev swp3.2  metric 256  pref medium
unreachable default dev lo  metric 240  error -101 pref medium

To see a list of links associated with a particular VRF table, run the ip link list <vrf-name> command. For example:

cumulus@switch:~$ ip link list rocket

VRF: rocket
--------------------
swp1.10@swp1     UP             6c:64:1a:00:5a:0c <BROADCAST,MULTICAST,UP,LOWER_UP> 
swp2.10@swp2     UP             6c:64:1a:00:5a:0d <BROADCAST,MULTICAST,UP,LOWER_UP>

To see a list of routes associated with a particular VRF table, run the ip route list <vrf-name> command. For example:

cumulus@switch:~$ ip route list rocket

VRF: rocket
--------------------
unreachable default  metric 8192
10.1.1.0/24 via 10.10.1.2 dev swp2.10
10.1.2.0/24 via 10.99.1.2 dev swp1.10
broadcast 10.10.1.0 dev swp2.10  proto kernel  scope link  src 10.10.1.1
10.10.1.0/28 dev swp2.10  proto kernel  scope link  src 10.10.1.1
local 10.10.1.1 dev swp2.10  proto kernel  scope host  src 10.10.1.1
broadcast 10.10.1.15 dev swp2.10  proto kernel  scope link  src 10.10.1.1
broadcast 10.99.1.0 dev swp1.10  proto kernel  scope link  src 10.99.1.1
10.99.1.0/30 dev swp1.10  proto kernel  scope link  src 10.99.1.1
local 10.99.1.1 dev swp1.10  proto kernel  scope host  src 10.99.1.1
broadcast 10.99.1.3 dev swp1.10  proto kernel  scope link  src 10.99.1.1

local fe80:: dev lo  proto none  metric 0  pref medium
local fe80:: dev lo  proto none  metric 0  pref medium
local fe80::6e64:1aff:fe00:5a0c dev lo  proto none  metric 0  pref medium
local fe80::6e64:1aff:fe00:5a0d dev lo  proto none  metric 0  pref medium
fe80::/64 dev swp1.10  proto kernel  metric 256  pref medium
fe80::/64 dev swp2.10  proto kernel  metric 256  pref medium
ff00::/8 dev swp1.10  metric 256  pref medium
ff00::/8 dev swp2.10  metric 256  pref medium
unreachable default dev lo  metric 8192  error -101 pref medium

You can also show routes in a VRF using the ip [-6] route show vrf <vrf-name> command. This command omits local and broadcast routes, which can clutter the output.

BGP Unnumbered Interfaces with VRF

BGP unnumbered interface configurations are supported with VRF. In BGP unnumbered, there are no addresses on any interface. However, debugging tools like traceroute need at least a single IP address per node as the node’s source IP address. Typically, this address is assigned to the loopback device. With VRF, you need a loopback device for each VRF table since VRF is based on interfaces, not IP addresses. While Linux does not support multiple loopback devices, it does support the concept of a dummy interface, which is used to achieve the same goal.

An IP address can be associated with the VRF device, which will then act as the dummy (loopback-like) interface for that VRF.

The BGP unnumbered configuration is the same as for a non-VRF, applied under the VRF context.

To configure BGP unnumbered:

cumulus@switch:~$ net add vrf vrf1 vrf-table auto
cumulus@switch:~$ net add vrf vrf1 ip address 6.1.0.6/32
cumulus@switch:~$ net add vrf vrf1 ipv6 address 2001:6:1::6/128
cumulus@switch:~$ net add interface swp1 link speed 10000
cumulus@switch:~$ net add interface swp1 link autoneg off
cumulus@switch:~$ net add interface swp1 vrf vrf1
cumulus@switch:~$ net add vlan 101 ip address 20.1.6.1/24
cumulus@switch:~$ net add vlan 101 ipv6 address 2001:20:1:6::1/80
cumulus@switch:~$ net add bridge bridge ports vlan101

Here is the FRRouting BGP configuration:

cumulus@switch:~$ net add bgp vrf vrf1 autonomous-system 65001
cumulus@switch:~$ net add bgp vrf vrf1 bestpath as-path multipath-relax
cumulus@switch:~$ net add bgp vrf vrf1 bestpath compare-routerid
cumulus@switch:~$ net add bgp vrf vrf1 neighbor LEAF peer-group
cumulus@switch:~$ net add bgp vrf vrf1 neighbor LEAF remote-as external
cumulus@switch:~$ net add bgp vrf vrf1 neighbor LEAF capability extended-nexthop
cumulus@switch:~$ net add bgp vrf vrf1 neighbor swp1.101 interface peer-group LEAF
cumulus@switch:~$ net add bgp vrf vrf1 neighbor swp2.101 interface peer-group LEAF
cumulus@switch:~$ net add bgp vrf vrf1 ipv4 unicast redistribute connected
cumulus@switch:~$ net add bgp vrf vrf1 ipv4 unicast neighbor LEAF activate
cumulus@switch:~$ net add bgp vrf vrf1 ipv6 unicast redistribute connected
cumulus@switch:~$ net add bgp vrf vrf1 ipv6 unicast neighbor LEAF activate
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/network/interfaces file. For example:

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto swp1
iface swp1
    link-autoneg on
    link-speed 10000
    vrf vrf1

auto bridge
iface bridge
    bridge-ports vlan101
    bridge-vids 101
    bridge-vlan-aware yes

auto vlan101
iface vlan101
    address 20.1.6.1/24
    address 2001:20:1:6::1/80
    vlan-id 101
    vlan-raw-device bridge

auto vrf1
iface vrf1
    address 6.1.0.6/32
    address 2001:6:1::6/128
    vrf-table auto
...

Here is the FRRouting BGP configuration:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# router bgp 65001 vrf vrf1
switch(config-router)# no bgp default ipv4-unicast
switch(config-router)# bgp bestpath as-path multipath-relax
switch(config-router)# bgp bestpath compare-routerid
switch(config-router)# neighbor LEAF peer-group
switch(config-router)# neighbor LEAF remote-as external
switch(config-router)# neighbor LEAF capability extended-nexthop
switch(config-router)# neighbor swp1.101 interface peer-group LEAF
switch(config-router)# neighbor swp2.101 interface peer-group LEAF
switch(config-router)# address-family ipv4 unicast
switch(config-router-af)# redistribute connected
switch(config-router-af)# neighbor LEAF activate
switch(config-router-af)# exit
switch(config-router)# address-family ipv6 unicast
switch(config-router-af)# redistribute connected
switch(config-router-af)# neighbor LEAF activate
switch(config-router-af)# end
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
router bgp 65001 vrf vrf1
 no bgp default ipv4-unicast
 bgp bestpath as-path multipath-relax
 bgp bestpath compare-routerid
 neighbor LEAF peer-group
 neighbor LEAF remote-as external
 neighbor LEAF capability extended-nexthop
 neighbor swp1.101 interface peer-group LEAF
 neighbor swp2.101 interface peer-group LEAF
 !
 address-family ipv4 unicast
  redistribute connected
  neighbor LEAF activate
  exit-address-family
  !
 address-family ipv6 unicast
  redistribute connected
  neighbor LEAF activate
 exit-address-family
...

DHCP with VRF

Because you can use VRF to bind IPv4 and IPv6 sockets to non-default VRF tables, you can start DHCP servers and relays in any non-default VRF table using the dhcpd and dhcrelay services. These services must be managed by systemd to run in a VRF context. In addition, the services must be listed in the /etc/vrf/systemd.conf file. By default, this file already lists these two services, as well as others. You can add more services as needed, such as dhcpd6 and dhcrelay6 for IPv6.

If you edit /etc/vrf/systemd.conf, run sudo systemctl daemon-reload to generate the systemd instance files for the newly added services. Then you can start the service in the VRF using systemctl start <service>@<vrf-name>.service, where <service> is the name of the service (such as dhcpd or dhcrelay) and <vrf-name> is the name of the VRF.

For example, to start the dhcrelay service after you configure a VRF named turtle, run:

cumulus@switch:~$ sudo systemctl start dhcrelay@turtle.service

To enable the service at boot time, you must also enable the service:

cumulus@switch:~$ sudo systemctl enable dhcrelay@turtle.service

In addition, you need to create a separate default file in /etc/default for every instance of a DHCP server and/or relay in a non-default VRF; this is where you set the server and relay options. To run multiple instances of any of these services, you need a separate file for each instance. The files must be named as follows:

See the example configuration below for more details.

  • Cumulus Linux does not support DHCP server and relay across VRFs; the server and host cannot be in different VRF tables. In addition, the server and relay cannot be in different VRF tables.
  • Typically, a service running in the default VRF owns a port across all VRFs. If the VRF local instance is preferred, first disable and stop the global instance.
  • VRF is a layer 3 routing feature; only run programs that use AF_INET and AF_INET6 sockets in a VRF. VRF context does not affect any other aspects of the operation of a program.
  • This method only works with systemd-based services.

Example Configuration

In the following example, there is one IPv4 network with a VRF named rocket and one IPv6 network with a VRF named turtle.

IPv4 DHCP Server/relay network IPv6 DHCP Server/relay network

Configure each DHCP server and relay as follows:

  1. Create the file isc-dhcp-server-rocket in /etc/default/. Here is sample content:

    # Defaults for isc-dhcp-server initscript
    # sourced by /etc/init.d/isc-dhcp-server
    # installed at /etc/default/isc-dhcp-server by the maintainer scripts
    #
    # This is a POSIX shell fragment
    #
    # Path to dhcpd's config file (default: /etc/dhcp/dhcpd.conf).
    DHCPD_CONF="-cf /etc/dhcp/dhcpd-rocket.conf"
    # Path to dhcpd's PID file (default: /var/run/dhcpd.pid).
    DHCPD_PID="-pf /var/run/dhcpd-rocket.pid"
    # Additional options to start dhcpd with.
    # Don't use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead
    #OPTIONS=""
    # On what interfaces should the DHCP server (dhcpd) serve DHCP requests?
    # Separate multiple interfaces with spaces, e.g. "eth0 eth1".
    INTERFACES="swp2"
    
  2. Enable the DHCP server:

    cumulus@switch:~$ sudo systemctl enable dhcpd@rocket.service
    
  3. Start the DHCP server:

    cumulus@switch:~$ sudo systemctl start dhcpd@rocket.service
    
  4. Check status:

    cumulus@switch:~$ sudo systemctl status dhcpd@rocket.service
    

You can create this configuration using the vrf command (see IPv4 and IPv6 Commands in a VRF Context above for more details):

cumulus@switch:~$ sudo ip vrf exec rocket /usr/sbin/dhcpd -f -q -cf /
    /etc/dhcp/dhcpd-rocket.conf -pf /var/run/dhcpd-rocket.pid swp2
  1. Create the file isc-dhcp-server6-turtle in /etc/default/. Here is sample content:

    # Defaults for isc-dhcp-server initscript
    # sourced by /etc/init.d/isc-dhcp-server
    # installed at /etc/default/isc-dhcp-server by the maintainer scripts
    #
    # This is a POSIX shell fragment
    #
    # Path to dhcpd's config file (default: /etc/dhcp/dhcpd.conf).
    DHCPD_CONF="-cf /etc/dhcp/dhcpd6-turtle.conf"
    # Path to dhcpd's PID file (default: /var/run/dhcpd.pid).
    DHCPD_PID="-pf /var/run/dhcpd6-turtle.pid"
    # Additional options to start dhcpd with.
    # Don't use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead
    #OPTIONS=""
    # On what interfaces should the DHCP server (dhcpd) serve DHCP requests?
    # Separate multiple interfaces with spaces, e.g. "eth0 eth1".
    INTERFACES="swp3"
    
  2. Enable the DHCP server:

    cumulus@switch:~$ sudo systemctl enable dhcpd6@turtle.service
    
  3. Start the DHCP server:

    cumulus@switch:~$ sudo systemctl start dhcpd6@turtle.service
    
  4. Check status:

    cumulus@switch:~$ sudo systemctl status dhcpd6@turtle.service
    

You can create this configuration using the vrf command (see IPv4 and IPv6 Commands in a VRF Context above for more details):

cumulus@switch:~$ sudo ip vrf exec turtle dhcpd -6 -q -cf /
    /etc/dhcp/dhcpd6-turtle.conf -pf /var/run/dhcpd6-turtle.pid swp3
  1. Create the file isc-dhcp-relay-rocket in /etc/default/. Here is sample content:

    # Defaults for isc-dhcp-relay initscript
    # sourced by /etc/init.d/isc-dhcp-relay
    # installed at /etc/default/isc-dhcp-relay by the maintainer scripts
    #
    # This is a POSIX shell fragment
    #
    # What servers should the DHCP relay forward requests to?
    SERVERS="102.0.0.2"
    # On what interfaces should the DHCP relay (dhrelay) serve DHCP requests?
    # Always include the interface towards the DHCP server.
    # This variable requires a -i for each interface configured above.
    # This will be used in the actual dhcrelay command
    # For example, "-i eth0 -i eth1"
    INTF_CMD="-i swp2s2 -i swp2s3"
    # Additional options that are passed to the DHCP relay daemon?
    OPTIONS=""
    
  2. Enable the DHCP relay:

    cumulus@switch:~$ sudo systemctl enable dhcrelay@rocket.service
    
  3. Start the DHCP relay:

    cumulus@switch:~$ sudo systemctl start dhcrelay@rocket.service
    
  4. Check status:

    cumulus@switch:~$ sudo systemctl status dhcrelay@rocket.service
    

You can create this configuration using the vrf command (see IPv4 and IPv6 Commands in a VRF Context above for more details):

cumulus@switch:~$ sudo ip vrf exec rocket /usr/sbin/dhcrelay -d -q -i /
    swp2s2 -i swp2s3 102.0.0.2
  1. Create the file isc-dhcp-relay6-turtle in /etc/default/. Here is sample content:

    # Defaults for isc-dhcp-relay initscript
    # sourced by /etc/init.d/isc-dhcp-relay
    # installed at /etc/default/isc-dhcp-relay by the maintainer scripts
    #
    # This is a POSIX shell fragment
    #
    # What servers should the DHCP relay forward requests to?
    #SERVERS="103.0.0.2"
    # On what interfaces should the DHCP relay (dhrelay) serve DHCP requests?
    # Always include the interface towards the DHCP server.
    # This variable requires a -i for each interface configured above.
    # This will be used in the actual dhcrelay command
    # For example, "-i eth0 -i eth1"
    INTF_CMD="-l swp18s0 -u swp18s1"
    # Additional options that are passed to the DHCP relay daemon?
    OPTIONS="-pf /var/run/dhcrelay6@turtle.pid"
    
  2. Enable the DHCP relay:

    cumulus@switch:~$ sudo systemctl enable dhcrelay6@turtle.service
    
  3. Start the DHCP relay:

    cumulus@switch:~$ sudo systemctl start dhcrelay6@turtle.service
    
  4. Check status:

    cumulus@switch:~$ sudo systemctl status dhcrelay6@turtle.service
    

You can create this configuration using the vrf command (see IPv4 and IPv6 Commands in a VRF Context above for more details):

cumulus@switch:~$ sudo ip vrf exec turtle /usr/sbin/dhcrelay -d -q -6 -l /
    swp18s0 -u swp18s1 -pf /var/run/dhcrelay6@turtle.pid

Use ping or traceroute on a VRF

You can run ping or traceroute on a VRF from the default VRF.

To ping a VRF from the default VRF, run the ping -I <vrf-name> command. For example:

cumulus@switch:~$ ping -I turtle

To run traceroute on a VRF from the default VRF, run the traceroute -i <vrf-name> command. For example:

cumulus@switch:~$ sudo traceroute -i turtle

Caveats and Errata

Management VRF

In Cumulus Linux 4.0, management VRF is enabled by default. This is a change from earlier Cumulus Linux releases, where management VRF is disabled by default. Be sure to update any configuration scripts, if necessary.

Management VRF is a subset of Virtual Routing and Forwarding - VRF (virtual routing tables and forwarding) and provides a separation between the out-of-band management network and the in-band data plane network. For all VRFs, the main routing table is the default table for all of the data plane switch ports. With management VRF, a second table, mgmt, is used for routing through the Ethernet ports of the switch. The mgmt name is special cased to identify the management VRF from a data plane VRF. FIB rules are installed for DNS servers because this is the typical deployment case.

Cumulus Linux only supports eth0 (or eth1, depending on the switch platform) for out-of-band management. The Ethernet ports are software-only ports that are not hardware accelerated by switchd. VLAN subinterfaces, bonds, bridges, and the front panel switch ports are not supported as OOB management interfaces.

In band management of Cumulus Linux is possible using loopbacks and SVIs (switch virtual interfaces).

Management VRF is enabled by default in Cumulus Linux so logins to the switch are set into the management VRF context. IPv4 and IPv6 networking applications (for example, Ansible, Chef, and apt-get) run by an administrator communicate out the management network by default. This default context does not impact services run through systemd and the systemctl command, and does not impact commands examining the state of the switch, such as the ip command to list links, neighbors, or routes.

The management VRF configurations in this chapter contain a localhost loopback IPv4 address of 127.0.0.1/8 and IPv6 address of ::1/128. Management VRF must have an IPv6 address as well as an IPv4 address to work correctly. Adding the loopback address to the layer 3 domain of the management VRF prevents issues with applications that expect the loopback IP address to exist in the VRF, such as NTP.

To disable management VRF, either run the NCLU net del vrf mgmt command or remove the auto mgmt and auto eth0 stanzas from the /etc/network/interfaces file, then reboot the switch:

Bring Up the Management VRF

If you take down the management VRF using ifdown, to bring it back up you need to do one of two things:

The following command example brings down the management VRF, then brings it back up with the ifup --with-depends mgmt command:

cumulus@switch:~$ sudo ifdown mgmt
cumulus@switch:~$ sudo ifup --with-depends mgmt

Running ifreload -a disconnects the session for any interface configured as auto.

Run Services within the Management VRF

At installation, the only enabled service that runs in the management VRF is NTP (ntp@mgmt.service). However, you can run a variety of services within the management VRF instead of the default VRF. When you run a systemd service inside the management VRF, that service runs only on eth0. You cannot configure the same service to run successfully in both the management VRF and the default VRF; you must stop and disable the normal service with systemctl.

You must disable the following services in the default VRF if you want to run them in the management VRF:

You can configure certain services (such as snmpd) to use multiple routing tables, some in the management VRF, some in the default or additional VRFs. The kernel provides a sysctl that allows a single instance to accept connections over all VRFs.

For TCP, connected sockets are bound to the VRF on which the first packet is received.

The following steps show how to enable the SNMP service to run in the management VRF. You can enable any of the services listed above, except for dhcrelay (see DHCP Relays).

  1. If SNMP is running, stop the service:

    cumulus@switch:~$ sudo systemctl stop snmpd.service
    
  2. Disable SNMP from starting automatically in the default VRF:

    cumulus@switch:~$ sudo systemctl disable snmpd.service
    
  3. Start SNMP in the management VRF:

    cumulus@switch:~$ sudo systemctl start snmpd@mgmt.service
    
  4. Enable snmpd@mgmt so that it starts when the switch boots:

    cumulus@switch:~$ sudo systemctl enable snmpd@mgmt.service
    
  5. Verify that the SNMP service is running in the management VRF:

    cumulus@switch:~$ ps aux | grep snmpd
    snmp      3083  0.1  1.9  35916 13292 ?        Ss   21:07   0:00 /usr/sbin/snmpd -y -LS 0-4 d -Lf /dev/null -u snmp -g snmp -I -smux -p /run/snmpd.pid -f
    cumulus   3225  0.0  0.1   6076   884 pts/0    S+   21:07   0:00 grep snmpd
    

Run the following command to show the process IDs associated with the management VRF:

cumulus@switch:~$ ip vrf pids mgmt
1149  ntpd
 1159  login
 1227  bash
16178  vi
  948  dhclient
20934  sshd
20975  bash
21343  sshd
21384  bash
21477  ip

Run the following command to show the VRF association of the specified process:

cumulus@switch:~$ ip vrf identify 2055
mgmt

Run ip vrf help for additional ip vrf commands.

You might see a warning, similar to the one below from systemctl for any management VRF service. You can ignore this warning. This is a problem in systemd in Debian 10 (buster).

Warning: The unit file, source configuration file or drop-ins of ntp@mgmt.service changed on disk. Run ‘systemctl daemon-reload’ to reload unit

Enable Polling with snmpd in a Management VRF

When you enable snmpd to run in the management VRF, you need to specify that VRF so that snmpd listens on eth0 in the management VRF; you can also configure snmpd to listen on other ports. In Cumulus Linux, SNMP configuration is VRF aware so snmpd can bind to multiple IP addresses each configured with a particular VRF (routing table). The snmpd daemon responds to polling requests on the interfaces of the VRF on which the request comes in. For information about configuring SNMP version 1, 2c, and 3 Traps and (v3) Inform messages, refer to Simple Network Management Protocol - SNMP.

The message Duplicate IPv4 address detected, some interfaces may not be visible in IP-MIB displays after starting snmpd in the management VRF. This is because the IP-MIB assumes that the same IP address cannot be used twice on the same device; the IP-MIB is not VRF aware. This message is a warning that the SNMP IP-MIB detects overlapping IP addresses on the system; it does not indicate a problem and is non-impacting to the operation of the switch.

ping or traceroute on the Management VRF

By default, when you issue a ping or traceroute, the packet is sent to the dataplane network (the main routing table). To use ping or traceroute on the management network, use ping -I mgmt or traceroute -i mgmt. To select a source address within the management VRF, use the -s flag for traceroute.

cumulus@switch:~$ ping -I mgmt <destination-ip>

Or:

cumulus@switch:~$ traceroute -s <source-ip> <destination-ip>

For additional information on using ping and traceroute, see Network Troubleshooting.

Run Services as a Non-root User

To run services in the management VRF as a non-root user, you need to create a custom service based on the original service file. The following example commands configure the SSH service to run in the management VRF as a non-root user.

  1. Run the following command to create a custom service file in the /etc/systemd/system direcotry.

    cumulus@switch:~$ sudo -E systemctl edit --full ssh.service
    
  2. If a User directive exists under [Service], comment it out.

    cumulus@switch:~$ sudo nano /etc/systemd/system/ssh.service
    ...
    [Service]
    #User=username
    ExecStart=/usr/local/bin/ssh agent -data-dir=/tmp/ssh -bind=192.168.0.11
    ...
    
  3. Modify the ExecStart line to /usr/bin/ip vrf exec mgmt /sbin/runuser -u USER -- ssh:

    ...
    [Service]
    #User=username
    ExecStart=/usr/bin/ip vrf exec mgmt /sbin/runuser -u cumulus -- ssh
    ...
    

OSPF and BGP

FRRouting is VRF-aware and sends packets based on the switch port routing table. This includes BGP peering via loopback interfaces. BGP does routing lookups in the default table. However, depending on how your routes are redistributed, you might want to perform the following modification.

Management VRF uses the mgmt table, including local routes. It does not affect how the routes are redistributed when using routing protocols such as OSPF and BGP.

To redistribute the routes in your network, use the redistribute connected command under BGP or OSPF. This enables the directly-connected network out of eth0 to be advertised to its neighbor.

This also creates a route on the neighbor device to the management network through the data plane, which might not be desired.

Always use route maps to control the advertised networks redistributed by the redistribute connected command. For example, you can specify a route map to redistribute routes in this way (for both BGP and OSPF):

cumulus@switch:~$ net add routing route-map REDISTRIBUTE-CONNECTED deny 100 match interface eth0
cumulus@switch:~$ net add routing route-map REDISTRIBUTE-CONNECTED permit 1000
cumulus@switch:$ sudo vtysh

switch# configure terminal
switch(config)# route-map REDISTRIBUTE-CONNECTED deny 100 match interface eth0
switch(config)# route-map REDISTRIBUTE-CONNECTED permit 1000
switch(config)# redistribute connected route-map REDISTRIBUTE-CONNECTED
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

The NCLU and vtysh commands save the configuration in the /etc/frr/frr.conf file. For example:

...
<routing-protocol>
redistribute connected route-map REDISTRIBUTE-CONNECTED

route-map REDISTRIBUTE-CONNECTED deny 100
match interface eth0
!
route-map REDISTRIBUTE-CONNECTED permit 1000
...

SSH within a Management VRF Context

If you SSH to the switch through a switch port, SSH works as expected. If you need to SSH from the device out of a switch port, use the ip vrf exec default ssh <switch-port-ip-address> command. For example:

cumulus@switch:~$ sudo ip vrf exec default ssh 10.23.23.2 10.3.3.3

View the Routing Tables

The ip route show command shows the switch port (main) table. You can see the dataplane routing table with the net show route vrf main command.

To show information for eth0 (the management routing table), run the net show route vrf mgmt command:

cumulus@switch:~$ net show route vrf mgmt
default via 192.168.0.1 dev eth0
cumulus@switch:~$ net show route
default via 10.23.23.3 dev swp17  proto zebra  metric 20
10.3.3.3 via 10.23.23.3 dev swp17
10.23.23.0/24 dev swp17  proto kernel  scope link  src 10.23.23.2
192.168.0.0/24 dev eth0  proto kernel  scope link  src 192.168.0.11

If you run the ip route get command to return information about a single route, the command resolves over the mgmt table by default. To obtain information about the route in the switching silicon, run this command:

cumulus@switch:~$ net show route <ip-address>

To show the route for any VRF, run the net show route vrf <vrf-name> <ip-address> command:

cumulus@switch:~$ net show route vrf mgmt <ip-address>

When you use ip route get to return information about a single route, the command resolves over the mgmt table by default. To show information about the route in the switching silicon, run this command:

cumulus@switch:~$ ip route get <ip-address>

Alternatively, you can run this command:

cumulus@switch:~$ sudo cl-rctl ip route show <ip-address> 

To get the route for any VRF, run the ip route get <ip-address> oif <vrf-name> command. For example, to show the route for the management VRF, run:

cumulus@switch:~$ ip route get <ip-address> oif mgmt

mgmt Interface Class

In ifupdown2, interface classes are used to create a user-defined grouping for interfaces. The special class mgmt is available to separate the management interfaces of the switch from the data interfaces. This allows you to manage the data interfaces by default using ifupdown2 commands. Performing operations on the mgmt interfaces requires specifying the --allow-mgmt option, which prevents inadvertent outages on the management interfaces. Cumulus Linux by default brings up all interfaces in both the auto (default) class and the mgmt interface class when the switch boots.

The management VRF interface class is not supported if you are configuring Cumulus Linux using NCLU.

You configure the management interface in the /etc/network/interfaces file. In the example below, the management interface eth0 and the management VRF stanzas are added to the mgmt interface class:

...
auto lo
iface lo inet loopback

allow-mgmt eth0
iface eth0 inet dhcp
    vrf mgmt

allow-mgmt mgmt
iface mgmt
    address 127.0.0.1/8
    address ::1/128
    vrf-table auto
...

When you run ifupdown2 commands against the interfaces in the mgmt class, include --allow=mgmt with the commands. For example, to see which interfaces are in the mgmt interface class, run:

cumulus@switch:~$ ifquery l --allow=mgmt
eth0
mgmt

To reload the configurations for interfaces in the mgmt class, run:

cumulus@switch:~$ sudo ifreload --allow=mgmt

You can still bring the management interface up and down using ifup eth0 and ifdown eth0.

Management VRF and DNS

Cumulus Linux supports both DHCP and static DNS entries over management VRF through IP FIB rules. These rules are added to direct lookups to the DNS addresses out of the management VRF.

For DNS to use the management VRF, the static DNS entries must reference the management VRF in the /etc/resolv.conf file. You cannot specify the same DNS server address twice to associate it with different VRFs.

For example, to specify DNS servers and associate some of them with the management VRF, run the following commands:

cumulus@switch:~$ net add dns nameserver ipv4 192.0.2.1
cumulus@switch:~$ net add dns nameserver ipv4 198.51.100.31 vrf mgmt
cumulus@switch:~$ net add dns nameserver ipv4 203.0.113.13 vrf mgmt
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Edit the /etc/resolv.conf file to add the DNS servers and associate some of them with the management VRF. For example:

cumulus@switch:~$ sudo nano /etc/resolv.conf
nameserver 192.0.2.1
nameserver 198.51.100.31 # vrf mgmt
nameserver 203.0.113.13 # vrf mgmt

Run the ifreload -a command to load the new configuration:

cumulus@switch:~$ ifreload -a

Because DNS lookups are forced out of the management interface using FIB rules, this might affect data plane ports if you use overlapping addresses. For example, when the DNS server IP address is learned over the management VRF, a FIB rule is created for that IP address. When DHCP relay is configured for the same IP address, a DHCP discover packet received on the front panel port is forwarded out of the management interface (eth0) even though a route is present out the front-panel port.

If you do not specify a DNS server and you lose in band connectivity, DNS does not work through the management VRF. Cumulus Linux does not assume all DNS servers are reachable through the management VRF.

Protocol Independent Multicast - PIM

Protocol Independent Multicast (PIM) is a multicast control plane protocol that advertises multicast sources and receivers over a routed layer 3 network. Layer 3 multicast relies on PIM to advertise information about multicast capable routers, and the location of multicast senders and receivers. For this reason, multicast cannot be sent through a routed network without PIM.

Cumulus Linux does not support IPv6 multicast routing with PIM.

PIM has two modes of operation: Sparse Mode (PIM-SM) and Dense Mode (PIM-DM).

Cumulus Linux supports only PIM Sparse Mode.

PIM Overview

The following illustration shows a PIM configuration. The table below the illustration describes the network elements.

Network Element
Description
First Hop Router (FHR) The router attached to the source. The FHR is responsible for the PIM register process.
Last Hop Router (LHR) The last router in the path, attached to an interested multicast receiver. There is a single LHR for each network subnet with an interested receiver, however multicast groups can have multiple LHRs throughout the network.
Rendezvous Point (RP) Allows for the discovery of multicast sources and multicast receivers. The RP is responsible for sending PIM Register Stop messages to FHRs. The PIM RP address must be globally routable.

  • zebra does not resolve the next hop for the RP through the default route. To prevent multicast forwarding from failing, either provide a specific route to the RP or specify the following command to be able to resolve the next hop for the RP through the default route:
    cumulus@switch:~$ sudo vtysh
    switch# configure terminal
    switch(config)# ip nht resolve-via-default
    switch(config)# exit
    switch# write memory
  • Do not use a spine switch as an RP. If you are running BGP on a spine switch and it is not configured for allow-as in origin, BGP does not accept routes learned through other spines that do not originate on the spine itself. The RP must route to a multicast source. During a single failure scenario, this is not possible if the RP is on the spine. This also applies to Multicast Source Discovery Protocol (MSDP).
PIM Shared Tree (RP Tree) or (*,G) Tree The multicast tree rooted at the RP. When receivers want to join a multicast group, join messages are sent along the shared tree towards the RP.
PIM Shortest Path Tree (SPT) or (S,G) Tree The multicast tree rooted at the multicast source for a given group. Each multicast source has a unique SPT. The SPT can match the RP Tree, but this is not a requirement. The SPT represents the most efficient way to send multicast traffic from a source to the interested receivers.
Outgoing Interface (OIF) Indicates the interface on which a PIM or multicast packet is to be sent out. OIFs are the interfaces towards the multicast receivers.
Incoming Interface (IIF) Indicates the interface on which a multicast packet is received. An IIF can be the interface towards the source or towards the RP.
Reverse Path Forwarding Interface (RPF Interface) The path used to reach the RP or source. There must be a valid PIM neighbor to determine the RPF unless directly connected to source.
Multicast Route (mroute) Indicates the multicast source and multicast group as well as associated OIFs, IIFs, and RPF information.
Star-G mroute (*,G) Represents the RP Tree. The * is a wildcard indicating any multicast source. The G is the multicast group. An example (*,G) is (*, 239.1.2.9).
S-G mroute (S,G) This is the mroute representing the source entry. The S is the multicast source IP. The G is the multicast group. An example (S,G) is (10.1.1.1, 239.1.2.9).

PIM Messages

PIM Message
Description
PIM Hello Announce the presence of a multicast router on a segment. PIM hellos are sent every 30 seconds by default. For example:
22.1.2.2 > 224.0.0.13
PIMv2, length 34
Hello, cksum 0xfdbb (correct)
Hold Time Option (1), length 2, Value: 1m45s
0x0000: 0069
LAN Prune Delay Option (2), length 4, Value:
T-bit=0, LAN delay 500ms, Override interval 2500ms
0x0000: 01f4 09c4
DR Priority Option (19), length 4, Value: 1
0x0000: 0000 0001
Generation ID Option (20), length 4, Value
0x2459b190
0x0000: 2459 b190
PIM Join/Prune (J/P) Indicate the groups that a multicast router wants to receive or no longer receive. Often PIM join/prune messages are described as distinct message types, but are actually a single PIM message with a list of groups to join and a second list of groups to leave. PIM J/P messages can be to join or prune from the SPT or RP trees (also called (*,G) joins or (S,G) joins).

Note: PIM join/prune messages are sent to PIM neighbors on individual interfaces. Join/prune messages are never unicast.

This PIM join/prune is for group 239.1.1.9, with 1 join and 0 prunes for the group.
Join/prunes for multiple groups can exist in a single packet.
The following shows an S,G Prune example:
21:49:59.470885 IP (tos 0x0, ttl 255, id 138, offset 0, flags [none], proto PIM (103), length 54)
22.1.2.2 > 224.0.0.13: PIMv2, length 34
Join / Prune, cksum 0xb9e5 (correct), upstream-neighbor: 22.1.2.1
1 group(s), holdtime: 3m30s
group #1: 225.1.0.0, joined sources: 0, pruned sources:
1 pruned source #1: 33.1.1.1(S)
PIM Register Unicast packets sent from an FHR destined to the RP to advertise a multicast group. The FHR fully encapsulates the original multicast packet in PIM register messages. The RP is responsible for decapsulating the PIM register message and forwarding it along the (*,G) tree towards the receivers.
PIM Null Register A special type of PIM register message where the Null-Register flag is set within the packet. Null register messages are used for an FHR to signal to an RP that a source is still sending multicast traffic. Unlike normal PIM register messages, null register messages do not encapsulate the original data packet.
PIM Register Stop Sent by an RP to the FHR to indicate that PIM register messages must no longer be sent. For example:
21:37:00.419379 IP (tos 0x0, ttl 255, id 24, offset 0, flags [none], proto PIM (103), length 38)
100.1.2.1 > 33.1.1.10: PIMv2, length 18
Register Stop, cksum 0xd8db (correct) group=225.1.0.0 source=33.1.1.1
IGMP Membership Report (IGMP Join) Sent by multicast receivers to tell multicast routers of their interest in a specific multicast group. IGMP join messages trigger PIM *,G joins. IGMP version 2 queries are sent to the all hosts multicast address, 224.0.0.1. IGMP version 2 reports (joins) are sent to the group’s multicast address. IGMP version 3 messages are sent to an IGMP v3 specific multicast address, 224.0.0.22.
IGMP Leave Tell a multicast router that a multicast receiver no longer wants the multicast group. IGMP leave messages trigger PIM *,G prunes.

PIM Neighbors

When PIM is configured on an interface, PIM Hello messages are sent to the link local multicast group 224.0.0.13. Any other router configured with PIM on the segment that hears the PIM Hello messages builds a PIM neighbor with the sending device.

PIM neighbors are stateless. No confirmation of neighbor relationship is exchanged between PIM endpoints.

Configure PIM

To configure PIM, run the following commands:

  1. Configure the PIM interfaces. You must enable PIM on all interfaces facing multicast sources or multicast receivers, as well as on the interface where the RP address is configured.

    cumulus@switch:~$ net add interface swp1 pim
    

    In Cumulus Linux 4.0 the sm keyword is no longer required. In Cumulus Linux releases 3.7 and earlier, the correct command is net add interface swp1 pim sm.

  2. Enable IGMP on all interfaces with hosts attached. IGMP version 3 is the default. Only specify the version if you exclusively want to use IGMP version 2. SSM requires the use of IGMP version 3. You must configure IGMP on all interfaces where multicast receivers exist.

    cumulus@switch:~$ net add interface swp1 igmp
    
  3. For ASM, configure a group mapping for a static RP:

    cumulus@switch:~$ net add pim rp 192.168.0.1
    cumulus@switch:~$ net pending
    cumulus@switch:~$ net commit
    

Each PIM enabled device must configure a static RP to a group mapping and all PIM-SM enabled devices must have the same RP to group mapping configuration.

IP PIM RP group ranges can overlap. Cumulus Linux performs a longest prefix match (LPM) to determine the RP. In the following example, if the group is in 224.10.2.5, RP 192.168.0.2 is selected. If the group is in 224.10.15, RP 192.168.0.1 is selected:

cumulus@switch:~$ net add pim rp 192.168.0.1 224.10.0.0/16
cumulus@switch:~$ net add pim rp 192.168.0.2 224.10.2.0/24

PIM is included in the FRRouting package. For proper PIM operation, PIM depends on Zebra. PIM also relies on unicast routing to be configured and operational for RPF operations. You must configure a routing protocol or static routes.

  1. Edit the /etc/frr/daemons file and add pimd=yes to the end of the file:

    cumulus@switch:~$ sudo nano /etc/frr/daemons
    ...
    pimd=yes
    ...
    
  2. Restart FRR with this command:

cumulus@switch:~$ sudo systemctl restart frr.service

Restarting FRR restarts all the routing protocol daemons that are enabled and running.

  1. In the vtysh shell, run the following commands to configure the PIM interfaces. PIM must be enabled on all interfaces facing multicast sources or multicast receivers, as well as on the interface where the RP address is configured.

    In Cumulus Linux 4.0 the sm keyword is no longer required.

    cumulus@switch:~$ sudo vtysh
    
    switch# configure terminal
    switch(config)# interface swp1
    switch(config-if)# ip pim
    
  2. Enable IGMP on all interfaces with hosts attached. IGMP version 3 is the default. Only specify the version if you exclusively want to use IGMP version 2.

    switch(config-if)# ip igmp
    switch(config-if)# exit
    switch(config)#
    

You must configure IGMP on all interfaces where multicast receivers exist.

  1. For ASM, configure a group mapping for a static RP:

    switch(config)# ip pim rp 192.168.0.1
    switch(config)# exit
    switch# write memory
    switch#  exit
    cumulus@switch:~$
    

Each PIM enabled device must configure a static RP to a group mapping and all PIM-SM enabled devices must have the same RP to group mapping configuration.

IP PIM RP group ranges can overlap. Cumulus Linux performs a longest prefix match (LPM) to determine the RP. In the following example, if the group is in 224.10.2.5, RP 192.168.0.2 is selected. If the group is in 224.10.15, RP 192.168.0.1 is selected:

switch(config)# ip pim rp 192.168.0.1 224.10.0.0/16
switch(config)# ip pim rp 192.168.0.2 224.10.2.0/24

PIM Sparse Mode (PIM-SM)

PIM Sparse Mode (PIM-SM) is a pull multicast distribution method; multicast traffic is only sent through the network if receivers explicitly ask for it. When a receiver pulls multicast traffic, the network must be periodically notified that the receiver wants to continue the multicast stream.

This behavior is in contrast to PIM Dense Mode (PIM-DM), where traffic is flooded, and the network must be periodically notified that the receiver wants to stop receiving the multicast stream.

PIM-SM has three configuration options:

Cumulus Linux only supports ASM and SSM. PIM BiDir is not currently supported.

For additional information, see RFC 7761 - Protocol Independent Multicast - Sparse Mode.

Any-source Multicast Routing (ASM)

Multicast routing behaves differently depending on whether the source is sending before receivers request the multicast stream, or if a receiver tries to join a stream before there are any sources.

Receiver Joins First

When a receiver joins a group, an IGMP membership join message is sent to the IGMPv3 multicast group, 224.0.0.22. The PIM multicast router for the segment that is listening to the IGMPv3 group receives the IGMP membership join message and becomes an LHR for this group.

This creates a (*,G) mroute with an OIF of the interface on which the IGMP Membership Report is received and an IIF of the RPF interface for the RP.

The LHR generates a PIM (*,G) join message and sends it from the interface towards the RP. Each multicast router between the LHR and the RP builds a (*,G) mroute with the OIF being the interface on which the PIM join message is received and an Incoming Interface of the reverse path forwarding interface for the RP.

When the RP receives the (*,G) Join message, it does not send any additional PIM join messages. The RP maintains a (*,G) state as long as the receiver wants to receive the multicast group.

Unlike multicast receivers, multicast sources do not send IGMP (or PIM) messages to the FHR. A multicast source begins sending, and the FHR receives the traffic and builds both a (*,G) and an (S,G) mroute. The FHR then begins the PIM register process.

PIM Register Process

When a first hop router (FHR) receives a multicast data packet from a source, the FHR does not know if there are any interested multicast receivers in the network. The FHR encapsulates the data packet in a unicast PIM register message. This packet is sourced from the FHR and destined to the RP address. The RP builds an (S,G) mroute, decapsulates the multicast packet, and forwards it along the (*,G) tree.

As the unencapsulated multicast packet travels down the (*,G) tree towards the interested receivers, at the same time, the RP sends a PIM (S,G) join towards the FHR. This builds an (S,G) state on each multicast router between the RP and FHR.

When the FHR receives a PIM (S,G) join, it continues encapsulating and sending PIM register messages, but also makes a copy of the packet and sends it along the (S,G) mroute.

The RP then receives the multicast packet along the (S,G) tree and sends a PIM register stop to the FHR to end the register process.

PIM SPT Switchover

When the LHR receives the first multicast packet, it sends a PIM (S,G) join towards the FHR to efficiently forward traffic through the network. This builds the shortest path tree (SPT), or the tree that is the shortest path to the source. When the traffic arrives over the SPT, a PIM (S,G) RPT prune is sent up the shared tree towards the RP. This removes multicast traffic from the shared tree; multicast data is only sent over the SPT.

You can configure SPT switchover on a per-group basis, allowing for some groups to never switch to a shortest path tree; this is also called SPT infinity. The LHR now sends both (*,G) joins and (S,G) RPT prune messages towards the RP.

To configure a group to never follow the SPT, create the necessary prefix-lists, then configure SPT switchover for the spt-range prefix-list:

cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# ip prefix-list spt-range permit 235.0.0.0/8 ge 32
switch(config)# ip prefix-list spt-range permit 238.0.0.0/8 ge 32
switch(config)# ip pim spt-switchover infinity prefix-list spt-range
switch(config)# end
switch# exit
cumulus@switch:~$

To view the configured prefix-list, run the vtysh show ip mroute command or the NCLU net show mroute command. The following command shows that 235.0.0.0 is configured for SPT switchover, identified by pimreg.

switch# show ip mroute
Source          Group           Proto  Input      Output     TTL  Uptime
*               235.0.0.0       IGMP   swp31s0    pimreg     1    00:03:3
                                IGMP              br1        1    00:03:38
*               238.0.0.0       IGMP   swp31s0    br1        1    00:02:08

Sender Starts Before Receivers Join

A multicast sender can send multicast data without any additional IGMP or PIM signaling. When the FHR receives the multicast traffic, it encapsulates it and sends a PIM register to the rendezvous point (RP).

When the RP receives the PIM register, it builds an (S,G) mroute; however, there is no (*,G) mroute and no interested receivers.

The RP drops the PIM register message and immediately sends a PIM register stop message to the FHR.

Receiving a PIM register stop without any associated PIM joins leaves the FHR without any outgoing interfaces. The FHR drops this multicast traffic until a PIM join is received.

PIM register messages are sourced from the interface that receives the multicast traffic and are destined to the RP address. The PIM register is not sourced from the interface towards the RP.

PIM Null-Register

To notify the RP that multicast traffic is still flowing when the RP has no receiver, or if the RP is not on the SPT tree, the FHR periodically sends PIM null register messages. The FHR sends a PIM register with the Null-Register flag set, but without any data. This special PIM register notifies the RP that a multicast source is still sending, in case any new receivers come online.

After receiving a PIM Null-Register, the RP immediately sends a PIM register stop to acknowledge the reception of the PIM null register message.

Source Specific Multicast Mode (SSM)

The source-specific multicast method uses prefix lists to configure a receiver to only allow traffic to a multicast address from a single source. This removes the need for an RP, as the source must be known before traffic can be accepted. There is no additional PIM configuration required to enable SSM beyond enabling PIM and IGMPv3 on the relevant interfaces.

Receiver Joins First

When a receiver sends an IGMPv3 Join with the source defined the LHR builds an S,G entry and sends a PIM S,G join to the PIM neighbor closest to the source, according to the routing table.

The full path between LHR and FHR contains an S,G state, although no multicast traffic is flowing. Periodic IGMPv3 joins between the receiver and LHR, as well as PIM S,G joins between PIM neighbors, maintain this state until the receiver leaves.

When the sender begins, traffic immediately flows over the pre-built SPT from the sender to the receiver.

Sender Starts Before Receivers Join

In SSM when a sender begins sending, the FHR does not have any existing mroutes. The traffic is dropped and nothing further happens until a receiver joins. SSM does no rely on an RP; there is no PIM Register process.

Differences between Source Specific Multicast and Any Source Multicast

SSM differs from ASM multicast in the following ways:

PIM Active-Active with MLAG

For a multicast sender or receiver to be supported over a dual-attached MLAG bond, you must configure pim active-active.

To configure PIM active-active with MLAG, run the following commands:

  1. On the VLAN interface where multicast sources or receivers exist, configure pim active-active and igmp. For example:

    cumulus@switch:~$ net add vlan 12 pim active-active
    cumulus@switch:~$ net add vlan 12 igmp
    cumulus@switch:~$ net pending
    cumulus@switch:~$ net commit
    

Enabling PIM active-active automatically enables PIM on that interface.

  1. Confirm PIM active-active is configured with the net show pim mlag summary command:

    cumulus@leaf01:mgmt:~$ net show pim mlag summary
    MLAG daemon connection: up
    MLAG peer state: up
    Zebra peer state: up
    MLAG role: PRIMARY
    Local VTEP IP: 0.0.0.0
    Anycast VTEP IP: 0.0.0.0
    Peerlink: peerlink.4094
    Session flaps: mlagd: 0 mlag-peer: 0 zebra-peer: 0
    Message Statistics:
    mroute adds: rx: 5, tx: 5
    mroute dels: rx: 0, tx: 0
    peer zebra status updates: 1
    PIM status updates: 0
    VxLAN updates: 0
    
  1. Configure ip pim active-active on the VLAN interface where the multicast source or receiver exists along with the required ip igmp command.

    cumulus@leaf01:~$ sudo vtysh
    
    leaf01# configure terminal
    leaf01(config)# interface vlan12
    leaf01(config-if)# ip pim active-active
    leaf01(config-if)# ip igmp
    

Enabling PIM active-active automatically enables PIM on that interface.

  1. Confirm that PIM active-active is configured with the show ip pim mlag summary command:

    leaf01# show ip pim mlag summary
    MLAG daemon connection: up
    MLAG peer state: up
    Zebra peer state: up
    MLAG role: PRIMARY
    Local VTEP IP: 0.0.0.0
    Anycast VTEP IP: 0.0.0.0
    Peerlink: peerlink.4094
    Session flaps: mlagd: 0 mlag-peer: 0 zebra-peer: 0
    Message Statistics:
    mroute adds: rx: 5, tx: 5
    mroute dels: rx: 0, tx: 0
    peer zebra status updates: 1
    PIM status updates: 0
    VxLAN updates: 0
    

Multicast Sender

When a multicast sender is attached to an MLAG bond, the sender hashes the outbound multicast traffic over a single member of the bond. Traffic is received on one of the MLAG enabled switches. Regardless of which switch receives the traffic, it is forwarded over the MLAG peer link to the other MLAG-enabled switch, because the peerlink is always considered a multicast router port and will always receive the multicast stream.

Traffic from multicast sources attached to an MLAG bond is always sent over the MLAG peerlink. Be sure to size the peerlink appropriately to accommodate this traffic.

The PIM DR for the VLAN where the source resides is responsible for sending the PIM register towards the RP. The PIM DR is the PIM speaker with the highest IP address on the segment. After the PIM register process is complete and traffic is flowing along the Shortest Path Tree (SPT), either MLAG switch will forward traffic towards the receivers.

Examples are provided below that show the flow of traffic between server02 and server03:

Step 1 Step 2

To show the PIM DR, run the NCLU net show pim interface command or the vtysh show ip pim interface command. The following example shows that in Vlan12 the DR is 10.1.2.12.

cumulus@leaf01:mgmt:~$ net show pim interface
Interface         State          Address  PIM Nbrs           PIM DR  FHR IfChannels
lo                   up        10.0.0.11         0            local    0          0
pimreg               up          0.0.0.0         0            local    0          0
swp51                up        10.0.0.11         1        10.0.0.21    0          4
swp52                up        10.0.0.11         1        10.0.0.22    0          0
vlan12               up        10.1.2.11         1        10.1.2.12    0          2

PIM joins sent towards the source can be ECMP load shared by upstream PIM neighbors (spine01 and spine02 in the example above). Either MLAG member can receive the PIM join and forward traffic, regardless of DR status.

Multicast Receiver

A dual-attached multicast receiver sends an IGMP join on the attached VLAN. The specific interface that is used is determined based on the host. The IGMP join is received on one of the MLAG switches, and the IGMP join is added to the IGMP Join table and layer 2 MDB table. The layer 2 MDB table, like the unicast MAC address table, is synced via MLAG control messages over the peerlink. This allows both MLAG switches to program IGMP and MDB table forwarding information.

Both switches send *,G PIM Join messages towards the RP. If the source is already sending, both MLAG switches receive the multicast stream.

Traditionally, the PIM DR is the only node to send the PIM *,G Join, but to provide resiliency in case of failure, both MLAG switches send PIM *,G Joins towards the RP to receive the multicast stream.

To prevent duplicate multicast packets, a Designated Forward (DF) is elected. The DF is the primary member of the MLAG pair. As a result, the MLAG secondary puts the VLAN in the Outgoing Interface List (OIL), preventing duplicate multicast traffic.

Verify PIM

The following outputs are based on the Cumulus Reference Topology with cldemo-pim.

Source Starts First

On the FHR, an mroute is built, but the upstream state is Prune. The FHR flag is set on the interface receiving multicast. Run the NCLU net show commands to review detailed output for the FHR. For example:

cumulus@fhr:~$ net show mroute
Source          Group           Proto  Input      Output     TTL  Uptime
172.16.5.105    239.1.1.1       none   br0        none       0    --:--:--
!
cumulus@fhr:~$ net show pim upstream
Iif Source Group State Uptime JoinTimer RSTimer KATimer RefCnt
br0 172.16.5.105 239.1.1.1 Prune 00:07:40 --:--:-- 00:00:36 00:02:50 1
!
cumulus@fhr:~$ net show pim upstream-join-desired
Interface Source          Group           LostAssert Joins PimInclude JoinDesired EvalJD
!
cumulus@fhr:~$ net show pim interface
Interface  State          Address  PIM Nbrs           PIM DR  FHR
br0           up       172.16.5.1         0            local    1
swp51         up        10.1.0.17         1            local    0
swp52         up        10.1.0.19         0            local    0
!
cumulus@fhr:~$ net show pim state
Source           Group            IIF    OIL
172.16.5.105     239.1.1.1        br0
!
cumulus@fhr:~$ net show pim interface detail
Interface : br0
State     : up
Address   : 172.16.5.1
Designated Router
-----------------
Address   : 172.16.5.1
Priority  : 1
Uptime    : --:--:--
Elections : 2
Changes   : 0

FHR - First Hop Router
----------------------
239.1.1.1 : 172.16.5.105 is a source, uptime is 00:27:43

On the RP, no mroute state is created, but the net show pim upstream output includes the Source and Group:

cumulus@rp01:~$ net show mroute
Source          Group           Proto  Input      Output     TTL  Uptime
!
cumulus@rp01:~$ net show pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
swp30     172.16.5.105    239.1.1.1       Prune       00:00:19 --:--:--  --:--:--  00:02:46       1

As a receiver joins the group, the mroute output interface on the FHR transitions from none to the RPF interface of the RP:

cumulus@fhr:~$ net show mroute
Source          Group           Proto  Input      Output     TTL  Uptime
172.16.5.105    239.1.1.1       PIM    br0        swp51      1    00:05:40
!
cumulus@fhr:~$ net show pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
br0       172.16.5.105    239.1.1.1       Prune       00:48:23 --:--:--  00:00:00  00:00:37       2
!

cumulus@fhr:~$ net show pim upstream-join-desired
Interface Source          Group           LostAssert Joins PimInclude JoinDesired EvalJD
swp51     172.16.5.105    239.1.1.1       no         yes   no         yes         yes
!
cumulus@fhr:~$ net show pim state
Source           Group            IIF    OIL
172.16.5.105     239.1.1.1        br0    swp51

cumulus@rp01:~$ net show mroute
Source          Group           Proto  Input      Output     TTL  Uptime
*               239.1.1.1       PIM    lo         swp1       1    00:09:59
172.16.5.105    239.1.1.1       PIM    swp30      swp1       1    00:09:59
!
cumulus@rp01:~$ net show pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
lo        *               239.1.1.1       Joined      00:10:01 00:00:59  --:--:--  --:--:--       1
swp30     172.16.5.105    239.1.1.1       Joined      00:00:01 00:00:59  --:--:--  00:02:35       1
!
cumulus@rp01:~$ net show pim upstream-join-desired
Interface Source          Group           LostAssert Joins PimInclude JoinDesired EvalJD
swp1      *               239.1.1.1       no         yes   no         yes         yes
!
cumulus@rp01:~$ net show pim state
Source           Group            IIF    OIL
*                239.1.1.1        lo     swp1
172.16.5.105     239.1.1.1        swp30  swp1

Receiver Joins First

On the LHR attached to the receiver:

cumulus@lhr:~$ net show mroute
Source          Group           Proto  Input      Output     TTL  Uptime
*               239.2.2.2       IGMP   swp51      br0        1    00:01:19
!
cumulus@lhr:~$ net show pim local-membership
Interface Address         Source          Group           Membership
br0       172.16.1.1      *               239.2.2.2       INCLUDE
!
cumulus@lhr:~$ net show pim state
Source           Group            IIF    OIL
*                239.2.2.2        swp51  br0
!
cumulus@lhr:~$ net show pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
swp51     *               239.2.2.2       Joined      00:02:07 00:00:53  --:--:--  --:--:--       1
!
cumulus@lhr:~$ net show pim upstream-join-desired
Interface Source          Group           LostAssert Joins PimInclude JoinDesired EvalJD
br0       *               239.2.2.2       no         no    yes        yes         yes
!
cumulus@lhr:~$ net show igmp groups
Interface Address         Group           Mode Timer    Srcs V Uptime
br0       172.16.1.1      239.2.2.2       EXCL 00:04:02    1 3 00:04:12
!
cumulus@lhr:~$ net show igmp sources
Interface Address         Group           Source          Timer Fwd Uptime
br0       172.16.1.1      239.2.2.2       *               03:54   Y 00:04:21

On the RP

cumulus@rp01:~$ net show mroute
Source          Group           Proto  Input      Output     TTL  Uptime
*               239.2.2.2       PIM    lo         swp1       1    00:00:03
!
cumulus@rp01:~$ net show pim state
Source           Group            IIF    OIL
*                239.2.2.2        lo     swp1
!
cumulus@rp01:~$ net show pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
lo        *               239.2.2.2       Joined      00:05:17 00:00:43  --:--:--  --:--:--       1
!
cumulus@rp01:~$ net show pim upstream-join-desired
Interface Source          Group           LostAssert Joins PimInclude JoinDesired EvalJD
swp1      *               239.2.2.2       no         yes   no         yes         yes

Source Starts First

On the FHR, an mroute is built, but the upstream state is Prune. The FHR flag is set on the interface receiving multicast.

Use the vtysh show ip commands to review detailed output for the FHR. For example:

cumulus@fhr:~$ sudo vtysh
fhr# show ip mroute
Source          Group           Proto  Input      Output     TTL  Uptime
172.16.5.105    239.1.1.1       none   br0        none       0    --:--:--

fhr# show ip pim upstream
Iif Source Group State Uptime JoinTimer RSTimer KATimer RefCnt
br0 172.16.5.105 239.1.1.1 Prune 00:07:40 --:--:-- 00:00:36 00:02:50 1

fhr# show ip pim upstream-join-desired
Interface Source          Group           LostAssert Joins PimInclude JoinDesired EvalJD
!
fhr# show ip pim interface
Interface  State          Address  PIM Nbrs           PIM DR  FHR
br0           up       172.16.5.1         0            local    1
swp51         up        10.1.0.17         1            local    0
swp52         up        10.1.0.19         0            local    0

fhr# show ip pim state
Source           Group            IIF    OIL
172.16.5.105     239.1.1.1        br0

fhr# show ip pim interface detail
Interface : br0
State     : up
Address   : 172.16.5.1
Designated Router
-----------------
Address   : 172.16.5.1
Priority  : 1
Uptime    : --:--:--
Elections : 2
Changes   : 0

FHR - First Hop Router
----------------------
239.1.1.1 : 172.16.5.105 is a source, uptime is 00:27:43

On the RP, no mroute state is created, but the show ip pim upstream output includes the Source and Group:

rp01# show ip mroute
Source          Group           Proto  Input      Output     TTL  Uptime

rp01# show ip pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
swp30     172.16.5.105    239.1.1.1       Prune       00:00:19 --:--:--  --:--:--  00:02:46       1

As a receiver joins the group, the mroute output interface on the FHR transitions from none to the RPF interface of the RP:

fhr# show ip mroute
Source          Group           Proto  Input      Output     TTL  Uptime
172.16.5.105    239.1.1.1       PIM    br0        swp51      1    00:05:40

fhr# show ip pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
br0       172.16.5.105    239.1.1.1       Prune       00:48:23 --:--:--  00:00:00  00:00:37       2

fhr# show ip pim upstream-join-desired
Interface Source          Group           LostAssert Joins PimInclude JoinDesired EvalJD
swp51     172.16.5.105    239.1.1.1       no         yes   no         yes         yes

fhr# show ip pim state
Source           Group            IIF    OIL
172.16.5.105     239.1.1.1        br0    swp51

rp01# show ip mroute
Source          Group           Proto  Input      Output     TTL  Uptime
*               239.1.1.1       PIM    lo         swp1       1    00:09:59
172.16.5.105    239.1.1.1       PIM    swp30      swp1       1    00:09:59

rp01# show ip pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
lo        *               239.1.1.1       Joined      00:10:01 00:00:59  --:--:--  --:--:--       1
swp30     172.16.5.105    239.1.1.1       Joined      00:00:01 00:00:59  --:--:--  00:02:35       1

rp01# show ip pim upstream-join-desired
Interface Source          Group           LostAssert Joins PimInclude JoinDesired EvalJD
swp1      *               239.1.1.1       no         yes   no         yes         yes

rp01# show ip pim state
Source           Group            IIF    OIL
*                239.1.1.1        lo     swp1
172.16.5.105     239.1.1.1        swp30  swp1

Receiver Joins First

On the LHR attached to the receiver:

lhr# show ip mroute
Source          Group           Proto  Input      Output     TTL  Uptime
*               239.2.2.2       IGMP   swp51      br0        1    00:01:19

lhr# show ip pim local-membership
Interface Address         Source          Group           Membership
br0       172.16.1.1      *               239.2.2.2       INCLUDE

lhr# show ip pim state
Source           Group            IIF    OIL
    *                239.2.2.2        swp51  br0

lhr# show ip pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
swp51     *               239.2.2.2       Joined      00:02:07 00:00:53  --:--:--  --:--:--       1

lhr# show ip pim upstream-join-desired
Interface Source          Group           LostAssert Joins PimInclude JoinDesired EvalJD
br0       *               239.2.2.2       no         no    yes        yes         yes

lhr# show ip igmp groups
Interface Address         Group           Mode Timer    Srcs V Uptime
    br0       172.16.1.1      239.2.2.2       EXCL 00:04:02    1 3 00:04:12

lhr# show ip igmp sources
Interface Address         Group           Source          Timer Fwd Uptime
br0       172.16.1.1      239.2.2.2       *               03:54   Y 00:04:21

On the RP:

rp01# show ip mroute
Source          Group           Proto  Input      Output     TTL  Uptime
*               239.2.2.2       PIM    lo         swp1       1    00:00:03

rp01# show ip pim state
    Source           Group            IIF    OIL
    *                239.2.2.2        lo     swp1

rp01# show ip pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
lo        *               239.2.2.2       Joined      00:05:17 00:00:43  --:--:--  --:--:--       1
rp01# show ip pim upstream-join-desired
Interface Source          Group           LostAssert Joins PimInclude JoinDesired EvalJD
swp1      *               239.2.2.2       no         yes   no         yes         yes

Additional PIM Features

Custom SSM multicast group ranges

PIM considers 232.0.0.0/8 the default SSM range. You can change the SSM range by defining a prefix-list and attaching it to the ssm-range command. You can change the default SSM group or add additional group ranges to be treated as SSM groups.

If you use the ssm-range command, all SSM ranges must be in the prefix-list, including 232.0.0.0/8.

Create a prefix-list with the permit keyword to match address ranges that should be treated as SSM groups and deny keyword for those ranges which should not be treated as SSM enabled ranges.

cumulus@switch:~$ net add routing prefix-list ipv4 my-custom-ssm-range seq 5 permit 232.0.0.0/8 ge 32
cumulus@switch:~$ net add routing prefix-list ipv4 my-custom-ssm-range seq 10 permit 238.0.0.0/8 ge 32

Apply the custom prefix-list as an ssm-range

cumulus@switch:~$ net add pim ssm prefix-list my-custom-ssm-range
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

To view the configured prefix-lists, run the net show ip prefix-list command:

cumulus@switch:~$ net show ip prefix-list my-custom-ssm-range
ZEBRA: ip prefix-list my-custom-ssm-range: 1 entries
   seq 5 permit 232.0.0.0/8 ge 32
PIM: ip prefix-list my-custom-ssm-range: 1 entries
   seq 10 permit 232.0.0.0/8 ge 32

Create a prefix-list with the permit keyword to match address ranges that you want to treat as SSM groups and the deny keyword for the ranges you do not want to treat as SSM-enabled ranges:

cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# ip prefix-list ssm-range seq 5 permit 232.0.0.0/8 ge 32
switch(config)# ip prefix-list ssm-range seq 10 permit 238.0.0.0/8 ge 32

Apply the custom prefix-list as an ssm-range:

switch(config)# ip pim ssm prefix-list ssm-range
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

To view the configured prefix-lists, run the show ip prefix-list my-custom-ssm-range command:

switch#  show ip prefix-list my-custom-ssm-range
ZEBRA: ip prefix-list my-custom-ssm-range: 1 entries
   seq 5 permit 232.0.0.0/8 ge 32
PIM: ip prefix-list my-custom-ssm-range: 1 entries
   seq 10 permit 232.0.0.0/8 ge 32

PIM and ECMP

PIM uses the RPF procedure to choose an upstream interface to build a forwarding state. If you configure equal-cost multipaths (ECMP), PIM chooses the RPF based on the ECMP hash algorithm.

Run the net add pim ecmp command to enable PIM to use all the available nexthops for the installation of mroutes. For example, if you have four-way ECMP, PIM spreads the S,G and *,G mroutes across the four different paths.

cumulus@switch:~$ net add pim ecmp
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

Run the ip pim ecmp rebalance command to recalculate all stream paths in the event of a loss of path over one of the ECMP paths. Without this command, only the streams that are using the path that is lost are moved to alternate ECMP paths. Rebalance does not affect existing groups.

cumulus@switch:~$ net add pim ecmp rebalance
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

The rebalance command might cause some packet loss.

Run the ip pim ecmp command to enable PIM to use all the available nexthops for the installation of mroutes. For example, if you have four-way ECMP, PIM spreads the S,G and *,G mroutes across the four different paths.

cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# ip pim ecmp
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

Run the ip pim ecmp rebalance command to recalculate all stream paths in the event of a loss of path over one of the ECMP paths. Without this command, only the streams that are using the path that is lost are moved to alternate ECMP paths. Rebalance does not affect existing groups.

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# ip pim ecmp rebalance
switch(config)# exit
switch# write memory
switch# exit
cumulus@switch:~$

The rebalance command might cause some packet loss.

To show which nexthop is selected for a specific source/group, run the show ip pim nexthop command from the vtysh shell:

cumulus@switch:~$ sudo vtysh
switch# show ip pim nexthop
Number of registered addresses: 3
Address         Interface      Nexthop
-------------------------------------------
6.0.0.9         swp31s0        169.254.0.9
6.0.0.9         swp31s1        169.254.0.25
6.0.0.11        lo             0.0.0.0
6.0.0.10        swp31s0        169.254.0.9
6.0.0.10        swp31s1        169.254.0.25

IP Multicast Boundaries

Multicast boundaries enable you to limit the distribution of multicast traffic by setting boundaries with the goal of pushing multicast to a subset of the network.

With such boundaries in place, any incoming IGMP or PIM joins are dropped or accepted based upon the prefix-list specified. The boundary is implemented by applying an IP multicast boundary OIL (outgoing interface list) on an interface.

To configure the boundary, first create a prefix-list as described above, then run the following commands to configure the IP multicast boundary:

cumulus@switch:~$ net add interface swp1 multicast boundary oil <prefix-list>
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh
switch# configure terminal
switch(config)# interface swp1
switch(config-if)# ip multicast boundary oil <prefix-list>
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

Multicast Source Discovery Protocol (MSDP)

You can use the Multicast Source Discovery Protocol (MSDP) to connect multiple PIM-SM multicast domains together, using the PIM-SM RPs. By configuring any cast RPs with the same IP address on multiple multicast switches (primarily on the loopback interface), the PIM-SM limitation of only one RP per multicast group is relaxed. This allows for an increase in both failover and load-balancing throughout.

When an RP discovers a new source (typically a PIM-SM register message), a source-active (SA) message is sent to each MSDP peer. The peer then determines if any receivers are interested.

Cumulus Linux MSDP support is primarily for anycast-RP configuration, rather than multiple multicast domains. You must configure each MSDP peer in a full mesh, as SA messages are not received and reforwarded.

Cumulus Linux currently only supports one MSDP mesh group.

The following steps demonstrate how to configure a Cumulus switch to use the MSDP:

  1. Add an anycast IP address to the loopback interface for each RP in the domain:

    cumulus@rp01:~$ net add loopback lo ip address 10.1.1.1/32
    cumulus@rp01:~$ net add loopback lo ip address 10.1.1.100/32
    
  2. On every multicast switch, configure the group to RP mapping using the anycast address:

    cumulus@switch:$ net add pim rp 10.1.1.100 224.0.0.0/4
    cumulus@switch:$ net pending
    cumulus@switch:$ net commit
    
  3. Configure the MSDP mesh group for all active RPs (the following example uses 3 RPs). The mesh group must include all RPs in the domain as members, with a unique address as the source. This configuration results in MSDP peerings between all RPs.

    cumulus@rp01:$ net add msdp mesh-group cumulus member 100.1.1.2
    cumulus@rp01:$ net add msdp mesh-group cumulus member 100.1.1.3
    
    cumulus@rp02:$ net add msdp mesh-group cumulus member 100.1.1.1
    cumulus@rp02:$ net add msdp mesh-group cumulus member 100.1.1.3
    
    cumulus@rp03:$ net add msdp mesh-group cumulus member 100.1.1.1
    cumulus@rp03:$ net add msdp mesh-group cumulus member 100.1.1.2
    
  4. Pick the local loopback address as the source of the MSDP control packets:

    cumulus@rp01:$ net add msdp mesh-group cumulus source 100.1.1.1
    
    cumulus@rp02:$ net add msdp mesh-group cumulus source 100.1.1.2
    
    cumulus@rp03:$ net add msdp mesh-group cumulus source 100.1.1.3
    
  5. Inject the anycast IP address into the IGP of the domain. If the network is unnumbered and uses unnumbered BGP as the IGP, avoid using the anycast IP address for establishing unicast or multicast peerings. For PIM-SM, ensure that the unique address is used as the PIM hello source by setting the source:

    cumulus@rp01:$ net add loopback lo pim use-source 100.1.1.1
    cumulus@rp01:$ net pending
    cumulus@rp01:$ net commit
    
  1. Edit the /etc/network/interfaces file to add an anycast IP address to the loopback interface for each RP in the domain. For example:

    cumulus@rp01:~$ sudo nano /etc/network/interfaces
    auto lo
    iface lo inet loopback
       address 10.0.0.11/32
       address 10.1.1.1/32
    ...
    
  2. Run the ifreload -a command to load the new configuration:

    cumulus@switch:~$ ifreload -a
    
  3. On every multicast switch, configure the group to RP mapping using the anycast address:

    cumulus@rp01:~$ sudo vtysh
    
    rp01# configure terminal
    rp01(config)# ip pim rp 10.1.1.100 224.0.0.0/4
    
  4. Configure the MSDP mesh group for all active RPs (the following example uses 3 RPs). The mesh group must include all RPs in the domain as members, with a unique address as the source. This configuration results in MSDP peerings between all RPs.

    rp01(config)# ip msdp mesh-group cumulus member 100.1.1.2
    rp01(config)# ip msdp mesh-group cumulus member 100.1.1.3
    
    rp02(config)# ip msdp mesh-group cumulus member 100.1.1.1
    rp02(config)# ip msdp mesh-group cumulus member 100.1.1.3
    
    rp03(config)# ip msdp mesh-group cumulus member 100.1.1.1
    rp03(config)# ip msdp mesh-group cumulus member 100.1.1.2
    
  5. Pick the local loopback address as the source of the MSDP control packets

    rp01# ip msdp mesh-group cumulus source 100.1.1.1
    rp02# ip msdp mesh-group cumulus source 100.1.1.2
    rp03# ip msdp mesh-group cumulus source 100.1.1.3
    
  6. Inject the anycast IP address into the IGP of the domain. If the network is unnumbered and uses unnumbered BGP as the IGP, avoid using the anycast IP address for establishing unicast or multicast peerings. For PIM-SM, ensure that the unique address is used as the PIM hello source by setting the source:

    rp01# interface lo
    rp01(config-if)# ip pim use-source 100.1.1.1
    rp01(config-if)# end
    rp01# write memory
    rp01# exit
    cumulus@rp01:~$
    

PIM in a VRF

VRFs divide the routing table on a per-tenant basis, ultimately providing for separate layer 3 networks over a single layer 3 infrastructure. With a VRF, each tenant has its own virtualized layer 3 network, so IP addresses can overlap between tenants.

PIM in a VRF enables PIM trees and multicast data traffic to run inside a layer 3 virtualized network, with a separate tree per domain or tenant. Each VRF has its own multicast tree with its own RP(s), sources, and so on. Therefore, you can have one tenant per corporate division, client, or product; for example.

VRFs on different switches typically connect or are peered over subinterfaces, where each subinterface is in its own VRF, provided MP-BGP VPN is not enabled or supported.

To configure PIM in a VRF, run the following commands.

First, add the VRFs and associate them with switch ports:

cumulus@switch:~$ net add vrf blue
cumulus@switch:~$ net add vrf purple
cumulus@switch:~$ net add interface swp1 vrf blue
cumulus@switch:~$ net add interface swp2 vrf purple

Then add the PIM configuration to FRR, review and commit the changes:

cumulus@switch:~$ net add interface swp1 pim sm
cumulus@switch:~$ net add interface swp2 pim sm
cumulus@switch:~$ net add bgp vrf blue auto 65001
cumulus@switch:~$ net add bgp vrf purple auto 65000
cumulus@switch:~$ net add bgp vrf blue router-id 10.1.1.1
cumulus@switch:~$ net add bgp vrf purple router-id 10.1.1.2
cumulus@switch:~$ net add bgp vrf blue neighbor swp1 interface remote-as external
cumulus@switch:~$ net add bgp vrf purple neighbor swp2 interface remote-as external
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

First, edit the /etc/network/interfaces file and to the VRFs and associate them with switch ports, then run ifreload -a to reload the configuration.

cumulus@switch:~$ sudo nano /etc/network/interfaces
...
auto swp1
iface swp1
    vrf blue

auto swp2
iface swp2
    vrf purple

auto blue
iface blue
    vrf-table auto

auto purple
iface purple
    vrf-table auto
...

Then add the PIM configuration to FRR. You can do this in vtysh:

cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface swp1
switch(config-if)# ip pim sm
switch(config-if)# exit
switch(config)# interface swp2
switch(config-if)# ip pim sm
switch(config-if)# exit
switch(config)# router bgp 65001 vrf blue
switch(config-router)# bgp router-id 10.1.1.2
switch(config-router)# neighbor swp1 interface remote-as external
switch(config-router)# exit
switch(config)# router bgp 65000 vrf purple
switch(config-router)# bgp router-id 10.1.1.1
switch(config-router)# neighbor swp2 interface remote-as external
switch(config-router)# end
switch# write memory
switch# exit
cumulus@switch:~$

To show VRF information, run the NCLU net show mroute vrf <vrf-name> command or the vtysh show ip mroute vrf <vrf-name> command:

cumulus@fhr:~$ net show mroute vrf blue
Source          Group           Proto  Input      Output     TTL  Uptime
11.1.0.1        239.1.1.1       IGMP   swp32s0    swp32s1    1    00:01:13
                                IGMP              br0.200    1    00:01:13
*               239.1.1.2       IGMP   mars       pimreg1001 1    00:01:13
                                IGMP              swp32s1    1    00:01:12
                                IGMP              br0.200    1    00:01:13

BFD for PIM Neighbors

You can use bidirectional forward detection (BFD) for PIM neighbors to quickly detect link failures. When you configure an interface, include the pim bfd option. For example:

cumulus@switch:~$ net add interface swp31s3 pim bfd
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
cumulus@switch:~$ sudo vtysh

switch# configure terminal
switch(config)# interface swp31s3
switch(config-if)# ip pim bfd
switch(config-if)# end
switch# write memory
switch# exit
cumulus@switch:~$

Troubleshooting

FHR Stuck in Registering Process

When a multicast source starts, the FHR sends unicast PIM register messages from the RPF interface towards the source. After the PIM register is received by the RP, a PIM register stop message is sent from the RP to the FHR to end the register process. If an issue occurs with this communication, the FHR becomes stuck in the registering process, which can result in high CPU, as PIM register packets are generated by the FHR CPU and sent to the RP CPU.

To assess this issue:

Review the FHR. The output interface of pimreg can be seen here. If this does not change to an interface within a few seconds, the FHR is likely stuck.

cumulus@fhr:~$ net show mroute
Source          Group           Proto  Input      Output     TTL  Uptime
172.16.5.105    239.2.2.3       PIM    br0        pimreg     1    00:03:59

To troubleshoot the issue:

  1. Validate that the FHR can reach the RP. If the RP and FHR can not communicate, the registration process fails:

    cumulus@fhr:~$ ping 10.0.0.21 -I br0
    PING 10.0.0.21 (10.0.0.21) from 172.16.5.1 br0: 56(84) bytes of data.
    ^C
    --- 10.0.0.21 ping statistics ---
    4 packets transmitted, 0 received, 100% packet loss, time 3000ms
    
  2. On the RP, use tcpdump to see if the PIM register packets are arriving:

    cumulus@rp01:~$ sudo tcpdump -i swp30
    tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
    listening on swp30, link-type EN10MB (Ethernet), capture size 262144 bytes
    23:33:17.524982 IP 172.16.5.1 > 10.0.0.21: PIMv2, Register, length 66
    
  3. If PIM registration packets are being received, verify that they are seen by PIM by issuing debug pim packets from within FRRouting:

    cumulus@fhr:~$ sudo vtysh -c "debug pim packets"
    PIM Packet debugging is on
    
    cumulus@rp01:~$ sudo tail /var/log/frr/frr.log
    2016/10/19 23:46:51 PIM: Recv PIM REGISTER packet from 172.16.5.1 to 10.0.0.21 on swp30: ttl=255 pim_version=2 pim_msg_size=64 checksum=a681
    
  4. Repeat the process on the FHR to see if PIM register stop messages are being received on the FHR and passed to the PIM process:

    cumulus@fhr:~$ sudo tcpdump -i swp51
    23:58:59.841625 IP 172.16.5.1 > 10.0.0.21: PIMv2, Register, length 28
    23:58:59.842466 IP 10.0.0.21 > 172.16.5.1: PIMv2, Register Stop, length 18
    
    cumulus@fhr:~$ sudo vtysh -c "debug pim packets"
    PIM Packet debugging is on
    
    cumulus@fhr:~$ sudo tail -f /var/log/frr/frr.log
    2016/10/19 23:59:38 PIM: Recv PIM REGSTOP packet from 10.0.0.21 to 172.16.5.1 on swp51: ttl=255 pim_version=2 pim_msg_size=18 checksum=5a39
    

No *,G Is Built on LHR

The most common reason for a *,G to not be built on an LHR is for if both PIM and IGMP are not enabled on an interface facing a receiver.

lhr# show run
!
interface br0
 ip igmp
 ip ospf area 0.0.0.0
 ip pim sm

To troubleshoot this issue, if both PIM and IGMP are enabled, ensure that IGMPv3 joins are being sent by the receiver:

cumulus@lhr:~$ sudo tcpdump -i br0 igmp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on br0, link-type EN10MB (Ethernet), capture size 262144 bytes
00:03:55.789744 IP 172.16.1.101 > igmp.mcast.net: igmp v3 report, 1 group record(s)

No mroute Created on FHR

To troubleshoot this issue:

  1. Verify that multicast traffic is being received:

    cumulus@fhr:~$ sudo tcpdump -i br0
    tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
    listening on br0, link-type EN10MB (Ethernet), capture size 262144 bytes
    00:11:52.944745 IP 172.16.5.105.51570 > 239.2.2.9.1000: UDP, length 9
    
  2. Verify that PIM is configured on the interface facing the source:

    fhr# show run
    !
    interface br0
    ip ospf area 0.0.0.0
    ip pim sm
    
  3. If PIM is configured, verify that the RPF interface for the source matches the interface on which the multicast traffic is received:

    fhr# show ip rpf 172.16.5.105
    Routing entry for 172.16.5.0/24 using Multicast RIB
    Known via "connected", distance 0, metric 0, best
    * directly connected, br0
    
  4. Verify that an RP is configured for the multicast group:

    fhr# show ip pim rp-info
    RP address       group/prefix-list   OIF         I am RP
    10.0.0.21        224.0.0.0/4         swp51       no
    

No S,G on RP for an Active Group

An RP does not build an mroute when there are no active receivers for a multicast group, even though the mroute was created on the FHR.

cumulus@rp01:~$ net show mroute
Source          Group           Proto  Input      Output     TTL  Uptime
spine01#

cumulus@rp01:~$ net show mroute
Source          Group           Proto  Input      Output     TTL  Uptime
172.16.5.105    239.2.2.9       none   br0        none       0    --:--:--

This is expected behavior. You can see the active source on the RP with either the NCLU net show pim upstream command or the vtysh show ip pim upstream command:

cumulus@rp01:~$ net show pim upstream
Iif       Source          Group           State       Uptime   JoinTimer RSTimer   KATimer   RefCnt
swp30     172.16.5.105    239.2.2.9       Prune       00:08:03 --:--:--  --:--:--  00:02:20       1

No mroute Entry Present in Hardware

Use the cl-resource-query command to verify that the hardware IP multicast entry is the maximum value:

cumulus@switch:~$ cl-resource-query  | grep Mcast
  Total Mcast Routes:         450,   0% of maximum value    450

For Spectrum chipsets, refer to TCAM Resource Profiles for Spectrum Switches.

Verify MSDP Session State

To verify the state of MSDP sessions, run either the NCLU net show msdp mesh-group command or the vtysh show ip msdp mesh-group command:

cumulus@switch:~$ net show msdp mesh-group 
Mesh group : pod1
  Source : 100.1.1.1
  Member                 State
  100.1.1.2        established
  100.1.1.3        established
cumulus@switch:~$ 
cumulus@switch:~$ net show msdp peer
Peer                       Local        State    Uptime   SaCnt
100.1.1.2              100.1.1.1  established  00:07:21       0
100.1.1.3              100.1.1.1  established  00:07:21       0

View the Active Sources

To review the active sources learned locally (through PIM registers) and from MSDP peers, run either the NCLU net show msdp sa command or the vtysh show ip msdp sa command:

cumulus@switch:~$ net show msdp sa
Source                     Group               RP  Local  SPT    Uptime
44.1.11.2              239.1.1.1        100.1.1.1      n    n  00:00:40
44.1.11.2              239.1.1.2        100.1.1.1      n    n  00:00:25

Example Configurations

Complete Multicast Network Configuration Example
RP# show run
Building configuration...
Current configuration:
!
log syslog
ip multicast-routing
ip pim rp 192.168.0.1 224.0.0.0/4
username cumulus nopassword
!
!
interface lo
 description RP Address interface
 ip ospf area 0.0.0.0
 ip pim sm
!
interface swp1
 description interface to FHR
 ip ospf area 0.0.0.0
 ip ospf network point-to-point
 ip pim sm
!
interface swp2
 description interface to LHR
 ip ospf area 0.0.0.0
 ip ospf network point-to-point
 ip pim sm
!
router ospf
 ospf router-id 192.168.0.1
!
line vty
!
end
FHR# show run
!
log syslog
ip multicast-routing
ip pim rp 192.168.0.1 224.0.0.0/4
username cumulus nopassword
!
interface bridge10.1
 description Interface to multicast source
 ip ospf area 0.0.0.0
 ip ospf network point-to-point
 ip pim sm
!
interface lo
 ip ospf area 0.0.0.0
 ip pim sm
!
interface swp49
 description interface to RP
 ip ospf area 0.0.0.0
 ip ospf network point-to-point
 ip pim sm
!
interface swp50
 description interface to LHR
 ip ospf area 0.0.0.0
 ip ospf network point-to-point
 ip pim sm
 !
router ospf
 ospf router-id 192.168.1.1
!
line vty
!
end
LHR# show run
!
log syslog
ip multicast-routing
ip pim rp 192.168.0.1 224.0.0.0/4
username cumulus nopassword
!
interface bridge10.1
 description interface to multicast receivers
 ip igmp
 ip ospf area 0.0.0.0
 ip ospf network point-to-point
 ip pim sm
!
interface lo
 ip ospf area 0.0.0.0
 ip pim sm
!
interface swp49
 description interface to RP
 ip ospf area 0.0.0.0
 ip ospf network point-to-point
 ip pim sm
!
interface swp50
 description interface to FHR
 ip ospf area 0.0.0.0
 ip ospf network point-to-point
 ip pim sm
!
router ospf
 ospf router-id 192.168.2.2
!
line vty
!
end

Caveats and Errata

Monitoring and Troubleshooting

This chapter introduces monitoring and troubleshooting Cumulus Linux.

Serial Console

The serial console is a useful tool for debugging issues, especially when you find yourself rebooting the switch often or if you do not have a reliable network connection.

The default serial console baud rate is 115200, which is the baud rate ONIE uses.

Configure the Serial Console on ARM Switches

On ARM switches, the U-Boot environment variable baudrate identifies the baud rate of the serial console. To change the baudrate variable, use the fw_setenv command:

cumulus@switch:~$ sudo fw_setenv baudrate 9600
Updating environment variable: `baudrate'
Proceed with update [N/y]? y

You must reboot the switch for the baudrate change to take effect.

The valid values for baudrate are:

Configure the Serial Console on x86 Switches

On x86 switches, you configure serial console baud rate by editing grub.

Incorrect configuration settings in grub can cause the switch to be inaccessible via the console. Review grub changes carefully before you implement them.

The valid values for the baud rate are:

To change the serial console baud rate:

  1. Edit the /etc/default/grub file. The two relevant lines in /etc/default/grub are as follows; replace the 115200 value with a valid value specified above in the --speed variable in the first line and in the console variable in the second line:

    GRUB_SERIAL_COMMAND="serial --port=0x2f8 --speed=115200 --word=8 --parity=no --stop=1"
    GRUB_CMDLINE_LINUX="console=ttyS1,115200n8 cl_platform=accton_as5712_54x"
    
  2. After you save your changes to the grub configuration, type the following at the command prompt:

    cumulus@switch:~$ update-grub
    
  3. If you plan on accessing the switch BIOS over the serial console, you need to update the baud rate in the switch BIOS. For more information, see this knowledge base article.

  4. Reboot the switch.

Change the Console Log Level

By default, the console prints all log messages except debug messages. To tune console logging to be less verbose so that certain levels of messages are not printed, run the dmesg -n <level> command, where the log levels are:

Level Description
0 Emergency messages (the system is about to crash or is unstable).
1 Serious conditions; you must take action immediately.
2 Critical conditions (serious hardware or software failures).
3 Error conditions (often used by drivers to indicate difficulties with the hardware).
4 Warning messages (nothing serious but might indicate problems).
5 Message notifications for many conditions, including security events.
6 Informational messages.
7 Debug messages.

Only messages with a value lower than the level specified are printed to the console. For example, if you specify level 3, only level 2 (critical conditions), level 1 (serious conditions), and level 0 (emergency messages) are printed to the console:

cumulus@switch:~$ sudo dmesg -n 3

Alternatively, you can run dmesg --console-level <level> command, where the log levels are emerg, alert, crit, err, warn, notice, info, or debug. For example, to print critical conditions, run the following command:

cumulus@switch:~$ sudo dmesg --console-level crit

The dmesg command is applied until the next reboot.

For more details about the dmesg command, run man dmesg.

Show General System Information

Two commands are helpful for getting general information about the switch and the version of Cumulus Linux you are running. These are helpful with system diagnostics and if you need to submit a support request.

For information about the version of Cumulus Linux running on the switch, run the net show version,command which displays the contents of /etc/lsb-release:

cumulus@switch:~$ net show version
NCLU_VERSION=1.0-cl4u1
DISTRIB_ID="Cumulus Linux"
DISTRIB_RELEASE=4.0.0
DISTRIB_DESCRIPTION="Cumulus Linux 4.0.0"

For general information about the switch, run net show system, which gathers information about the switch from a number of files in the system:

cumulus@switch:~$ net show system
Hostname......... celRED

Build............ Cumulus Linux 4.0.0
Uptime........... 8 days, 12:24:01.770000

Model............ Cel REDSTONE
CPU.............. x86_64 Intel Atom C2538 2.4 GHz
Memory........... 4GB
Disk............. 14.9GB
ASIC............. Broadcom Trident2 BCM56854
Ports............ 48 x 10G-SFP+ & 6 x 40G-QSFP+
Base MAC Address. a0:00:00:00:00:50

Diagnostics Using cl-support

You can use cl-support to generate a single export file that contains various details and the configuration from a switch. This is useful for remote debugging and troubleshooting. For more information about cl-support, read Understanding the cl-support Output File.

Run cl-support before you submit a support request as this file helps in the investigation of issues.

cumulus@switch:~$ sudo cl-support -h
Usage: [-h (help)] [-cDjlMsv] [-d m1,m2,...] [-e m1,m2,...]
  [-p prefix] [-r reason] [-S dir] [-T Timeout_seconds] [-t tag]
  -h: Display this help message
  -c: Run only modules matching any core files, if no -e modules
  -D: Display debugging information
  -d: Disable (do not run) modules in this comma separated list
  -e: Enable (only run) modules in this comma separated list; "-e all" runs
      all modules and sub-modules, including all optional modules
...

Send Log Files to a syslog Server

You can configure the remote syslog server on the switch using the following configuration:

cumulus@switch:~$ net add syslog host ipv4 192.168.0.254 port udp 514
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

This creates a file called /etc/rsyslog.d/11-remotesyslog.conf in the rsyslog directory. The file has the following content:

cumulus@switch:~$ cat /etc/rsyslog.d/11-remotesyslog.conf
# This file was automatically generated by NCLU.
*.*   @192.168.0.254:514   # UDP

NCLU cannot configure a remote syslog if management VRF is enabled on the switch. Refer to Monitoring and Troubleshooting below.

Log Technical Details

Logging on Cumulus Linux is done with rsyslog. rsyslog provides both local logging to the syslog file as well as the ability to export logs to an external syslog server. High precision timestamps are enabled for all rsyslog log files; for example:

2015-08-14T18:21:43.337804+00:00 cumulus switchd[3629]: switchd.c:1409 switchd version 1.0-cl2.5+5

There are applications in Cumulus Linux that can write directly to a log file without going through rsyslog. These files are typically located in /var/log/.

All Cumulus Linux rules are stored in separate files in /etc/rsyslog.d/, which are called at the end of the GLOBAL DIRECTIVES section of /etc/rsyslog.conf. As a result, the RULES section at the end of rsyslog.conf is ignored because the messages have to be processed by the rules in /etc/rsyslog.d and then dropped by the last line in /etc/rsyslog.d/99-syslog.conf.

Local Logging

Most logs within Cumulus Linux are sent through rsyslog, which writes them to files in the /var log directory. There are default rules in the /etc/rsyslog.d/ directory that define where the logs are written:

Rule Purpose
10-rules.conf Sets defaults for log messages, include log format and log rate limits.
15-crit.conf Logs crit, alert or emerg log messages to /var/log/crit.log to ensure they are not rotated away rapidly.
20-clagd.conf Logs clagd messages to /var/log/clagd.log for MLAG.
22-linkstate.conf Logs link state changes for all physical and logical network links to /var/log/linkstate.
25-switchd.conf Logs switchd messages to /var/log/switchd.log.
30-ptmd.conf Logs ptmd messages to /var/log/ptmd.log for Prescription Topology Manager.
35-rdnbrd.conf Logs rdnbrd messages to /var/log/rdnbrd.log for Redistribute Neighbor.
40-netd.conf Logs netd messages to /var/log/netd.log for NCLU.
45-frr.conf Logs routing protocol messages to /var/log/frr/frr.log. This includes BGP and OSPF log messages.
99-syslog.conf All remaining processes that use rsyslog are sent to /var/log/syslog.

Log files that are rotated are compressed into an archive. Processes that do not use rsyslog write to their own log files within the /var/log directory. For more information on specific log files, see Troubleshooting Log Files.

Enable Remote syslog

By default not all log messages are sent to a remote server

To send other log files (such as switchd logs) to a syslog server:

  1. Create a file in /etc/rsyslog.d/. Make sure the filename starts with a number lower than 99 so that it executes before log messages are dropped in, such as 20-clagd.conf or 25-switchd.conf. The example file below is called /etc/rsyslog.d/11-remotesyslog.conf. Add content similar to the following:

    ## Logging switchd messages to remote syslog server
    
    @192.168.1.2:514
    

    This configuration sends log messages to a remote syslog server for the following processes: clagd, switchd, ptmd, rdnbrd, netd and syslog. It follows the same syntax as the /var/log/syslog file, where @ indicates UDP, 192.168.1.2 is the IP address of the syslog server, and 514 is the UDP port.

    • For TCP-based syslog, use two @@ before the IP address @@192.168.1.2:514.
    • The numbering of the files in /etc/rsyslog.d/ dictates how the rules are installed into rsyslog.d. Lower numbered rules are processed first, and rsyslog processing terminates with the stop keyword. For example, the rsyslog configuration for FRR is stored in the 45-frr.conf file with an explicit stop at the bottom of the file. FRR messages are logged to the /var/log/frr/frr.log file on the local disk only (these messages are not sent to a remote server using the default configuration). To log FRR messages remotely in addition to writing FRR messages to the local disk, rename the 99-syslog.conf file to 11-remotesyslog.conf. FRR messages are first processed by the 11-remotesyslog.conf rule (transmit to remote server), then continue to be processed by the 45-frr.conf file (write to local disk in the /var/log/frr/frr.log file).
    • Do not use the imfile module with any file written by rsyslogd.

  2. Restart rsyslog.

    cumulus@switch:~$ sudo systemctl restart rsyslog.service
    

Write to syslog with Management VRF Enabled

You can write to syslog with management VRF enabled by applying the following configuration; this configuration is commented out in the /etc/rsyslog.d/11-remotesyslog.conf file:

cumulus@switch:~$ cat /etc/rsyslog.d/11-remotesyslog.conf
## Copy all messages to the remote syslog server at 192.168.0.254 port 514
action(type="omfwd" Target="192.168.0.254" Device="mgmt" Port="514" Protocol="udp")

For each syslog server, configure a unique action line. For example, to configure two syslog servers at 192.168.0.254 and 10.0.0.1:

cumulus@switch:~$ cat /etc/rsyslog.d/11-remotesyslog.conf
## Copy all messages to the remote syslog servers at 192.168.0.254 and 10.0.0.1 port 514
action(type="omfwd" Target="192.168.0.254" Device="mgmt" Port="514" Protocol="udp")
action(type="omfwd" Target="10.0.0.1" Device="mgmt" Port="514" Protocol="udp")

If you configure remote logging to use the TCP protocol, local logging might stop when the remote syslog server is unreachable. To avoid this behavior, configure a disk queue size and maximum retry count in your rsyslog configuration:

action(type="omfwd" Target="172.28.240.15" Device="mgmt" Port="1720" Protocol="tcp" action.resumeRetryCount="100" queue.type="linkedList" queue.size="10000")

Rate-limit syslog Messages

If you want to limit the number of syslog messages that can be written to the syslog file from individual processes, add the following configuration to the /etc/rsyslog.conf file. Adjust the interval and burst values to rate-limit messages to the appropriate levels required by your environment. For more information, read the rsyslog documentation.

module(load="imuxsock"
      SysSock.RateLimit.Interval="2" SysSock.RateLimit.Burst="50")
Example rate-limit Output
root@leaf1:mgmt-vrf:/home/cumulus# cat ./syslog.py 
#!/usr/bin/python
import syslog
message_count=100
print "Sending %s Messages..."%(message_count)
for i in range(0,message_count):
syslog.syslog("Message Number:%s"%(i))
print "DONE."

root@leaf1:mgmt-vrf:/home/cumulus# ./syslog.py
Sending 100 Messages...
DONE.

root@leaf1:mgmt-vrf:/home/cumulus# tail -n 60 /var/log/syslog
2017-02-22T19:59:50.043342+00:00 leaf1 syslog.py[22830]: Message Number:0
2017-02-22T19:59:50.043723+00:00 leaf1 syslog.py[22830]: Message Number:1
2017-02-22T19:59:50.043941+00:00 leaf1 syslog.py[22830]: Message Number:2
2017-02-22T19:59:50.044565+00:00 leaf1 syslog.py[22830]: Message Number:3
2017-02-22T19:59:50.044830+00:00 leaf1 syslog.py[22830]: Message Number:4
2017-02-22T19:59:50.045680+00:00 leaf1 syslog.py[22830]: Message Number:5
<...snip...>
2017-02-22T19:59:50.056727+00:00 leaf1 syslog.py[22830]: Message Number:45
2017-02-22T19:59:50.057599+00:00 leaf1 syslog.py[22830]: Message Number:46
2017-02-22T19:59:50.057741+00:00 leaf1 syslog.py[22830]: Message Number:47
2017-02-22T19:59:50.057936+00:00 leaf1 syslog.py[22830]: Message Number:48
2017-02-22T19:59:50.058125+00:00 leaf1 syslog.py[22830]: Message Number:49
2017-02-22T19:59:50.058324+00:00 leaf1 rsyslogd-2177: imuxsock[pid 22830]: begin to drop messages due to rate-limiting

Harmless syslog Error: Failed to reset devices.list

The following message is logged to /var/log/syslog when you run systemctl daemon-reload and during system boot:

systemd[1]: Failed to reset devices.list on /system.slice: Invalid argument

This message is harmless, and can be ignored. It is logged when systemd attempts to change group attributes that are read only. The upstream version of systemd has been modified to not log this message by default.

The systemctl daemon-reload command is often issued when Debian packages are installed, so the message may be seen multiple times when upgrading packages.

Syslog Troubleshooting Tips

You can use the following commands to troubleshoot syslog issues.

Verifying that rsyslog is Running

To verify that the rsyslog service is running, use the sudo systemctl status rsyslog.service command:

cumulus@leaf01:mgmt-vrf:~$ sudo systemctl status rsyslog.service
rsyslog.service - System Logging Service
  Loaded: loaded (/lib/systemd/system/rsyslog.service; enabled)
  Active: active (running) since Sat 2017-12-09 00:48:58 UTC; 7min ago
    Docs: man:rsyslogd(8)
          http://www.rsyslog.com/doc/
Main PID: 11751 (rsyslogd)
  CGroup: /system.slice/rsyslog.service
          └─11751 /usr/sbin/rsyslogd -n

Dec 09 00:48:58 leaf01 systemd[1]: Started System Logging Service.

Verify your rsyslog Configuration

After making manual changes to any files in the /etc/rsyslog.d directory, use the sudo rsyslogd -N1 command to identify any errors in the configuration files that might prevent the rsyslog service from starting.

In the following example, a closing parenthesis is missing in the 11-remotesyslog.conf file, which is used to configure syslog for management VRF:

cumulus@leaf01:mgmt-vrf:~$ cat /etc/rsyslog.d/11-remotesyslog.conf
action(type="omfwd" Target="192.168.0.254" Device="mgmt" Port="514" Protocol="udp"

cumulus@leaf01:mgmt-vrf:~$ sudo rsyslogd -N1
rsyslogd: version 8.4.2, config validation run (level 1), master config /etc/rsyslog.conf
syslogd: error during parsing file /etc/rsyslog.d/15-crit.conf, on or before line 3: invalid character '$' in object definition - is there an invalid escape sequence somewhere? [try http: /www.rsyslog.com/e/2207 ]
rsyslogd: error during parsing file /etc/rsyslog.d/15-crit.conf, on or before line 3: syntax error on token 'crit_log' [try http://www.rsyslog.com/e/2207 ]

After correcting the invalid syntax, issuing the sudo rsyslogd -N1 command produces the following output.

cumulus@leaf01:mgmt-vrf:~$ cat /etc/rsyslog.d/11-remotesyslog.conf
action(type="omfwd" Target="192.168.0.254" Device="mgmt" Port="514" Protocol="udp")
cumulus@leaf01:mgmt-vrf:~$ sudo rsyslogd -N1
rsyslogd: version 8.4.2, config validation run (level 1), master config /etc/rsyslog.conf
rsyslogd: End of config validation run. Bye.

tcpdump

If a syslog server is not accessible to validate that syslog messages are being exported, you can use tcpdump.

In the following example, a syslog server has been configured at 192.168.0.254 for UDP syslogs on port 514:

cumulus@leaf01:mgmt-vrf:~$ sudo tcpdump -i eth0 host 192.168.0.254 and udp port 514

A simple way to generate syslog messages is to use sudo in another session, such as sudo date. Using sudo generates an authpriv log.

cumulus@leaf01:mgmt-vrf:~$ sudo tcpdump -i eth0 host 192.168.0.254 and udp port 514
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
00:57:15.356836 IP leaf01.lab.local.33875 > 192.168.0.254.syslog: SYSLOG authpriv.notice, length: 105
00:57:15.364346 IP leaf01.lab.local.33875 > 192.168.0.254.syslog: SYSLOG authpriv.info, length: 103
00:57:15.369476 IP leaf01.lab.local.33875 > 192.168.0.254.syslog: SYSLOG authpriv.info, length: 85

To see the contents of the syslog file, use the tcpdump -X option:

cumulus@leaf01:mgmt-vrf:~$ sudo tcpdump -i eth0 host 192.168.0.254 and udp port 514 -X -c 3
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
00:59:15.980048 IP leaf01.lab.local.33875 > 192.168.0.254.syslog: SYSLOG authpriv.notice, length: 105
0x0000: 4500 0085 33ee 4000 4011 8420 c0a8 000b E...3.@.@.......
0x0010: c0a8 00fe 8453 0202 0071 9d18 3c38 353e .....S...q..<85>
0x0020: 4465 6320 2039 2030 303a 3539 3a31 3520 Dec..9.00:59:15.
0x0030: 6c65 6166 3031 2073 7564 6f3a 2020 6375 leaf01.sudo:..cu
0x0040: 6d75 6c75 7320 3a20 5454 593d 7074 732f mulus.:.TTY=pts/
0x0050: 3120 3b20 5057 443d 2f68 6f6d 652f 6375 1.;.PWD=/home/cu
0x0060: 6d75 6c75 7320 3b20 5553 4552 3d72 6f6f mulus.;.USER=roo
0x0070: 7420 3b20 434f 4d4d 414e 443d 2f62 696e t.;.COMMAND=/bin
0x0080: 2f64 6174 65 /date

Single User Mode - Password Recovery

Use single user mode to assist in troubleshooting system boot issues or for password recovery.

To enter single user mode:

  1. Boot the switch, then as soon as you see the GRUB menu, use the arrow keys to select Advanced options for Cumulus Linux GNU/Linux.

    Before the GRUB menu appears, the switch goes through the boot cycle. Do not interrupt this autoboot process when you see the following lines; wait until you see the GRUB menu.

    ...
    CLOCKS:ARM Core=1000Hz, AXI=500Hz, APB=125Hz, Peripheral=500Hz
    USB0:  Bringing USB2 host out of reset...
    Net:   eth-0
    SF:    MX25L6405D with page size 4 KiB, total 8 MiB
    Hit any key to stop autoboot:  2
    

                    GNU GRUB  version 2.02+dfsg1-20
    
    +----------------------------------------------------------------------------+
    |*Cumulus Linux GNU/Linux                                                    |
    | Advanced options for Cumulus Linux GNU/Linux                               |
    | ONIE                                                                       |
    |                                                                            |
    +----------------------------------------------------------------------------+
    
  2. Select Cumulus Linux GNU/Linux, with Linux 4.19.0-cl-1-amd64 (recovery mode).

                    GNU GRUB  version 2.02+dfsg1-20
    
    +----------------------------------------------------------------------------+
    | Cumulus Linux GNU/Linux, with Linux 4.19.0-cl-1-amd64                       |
    |*Cumulus Linux GNU/Linux, with Linux 4.19.0-cl-1-amd64 (recovery mode)       |
    |                                                                            |
    +----------------------------------------------------------------------------+  
    
  3. After the system reboots, set a new root password. The root user provides complete control over the switch.

    root@switch:~# passwd
    Enter new UNIX password:
    Retype new UNIX password:
    passwd: password updated successfully
    

    You can take this opportunity to reset the password for the cumulus account.

    root@switch:~# passwd cumulus
    Enter new UNIX password:
    Retype new UNIX password:
    passwd: password updated successfully
    
  4. Sync the /etc directory, then reboot the system:

    root@switch:~# sync
    root@switch:~# reboot -f
    Restarting the system.
    

Resource Diagnostics Using cl-resource-query

You can use the cl-resource-query command to retrieve information about host entries, MAC entries, layer 2 and layer 3 routes, and ECMP routes that are in use. Because Cumulus Linux synchronizes routes between the kernel and the switching silicon, if the required resource pools in hardware fill up, new kernel routes can cause existing routes to move from being fully allocated to being partially allocated. To avoid this, monitor the routes in the hardware to keep them below the ASIC limits. For example, on a Broadcom Tomahawk switch, the limits are as follows:

routes: 8192 <<<< if all routes are IPv6, or 65536 if all routes are IPv4
route mask limit 64
host_routes: 73728
ecmp_nhs: 16327
ecmp_nhs_per_route: 52

This translates to about 314 routes with ECMP nexthops, if every route has the maximum ECMP nexthops.

To monitor the routes in Cumulus Linux hardware, use the cl-resource-query command. The results ary between switches running on different chipsets.

The example below shows cl-resource-query results for a Broadcom Tomahawk switch:

cumulus@switch:~$ sudo cl-resource-query
IPv4/IPv6 host entries:                 0,   0% of maximum value  40960
IPv4 neighbors:                         0
IPv6 neighbors:                         0
IPv4 route entries:                     4,   0% of maximum value  65536
IPv6 route entries:                     8,   0% of maximum value   8192
IPv4 Routes:                            4
IPv6 Routes:                            8
Total Routes:                          12,   0% of maximum value  65536
ECMP nexthops:                          0,   0% of maximum value  16327
MAC entries:                            1,   0% of maximum value  40960
Total Mcast Routes:                     0,   0% of maximum value  20480
Ingress ACL entries:                  195,  12% of maximum value   1536
Ingress ACL counters:                 195,  12% of maximum value   1536
Ingress ACL meters:                    21,   1% of maximum value   2048
Ingress ACL slices:                     6, 100% of maximum value      6
Egress ACL entries:                    58,  11% of maximum value    512
Egress ACL counters:                   58,   5% of maximum value   1024
Egress ACL meters:                     29,   5% of maximum value    512
Egress ACL slices:                      2, 100% of maximum value      2
Ingress ACL ipv4_mac filter table:     36,  14% of maximum value    256 (allocated: 256)
Ingress ACL ipv6 filter table:         29,  11% of maximum value    256 (allocated: 256)
Ingress ACL mirror table:               0,   0% of maximum value      0 (allocated: 0)
Ingress ACL 8021x filter table:         0,   0% of maximum value      0 (allocated: 0)
Ingress PBR ipv4_mac filter table:      0,   0% of maximum value      0 (allocated: 0)
Ingress PBR ipv6 filter table:          0,   0% of maximum value      0 (allocated: 0)
Ingress ACL ipv4_mac mangle table:      0,   0% of maximum value      0 (allocated: 0)
Ingress ACL ipv6 mangle table:          0,   0% of maximum value      0 (allocated: 0)
Egress ACL ipv4_mac filter table:      29,  11% of maximum value    256 (allocated: 256)
Egress ACL ipv6 filter table:           0,   0% of maximum value      0 (allocated: 0)
ACL L4 port range checkers:             2,   6% of maximum value     32

The example below shows cl-resource-query results for a Broadcom Trident II switch:

cumulus@switch:~$ sudo cl-resource-query
IPv4/IPv6 host entries:                 0,   0% of maximum value  16384
IPv4 neighbors:                         0
IPv6 neighbors:                         0
IPv4 route entries:                     0,   0% of maximum value 131072
IPv6 route entries:                     1,   0% of maximum value  20480
IPv4 Routes:                            0
IPv6 Routes:                            1
Total Routes:                           1,   0% of maximum value 131072
ECMP nexthops:                          0,   0% of maximum value  16346
MAC entries:                            0,   0% of maximum value  32768
Total Mcast Routes:                     0,   0% of maximum value   8192
Ingress ACL entries:                  130,   6% of maximum value   2048
Ingress ACL counters:                  86,   4% of maximum value   2048
Ingress ACL meters:                    21,   0% of maximum value   4096
Ingress ACL slices:                     4,  66% of maximum value      6
Egress ACL entries:                    58,  11% of maximum value    512
Egress ACL counters:                   58,   5% of maximum value   1024
Egress ACL meters:                     29,   5% of maximum value    512
Egress ACL slices:                      2, 100% of maximum value      2
Ingress ACL ipv4_mac filter table:     36,   7% of maximum value    512 (allocated: 256)
Ingress ACL ipv6 filter table:         29,   3% of maximum value    768 (allocated: 512)
Ingress ACL mirror table:               0,   0% of maximum value      0 (allocated: 0)
Ingress ACL 8021x filter table:         0,   0% of maximum value      0 (allocated: 0)
Ingress PBR ipv4_mac filter table:      0,   0% of maximum value      0 (allocated: 0)
Ingress PBR ipv6 filter table:          0,   0% of maximum value      0 (allocated: 0)
Ingress ACL ipv4_mac mangle table:      0,   0% of maximum value      0 (allocated: 0)
Ingress ACL ipv6 mangle table:          0,   0% of maximum value      0 (allocated: 0)
Egress ACL ipv4_mac filter table:      29,  11% of maximum value    256 (allocated: 256)
Egress ACL ipv6 filter table:           0,   0% of maximum value      0 (allocated: 0)
ACL L4 port range checkers:             2,   8% of maximum value     24

On a switch with a Spectrum ASIC, the cl-resource-query command shows the number of TCAM entries used by the different types of ACL resources.

Ingress ACL and Egress ACL entries show the counts in single wide (not double-wide). For information about ACL entries, see Estimate the Number of ACL Rules.

Monitoring System Hardware

You monitor system hardware using the following commands and utilities:

Retrieve Hardware Information Using decode-syseeprom

The decode-syseeprom command enables you to retrieve information about the switch’s EEPROM. If the EEPROM is writable, you can set values on the EEPROM.

The following is an example. The command output is different on different switches:

cumulus@switch:~$ decode-syseeprom
TlvInfo Header:
    Id String:    TlvInfo
    Version:      1
    Total Length: 114
TLV Name             Code Len Value
-------------------- ---- --- -----
Product Name         0x21   4 4804
Part Number          0x22  14 R0596-F0009-00
Device Version       0x26   1 2
Serial Number        0x23  19 D1012023918PE000012
Manufacture Date     0x25  19 10/09/2013 20:39:02
Base MAC Address     0x24   6 00:E0:EC:25:7B:D0
MAC Addresses        0x2A   2 53
Vendor Name          0x2D  17 Penguin Computing
Label Revision       0x27   4 4804
Manufacture Country  0x2C   2 CN
CRC-32               0xFE   4 0x96543BC5
(checksum valid)

Command Options

Usage: /usr/cumulus/bin/decode-syseeprom [-a][-r][-s [args]][-t <target>][-e][-m]

Option Description
-h, -help Displays the help message and exits.
-a Prints the base MAC address for switch interfaces.
-r Prints the number of MACs allocated for switch interfaces.
-s Sets the EEPROM content if the EEPROM is writable. args can be supplied in the command line in a comma separated list of the form <field>=<value>. . , and = are illegal characters in field names and values. Fields that are not specified default to their current values. If args are supplied in the command line, they will be written without confirmation. If args is empty, the values will be prompted interactively.
NVIDIA Spectrum switches do not support this option.
-j, --json Displays JSON output.
-t <target> Prints the target EEPROM (board, psu2, psu1) information.

Note: Some systems that use a BMC to manage sensors (such as the Dell Z9264 and EdgeCore Minipack AS8000) do not provide the PSU EEPROM contents. This is because the BMC connects to the PSUs via I2C and the main CPU of the switch has no direct access.
--serial, -e Prints the device serial number.
-m Prints the base MAC address for management interfaces.
--init Clears and initializes the board EEPROM cache

You can also use the dmidecode command to retrieve hardware configuration information that is populated in the BIOS.

You can use apt-get to install the lshw program on the switch, which also retrieves hardware configuration information.

Monitor System Units Using smond

The smond daemon monitors system units like power supply and fan, updates their corresponding LEDs, and logs the change in the state. Changes in system unit state are detected via the cpld registers. smond utilizes these registers to read all sources, which impacts the health of the system unit, determines the unit’s health, and updates the system LEDs.

Use smonctl to display sensor information for the various system units:

cumulus@switch:~$ sudo smonctl
Board                                             :  OK
Fan                                               :  OK
PSU1                                              :  OK
PSU2                                              :  BAD
Temp1     (Networking ASIC Die Temp Sensor       ):  OK
Temp10    (Right side of the board               ):  OK
Temp2     (Near the CPU (Right)                  ):  OK
Temp3     (Top right corner                      ):  OK
Temp4     (Right side of Networking ASIC         ):  OK
Temp5     (Middle of the board                   ):  OK
Temp6     (P2020 CPU die sensor                  ):  OK
Temp7     (Left side of the board                ):  OK
Temp8     (Left side of the board                ):  OK
Temp9     (Right side of the board               ):  OK

When the switch is not powered on, smonctl shows the PSU status as BAD instead of POWERED OFF or NOT DETECTED. This is a known limitation.

On the Dell S4148 switch, smonctl shows PSU1 and PSU2; however in the sensors output, both PSUs are listed as PSU1.

Some switch models lack the sensor for reading voltage information, so this data is not output from the smonctl command.

For example, the Dell S4048 series has this sensor and displays power and voltage information:

cumulus@dell-s4048-ON:~$ sudo smonctl -v -s PSU2
PSU2:  OK
power:8.5 W   (voltages = ['11.98', '11.87'] V currents = ['0.72'] A)

The Penguin Arctica 3200c does not have this sensor:

cumulus@cel-sea:~/tmp$ sudo smonctl -v -s PSU1
PSU1:  OK

The following table shows the smonctl command options.

Usage: smonctl [OPTION]... [CHIP]...

Option Description
-s <sensor>, --sensor <sensor> Displays data for the specified sensor.
-v, --verbose Displays detailed hardware sensors data.

For more information, read man smond and man smonctl.

Monitor Hardware Using sensors

Use the sensors command to monitor the health of your switch hardware, such as power, temperature and fan speeds. This command executes lm-sensors.

Even though you can use the sensors command to monitor the health of your switch hardware, the smond daemon is the recommended method for monitoring hardware health. See Monitor System Units Using smond above.

For example:

cumulus@switch:~$ sensors
tmp75-i2c-6-48
Adapter: i2c-1-mux (chan_id 0)
temp1:        +39.0 C  (high = +75.0 C, hyst = +25.0 C)

tmp75-i2c-6-49
Adapter: i2c-1-mux (chan_id 0)
temp1:        +35.5 C  (high = +75.0 C, hyst = +25.0 C)

ltc4215-i2c-7-40
Adapter: i2c-1-mux (chan_id 1)
in1:         +11.87 V
in2:         +11.98 V
power1:       12.98 W
curr1:        +1.09 A

max6651-i2c-8-48
Adapter: i2c-1-mux (chan_id 2)
fan1:        13320 RPM  (div = 1)
fan2:        13560 RPM

  • Output from the sensors command varies depending upon the switch hardware you use, as each platform ships with a different type and number of sensors.
  • On a Mellanox switch, if only one PSU is plugged in, the fan is at maximum speed.

The following table shows the sensors command options.

Usage: sensors [OPTION]... [CHIP]...

Option Description
-c, --config-file Specify a config file; use - after -c to read the config file from stdin; by default, sensors references the configuration file in /etc/sensors.d/.
-s, --set Executes set statements in the config file (root only); sensors -s is run once at boot time and applies all the settings to the boot drivers.
-f, --fahrenheit Show temperatures in degrees Fahrenheit.
-A, --no-adapter Do not show the adapter for each chip.
--bus-list Generate bus statements for sensors.conf.

If [CHIP] is not specified in the command, all chip information is printed. Example chip names include:

Monitor Switch Hardware Using SNMP

The Net-SNMP documentation is discussed here.

Keep the Switch Alive Using the Hardware Watchdog

Cumulus Linux includes a simplified version of the wd_keepalive(8) daemon from the standard watchdog Debian package. wd_keepalive writes to a file called /dev/watchdog periodically to keep the switch from resetting, at least once per minute. Each write delays the reboot time by another minute. After one minute of inactivity where wd_keepalive doesn’t write to /dev/watchdog, the switch resets itself.

The watchdog is enabled by default on all supported switches, and starts when you boot the switch, before switchd starts.

To disable the watchdog, disable and stop the wd_keepalive service:

cumulus@switch:~$ sudo systemctl disable wd_keepalive ; systemctl stop wd_keepalive 

You can modify the settings for the watchdog — like the timeout setting and scheduler priority — in the configuration file, /etc/watchdog.conf. Here is the default configuration file:

cumulus@switch:~$ cat /etc/watchdog.conf

watchdog-device	= /dev/watchdog

# Set the hardware watchdog timeout in seconds
watchdog-timeout = 30

# Kick the hardware watchdog every 'interval' seconds
interval = 5

# Log a status message every (interval * logtick) seconds.  Requires
# --verbose option to enable.
logtick = 240

# Run the daemon using default scheduler SCHED_OTHER with slightly
# elevated process priority.  See man setpriority(2).
realtime = no
priority = -2

Network Switch Port LED and Status LED Guidelines

Data centers today have a large number of network switches manufactured by different hardware vendors running network operating systems (NOS) from different providers. This chapter provides a set of guidelines for how network port and status LEDs should appear on the front panel of a network switch. This provides a network operator with a standard way to identify the state of a switch and its ports by looking at its front panel, irrespective of the hardware vendor or NOS.

Network Port LEDs

A network port LED indicates the state of the link, such as link UP or Tx/Rx activity. Here are the requirements for these LEDs:

Status LEDs

A set of status LEDs are typically located on one side of a network switch. The status LEDs provide a visual indication on what is physically wrong with the network switch. Typical LEDs on the front panel are for PSUs (power supply units), fans and system. Locator LEDs are also found on the front panel of a switch. Each component that has an LED is known as a unit below.

Locate a Switch

Cumulus Linux supports the locator LED functionality for identifying a switch, by blinking a single LED on a specified network port, on the following switches:

To use the locator LED functionality, run:

cumulus@switch:~$ ethtool -p --identify PORT_NAME TIME

In the example above, INTERFACE_NAME should be replaced with the name of the port, and TIME should be replaced with the length of time, in seconds, that the port LED should blink.

This functionality is only supported on swp* ports, not eth* management interfaces.

Caveats and Errata

Dell-N3048EP-ON LED Colors at Low Speeds

Across all 48 ports on a Dell-N3048EP-ON switch, if the link speed of a device is 10Mbps, the link light does not come on and only the activity light is seen. Traffic does work properly at this speed.

Cumulus Linux does not support 10M speeds.

If you set the ports to 100M, the link lights for ports 1-46 are orange, while the lights for ports 47 and 48 are green.

When all of the ports are set to 1G, all the link lights are green.

The port LED blink state that indicates link activity is not implemented; the ports only have ON/OFF states.

Penguin Arctica 3200c Front Panel ALARM LED

On the Penguin Arctica 3200c switch, the front panel ALARM LED is not functional and remains off when you remove or insert a power module. The rear panel ALARM always flashes yellow.

TDR Cable Diagnostics

Cumulus Linux provides the Time Domain Reflectometer (TDR) cable diagnostic tool, which enables you to isolate cable faults on unshielded twisted pair (UTP) cable runs.

TDR is supported only on the EdgeCore AS4610 switch. Pluggable modules are not supported.

Run Cable Diagnostics

Cumulus Linux TDR runs, checks, and reports on the status of the cable diagnostic circuitry for specified ports.

Running TDR is disruptive to an active link; If the link is up on an enabled port when you start diagnostics on the port, the link is brought down, then brought back up when the diagnostics are complete.

To obtain the most accurate results, make sure that auto-negotiation is enabled on both the switch port and the link partner (for fixed copper ports, auto-negotiation is enabled by default in Cumulus Linux and cannot be disabled).

To run cable diagnostics and report results, issue the cl-tdr <port-list> command. You must have root permissions to run the command. Because the test is disruptive, a warning message displays and you are prompted to continue.

The following example command runs cable diagnostics on swp39:

cumulus@switch:~$ sudo cl-tdr swp39

Time Domain Reflectometer (TDR) diagnostics tests are disruptive.
When TDR is run on an interface, it will cause the interface to
go down momentarily during the test. The interface will be restarted
at the conclusion of the test.

The following interfaces may be affected:
swp39

Are you sure you want to continue? [yes/NO]yes
swp39 current results @ 2019-08-05 09:37:53 EDT
      cable(4 pairs)
      pair A Ok, length 15 meters (+/-10)  
      pair B Ok, length 15 meters (+/-10)
      pair C Ok, length 17 meters (+/-10)
      pair D Ok, length 13 meters (+/-10)

Command Options

The cl-tdr command includes several options, described below:

Option Description
-h Displays this list of command options.
-d <delay> The delay in seconds between diagnostics on different ports when you run the command on multiple ports. You can specify 0 through 30 seconds. The default is 2 seconds.
-j Displays diagnostic results in JSON format.
-y Proceeds automatically without the warning or prompt.

Example Commands

The following command runs diagnostics on ports swp39, swp40, and swp32 and sets the delay to one second:

cumulus@switch:~$  sudo cl-tdr swp39-40,swp32 -d 1

The following command example runs diagnostics on swp39 and reports the results in json format:

cumulus@switch:~$  sudo cl-tdr swp39 -j

The following command runs diagnostics on ports swp39 and swp40 without displaying the warning or prompting to continue:

cumulus@switch:~$   sudo cl-tdr swp39-40 -y

Understanding Diagnostic Results

The TDR tool reports diagnostic test results per pair for each port. For example:

 swp39 current results @ 2019-08-05 09:37:53 EDT
      cable(4 pairs)
      pair A Ok, length 15 meters (+/-10)  
      pair B Ok, length 15 meters (+/-10)
      pair C Ok, length 17 meters (+/-10)
      pair D Ok, length 13 meters (+/-10)

Possible cable pair states are as follows:

State Description
Ok No cable fault is detected.
Open A lack of continuity is detected between the pins at each end of the cable.
Short A short-circuit is detected on the cable.
Open/Short Either a lack of continuity between the pins at each end of the cable or a short-circuit is detected on the cable.
Crosstalk A signal transmitted on one pair is interfering with and degrading the transmission on another pair.
Unknown An unknown issue is detected.

Per pair cable faults are detected within plus or minus 5 meters. Good cable accuracy is detected within plus or minus 10 meters.

Cable Diagnostic Logs

Cable diagnostic results are also logged to the /var/log/switchd.log file. For example:

2019-08-05T10:02:30.691513-04:00 act-4610p-53 switchd[3037]: hal_bcm_port.c:3495 swp39 Enhanced Cable Diagnostics (TDR) started
2019-08-05T10:02:31.466523-04:00 act-4610p-53 switchd[3037]: hal_bcm_port.c:3446 swp39 TDR state=Ok npairs=4 +/- 10
2019-08-05T10:02:31.468735-04:00 act-4610p-53 switchd[3037]: hal_bcm_port.c:3449 swp39 TDR pair A state=Ok len=17
2019-08-05T10:02:31.471958-04:00 act-4610p-53 switchd[3037]: hal_bcm_port.c:3453 swp39 TDR pair B state=Ok len=18
2019-08-05T10:02:31.475047-04:00 act-4610p-53 switchd[3037]: hal_bcm_port.c:3457 swp39 TDR pair C state=Ok len=18
2019-08-05T10:02:31.477109-04:00 act-4610p-53 switchd[3037]: hal_bcm_port.c:3461 swp39 TDR pair D state=Ok len=15

Monitoring Virtual Device Counters

Cumulus Linux gathers statistics for VXLANs and VLANs using virtual device counters. These counters are supported on Tomahawk, Trident II+ and Trident II-based platforms only.

You can retrieve the data from these counters using tools like ip -s link show, ifconfig, /proc/net/dev, or netstat -i.

On Mellanox switches, Cumulus Linux updates physical counters to the kernel every two seconds and virtual interfaces (such as VLAN interfaces) every ten seconds. You cannot change these values. Because the update process takes a lower priority than other switchd processes, the interval might be longer when the system is under a heavy load.

Sample VXLAN Statistics

VXLAN statistics are available as follows:

To show interface information about the VXLAN bridge:

cumulus@switch:~$ brctl show br-vxln16757104
bridge name        bridge id            STP enabled    interfaces
-vxln16757104      8000.443839006988    no             swp2s0.6
                                                       swp2s1.6
                                                       swp2s2.6
                                                       swp2s3.6
                                                       vxln16757104

To show VNI statistics, run:

cumulus@switch:~$ ip -s link show br-vxln16757104
62: br-vxln16757104: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT
    link/ether 44:38:39:00:69:88 brd ff:ff:ff:ff:ff:ff
    RX: bytes  packets  errors  dropped overrun mcast
    10848      158      0       0       0       0
    TX: bytes  packets  errors  dropped carrier collsns
    27816      541      0       0       0       0

To show access statistics, run:

cumulus@switch:~$ ip -s link show swp2s0.6
63: swp2s0.6@swp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-vxln16757104 state UP mode DEFAULT
    link/ether 44:38:39:00:69:88 brd ff:ff:ff:ff:ff:ff
    RX: bytes  packets  errors  dropped overrun mcast
    2680       39       0       0       0       0
    TX: bytes  packets  errors  dropped carrier collsns
    7558       140      0       0       0       0

To show network statistics, run:

cumulus@switch:~$ ip -s link show vxln16757104
61: vxln16757104: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br-vxln16757104 state UNKNOWN mode DEFAULT
    link/ether e2:37:47:db:f1:94 brd ff:ff:ff:ff:ff:ff
    RX: bytes  packets  errors  dropped overrun mcast
    0          0        0       0       0       0
    TX: bytes  packets  errors  dropped carrier collsns
    0          0        0       9       0       0

Sample VLAN Statistics

For VLANs Using the VLAN-aware Bridge Mode Driver

For a bridge using the VLAN-aware bridge mode driver, the bridge is a just a container and each VLAN (VID/PVID) in the bridge is an independent layer 2 broadcast domain. As there is no netdev available to display these VLAN statistics, the switchd nodes are used instead:

cumulus@switch:~$ ifquery bridge
auto bridge
iface bridge inet static
  bridge-vlan-aware yes
  bridge-ports swp2s0 swp2s1
  bridge-stp on
  bridge-vids 2000-2002 4094

cumulus@switch:~$ ls /cumulus/switchd/run/stats/vlan/
2  2000  2001  2002  all

cumulus@switch:~$ cat /cumulus/switchd/run/stats/vlan/2000/aggregate
Vlan id                         : 2000
L3 Routed In Octets             : -
L3 Routed In Packets            : -
L3 Routed Out Octets            : -
L3 Routed Out Packets           : -
Total In Octets                 : 375
Total In Packets                : 3
Total Out Octets                : 387
Total Out Packets               : 3

For VLANs Using the Traditional Bridge Mode Driver

For a bridge using the traditional bridge mode driver, each bridge is a single L2 broadcast domain and is associated with an internal VLAN. This internal VLAN’s counters are displayed as bridge netdev stats.

cumulus@switch:~$ brctl show br0
bridge name   bridge id            STP enabled   interfaces
br0           8000.443839006989    yes           bond0.100
                                                 swp2s2.100
cumulus@switch:~$ ip -s link show br0
42: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT
    link/ether 44:38:39:00:69:89 brd ff:ff:ff:ff:ff:ff
    RX: bytes  packets  errors  dropped overrun mcast
    23201498   227514   0       0       0       0
    TX: bytes  packets  errors  dropped carrier collsns
    18198262   178443   0       0       0       0

Configure the Counters in switchd

These counters are enabled by default. To configure them, use cl-cfg and configure them as you would any other switchd parameter. The switchd parameters are:

The values for each parameter can be one of the following:

If you change one of these settings on the fly, the new configuration applies only to those VNIs or VLANs set up after the configuration changed; previously allocated counters remain as is.

Configure the Poll Interval

The virtual device counters are polled periodically. This can be CPU intensive, so the interval is configurable in switchd, with a default of 2 seconds.

# Virtual devices hw-stat poll interval (in seconds)
#stats.vdev_hw_poll_interval = 2

Configure Internal VLAN Statistics

For debugging purposes, you can access packet statistics associated with internal VLAN IDs. These statistics are hidden by default, but you can configure them in switchd:

#stats.vlan.show_internal_vlans = FALSE

Clear Statistics

Because ethtool is not supported for virtual devices, you cannot clear the statistics cache maintained by the kernel. You can clear the hardware statistics via switchd:

cumulus@switch:~$ sudo echo 1 > /cumulus/switchd/clear/stats/vlan
cumulus@switch:~$ sudo echo 1 > /cumulus/switchd/clear/stats/vxlan Caveats and Errata

ASIC Monitoring

Cumulus Linux provides an ASIC monitoring tool that collects and distributes data about the state of the ASIC. The monitoring tool polls for data at specific intervals and takes certain actions so that you can quickly identify and respond to problems, such as:

ASIC monitoring is currently supported on switches with Spectrum ASICs only.

What Type of Statistics Can You Collect?

You can collect the following type of statistics with the ASIC monitoring tool:

Collecting Queue Lengths in Histograms

The Mellanox Spectrum ASIC provides a mechanism to measure and report egress queue lengths in histograms (a graphical representation of data, which is divided into intervals or bins). You can configure the ASIC to measure up to 64 egress queues. Each queue is reported through a histogram with 10 bins, where each bin represents a range of queue lengths.

You configure the histogram with a minimum size boundary (Min) and a histogram size. You then derive the maximum size boundary (Max) by adding the minimum size boundary and the histogram size.

The 10 bins are numbered 0 through 9. Bin 0 represents queue lengths up to the Min specified, including queue length 0. Bin 9 represents queue lengths of Max and above. Bins 1 through 8 represent equal-sized ranges between the Min and Max, which is determined by dividing the histogram size by 8.

For example, consider the following histogram queue length ranges, in bytes:

The following illustration demonstrates a histogram showing how many times the queue length for a port was in the ranges specified by each bin. The example shows that the queue length was between 960 and 2495 bytes 125 times within one second.

Configure ASIC Monitoring

The ASIC monitoring tool is managed by the asic-monitor service, (which is managed by systemd). The asic-monitor service reads the /etc/cumulus/datapath/monitor.conf configuration file to determine what statistics to collect and when to trigger. The service always starts; however, if the configuration file is empty, the service exits.

The monitor.conf configuration file provides information about the type of data to collect, the switch ports to monitor, how and when to start reading the ASIC (such as when a specific queue length or number of packets dropped is reached), and what actions to take (create a snapshot file, send a message to the /var/log/syslog file, or collect more data).

To configure ASIC monitoring, edit the /etc/cumulus/datapath/monitor.conf file and restart the asic-monitor service. The asic-monitor service reads the new configuration file and then runs until it is stopped.

The following procedure describes how to monitor queue lengths using a histogram. The settings are configured to collect data every second and write the results to a snapshot file. When the size of the queue reaches 500 bytes, the system sends a message to the /var/log/syslog file.

To monitor queue lengths using a histogram:

  1. Open the /etc/cumulus/datapath/monitor.conffile in a text editor.

    cumulus@switch:~$ sudo nano /etc/cumulus/datapath/monitor.conf
    
  2. At the end of the file, add the following line to specify the name of the histogram monitor (port group). The example uses histogram_pg; however, you can use any name you choose. You must use the same name with all histogram settings.

    monitor.port_group_list = [histogram_pg]
    
  3. Add the following line to specify the ports you want to monitor. The following example sets swp1 through swp50.

    monitor.histogram_pg.port_set = swp1-swp50
    
  4. Add the following line to set the data type to histogram. This is the data type for histogram monitoring.

    monitor.histogram_pg.stat_type = histogram 
    
  5. Add the following line to set the trigger type to timer. Currently, the only trigger type available is timer.

    monitor.histogram_pg.trigger_type = timer
    
  6. Add the following line to set the frequency at which data collection starts. In the following example, the frequency is set to one second.

    monitor.histogram_pg.timer = 1s
    
  7. Add the following line to set the actions you want to take when data is collected. In the following example, the system writes the results of data collection to a snapshot file and sends a message to the /var/log/syslog file .

    monitor.histogram_pg.action_list = [snapshot,log]
    
  8. Add the following line to specify a name and location for the snapshot file. In the following example, the system writes the snapshot to a file called histogram_stats in the /var/lib/cumulus directory and adds a suffix to the file name with the snapshot file count (see the following step).

    monitor.histogram_pg.snapshot.file = /var/lib/cumulus/histogram_stats
    
  9. Add the following line to set the number of snapshots that are taken before the system starts overwriting the earliest snapshot files. In the following example, because the snapshot file count is set to 64, the first snapshot file is named histogram_stats_0 and the 64th snapshot is named histogram_stats_63. When the 65th snapshot is taken, the original snapshot file (histogram_stats_0) is overwritten and the sequence continues until histogram_stats_63 is written. Then, the sequence restarts.

    monitor.histogram_pg.snapshot.file_count = 64
    
  10. Add the following line to include a threshold, which determines how to collect data. Setting a threshold is optional. In the following example, when the size of the queue reaches 500 bytes, the system sends a message to the /var/log/syslog file.

    monitor.histogram_pg.log.queue_bytes = 500
    
  11. Add the following lines to set the size, minimum boundary, and sampling time of the histogram. Adding the histogram size and the minimum boundary size together produces the maximum boundary size. These settings are used to represent the range of queue lengths per bin.

    monitor.histogram_pg.histogram.minimum_bytes_boundary = 960
    monitor.histogram_pg.histogram.histogram_size_bytes   = 12288
    monitor.histogram_pg.histogram.sample_time_ns         = 1024
    
  12. Save the file, then restart the asic-monitor service with the following command.

    cumulus@switch:~$ systemctl restart asic-monitor.service
    

    Restarting the asic-monitor service does not disrupt traffic or require you to restart switchd. The service is enabled by default when you boot the switch and restarts when you restart switchd.

    Overhead is involved in collecting the data, which uses both the CPU and SDK process and can affect execution of switchd. Snapshots and logs can occupy a lot of disk space if you do not limit their number.

To collect other data, such as all packets per port, buffer congestion, or packet drops due to error, follow the procedure above but change the port group list setting to include the port group name you want to use. For example, to monitor packet drops due to buffer congestion:

```
monitor.port_group_list = [buffers_pg]
monitor.buffers_pg.port_set  = swp1-swp50
monitor.buffers_pg.stat_type = buffer
...
```

Certain settings in the procedure above (such as the histogram size, boundary size, and sampling time) only apply to the histogram monitor. All ASIC monitor settings are described in ASIC Monitoring.

Configuration Examples

Several configuration examples are provided below.

Queue Length Histograms

In the following example:

monitor.port_group_list                               = [histogram_pg]
monitor.histogram_pg.port_set                         = swp1-swp50
monitor.histogram_pg.stat_type                        = histogram
monitor.histogram_pg.cos_list                         = [0]
monitor.histogram_pg.trigger_type                     = timer
monitor.histogram_pg.timer                            = 1s
monitor.histogram_pg.action_list                      = [snapshot,log]
monitor.histogram_pg.snapshot.file                    = /var/lib/cumulus/histogram_stats
monitor.histogram_pg.snapshot.file_count              = 64
monitor.histogram_pg.log.queue_bytes                  = 500
monitor.histogram_pg.histogram.minimum_bytes_boundary = 960
monitor.histogram_pg.histogram.histogram_size_bytes   = 12288
monitor.histogram_pg.histogram.sample_time_ns         = 1024

Packet Drops Due to Errors

In the following example:

monitor.port_group_list                            = [discards_pg]
monitor.discards_pg.port_set                       = swp1-swp50
monitor.discards_pg.stat_type                      = packet
monitor.discards_pg.action_list                    = [snapshot,log]
monitor.discards_pg.trigger_type                   = timer
monitor.discards_pg.timer                          = 2s
monitor.discards_pg.log.packet_error_drops         = 100
monitor.discards_pg.snapshot.packet_error_drops    = 100
monitor.discards_pg.snapshot.file                  = /var/lib/cumulus/discard_stats
monitor.discards_pg.snapshot.file_count            = 16

Queue Length (Histogram) with Collect Actions

A collect action triggers the collection of additional information. You can daisy chain multiple monitors (port groups) into a single collect action.

In the following example:

monitor.port_group_list                               = [histogram_pg,discards_pg]

monitor.histogram_pg.port_set                         = swp1-swp50
monitor.histogram_pg.stat_type                        = buffer
monitor.histogram_pg.cos_list                         = [0]
monitor.histogram_pg.trigger_type                     = timer
monitor.histogram_pg.timer                            = 1s
monitor.histogram_pg.action_list                      = [snapshot,collect,log]
monitor.histogram_pg.snapshot.file                    = /var/lib/cumulus/histogram_stats
monitor.histogram_pg.snapshot.file_count              = 64
monitor.histogram_pg.histogram.minimum_bytes_boundary = 960
monitor.histogram_pg.histogram.histogram_size_bytes   = 12288
monitor.histogram_pg.histogram.sample_time_ns         = 1024
monitor.histogram_pg.log.queue_bytes                  = 500
monitor.histogram_pg.collect.queue_bytes              = 500
monitor.histogram_pg.collect.port_group_list          = [buffers_pg,all_packet_pg]

monitor.buffers_pg.port_set                           = swp1-swp50
monitor.buffers_pg.stat_type                          = buffer
monitor.buffers_pg.action_list                        = [snapshot]
monitor.buffers_pg.snapshot.file                      = /var/lib/cumulus/buffer_stats
monitor.buffers_pg.snapshot.file_count                = 8

monitor.all_packet_pg.port_set                        = swp1-swp50
monitor.all_packet_pg.stat_type                       = packet_all
monitor.all_packet_pg.action_list                     = [snapshot]
monitor.all_packet_pg.snapshot.file                   = /var/lib/cumulus/all_packet_stats
monitor.all_packet_pg.snapshot.file_count             = 8

monitor.discards_pg.port_set                          = swp1-swp50
monitor.discards_pg.stat_type                         = packet
monitor.discards_pg.action_list                       = [snapshot,log]
monitor.discards_pg.trigger_type                      = timer
monitor.discards_pg.timer                             = 2s
monitor.discards_pg.log.packet_error_drops            = 100
monitor.discards_pg.snapshot.packet_error_drops       = 100
monitor.discards_pg.snapshot.file                     = /var/lib/cumulus/discard_stats
monitor.discards_pg.snapshot.file_count               = 16

Certain actions require additional settings. For example, if the snapshot action is specified, a snapshot file is also required. If the log action is specified, a log threshold is also required. See action_list for additional settings required for each action.

Example Snapshot File

A snapshot action writes a snapshot of the current state of the ASIC to a file. Because parsing the file and finding the information can be tedious, you can use a third-party analysis tool to analyze the data in the file. The following example shows a snapshot of queue lengths.

{"timestamp_info": {"start_datetime": "2017-03-16 21:36:40.775026", "end_datetime": "2017-03-16 21:36:40.775848"}, "buffer_info": null, "packet_info": null, "histogram_info": {"swp2": {"0": 55531}, "swp32": {"0": 48668}, "swp1": {"0": 64578}}}

Example Log Message

A log action writes out the ASIC state to the /var/log/syslog file. In the following example, when the size of the queue reaches 500 bytes, the system sends this message to the /var/log/syslog file:

2018-02-26T20:14:41.560840+00:00 cumulus asic-monitor-module INFO:  2018-02-26 20:14:41.559967: Egress queue(s) greater than 500 bytes in monitor port group histogram_pg.

ASIC Monitoring Settings

The following table provides descriptions of the ASIC monitor settings.

Setting Description
port_group_list Specifies the names of the monitors (port groups) you want to use to collect data, such as discards_pg, histogram_pg, all_packet_pg, buffers_pg. You can provide any name you want for the port group; the names above are just examples. You must use the same name for all the settings of a particular port group.

Example:
monitor.port_group_list = [histogram_pg,discards_pg,buffers_pg, all_packets_pg]


Note: You must specify at least one port group. If the port group list is empty, systemd shuts down the asic-monitor service.
<port_group_name>.port_set Specifies the range of ports monitored. You can specify GLOBs and comma-separated lists; for example, swp1 swp4,swp8,swp10-swp50.

Example:
monitor.histogram_pg.port_set = swp1-swp50
<port_group_name>.stat_type Specifies the type of data that the port group collects.
For histograms, specify histogram. For example:
monitor.histogram_pg.stat_type = histogram
For packet drops due to errors, specify packet. For example:
monitor.discards_pg.stat_type = packet

For packet occupancy statistics, specify buffer. For example:
monitor.buffers_pg.stat_type = buffer
For all packets per port, specify packet_all.
Example:
monitor.all_packet_pg.stat_type = packet_all
<port_group_name>.cos_list For histogram monitoring, each CoS (Class of Service) value in the list has its own histogram on each port. The global limit on the number of histograms is an average of one histogram per port.

Example:
monitor.histogram_pg.cos_list = [0]
<port_group_name>.trigger_type Specifies the type of trigger that initiates data collection. Currently, the only option is timer. At least one port group must have a timer configured, otherwise no data is ever collected.

Example:
monitor.histogram_pg.trigger_type = timer
<port_group_name>.timer Specifies the frequency at which data is collected; for example, a setting of 1s indicates that data is collected once per second. You can set the timer to the following:
1 to 60 seconds: 1s, 2s, and so on up to 60s
1 to 60 minutes: 1m, 2m, and so on up to 60m
1 to 24 hours: 1h, 2h, and so on up to 24h
1 to 7 days: 1d, 2d and so on up to 7d

Example:
monitor.histogram_pg.timer = 4s
<port_group_name>.action_list Specifies one or more actions that occur when data is collected:
snapshot writes a snapshot of the data collection results to a file. If you specify this action, you must also specify a snapshot file (described below). You can also specify a threshold that initiates the snapshot action, but this is not required.

Example:
monitor.histogram_pg.action_list = [snapshot]
monitor.histogram_pg.snapshot.file = /var/lib/cumulus/histogram_stats
collect gathers additional data. If you specify this action, you must also specify the port groups for the additional data you want to collect.
Example:
monitor.histogram_pg.action_list = [collect
monitor.histogram_pg.collect.port_group_list = [buffers_pg,all_packet_pg]
log sends a message to the /var/log/syslog file. If you specify this action, you must also specify a threshold that initiates the log action.
Example:
monitor.histogram_pg.action_list = [log]
monitor.histogram_pg.log.queue_bytes = 500
You can use all three of these actions in one monitoring step. For example
monitor.histogram_pg.action_list = [snapshot,collect,log]
Note: If an action appears in the action list but does not have the required settings (such as a threshold for the log action), the ASIC monitor stops and reports an error.
<port_group_name>.snapshot.file Specifies the name for the snapshot file. All snapshots use this name, with a sequential number appended to it. See the snapshot.file_count setting.

Example:
monitor.histogram_pg.snapshot.file = /var/lib/cumulus/histogram_stats
<port_group_name>.snapshot.file_count Specifies the number of snapshots that can be created before the first snapshot file is overwritten. In the following example, because the snapshot file count is set to 64, the first snapshot file is named histogram_stats_0 and the 64th snapshot is named histogram_stats_63. When the 65th snapshot is taken, the original snapshot file (histogram_stats_0) is overwritten and the sequence restarts.

Example:
monitor.histogram_pg.snapshot.file_count = 64
Note: While more snapshots provide you with more data, they can occupy a lot of disk space on the switch.
<port_group_name>.<action>.queue_bytes For histogram monitoring.
Specifies a threshold for the histogram monitor. This is the length of the queue in bytes that initiates a specified action (snapshot, log, collect).
Examples:
monitor.histogram_pg.snapshot.queue_bytes = 500
monitor.histogram_pg.log.queue_bytes = 500
monitor.histogram_pg.collect.queue_bytes = 500
<port_group_name>.<action>.packet_error_drops For monitoring packet drops due to error.
Specifies a threshold for the packet drops due to error monitor. This is the number of packet drops due to error that initiates a specified action (snapshot, log, collect).

Examples:
monitor.discards_pg.snapshot.packet_error_drops = 500
monitor.discards_pg.log.packet_error_drops = 500
monitor.discards_pg.collect.packet_error_drops = 500
<port_group_name>.<action>.packet_congestion_drops For monitoring packet drops due to buffer congestion.
Specifies a threshold for the packet drops due to buffer congestion monitor. This is the number of packet drops due to buffer congestion that initiates a specified action (log or collect).

Examples:
monitor.buffers_pg.log.packet_congestion_drops = 500
monitor.buffers_pg.snapshot.packet_congestion_drops = 500
monitor.buffers_pg.collect.packet_congestion_drops = 500
<port_group_name>.histogram.minimum_bytes_boundary For histogram monitoring.
The minimum boundary size for the histogram in bytes. On a Spectrum switch, this number must be a multiple of 96. Adding this number to the size of the histogram produces the maximum boundary size. These values are used to represent the range of queue lengths per bin.

Example:
monitor.histogram_pg.histogram.minimum_bytes_boundary = 960
<port_group_name>.histogram.histogram_size_bytes For histogram monitoring.
The size of the histogram in bytes. Adding this number and the minimum_bytes_boundary value together produces the maximum boundary size. These values are used to represent the range of queue lengths per bin.

Example:
monitor.histogram_pg.histogram.histogram_size_bytes = 12288
<port_group_name>.histogram.sample_time_ns For histogram monitoring.
The sampling time of the histogram in nanoseconds.

Example:
monitor.histogram_pg.histogram.sample_time_ns = 1024

Understanding the cl-support Output File

The cl-support script generates a compressed archive file of useful information for troubleshooting. The system either creates the archive file automatically or you can create the archive file manually.

Automatic cl-support File

The system creates the cl-support archive file automatically for the following reasons:

Manual cl-support File

To create the cl-support archive file manually, run the cl-support command:

cumulus@switch:~$ sudo cl-support

If the support team requests that you submit the output from cl-support to help with the investigation of issues you might experience with Cumulus Linux and you need to include security-sensitive information, such as the sudoers file, use the -s option:

cumulus@switch:~$ sudo cl-support -s

On ARM switches, the cl-support FRR module might time out even when FRR is not running. To disable the timeout, run the cl-support command with the -M option; for example:

cumulus@switch:~$ sudo cl-support -M

For information on the directories included in the cl-support archive, see:

Troubleshooting Log Files

The only real unique entity for logging on Cumulus Linux compared to any other Linux distribution is switchd.log, which logs the HAL (hardware abstraction layer) from hardware like the Broadcom or Mellanox Spectrum ASIC.

Read this guide on NixCraft to understand how /var/log works.

Log Description
/var/log/alternatives.log Information from update-alternatives.
/var/log/apt Information from the apt utility. For example, from apt-get install and apt-get remove.
/var/log/audit/* Information stored by the Linux audit daemon, auditd.
/var/log/autoprovision Output generated by running the zero touch provisioning script (ZTP).
/var/log/boot.log Information that is logged when the system boots.
/var/log/btmp Information about failed login attempts. Use the last command to view the btmp file. For example:
cumulus@switch:~$ last -f /var/log/btmp | more
/var/log/clagd.log Status of the clagd service.
/var/log/dpkg.log Information logged when a package is installed or removed using the dpkg command.
/var/log/frr/* FRRouting - Used to troubleshoots routing, such as an MD5 or MTU mismatch with OSPF.
/var/log/gunicorn Error and access events in Gunicorn.
/var/log/installer/* Directory containing files related to the installation of Cumulus Linux.
/var/log/lastlog Formats and prints the contents of the last login log file.
/var/log/netd.log Log file for NCLU.
/var/log/netd-history.log Log file for NCLU configuration commits.
/var/log/nginx Errors and processed requests in NGINX.
/var/log/ntpstats Logs for network configuration protocol.
/var/log/openvswitch/* ovsdb-server logs.
/var/log/ptmd Prescriptive Topology Manager (PTM) errors and information.
/var/log/switchd.log The HAL log for Cumulus Linux.
This is specific to Cumulus Linux. Any switchd crashes are logged here.
/var/log/syslog The main system log, which logs everything except auth-related messages.
The primary log; grep this file to see what problem occurred.
/var/log/wtmp Login records file.

Troubleshooting the etc Directory

The cl-support script replicates the /etc directory, however, it deliberately excludes certain files, such as /etc/nologin, which prevents unprivileged users from logging into the system.

This is the alphabetical list of the output from running ls -l on the /etc directory structure created by cl-support.

File
acpi
adduser.conf
alternatives
apparmor.d
apt
audisp
audit
bash.bashrc
bash_completion
bash_completion.d
bcm.d
bindresvport.blacklist
binfmt.d
ca-certificates
ca-certificates.conf
calendar
console-setup
cron.d
cron.daily
cron.hourly
cron.monthly
crontab
cron.weekly
cruft
cumulus
dbus-1
debconf.conf
debian_version
debsums-ignore
default
deluser.conf
dhcp
discover.conf.d
discover-modprobe.conf
dnsmasq.conf
dnsmasq.d
dpkg
e2fsck.conf
emacs
environment
etckeeper
ethertypes
fonts
freeipmi
frr
fstab
gai.conf
groff
grub.d
gshadow
gshadow-
gss
gunicorn.conf.py
hostapd
hostapd.conf
host.conf
hostname
hsflowd
hsflowd.conf
hw_init.d
image-release
init
init.d
initramfs-tools
inputrc
insserv
insserv.conf
insserv.conf.d
iproute2
issue
issue.net
kernel
ldap
ld.so.cache
ld.so.conf
ld.so.conf.d
libaudit.conf
libnl
linuxptp
lldpd.d
locale.alias
locale.gen
localtime
logcheck
login.defs
login.defs.cumulus
login.defs.cumulus-orig
logrotate.conf
logrotate.conf.cumulus
logrotate.conf.cumulus-orig
logrotate.d
lsb-release
lvm
machine-id
magic
magic.mime
mailcap
mailcap.order
manpath.config
mime.types
mke2fs.conf
modprobe.d
modules
modules-load.d
motd
motd.distrib
mtab
mysql
nanorc
netd.conf
netq
network
networks
nginx
nsswitch.conf
ntp.conf
openvswitch
opt
os-release
perl
profile
profile.cumulus
profile.cumulus-orig
profile.d
protocols
ptm.d
ptp4l.conf
python
python2.7
python3
python3.7
ras
rc0.d
rc1.d
rc2.d
rc3.d
rc4.d
rc5.d
rc6.d
rcS.d
rdnbrd.conf
resolv.conf
resolvconf
resolv.conf.bak
restapi.conf
rmt
rpc
rsyslog.conf
rsyslog.conf.cumulus
rsyslog.conf.cumulus-orig
rsyslog.d
runit
screenrc
securetty
security
selinux
sensors3.conf
sensors.d
services
sgml
shells
skel
smartd.conf
smartmontools
snmp
ssh
subgid
subgid-
subuid
subuid-
sv
sysctl.conf
sysctl.d
systemd
terminfo
timezone
tmpfiles.d
ucf.conf
udev
ufw
update-motd.d
vim
vrf
watchdog.conf
wgetrc
X11
xattr.conf
xdg
xml

Troubleshooting Network Interfaces

The following sections describe various ways you can troubleshoot ifupdown2.

Enable Logging for Networking

To obtain verbose logs when you run systemctl [start|restart] networking.service as well as when the switch boots, create an overrides file with the systemctl edit networking.service command and add the following lines:

[Service]
# remove existing ExecStart rule
ExecStart=
# start ifup with verbose option
ExecStart=/sbin/ifup -av

When you run the systemctl edit command, you do not need to run systemctl daemon-reload.

To disable logging, either:

Exclude Certain Interfaces from Coming Up

To exclude an interface so that it does not come up when you boot the switch or start/stop/reload the networking service:

  1. Create a file in the /etc/systemd/system/networking.service.d directory (for example, /etc/systemd/system/networking.service.d/override.conf).

  2. Add the following lines to the file, where <interface> is the interface you want to exclude (such as eth0).

    [Service]
    ExecStart=
    ExecStart=/sbin/ifup -a -X <interface>
    ExecStop=
    ExecStop=/sbin/ifdown -a -X <interface>
    

You can exclude any interface specified in the /etc/network/interfaces file.

Use ifquery to Validate and Debug Interface Configurations

You use ifquery to print parsed interfaces file entries.

To use ifquery to pretty print iface entries from the interfaces file, run:

cumulus@switch:~$ sudo ifquery bond0
auto bond0
iface bond0
    address 14.0.0.9/30
    address 2001:ded:beef:2::1/64
    bond-slaves swp25 swp26

Use ifquery --check to check the current running state of an interface within the interfaces file. It will return exit code 0 or 1 if the configuration does not match. The line bond-xmit-hash-policy layer3+7 below fails because it should read bond-xmit-hash-policy layer3+4.

cumulus@switch:~$ sudo ifquery --check bond0
iface bond0
    bond-xmit-hash-policy layer3+7  [fail]
    bond-slaves swp25 swp26         [pass]
    address 14.0.0.9/30             [pass]
    address 2001:ded:beef:2::1/64   [pass]

ifquery --check is an experimental feature.

Use ifquery --running to print the running state of interfaces in the interfaces file format:

cumulus@switch:~$ sudo ifquery --running bond0
auto bond0
iface bond0
    bond-slaves swp25 swp26
    address 14.0.0.9/30
    address 2001:ded:beef:2::1/64

ifquery --syntax-help provides help on all possible attributes supported in the interfaces file. For complete syntax on the interfaces file, see man interfaces and man ifupdown-addons-interfaces.

You can use ifquery --print-savedstate to check the ifupdown2 state database. ifdown works only on interfaces present in this state database.

cumulus@leaf1$ sudo ifquery --print-savedstate eth0  
auto eth0
iface eth0 inet dhcp

Mako Template Errors

An easy way to debug and get details about template errors is to use the mako-render command on your interfaces template file or on /etc/network/interfaces itself.

cumulus@switch:~$ sudo mako-render /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet dhcp
#auto eth1
#iface eth1 inet dhcp

# Include any platform-specific interface configuration
source /etc/network/interfaces.d/*.if

# ssim2 added
auto swp45
iface swp45

auto swp46
iface swp46

cumulus@switch:~$ sudo mako-render /etc/network/interfaces.d/<interfaces_stub_file>

ifdown Cannot Find an Interface that Exists

If you are trying to bring down an interface that you know exists, use ifdown with the --use-current-config option to force ifdown to check the current /etc/network/interfaces file to find the interface. This can solve issues where the ifup command issues for that interface are interrupted before it updates the state database. For example:

cumulus@switch:~$ sudo ifdown br0
error: cannot find interfaces: br0 (interface was probably never up ?)

cumulus@switch:~$ sudo brctl show
bridge name   bridge id      STP enabled interfaces
br0      8000.44383900279f   yes     downlink
                             peerlink

cumulus@switch:~$ sudo ifdown br0 --use-current-config 

Remove All References to a Child Interface

If you have a configuration with a child interface, whether it is a VLAN, bond, or another physical interface and you remove that interface from a running configuration, you must remove every reference to it in the configuration. Otherwise, the parent interface continues to use the interface.

For example, consider the following configuration:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

auto bond1
iface bond1
    bond-slaves swp2 swp1

auto bond3
iface bond3
    bond-slaves swp8 swp6 swp7

auto br0
iface br0
    bridge-ports swp3 swp5 bond1 swp4 bond3
    bridge-pathcosts  swp3=4 swp5=4 swp4=4
    address 11.0.0.10/24
    address 2001::10/64

Notice that bond1 is a member of br0. If bond1 is removed, you must remove the reference to it from the br0 configuration. Otherwise, if you reload the configuration with ifreload -a, bond1 is still part of br0.

MTU Set on a Logical Interface Fails with Error: “Numerical result out of range”

This error occurs when the MTU you are trying to set on an interface is higher than the MTU of the lower interface or dependent interface. Linux expects the upper interface to have an MTU less than or equal to the MTU on the lower interface.

In the example below, the swp1.100 VLAN interface is an upper interface to physical interface swp1. If you want to change the MTU to 9000 on the VLAN interface, you must include the new MTU on the lower interface swp1 as well.

auto swp1.100
iface swp1.100
    mtu 9000

auto swp1 
iface swp1  
    mtu 9000

iproute2 batch Command Failures

ifupdown2 batches iproute2 commands for performance reasons. A batch command contains ip -force -batch - in the error message. The command number that failed is at the end of this line: Command failed -:1.

Below is a sample error for the command 1: link set dev host2 master bridge. There was an error adding the bond host2 to the bridge named bridge because host2 did not have a valid address.

error: failed to execute cmd 'ip -force -batch - [link set dev host2 master bridge
addr flush dev host2
link set dev host1 master bridge
addr flush dev host1
]'(RTNETLINK answers: Invalid argument
Command failed -:1)
warning: bridge configuration failed (missing ports)

This error can occur when the bridge port does not have a valid hardware address.

This occurs typically when the interface being added to the bridge is an incomplete bond; a bond without slaves is incomplete and does not have a valid hardware address.

Losing a large number of packets across an MLAG peerlink interface might not be a problem. This can occur to prevent looping of BUM (broadcast, unknown unicast and multicast) packets. For more details, and for information on how to detect these drops, read the MLAG chapter.

Monitoring Interfaces and Transceivers Using ethtool

The ethtool command enables you to query or control the network driver and hardware settings. It takes the device name (like swp1) as an argument. When the device name is the only argument to ethtool, it prints the current settings of the network device. See man ethtool(8) for details. Not all options are currently supported on switch port interfaces.

Monitor Interface Status Using ethtool

To check the status of an interface using ethtool:

cumulus@switch:~$ ethtool swp1
Settings for swp1:
        Supported ports: [ FIBRE ]
        Supported link modes:   1000baseT/Full
                                10000baseT/Full
        Supported pause frame use: No
        Supports auto-negotiation: No
        Advertised link modes:  1000baseT/Full
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Speed: 10000Mb/s
        Duplex: Full
        Port: FIBRE
        PHYAD: 0
        Transceiver: external
        Auto-negotiation: off
        Current message level: 0x00000000 (0)

Link detected: yes

The switch hardware contains the active port settings. The output of ethtool swpXX shows the port settings stored in the kernel. The switchd process keeps the hardware and kernel in sync for the important port settings (speed, auto-negotiation, and link detected) when they change. However, many of the fields in ethtool, like Supported Link Modes and Advertised Link Modes are not updated based on the actual module inserted in the port and therefore are incorrect or misleading.

To query interface statistics:

cumulus@switch:~$ sudo ethtool -S swp1
NIC statistics:
        HwIfInOctets: 1435339
        HwIfInUcastPkts: 11795
        HwIfInBcastPkts: 3
        HwIfInMcastPkts: 4578
        HwIfOutOctets: 14866246
        HwIfOutUcastPkts: 11791
        HwIfOutMcastPkts: 136493
        HwIfOutBcastPkts: 0
        HwIfInDiscards: 0
        HwIfInL3Drops: 0
        HwIfInBufferDrops: 0
        HwIfInAclDrops: 28
        HwIfInDot3LengthErrors: 0
        HwIfInErrors: 0
        SoftInErrors: 0
        SoftInDrops: 0
        SoftInFrameErrors: 0
        HwIfOutDiscards: 0
        HwIfOutErrors: 0
        HwIfOutQDrops: 0
        HwIfOutNonQDrops: 0
        SoftOutErrors: 0
        SoftOutDrops: 0
        SoftOutTxFifoFull: 0
        HwIfOutQLen: 0

View and Clear Interface Counters

Interface counters contain information about an interface. You can view this information when you run cl-netstat, ifconfig, or cat /proc/net/dev. You can also use cl-netstat to save or clear this information:

cumulus@switch:~$ sudo cl-netstat
Kernel Interface table
Iface   MTU Met        RX_OK RX_ERR RX_DRP RX_OVR        TX_OK TX_ERR TX_DRP TX_OVR    Flg
---------------------------------------------------------------------------------------------
eth0   1500   0          611      0      0      0          487      0      0      0   BMRU
lo    16436   0            0      0      0      0            0      0      0      0    LRU
swp1   1500   0            0      0      0      0            0      0      0      0    BMU

cumulus@switch:~$ sudo cl-netstat -c
Cleared counters
Option Description
-c Copies and clears statistics. It does not clear counters in the kernel or hardware.

Note: The -c argument is applied per user ID by default. You can override it by using the -t argument to save statistics to a different directory.
-d Deletes saved statistics, either the uid or the specified tag.

Note: The -d argument is applied per user ID by default. You can override it by using the -t argument to save statistics to a different directory.
-D Deletes all saved statistics.
-l Lists saved tags.
-r Displays raw statistics (unmodified output of cl-netstat).
-t <tag name> Saves statistics with <tag name>.
-v Prints cl-netstat version and exits.

On Mellanox switches, Cumulus Linux updates physical counters to the kernel every two seconds and virtual interfaces (such as VLAN interfaces) every ten seconds. You cannot change these values. Because the update process takes a lower priority than other switchd processes, the interval might be longer when the system is under a heavy load.

Monitor Switch Port SFP/QSFP Hardware Information Using ethtool

To see hardware capabilities and measurement information on the SFP or QSFP module installed in a particular port, use the ethtool -m command. If the SFP/QSFP supports Digital Optical Monitoring (that is, the Optical diagnostics support field in the output below is set to Yes), the optical power levels and thresholds are also printed below the standard hardware details.

In the sample output below, you can see that this module is a 1000BASE-SX short-range optical module, manufactured by JDSU, part number PLRXPL-VI-S24-22. The second half of the output displays the current readings of the Tx power levels (Laser output power) and Rx power (Receiver signal average optical power), temperature, voltage and alarm threshold settings.

cumulus@switch$ sudo ethtool -m swp3
        Identifier                                : 0x03 (SFP)
        Extended identifier                       : 0x04 (GBIC/SFP defined by 2-wire interface ID)
        Connector                                 : 0x07 (LC)
        Transceiver codes                         : 0x00 0x00 0x00 0x01 0x20 0x40 0x0c 0x05
        Transceiver type                          : Ethernet: 1000BASE-SX
        Transceiver type                          : FC: intermediate distance (I)
        Transceiver type                          : FC: Shortwave laser w/o OFC (SN)
        Transceiver type                          : FC: Multimode, 62.5um (M6)
        Transceiver type                          : FC: Multimode, 50um (M5)
        Transceiver type                          : FC: 200 MBytes/sec
        Transceiver type                          : FC: 100 MBytes/sec
        Encoding                                  : 0x01 (8B/10B)
        BR, Nominal                               : 2100MBd
        Rate identifier                           : 0x00 (unspecified)
        Length (SMF,km)                           : 0km
        Length (SMF)                              : 0m
        Length (50um)                             : 300m
        Length (62.5um)                           : 150m
        Length (Copper)                           : 0m
        Length (OM3)                              : 0m
        Laser wavelength                          : 850nm
        Vendor name                               : JDSU
        Vendor OUI                                : 00:01:9c
        Vendor PN                                 : PLRXPL-VI-S24-22
        Vendor rev                                : 1
        Optical diagnostics support               : Yes
        Laser bias current                        : 21.348 mA
        Laser output power                        : 0.3186 mW / -4.97 dBm
        Receiver signal average optical power     : 0.3195 mW / -4.96 dBm
        Module temperature                        : 41.70 degrees C / 107.05 degrees F
        Module voltage                            : 3.2947 V
        Alarm/warning flags implemented           : Yes
        Laser bias current high alarm             : Off
        Laser bias current low alarm              : Off
        Laser bias current high warning           : Off
        Laser bias current low warning            : Off
        Laser output power high alarm             : Off
        Laser output power low alarm              : Off
        Laser output power high warning           : Off
        Laser output power low warning            : Off
        Module temperature high alarm             : Off
        Module temperature low alarm              : Off
        Module temperature high warning           : Off
        Module temperature low warning            : Off
        Module voltage high alarm                 : Off
        Module voltage low alarm                  : Off
        Module voltage high warning               : Off
        Module voltage low warning                : Off
        Laser rx power high alarm                 : Off
        Laser rx power low alarm                  : Off
        Laser rx power high warning               : Off
        Laser rx power low warning                : Off
        Laser bias current high alarm threshold   : 10.000 mA
        Laser bias current low alarm threshold    : 1.000 mA
        Laser bias current high warning threshold : 9.000 mA
         Laser bias current low warning threshold  : 2.000 mA
        Laser output power high alarm threshold   : 0.8000 mW / -0.97 dBm
        Laser output power low alarm threshold    : 0.1000 mW / -10.00 dBm
        Laser output power high warning threshold : 0.6000 mW / -2.22 dBm
        Laser output power low warning threshold  : 0.2000 mW / -6.99 dBm
        Module temperature high alarm threshold   : 90.00 degrees C / 194.00 degrees F
        Module temperature low alarm threshold    : -40.00 degrees C / -40.00 degrees F
        Module temperature high warning threshold : 85.00 degrees C / 185.00 degrees F
        Module temperature low warning threshold  : -40.00 degrees C / -40.00 degrees F
        Module voltage high alarm threshold       : 4.0000 V
        Module voltage low alarm threshold        : 0.0000 V
        Module voltage high warning threshold     : 3.6450 V
        Module voltage low warning threshold      : 2.9550 V
        Laser rx power high alarm threshold       : 1.6000 mW / 2.04 dBm
        Laser rx power low alarm threshold        : 0.0100 mW / -20.00 dBm
        Laser rx power high warning threshold     : 1.0000 mW / 0.00 dBm
        Laser rx power low warning threshold      : 0.0200 mW / -16.99 dBm

Network Troubleshooting

Cumulus Linux includes a number of command line and analytical tools to help you troubleshoot issues with your network.

Check Reachability Using ping

Use ping to check reachability of a host. ping also calculates the time it takes for packets to travel the round trip. See man ping for details.

To test the connection to an IPv4 host:

cumulus@switch:~$ ping 192.0.2.45
PING 192.0.2.45 (192.0.2.45) 56(84) bytes of data.
64 bytes from 192.0.2.45: icmp_req=1 ttl=53 time=40.4 ms
64 bytes from 192.0.2.45: icmp_req=2 ttl=53 time=39.6 ms
...

To test the connection to an IPv6 host:

cumulus@switch:~$ ping6 -I swp1 2001::db8:ff:fe00:2
PING 2001::db8:ff:fe00:2(2001::db8:ff:fe00:2) from 2001::db8:ff:fe00:1 swp1: 56 data bytes
64 bytes from 2001::db8:ff:fe00:2: icmp_seq=1 ttl=64 time=1.43 ms
64 bytes from 2001::db8:ff:fe00:2: icmp_seq=2 ttl=64 time=0.927 ms

When troubleshooting intermittent connectivity issues, it is helpful to send continuous pings to a host.

traceroute tracks the route that packets take from an IP network on their way to a given host. See man traceroute for details.

To track the route to an IPv4 host:

cumulus@switch:~$ traceroute www.google.com
traceroute to www.google.com (74.125.239.49), 30 hops max, 60 byte packets
1  cumulusnetworks.com (192.168.1.1)  0.614 ms  0.863 ms  0.932 ms
...
5  core2-1-1-0.pao.net.google.com (198.32.176.31)  22.347 ms  22.584 ms  24.328 ms
6  216.239.49.250 (216.239.49.250)  24.371 ms  25.757 ms  25.987 ms
7  72.14.232.35 (72.14.232.35)  27.505 ms  22.925 ms  22.323 ms
8  nuq04s19-in-f17.1e100.net (74.125.239.49)  23.544 ms  21.851 ms  22.604 ms

Run Commands in a Non-default VRF

You can use ip vrf exec to run commands in a non-default VRF context. This is particularly useful for network utilities like ping, traceroute, and nslookup.

The full syntax is ip vrf exec <vrf-name> <command> <arguments>. For example:

cumulus@switch:~$ sudo ip vrf exec Tenant1 nslookup google.com - 8.8.8.8

By default, ping/ping6 and traceroute/traceroute6 all use the default VRF. This is done using a mechanism that checks the VRF context of the current shell - which can be seen when you run ip vrf id - at the time one of these commands is run. If the shell’s VRF context is mgmt, then these commands are run in the default VRF context.

ping and traceroute have additional arguments that you can use to specify an egress interface and/or a source address. In the default VRF, the source interface flag (ping -I or traceroute -i) specifies the egress interface for the ping/traceroute operation. However, you can use the source interface flag instead to specify a non-default VRF to use for the command. Doing so causes the routing lookup for the destination address to occur in that VRF.

With ping -I, you can specify the source interface or the source IP address, but you cannot use the flag more than once. Thus, you can choose either an egress interface/VRF or a source IP address. For traceroute, you can use traceroute -s to specify the source IP address.

You gain some additional flexibility if you run ip vrf exec in combination with ping/ping6 or traceroute/traceroute6, as the VRF context is specified outside of the ping and traceroute commands. This allows for the most granular control of ping and traceroute, as you can specify both the VRF and the source interface flag.

For ping, use the following syntax:

ip vrf exec <vrf-name> [ping|ping6] -I [<egress_interface> | <source_ip>] <destination_ip>

For example:

cumulus@switch:~$ sudo ip vrf exec Tenant1 ping -I swp1 8.8.8.8
cumulus@switch:~$ sudo ip vrf exec Tenant1 ping -I 192.0.1.1 8.8.8.8
cumulus@switch:~$ sudo ip vrf exec Tenant1 ping6 -I swp1 2001:4860:4860::8888
cumulus@switch:~$ sudo ip vrf exec Tenant1 ping6 -I 2001:db8::1 2001:4860:4860::8888

For traceroute, use the following syntax:

ip vrf exec <vrf-name> [traceroute|traceroute6] -i <egress_interface> -s <source_ip> <destination_ip>

For example:

cumulus@switch:~$ sudo ip vrf exec Tenant1 traceroute -i swp1 -s 192.0.1.1 8.8.8.8
cumulus@switch:~$ sudo ip vrf exec Tenant1 traceroute6 -i swp1 -s 2001:db8::1 2001:4860:4860::8888

Because the VRF context for ping and traceroute commands is automatically shifted to the default VRF context, you must use the source interface flag to specify the management VRF. Typically, this is not an issue since there is only a single interface in the management VRF - eth0 - and in most situations only a single IPv4 address or IPv6 global unicast address is assigned to it. But it is worth mentioning since, as stated earlier, you cannot specify both a source interface and a source IP address with ping -I.

Manipulate the System ARP Cache

arp manipulates or displays the kernel’s IPv4 network neighbor cache. See man arp for details.

To display the ARP cache:

cumulus@switch:~$ arp -a
? (11.0.2.2) at 00:02:00:00:00:10 [ether] on swp3
? (11.0.3.2) at 00:02:00:00:00:01 [ether] on swp4
? (11.0.0.2) at 44:38:39:00:01:c1 [ether] on swp1

To delete an ARP cache entry:

cumulus@switch:~$ arp -d 11.0.2.2
cumulus@switch:~$ arp -a
? (11.0.2.2) at <incomplete> on swp3
? (11.0.3.2) at 00:02:00:00:00:01 [ether] on swp4
? (11.0.0.2) at 44:38:39:00:01:c1 [ether] on swp1

To add a static ARP cache entry:

cumulus@switch:~$ arp -s 11.0.2.2 00:02:00:00:00:10
cumulus@switch:~$ arp -a
? (11.0.2.2) at 00:02:00:00:00:10 [ether] PERM on swp3
? (11.0.3.2) at 00:02:00:00:00:01 [ether] on swp4
? (11.0.0.2) at 44:38:39:00:01:c1 [ether] on swp1

If you need to flush or remove an ARP entry for a specific interface, you can disable dynamic ARP learning:

cumulus@switch:~$ ip link set arp off dev INTERFACE

Generate Traffic Using mz

mz (or mausezahn) is a fast traffic generator. It can generate a large variety of packet types at high speed. See man mz for details.

For example, to send two sets of packets to TCP port 23 and 24, with source IP address 11.0.0.1 and destination IP address 11.0.0.2:

cumulus@switch:~$ sudo mz swp1 -A 11.0.0.1 -B 11.0.0.2 -c 2 -v -t tcp "dp=23-24"

Mausezahn 0.40 - (C) 2007-2010 by Herbert Haas - https://packages.debian.org/unstable/mz
Use at your own risk and responsibility!
-- Verbose mode --

This system supports a high resolution clock.
  The clock resolution is 4000250 nanoseconds.
Mausezahn will send 4 frames...
  IP:  ver=4, len=40, tos=0, id=0, frag=0, ttl=255, proto=6, sum=0, SA=11.0.0.1, DA=11.0.0.2,
       payload=[see next layer]
  TCP: sp=0, dp=23, S=42, A=42, flags=0, win=10000, len=20, sum=0,
       payload=

  IP:  ver=4, len=40, tos=0, id=0, frag=0, ttl=255, proto=6, sum=0, SA=11.0.0.1, DA=11.0.0.2,
       payload=[see next layer]
  TCP: sp=0, dp=24, S=42, A=42, flags=0, win=10000, len=20, sum=0,
       payload=

  IP:  ver=4, len=40, tos=0, id=0, frag=0, ttl=255, proto=6, sum=0, SA=11.0.0.1, DA=11.0.0.2,
       payload=[see next layer]
  TCP: sp=0, dp=23, S=42, A=42, flags=0, win=10000, len=20, sum=0,
       payload=

  IP:  ver=4, len=40, tos=0, id=0, frag=0, ttl=255, proto=6, sum=0, SA=11.0.0.1, DA=11.0.0.2,
       payload=[see next layer]
  TCP: sp=0, dp=24, S=42, A=42, flags=0, win=10000, len=20, sum=0,
       payload=

Create Counter ACL Rules

In Linux, all ACL rules are always counted. To create an ACL rule for counting purposes only, set the rule action to ACCEPT. See the Netfilter chapter for details on how to use cl-acltool to set up iptables-/ip6tables-/ebtables-based ACLs.

Always place your rules files under /etc/cumulus/acl/policy.d/.

To count all packets going to a Web server:

cumulus@switch:~$ cat sample_count.rules

  [iptables]
  -A FORWARD -p tcp --dport 80 -j ACCEPT

  cumulus@switch:~$ sudo cl-acltool -i -p sample_count.rules
  Using user provided rule file sample_count.rules
  Reading rule file sample_count.rules ...
  Processing rules in file sample_count.rules ...
  Installing acl policy... done.

  cumulus@switch:~$ sudo iptables -L -v
  Chain INPUT (policy ACCEPT 16 packets, 2224 bytes)
  pkts bytes target     prot opt in     out     source          destination

  Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
  pkts bytes target     prot opt in     out     source          destination
    2   156 ACCEPT     tcp  --  any    any     anywhere         anywhere           tcp dpt:http

  Chain OUTPUT (policy ACCEPT 44 packets, 8624 bytes)
  pkts bytes target     prot opt in     out     source          destination

The -p option clears out all other rules. The -i option reinstalls all the rules.

Configure SPAN and ERSPAN

SPAN (Switched Port Analyzer) provides for the mirroring of all packets coming in from or going out of an interface (the SPAN source), and being copied and transmitted out of a local port (the SPAN destination) for monitoring. The SPAN destination port is also referred to as a mirror-to-port (MTP). The original packet is still switched, while a mirrored copy of the packet is sent out of the MTP.

ERSPAN (Encapsulated Remote SPAN) enables the mirrored packets to be sent to a monitoring node located anywhere across the routed network. The switch finds the outgoing port of the mirrored packets by doing a lookup of the destination IP address in its routing table. The original L2 packet is encapsulated with GRE for IP delivery. The encapsulated packets have the following format:

 ----------------------------------------------------------
| MAC_HEADER | IP_HEADER | GRE_HEADER | L2_Mirrored_Packet |
 ----------------------------------------------------------

  • Mirrored traffic is not guaranteed. If the MTP is congested, mirrored packets might be discarded.
  • A SPAN and ERSPAN destination interface that is oversubscribed might result in data plane buffer depletion and buffer drops. Exercise caution when enabling SPAN and ERSPAN when the aggregate speeds of all source ports exceeds the destination port. Selective SPAN is recommended when possible to limit traffic in this scenario.

SPAN and ERSPAN are configured via cl-acltool, the same utility for security ACL configuration. The match criteria for SPAN and ERSPAN is usually an interface; for more granular match terms, use selective spanning. The SPAN source interface can be a port, a subinterface, or a bond interface. Ingress traffic on interfaces can be matched, and on switches with Spectrum ASICs, egress traffic can be matched. See the list of limitations below.

Always place your rules files under /etc/cumulus/acl/policy.d/.

Limitations for SPAN and ERSPAN

Configure SPAN for Switch Ports

This section describes how to set up, install, verify and uninstall SPAN rules. In the examples that follow, you span (mirror) switch port swp4 input traffic and swp4 output traffic to destination switch port swp19.

First, create a rules file in /etc/cumulus/acl/policy.d/:

cumulus@switch:~$ sudo bash -c 'cat <<EOF > /etc/cumulus/acl/policy.d/span.rules
[iptables]
-A FORWARD --in-interface swp4 -j SPAN --dport swp19
-A FORWARD --out-interface swp4 -j SPAN --dport swp19
EOF'

Using cl-acltool with the --out-interface rule applies to transit traffic only; it does not apply to traffic sourced from the switch.

Next, verify all the rules that are currently installed:

cumulus@switch:~$ sudo iptables -L -v
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
  pkts bytes target     prot opt in     out     source               destination
     0     0 DROP       all  --  swp+   any     240.0.0.0/5          anywhere
     0     0 DROP       all  --  swp+   any     loopback/8           anywhere
     0     0 DROP       all  --  swp+   any     base-address.mcast.net/8  anywhere
     0     0 DROP       all  --  swp+   any     255.255.255.255      anywhere
     0     0 SETCLASS   ospf --  swp+   any     anywhere             anywhere             SETCLASS  class:7
     0     0 POLICE     ospf --  any    any     anywhere             anywhere             POLICE  mode:pkt rate:2000 burst:2000
     0     0 SETCLASS   tcp  --  swp+   any     anywhere             anywhere             tcp dpt:bgp SETCLASS  class:7
     0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp dpt:bgp POLICE  mode:pkt rate:2000 burst:2000
     0     0 SETCLASS   tcp  --  swp+   any     anywhere             anywhere             tcp spt:bgp SETCLASS  class:7
     0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp spt:bgp POLICE  mode:pkt rate:2000 burst:2000
     0     0 SETCLASS   tcp  --  swp+   any     anywhere             anywhere             tcp dpt:5342 SETCLASS  class:7
     0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp dpt:5342 POLICE  mode:pkt rate:2000 burst:2000
     0     0 SETCLASS   tcp  --  swp+   any     anywhere             anywhere             tcp spt:5342 SETCLASS  class:7
     0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp spt:5342 POLICE  mode:pkt rate:2000 burst:2000
     0     0 SETCLASS   icmp --  swp+   any     anywhere             anywhere             SETCLASS  class:2
     0     0 POLICE     icmp --  any    any     anywhere             anywhere             POLICE  mode:pkt rate:100 burst:40
    15  5205 SETCLASS   udp  --  swp+   any     anywhere             anywhere             udp  dpts:bootps:bootpc SETCLASS  class:2
    11  3865 POLICE     udp  --  any    any     anywhere             anywhere             udp dpt:bootps POLICE  mode:pkt rate:100 burst:100
     0     0 POLICE     udp  --  any    any     anywhere             anywhere             udp dpt:bootpc POLICE  mode:pkt rate:100 burst:100
     0     0 SETCLASS   tcp  --  swp+   any     anywhere             anywhere             tcp dpts:bootps:bootpc SETCLASS  class:2
     0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp dpt:bootps POLICE  mode:pkt rate:100 burst:100
     0     0 POLICE     tcp  --  any    any     anywhere             anywhere             tcp dpt:bootpc POLICE  mode:pkt rate:100 burst:100
    17  1088 SETCLASS   igmp --  swp+   any     anywhere             anywhere             SETCLASS class:6
    17  1156 POLICE     igmp --  any    any     anywhere             anywhere             POLICE  mode:pkt rate:300 burst:100
    394 41060 POLICE    all  --  swp+   any     anywhere             anywhere             ADDRTYPE match dst-type LOCAL POLICE  mode:pkt rate:1000 burst:1000 class:0
     0     0 POLICE     all  --  swp+   any     anywhere             anywhere             ADDRTYPE match dst-type IPROUTER POLICE  mode:pkt rate:400 burst:100 class:0
    988  279K SETCLASS  all  --  swp+   any      anywhere            anywhere             SETCLASS  class:0

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
  pkts bytes target     prot opt in     out     source               destination
     0     0 DROP       all  --  swp+   any     240.0.0.0/5          anywhere
     0     0 DROP       all  --  swp+   any     loopback/8           anywhere
     0     0 DROP       all  --  swp+   any     base-address.mcast.net/8  anywhere
     0     0 DROP       all  --  swp+   any     255.255.255.255      anywhere
 26864 4672K SPAN       all  --  swp4   any     anywhere             anywhere             dport:swp19  <---- input packets on swp4

40722   47M  SPAN       all  --  any    swp4     anywhere             anywhere             dport:swp19  <---- output packets on swp4

Chain OUTPUT (policy ACCEPT 67398 packets, 5757K bytes)
  pkts bytes target     prot opt in     out     source               destination

Install the rules:

cumulus@switch:~$ sudo cl-acltool -i
[sudo] password for cumulus:
Reading rule file /etc/cumulus/acl/policy.d/00control_plane.rules ...
Processing rules in file /etc/cumulus/acl/policy.d/00control_plane.rules ...
Reading rule file /etc/cumulus/acl/policy.d/99control_plane_catch_all.rules ...
Processing rules in file /etc/cumulus/acl/policy.d/99control_plane_catch_all.rules ...
Reading rule file /etc/cumulus/acl/policy.d/span.rules ...
Processing rules in file /etc/cumulus/acl/policy.d/span.rules ...
Installing acl policy
done.

Running the following command is incorrect and will remove all existing control-plane rules or other installed rules and only install the rules defined in span.rules:

cumulus@switch:~$ sudo cl-acltool -i  -P /etc/cumulus/acl/policy.d/span.rules

Verify that the SPAN rules are installed:

cumulus@switch:~$ sudo cl-acltool -L all | grep SPAN
38025 7034K SPAN       all  --  swp4   any     anywhere             anywhere             dport:swp19
50832   55M SPAN       all  --  any    swp4    anywhere             anywhere             dport:swp19

SPAN Sessions that Reference an Outgoing Interface

SPAN sessions that reference an outgoing interface create the mirrored packets based on the ingress interface before the routing/switching decision. For example, the following rule captures traffic that is ultimately destined to leave swp2 but mirrors the packets when they arrive on swp3. The rule transmits packets that reference the original VLAN tag and source/destination MAC address at the time the packet is originally received on swp3.

-A FORWARD --out-interface swp2 -j SPAN --dport swp1

Configure SPAN for Bonds

This section describes how to configure SPAN for all packets going out of bond0 locally to bond1.

First, create a rules file in /etc/cumulus/acl/policy.d/:

cumulus@switch:~$ sudo bash -c 'cat <<EOF > /etc/cumulus/acl/policy.d/span_bond.rules 
[iptables]
-A FORWARD --out-interface bond0 -j SPAN --dport bond1
EOF'

Using cl-acltool with the --out-interface rule applies to transit traffic only; it does not apply to traffic sourced from the switch.

Install the rules:

cumulus@switch:~$ sudo cl-acltool -i
[sudo] password for cumulus:
Reading rule file /etc/cumulus/acl/policy.d/00control_plane.rules ...
Processing rules in file /etc/cumulus/acl/policy.d/00control_plane.rules ...
Reading rule file /etc/cumulus/acl/policy.d/99control_plane_catch_all.rules ...
Processing rules in file /etc/cumulus/acl/policy.d/99control_plane_catch_all.rules ...
Reading rule file /etc/cumulus/acl/policy.d/span_bond.rules ...
Processing rules in file /etc/cumulus/acl/policy.d/span_bond.rules ...
Installing acl policy
done.

Verify that the SPAN rules are installed:

cumulus@switch:~$ sudo iptables -L -v | grep SPAN
    19  1938 SPAN       all  --  any    bond0   anywhere             anywhere             dport:bond1

Configure ERSPAN

This section describes how to configure ERSPAN for all packets coming in from swp1 to 12.0.0.2.

Cut-through mode is not supported for ERSPAN in Cumulus Linux on switches using Broadcom Tomahawk, Trident II+, and Trident II ASICs.

Cut-through mode is supported for ERSPAN in Cumulus Linux on switches using Mellanox Spectrum ASICs.

  1. First, create a rules file in /etc/cumulus/acl/policy.d/:

    cumulus@switch:~$ sudo bash -c 'cat <<EOF > /etc/cumulus/acl/policy.d/erspan.rules
    [iptables]
    -A FORWARD --in-interface swp1 -j ERSPAN --src-ip 12.0.0.1 --dst-ip 12.0.0.2  --ttl 64
    EOF'
    
  2. Install the rules:

    cumulus@switch:~$ sudo cl-acltool -i
    Reading rule file /etc/cumulus/acl/policy.d/00control_plane.rules ...
    Processing rules in file /etc/cumulus/acl/policy.d/00control_plane.rules ...
    Reading rule file /etc/cumulus/acl/policy.d/99control_plane_catch_all.rules ...
    Processing rules in file /etc/cumulus/acl/policy.d/99control_plane_catch_all.rules ...
    Reading rule file /etc/cumulus/acl/policy.d/erspan.rules ...
    Processing rules in file /etc/cumulus/acl/policy.d/erspan.rules ...
    Installing acl policy
    done.
    
  3. Verify that the ERSPAN rules are installed:

    cumulus@switch:~$ sudo iptables -L -v | grep SPAN
         69  6804 ERSPAN     all  --  swp1   any     anywhere             anywhere             ERSPAN   src-ip:12.0.0.1 dst-ip:12.0.0.2
    

The src-ip option can be any IP address, whether it exists in the routing table or not. The dst-ip option must be an IP address reachable via the routing table. The destination IP address must be reachable from a front-panel port, and not the management port. Use ping or ip route get <ip> to verify that the destination IP address is reachable. Setting the --ttl option is recommended.

If a SPAN destination IP address is not available, or if the interface type or types prevent using a laptop as a SPAN destination, read this knowledge base article for a workaround.

ERSPAN and Wireshark

Selective Spanning

SPAN and ERSPAN traffic rules can be configured to limit the traffic that is spanned, to reduce the volume of copied data.

Cumulus Linux supports selective spanning for iptables only. ip6tables and ebtables are not supported.

The following matching fields are supported:

With ERSPAN, a maximum of two --src-ip --dst-ip pairs are supported. Exceeding this limit produces an error when you install the rules with cl-acltool.

SPAN Examples

To mirror forwarded packets from all ports matching SIP 20.0.1.0 and DIP 20.0.1.2 to port swp1s1:

-A FORWARD --in-interface swp+ -s 20.0.0.2 -d 20.0.1.2 -j SPAN --dport swp1s2

To mirror icmp packets from all ports to swp1s2:

-A FORWARD --in-interface swp+ -s 20.0.0.2 -p icmp -j SPAN --dport swp1s2

To mirror forwarded UDP packets received from port swp1s0, towards DIP 20.0.1.2 and destination port 53:

-A FORWARD --in-interface swp1s0 -d 20.0.1.2 -p udp --dport 53 -j SPAN --dport swp1s2

To mirror all forwarded TCP packets with only SYN set:

-A FORWARD --in-interface swp+ -p tcp --tcp-flags ALL SYN -j SPAN --dport swp1s2

To mirror all forwarded TCP packets with only FIN set:

-A FORWARD --in-interface swp+ -p tcp --tcp-flags ALL FIN -j SPAN --dport swp1s2

ERSPAN Examples

To mirror forwarded packets from all ports matching SIP 20.0.1.0 and DIP 20.0.1.2:

-A FORWARD --in-interface swp+ -s 20.0.0.2 -d 20.0.1.2 -j ERSPAN --src-ip 90.0.0.1 --dst-ip 20.0.2.2

To mirror ICMP packets from all ports:

-A FORWARD --in-interface swp+ -s 20.0.0.2 -p icmp -j ERSPAN --src-ip 90.0.0.1 --dst-ip 20.0.2.2

To mirror forwarded UDP packets received from port swp1s0, towards DIP 20.0.1.2 and destination port 53:

-A FORWARD --in-interface swp1s0 -d 20.0.1.2 -p udp --dport 53 -j ERSPAN --src-ip 90.0.0.1 --dst-ip 20.0.2.2

To mirror all forwarded TCP packets with only SYN set:

-A FORWARD --in-interface swp+ -p tcp --tcp-flags ALL SYN -j ERSPAN --src-ip 90.0.0.1 --dst-ip 20.0.2.2

To mirror all forwarded TCP packets with only FIN set:

-A FORWARD --in-interface swp+ -p tcp --tcp-flags ALL FIN -j ERSPAN --src-ip 90.0.0.1 --dst-ip 20.0.2.2

Remove SPAN Rules

To remove your SPAN rules, run:

#Remove rules file:
cumulus@switch:~$ sudo rm  /etc/cumulus/acl/policy.d/span.rules
#Reload the default rules
cumulus@switch:~$ sudo cl-acltool -i
cumulus@switch:~$

To verify that the SPAN rules were removed:

cumulus@switch:~$ sudo cl-acltool -L all | grep SPAN
cumulus@switch:~$

Monitor Control Plane Traffic with tcpdump

You can use tcpdump to monitor control plane traffic - traffic sent to and coming from the switch CPUs. tcpdump does not monitor data plane traffic; use cl-acltool instead (see above).

For more information on tcpdump, read the documentation and the man page.

The following example incorporates a few tcpdump options:

cumulus@switch:~$ sudo tcpdump -i bond0 host 169.254.0.2 -c 10
tcpdump: WARNING: bond0: no IPv4 address assigned
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on bond0, link-type EN10MB (Ethernet), capture size 65535 bytes
16:24:42.532473 IP 169.254.0.2 > 169.254.0.1: ICMP echo request, id 27785, seq 6, length 64
16:24:42.532534 IP 169.254.0.1 > 169.254.0.2: ICMP echo reply, id 27785, seq 6, length 64
16:24:42.804155 IP 169.254.0.2.40210 > 169.254.0.1.5342: Flags [.], seq 266275591:266277039, ack 3813627681, win 58, options [nop,nop,TS val 590400681 ecr 530346691], length 1448
16:24:42.804228 IP 169.254.0.1.5342 > 169.254.0.2.40210: Flags [.], ack 1448, win 166, options [nop,nop,TS val 530348721 ecr 590400681], length 0
16:24:42.804267 IP 169.254.0.2.40210 > 169.254.0.1.5342: Flags [P.], seq 1448:1836, ack 1, win 58, options [nop,nop,TS val 590400681 ecr 530346691], length 388
16:24:42.804293 IP 169.254.0.1.5342 > 169.254.0.2.40210: Flags [.], ack 1836, win 165, options [nop,nop,TS val 530348721 ecr 590400681], length 0
16:24:43.532389 IP 169.254.0.2 > 169.254.0.1: ICMP echo request, id 27785, seq 7, length 64
16:24:43.532447 IP 169.254.0.1 > 169.254.0.2: ICMP echo reply, id 27785, seq 7, length 64
16:24:43.838652 IP 169.254.0.1.59951 > 169.254.0.2.5342: Flags [.], seq 2555144343:2555145791, ack 2067274882, win 58, options [nop,nop,TS val 530349755 ecr 590399688], length 1448
16:24:43.838692 IP 169.254.0.1.59951 > 169.254.0.2.5342: Flags [P.], seq 1448:1838, ack 1, win 58, options [nop,nop,TS val 530349755 ecr 590399688], length 390
10 packets captured
12 packets received by filter
0 packets dropped by kernel

Using NCLU to Troubleshoot Your Network Configuration

The Network Command Line Utility (NCLU) can quickly return a lot of information about your network configuration.

net show Commands

Running net show and pressing TAB displays all available command line arguments usable by net. The output looks like this:

cumulus@switch:~$ net show <TAB>
bfd            :  Bidirectional forwarding detection
bgp            :  Border Gateway Protocol
bridge         :  a layer2 bridge
clag           :  Multi-Chassis Link Aggregation
commit         :  apply the commit buffer to the system
configuration  :  settings, configuration state, etc
counters       :  net show counters
debugs         :  Debugs
dot1x          :  Configure, Enable, Delete or Show IEEE 802.1X EAPOL
evpn           :  Ethernet VPN
hostname       :  local hostname
igmp           :  Internet Group Management Protocol
interface      :  An interface, such as swp1, swp2, etc.
ip             :  Internet Protocol version 4/6
ipv6           :  Internet Protocol version 6
lldp           :  Link Layer Discovery Protocol
mpls           :  Multiprotocol Label Switching
mroute         :  Static unicast routes in MRIB for multicast RPF lookup
msdp           :  Multicast Source Discovery Protocol
ospf           :  Open Shortest Path First (OSPFv2)
ospf6          :  Open Shortest Path First (OSPFv3)
package        :  A Cumulus Linux package name
pbr            :  Policy Based Routing
pim            :  Protocol Independent Multicast
ptp            :  Precision Time Protocol
rollback       :  revert to a previous configuration state
route          :  Static routes
route-map      :  Route-map
snmp-server    :  Configure the SNMP server
system         :  System information
time           :  Time
version        :  Version number
vrf            :  Virtual Routing and Forwarding
vrrp           :  Virtual Router Redundancy Protocol

Show Interfaces

To show all available interfaces that are physically UP, run net show interface:

cumulus@switch:~$ net show interface

    Name    Speed    MTU    Mode           Summary
--  ------  -------  -----  -------------  --------------------------------------
UP  lo      N/A      65536  Loopback       IP: 10.0.0.11/32, 127.0.0.1/8, ::1/128
UP  eth0    1G       1500   Mgmt           IP: 192.168.0.11/24(DHCP)
UP  swp1    1G       1500   Access/L2      Untagged: br0
UP  swp2    1G       1500   NotConfigured
UP  swp51   1G       1500   NotConfigured
UP  swp52   1G       1500   NotConfigured
UP  blue    N/A      65536  NotConfigured
UP  br0     N/A      1500   Bridge/L3      IP: 172.16.1.1/24
                                           Untagged Members: swp1
                                           802.1q Tag: Untagged
                                           STP: RootSwitch(32768)
UP  red     N/A      65536  NotConfigured

To show every interface regardless of state, run net show interface all:

cumulus@leaf01:~$ net show interface all
State  Name     Spd  MTU    Mode           LLDP                    Summary
-----  -------  ---  -----  -------------  ----------------------  -------------------------
UP     lo       N/A  65536  Loopback                               IP: 127.0.0.1/8
        lo                                                         IP: 10.0.0.11/32
        lo                                                         IP: ::1/128
UP     eth0     1G   1500   Mgmt           oob-mgmt-switch (swp6)  IP: 192.168.0.11/24(DHCP)
UP     swp1     1G   1500   Access/L2      server01 (eth1)         Master: br0(UP)
ADMDN  swp2     N/A  1500   NotConfigured
ADMDN  swp45    N/A  1500   NotConfigured
ADMDN  swp46    N/A  1500   NotConfigured
ADMDN  swp47    N/A  1500   NotConfigured
ADMDN  swp48    N/A  1500   NotConfigured
ADMDN  swp49    N/A  1500   NotConfigured
ADMDN  swp50    N/A  1500   NotConfigured
UP     swp51    1G   1500   Default        spine01 (swp1)
UP     swp52    1G   1500   Default        spine02 (swp1)
UP     br0      N/A  1500   Bridge/L3                               IP: 172.16.1.1/24
ADMDN  vagrant  N/A  1500   NotConfigured

To get information about the switch itself, run net show system:

cumulus@switch:~$ net show system
Hostname......... celRED

Build............ Cumulus Linux 4.0.0~1555370771.772c26b6
Uptime........... 8 days, 12:24:01.770000

Model............ Cel REDSTONE
CPU.............. x86_64 Intel Atom C2538 2.4 GHz
Memory........... 4GB
Disk............. 14.9GB
ASIC............. Broadcom Trident2 BCM56854
Ports............ 48 x 10G-SFP+ & 6 x 40G-QSFP+
Base MAC Address. a0:00:00:00:00:50
Serial Number.... A1010B2A011212AB000001

network-docopt Package

NCLU uses the python network-docopt package. This is inspired by docopt and enables you to specify partial commands without tab completion or running the complete option. For example, net show int runs the net show interface command and net show sys runs the net show system command.

Mellanox What Just Happened (WJH)

Cumulus Linux supports the What Just Happened (WJH) feature for Mellanox switches to stream detailed and contextual telemetry for off-box analysis with tools, such as NVIDIA NetQ. This advanced streaming telemetry technology provides real time visibility into problems in the network, such as hardware packet drops due to buffer congestion, incorrect routing, ACL or layer 1 problems.

When WJH capabilities are combined with the analytics engine of NVIDIA NetQ, you have the ability to hone in on any loss, anywhere in the fabric, from a single management console. You can view any current or historic drops and specific drop reasons, and also identify any flow or endpoints and pin-point exactly where communication is failing in the network.

WJH is enabled by default on a Mellanox switch; no configuration is required in Cumulus Linux.

Monitoring System Statistics and Network Traffic with sFlow

sFlow is a monitoring protocol that samples network packets, application operations, and system counters. sFlow collects both interface counters and sampled 5-tuple packet information, so that you can monitor your network traffic as well as your switch state and performance metrics. An outside server, known as an sFlow collector, is required to collect and analyze this data.

hsflowd is the daemon that samples and sends sFlow data to configured collectors. By default, hsflowd is disabled and does not start automatically when the switch boots up.

  • sFlow is not supported on Broadcom switches with the Hurricane2 ASIC.
  • If you intend to run this service within a VRF, including the management VRF, follow these steps for configuring the service.

Configure sFlow

To configure hsflowd to send to the designated collectors, either:

Configure sFlow with DNS-SD

You can configure your DNS zone to advertise the collectors and polling information to all interested clients.

Add the following content to the zone file on your DNS server:

_sflow._udp SRV 0 0 6343 collector1
_sflow._udp SRV 0 0 6344 collector2
_sflow._udp TXT (
"txtvers=1"
"sampling.100M=100"
"sampling.1G=1000"
"sampling.10G=10000"
"sampling.40G=40000"
"sampling.100G=100000"
"polling=20"
)

The above snippet instructs hsflowd to send sFlow data to collector1 on port 6343 and to collector2 on port 6344. hsflowd will poll counters every 20 seconds and sample 1 out of every 2048 packets.

The maximum samples per second delivered from the hardware is limited to 16K. You can configure the number of samples per second in the /etc/cumulus/datapath/traffic.conf file, as shown below:

# Set sflow/sample ingress cpu packet rate and burst in packets/sec
# Values: {0..16384}
#sflow.rate = 16384
#sflow.burst = 16384

Start the sFlow daemon:

cumulus@switch:~$ sudo systemctl start hsflowd.service

No additional configuration is required in the /etc/hsflowd.conf file.

Manually Configure /etc/hsflowd.conf

You can set up the collectors and variables on each switch.

Edit the /etc/hsflowd.conf file to set up your collectors and sampling rates in /etc/hsflowd.conf. For example:

sflow {
# ====== Sampling/Polling/Collectors ======
  # EITHER: automatic (DNS SRV+TXT from _sflow._udp):
  #   DNS-SD { }
  # OR: manual:
  #   Counter Polling:
        polling = 20
  #   default sampling N:
  #     sampling = 400
  #   sampling N on interfaces with ifSpeed:
        sampling.100M = 100
        sampling.1G = 1000
        sampling.10G = 10000
        sampling.40G = 40000
  #   sampling N for apache, nginx:
  #     sampling.http = 50
  #     sampling N for application (requires json):
  #     sampling.app.myapp = 100
  #   collectors:
  collector { ip=192.0.2.100 udpport=6343 }
  collector { ip=192.0.2.200 udpport=6344 }
}

This configuration polls the counters every 20 seconds, samples 1 of every 40000 packets for 40G interfaces, and sends this information to a collector at 192.0.2.100 on port 6343 and to another collector at 192.0.2.200 on port 6344.

Some collectors require each source to transmit on a different port, others listen on only one port. Refer to the documentation for your collector for more information.

Configure sFlow Visualization Tools

For information on configuring various sFlow visualization tools, read this knowledge base article.

Considerations

Simple Network Management Protocol - SNMP

Cumulus Linux uses the open source Net-SNMP agent snmpd version 5.8, which provides support for most of the common industry-wide MIBs, including interface counters and TCP/UDP IP stack data.

History

SNMP is an IETF standards-based network management architecture and protocol that traces its roots back to Carnegie-Mellon University in 1982. Since then, it has been modified by programmers at the University of California. In 1995, this code was also made publicly available as the UCD project. After that, ucd-snmp was extended by work done at the University of Liverpool as well as later in Denmark. In late 2000, the project name changed to net-snmp and became a fully-fledged collaborative open source project. The version used by Cumulus Linux is based on the latest net-snmp 5.8 branch with added custom MIBs and pass-through and pass-persist scripts (see below for more information on pass persist scripts).

Introduction to Simple Network Management Protocol

SNMP Management servers gather information from different systems in a consistent manner and the paths to the relevant information are standardized in IETF RFCs. SNMPs longevity is due to the fact that it standardizes the objects collected from devices, the protocol used for transport, and architecture of the management systems. The most widely used, and most insecure, versions of SNMP are versions 1 and 2c and their popularity is largely due to implementations that have been in use for decades. SNMP version 3 is the recommended version because of its advanced security features. In general, a network being profiled by SNMP Management Stations mainly consist of devices containing SNMP agents. The agent running on Cumulus Linux switches and routers is the snmpd daemon.

SNMP Managers

An SNMP Network Management System (NMS) is a computer that is configured to poll SNMP agents (in this case, Cumulus Linux switches and routers) to gather information and present it. This manager can be any machine that can send query requests to SNMP agents with the correct credentials. This NMS can be a large set of monitoring suite or as simple as some scripts that collect and display data. The managers generally poll the agents and the agents respond with the data. There are a variety of polling command-line tools (snmpget, snmpgetnext, snmpwalk, snmpbulkget, snmpbulkwalk, and so on). SNMP agents can also send unsolicited Traps/Inform messages to the SNMP Manager based on predefined criteria (like link changes).

SNMP Agents

The SNMP agents (snmpd) running on the switches do the bulk of the work and are responsible for gathering information about the local system and storing data in a format that can be queried updating an internal database called the management information base, or MIB. The MIB is a standardized, hierarchical structure that stores information that can be queried. Parts of the MIB tree are available and provided to incoming requests originating from an NMS host that has authenticated with the correct credentials. You can configure the Cumulus Linux switch with usernames and credentials to provide authenticated and encrypted responses to NMS requests. The snmpd agent can also proxy requests and act as a master agent to sub-agents running on other daemons (FRR, LLDP).

Management Information Base (MIB)

The MIB is a database that is implemented on the daemon (or agent) and follows IETF RFC standards to which the manager and agents adhere. It is a hierarchical structure that, in many areas, is globally standardized, but also flexible enough to allow vendor-specific additions. Cumulus Linux uses a number of custom enterprise MIB tables and these are defined in text files located on the switch and in files named /usr/share/snmp/mibs/Cumulus*. The MIB structure is best understood as a top-down hierarchical tree. Each branch that forks off is labeled with both an identifying number (starting with 1) and an identifying string that is unique for that level of the hierarchy. These strings and numbers can be used interchangeably. A specific node of the tree can be traced from the unnamed root of the tree to the node in question. The parent IDs (numbers or strings) are strung together, starting with the most general to form an address for the MIB Object. Each junction in the hierarchy is represented by a dot in this notation so that the address ends up being a series of ID strings or numbers separated by dots. This entire address is known as an object identifier (OID).

Hardware vendors that embed SNMP agents in their devices sometimes implement custom branches with their own fields and data points. However, there are standard MIB branches that are well defined and can be used by any device. The standard branches discussed here are all under the same parent branch structure. This branch defines information that adheres to the MIB-2 specification, which is a revised standard for compliant devices. You can use various online and command-line tools to translate between numbers and string and to also provide definitions for the various MIB Objects. For example, you can view the sysLocation object in the system table with either a string of numbers 1.3.6.1.2.1.1.6 or the string representation iso.org.dod.internet.mgmt.mib-2.system.sysLocation. You can view the definition with the snmptranslate (1) command (found in the snmp Debian package).

/home/cumulus# snmptranslate -Td -On SNMPv2-MIB::sysLocation

.1.3.6.1.2.1.1.6
sysLocation OBJECT-TYPE
  -- FROM       SNMPv2-MIB
  -- TEXTUAL CONVENTION DisplayString
  SYNTAX        OCTET STRING (0..255)
  DISPLAY-HINT  "255a"
  MAX-ACCESS    read-write
  STATUS        current
  DESCRIPTION   "The physical location of this node (e.g., 'telephone
        closet, 3rd floor').  If the location is unknown, the
        value is the zero-length string."
::= { iso(1) org(3) dod(6) internet(1) mgmt(2) mib-2(1) system(1) 6 }

/home/cumulus# snmptranslate  -Tp -IR   system
+--system(1)
    |
    +-- -R-- String    sysDescr(1)
    |        Textual Convention: DisplayString
    |        Size: 0..255
    +-- -R-- ObjID     sysObjectID(2)
    +-- -R-- TimeTicks sysUpTime(3)
    |  |
    |  +--sysUpTimeInstance(0)
    |
    +-- -RW- String    sysContact(4)
    |        Textual Convention: DisplayString
    |        Size: 0..255
    +-- -RW- String    sysName(5)
    |        Textual Convention: DisplayString
    |        Size: 0..255
    +-- -RW- String    sysLocation(6)
    |        Textual Convention: DisplayString
    |        Size: 0..255
    +-- -R-- INTEGER   sysServices(7)
    |        Range: 0..127
    +-- -R-- TimeTicks sysORLastChange(8)
    |        Textual Convention: TimeStamp

The section 1.3.6.1 or iso.org.dod.internet is the OID that defines internet resources. The2 or mgmt that follows is for a management subcategory. The 1 or mib-2 under that defines the MIB-2 specification. And finally, the 1 or system is the parent for a number of child objects (sysDescr, sysObjectID, sysUpTime, sysContact, sysName, sysLocation, sysServices, and so on).

Getting Started

The simplest use case for using SNMP consists of creating a readonly community password and enabling a listening address for the loopback address (this is the default listening-address provided). This allows for testing functionality of snmpd before extending the listening addresses to IP addresses reachable from outside the switch or router. This first sample configuration adds a listening address on the loopback interface (this is not a change from the default so we get a message stating that the configuration has not changed), sets a simple community password (SNMPv2) for testing, changes the system-name object in the system table, commits the change, checks the status of snmpd, and gets the first MIB object in the system table:

cumulus@router1:~$ net add snmp-server listening-address localhost
Configuration has not changed
cumulus@router1:~$ net add snmp-server readonly-community mynotsosecretpassword access any
cumulus@router1:~$ net add snmp-server system-name my little router
cumulus@router1:~$ net commit

cumulus@router1:~$ net show snmp-server status

Simple Network Management Protocol (SNMP) Daemon.
---------------------------------  ----------------
Current Status                     active (running)
Reload Status                      enabled
Listening IP Addresses             localhost
Main snmpd PID                     13669
Version 1 and 2c Community String  Configured
Version 3 Usernames                Not Configured
---------------------------------  ----------------

cumulus@router1:~$ snmpgetnext -v 2c -c mynotsosecretpassword localhost SNMPv2-MIB::sysName
SNMPv2-MIB::sysName.0 = STRING: my little router

Configure SNMP

For external SNMP NMS systems to poll Cumulus Linux switches and routers, you must configure the SNMP agent (snmpd) running on the switch with one or more IP addresses (with net add snmp-server listening-address <ip>) on which the agent listens. You must configure these IP addresses on interfaces that have link state UP. By default, the SNMP configuration has a listening address of localhost (or 127.0.0.1), which allows the daemon to respond to SNMP requests originating on the switch itself. This is a useful method of checking the configuration for SNMP without exposing the switch to attacks from the outside. The only other required configuration is a readonly community password (configured with net add snmp-server readonly-community <password> access <ip | any>``), that allows polling of the various MIB objects on the device itself. SNMPv3 is recommended since SNMPv2c (with a community string) exposes the password in the GetRequest and GetResponse packets. SNMPv3 does not expose the username passwords and has the option of encrypting the packet contents.

  • Consider using NCLU to configure snmpd even though NCLU does not provide functionality to configure every snmpd feature. You are not restricted to using NCLU for configuration and can edit the /etc/snmp/snmpd.conf file and control snmpd with systemctl commands.
  • Cumulus Linux provides VRF listening-address, as well as Trap/Inform support. When management VRF is enabled, the eth0 interface is placed in the management VRF. When you configure the listening-address for snmp-server, you must run the net add snmp-server listening-address <address> vrf mgmt command to enable listening on the eth0 interface. These additional parameters are described in detail below.
  • You must add a default community string for v1 or v2c environments so that the snmpd daemon can respond to requests. For security reasons, the default configuration configures snmpd to listen to SNMP requests on the loopback interface so access to the switch is restricted to requests originating from the switch itself. The only required commands for snmpd to function are a listening-address and either a username or a readonly-community string.

Configure SNMP with NCLU

The table below highlights the structure of NCLU commands available for configuring SNMP. An example command set is provided below the table. NCLU restarts the snmpd daemon after configuration changes are made and committed.

Command Summary
net del all or net del snmp-server all Removes all entries in the /etc/snmp/snmpd.conf file and replaces them with defaults. The defaults remove all SNMPv3 usernames, readonly-communities, and a listening-address of localhost is configured.
net add snmp-server listening-address (localhost|localhost-v6) For security reasons, the localhost is set to a listening address 127.0.0.1 by default so that the SNMP agent only responds to requests originating on the switch itself. You can also configure listening only on the IPv6 localhost address with localhost-v6. When using IPv6 addresses or localhost, you can use a readonly-community-v6 for v1 and v2c requests. For v3 requests, you can use the username command to restrict access.
net add snmp-server listening-address localhost
net add snmp-server listening-address localhost-v6
net add snmp-server listening-address (all|all-v6) Configures the snmpd agent to listen on all interfaces for either IPv4 or IPv6 UDP port 161 SNMP requests. This command removes all other individual IP addresses configured.

Note: This command does not allow snmpd to cross VRF table boundaries. To listen on IP addresses in different VRF tables, use multiple listening-address commands each with a VRF name, as shown below.
net add snmp-server listening-address all
net add snmp-server listening-address all-v6
net add snmp-server listening-address IP_ADDRESS IP_ADDRESS … Sets snmpd to listen to a specific IPv4 or IPv6 address, or a group of addresses with space separated values, for incoming SNMP queries. If VRF tables are used, be sure to specify an IP address with an associated VRF name, as shown below. If you omit a VRF name, the default VRF is used.
net add snmp-server listening-address 10.10.10.10
net add snmp-server listening-address 10.10.10.10 44.44.44.44
net add snmp-server listening-address IP_ADDRESS vrf VRF_NAME Sets snmpd to listen to a specific IPv4 or IPv6 address on an interface within a particular VRF. With VRFs, identical IP addresses can exist in different VRF tables. This command restricts listening to a particular IP address within a particular VRF. If the VRF name is not given, the default VRF is used.
net add snmp-server listening-address 10.10.10.10 vrf mgmt
net add snmp-server username [user name] (auth-none|auth-md5|auth-sha) PASSWORD [(encrypt-des|encrypt-aes) PASSWORD] (oid |view <view name>) Creates an SNMPv3 username and the necessary credentials for access. You can restrict a user to a particular OID tree or predefined view name if these are specified. If you specify auth-none, no authentication password is required. Otherwise, an MD5 or SHA password is required for access to the MIB objects. If specified, an encryption password is used to hide the contents of the request and response packets.
net add snmp-server username testusernoauth  auth-none
net add snmp-server username testuserauth auth-md5 myauthmd5password
net add snmp-server username testuserboth auth-md5 mynewmd5password encrypt-aes myencryptsecret
net add snmp-server username limiteduser1 auth-md5 md5password1 encrypt-aes myaessecret oid 1.3.6.1.2.1.1
net add snmp-server viewname [view name] (included|excluded) [OID or name] Creates a view name that is used in readonly-community to restrict MIB tree exposure. By itself, this view definition has no effect; however, when linked to an SNMPv3 username or community password, and a host from a restricted subnet, any SNMP request with that username and password must have a source IP address within the configured subnet.

Note: OID can be either a string of period separated decimal numbers or a unique text string that identifies an SNMP MIB object. Some MIBs are not installed by default; you must install them either by hand or with the latest Debian package called snmp-mibs-downloader. You can remove specific view name entries with the delete command or with just a view name to remove all entries matching that view name. You can define a specific view name multiple times and fine tune to provide or restrict access using the included or excluded command to specify branches of certain MIB trees.
net add snmp-server viewname cumulusOnly included .1.3.6.1.4.1.40310
net add snmp-server viewname cumulusCounters included .1.3.6.1.4.1.40310.2
net add snmp-server readonly-community simplepassword access any view cumulusOnly
net add snmp-server username testusernoauth auth-none view cumulusOnly
net add snmp-server username limiteduser1 auth-md5 md5password1 encrypt-aes myaessecret view cumulusCounters
net add snmp-server (readonly-community | readonly-community-v6) [password] access (any | localhost | [network]) [(view [view name]) or [oid [oid or name]) This command defines the password required for SNMP version 1 or 2c requests for GET or GETNEXT. By default, this provides access to the full OID tree for such requests, regardless of from where they were sent. There is no default password set, so snmpd does not respond to any requests that arrive. Users often specify a source IP address token to restrict access to only that host or network given. You can specify a view name to restrict the subset of the OID tree.
Examples of readonly-community commands are shown below. The first command sets the read only community string to simplepassword for SNMP requests and this restricts requests to those sourced from hosts in the 10.10.10.0/24 subnet and restricts viewing to the mysystem view name defined with the viewname command. The second example creates a read-only community password showitall that allows access to the entire OID tree for requests originating from any source IP address.
net add snmp-server viewname mysystem included 1.3.6.1.2.1.1
net add snmp-server readonly-community simplepassword access 10.10.10.0/24 view mysystem
net add snmp-server readonly-community showitall access any
net add snmp-server trap-destination (localhost | [ipaddress]) [vrf vrf name] community-password [password] [version [1 | 2c]] For SNMP versions 1 and 2C, this command sets the SNMP Trap destination IP address. Multiple destinations can exist, but you must set up at least one to enable SNMP Traps to be sent. Removing all settings disables SNMP traps. The default version is 2c, unless otherwise configured. You must include a VRF name with the IP address to force Traps to be sent in a non-default VRF table.
net add snmp-server trap-destination 10.10.10.10 community-password mynotsosecretpassword version 1
net add snmp-server trap-destination 20.20.20.20 vrf mgmt community-password mymanagementvrfpassword version 2c
net add snmp-server trap-destination (localhost | [ipaddress]) [vrf vrf name] username <v3 username> (auth-md5|auth-sha) PASSWORD [(encrypt-des|encrypt-aes) PASSWORD] engine-id TEXT [inform] For SNMPv3 Trap and Inform messages, this command configures the trap destination IP address (with an optional VRF name). You must define the authentication type and password. The encryption type and password are optional. You must specify the engine ID/user name pair. The inform keyword is used to specify an Inform message where the SNMP agent waits for an acknowledgement.
For Traps, the engine ID/user name is for the CL switch sending the traps. This can be found at the end of the /var/lib/snmp/snmpd.conf file labelled oldEngineID. Configure this same engine ID/user name (with authentication and encryption passwords) for the Trap daemon receiving the trap to validate the received Trap.
net add snmp-server trap-destination 10.10.10.10 username myv3userrsion auth-md5 md5password1 encrypt-aes myaessecret engine-id  0x80001f888070939b14a514da5a00000000
net add snmp-server trap-destination 20.20.20.20 vrf mgmt username mymgmtvrfusername auth-md5 md5password2 encrypt-aes myaessecret2 engine-id 0x80001f888070939b14a514da5a00000000
For Inform messages (Informs are acknowledged version 3 Traps), the engine ID/user name is the one used to create the username on the receiving Trap daemon server. The Trap receiver sends the response for the Trap message using its own engine ID/user name. In practice, the trap daemon generates the usernames with its own engine ID and after these are created, the SNMP server (or agent) needs to use these engine ID/user names when configuring the Inform messages so that they are correctly authenticated and the correct response is sent to the snmpd agent that sent it.
net add snmp-server trap-destination 10.10.10.10 username myv3userrsion auth-md5 md5password1 encrypt-aes myaessecret engine-id  0x80001f888070939b14a514da5a00000000 inform
net add snmp-server trap-destination 20.20.20.20 vrf mgmt username mymgmtvrfusername auth-md5 md5password2 encrypt-aes myaessecret2 engine-id 0x80001f888070939b14a514da5a00000000 inform
net add snmp-server trap-link-up [check-frequency [seconds]] Enables notifications for interface link-up to be sent to SNMP Trap destinations.
net add snmp-server trap-link-up check-frequency 15
net add snmp-server trap-link-down [check-frequency [seconds]] Enables notifications for interface link-down to be sent to SNMP Trap destinations.
net add snmp-server trap-link-down check-frequency 10
net add snmp-server trap-snmp-auth-failures Enables SNMP Trap notifications to be sent for every SNMP authentication failure.
net add snmp-server trap-snmp-auth-failures
net add snmp-server trap-cpu-load-average one-minute [threshold] five-minute [5-min-threshold]fifteen-minute [15-min-threshold] Enables a trap when the cpu-load-average exceeds the configured threshold. You can only use integers or floating point numbers.
net add snmp-server trap-cpu-load-average one-minute 4.34 five-minute 2.32 fifteen-minute 6.5

This table describes system setting configuration commands for SNMPv2-MIB.

Command Summary
net add snmp-server system-location [string] Sets the system physical location for the node in the SNMPv2-MIB system table.
net add snmp-server system-location My private bunker
net add snmp-server system-contact [string] Sets the identification of the contact person for this managed node, together with information on how to contact this person.
net add snmp-server system-contact user X at myemail@example.com
net add snmp-server system-name [string] Sets an administratively-assigned name for the managed node. By convention, this is the fully-qualified domain name of the node.
net add snmp-server system-name CumulusBox number 1,543,567

The example commands below enable an SNMP agent to listen on all IPv4 addresses with a community string password, set the trap destination host IP address, and create four types of SNMP traps.

cumulus@switch:~$ net add snmp-server listening-address all
cumulus@switch:~$ net add snmp-server readonly-community tempPassword access any
cumulus@switch:~$ net add snmp-server trap-destination 1.1.1.1 community-password mypass version 2c
cumulus@switch:~$ net add snmp-server trap-link-up check-frequency 15
cumulus@switch:~$ net add snmp-server trap-link-down check-frequency 10
cumulus@switch:~$ net add snmp-server trap-cpu-load-average one-minute 7.45 five-minute 5.14
cumulus@switch:~$ net add snmp-server trap-snmp-auth-failures

Configure SNMP Manually

If you need to manually edit the SNMP configuration; for example, if the necessary option has not been implemented in NCLU, you need to edit the configuration directly, which is stored in the /etc/snmp/snmpd.conf file.

Use caution when editing this file. The next time you use NCLU to update your SNMP configuration, if NCLU is unable to correctly parse the syntax, some of the options might be overwritten.

Make sure you do not delete the snmpd.conf file; this can cause issues with the package manager the next time you update Cumulus Linux.

The SNMP daemon, snmpd, uses the /etc/snmp/snmpd.conf configuration file for most of its configuration. The syntax of the most important keywords are defined in the following table.

Syntax Meaning
agentaddress Required. This command sets the protocol, IP address, and the port for snmpd to listen for incoming requests. The IP address must exist on an interface that has link UP on the switch where snmpd is being used. By default, this is set to udp:127.0.0.1:161, which means snmpd listens on the loopback interface and only responds to requests (snmpwalk, snmpget, snmpgetnext) originating from the switch. A wildcard setting of udp:161,udp6:161 forces snmpd to listen on all IPv4 and IPv6 interfaces for incoming SNMP requests.

You can configure multiple IP addresses as comma-separated values; for example, udp:66.66.66.66:161,udp:77.77.77.77:161,udp6:[2001::1]:161. You can use multiple lines to define listening addresses. To bind to a particular IP address within a particular VRF table, follow the IP address with a @ and the name of the VRF table (for example, 10.10.10.10@mgmt).
rocommunity Required. This command defines the password that is required for SNMP version 1 or 2c requests for GET or GETNEXT. By default, this provides access to the full OID tree for such requests, regardless of from where they were sent. There is no default password set, so snmpd does not respond to any requests that arrive. Specify a source IP address token to restrict access to only that host or network given. Specify a view name (as defined above) to restrict the subset of the OID tree.

Examples of rocommunity commands are shown below. The first command sets the read only community string to simplepassword for SNMP requests sourced from the 10.10.10.0/24 subnet and restricts viewing to the systemonly view name defined previously with the view command. The second example creates a read-only community password that allows access to the entire OID tree from any source IP address.
rocommunity simplepassword 10.10.10.0/24 -V systemonly
rocommunity cumulustestpassword
view This command defines a view name that specifies a subset of the overall OID tree. You can reference this restricted view by name in the rocommunity command to link the view to a password that is used to see this restricted OID subset. By default, the snmpd.conf file contains numerous views with the systemonly view name.
view   systemonly  included   .1.3.6.1.2.1.1 
view systemonly included .1.3.6.1.2.1.2
view systemonly included .1.3.6.1.2.1.3
The systemonly view is used by rocommunity to create a password for access to only these branches of the OID tree.
trapsink
trap2sink
This command defines the IP address of the notification (or trap) receiver for either SNMPv1 traps or SNMPv2 traps. If you specify several sink directives, multiple copies of each notification (in the appropriate formats) are generated. You must configure a trap server to receive and decode these trap messages (for example, snmptrapd). You can configure the address of the trap receiver with a different protocol and port but this is most often left out. The defaults are to use the well-known UDP packets and port 162.
createuser
iquerysecName
rouser
These three commands define an internal SNMPv3 username that is required for snmpd to send traps. This username is required to authorize the DisMan service even though SNMPv3 is not being configured for use. The example snmpd.conf configuration shown below creates snmptrapusernameX as the username (this is just an example username) using the createUser command. iquerysecname defines the default SNMPv3 username to be used when making internal queries to retrieve monitored expressions. rouser specifies the username for these SNMPv3 queries. All three are required for snmpd to retrieve information and send built-in traps or for those configured with the monitor command shown below in the examples.
createuser snmptrapusernameX
iquerysecname snmptrapusernameX
rouser snmptrapusernameX
linkUpDownNotifications yes This command enables link up and link down trap notifications, assuming the other trap configurations settings are set. This command configures the Event MIB tables to monitor the ifTable for network interfaces being taken up or down, and triggering a linkUp or linkDown notification as appropriate. This is equivalent to the following configuration:
notificationEvent  linkUpTrap    linkUp   ifIndex ifAdminStatus ifOperStatus
notificationEvent linkDownTrap linkDown ifIndex ifAdminStatus ifOperStatus
monitor -r 60 -e linkUpTrap “Generate linkUp” ifOperStatus != 2
monitor -r 60 -e linkDownTrap “Generate linkDown” ifOperStatus == 2
defaultMonitors yes This command configures the Event MIB tables to monitor the various UCD-SNMP-MIB tables for problems (as indicated by the appropriate xxErrFlag column objects) and send a trap. This assumes you have downloaded the snmp-mibs-downloader Debian package and commented out mibs from the /etc/snmp/snmp.conf file (#mibs). This command is exactly equivalent to the following configuration:
monitor   -o prNames -o prErrMessage “process table” prErrorFlag != 0
monitor -o memErrorName -o memSwapErrorMsg “memory” memSwapError != 0
monitor -o extNames -o extOutput “extTable” extResult != 0
monitor -o dskPath -o dskErrorMsg “dskTable” dskErrorFlag != 0
monitor -o laNames -o laErrMessage “laTable” laErrorFlag != 0
monitor -o fileName -o fileErrorMsg “fileTable” fileErrorFlag != 0

Start the SNMP Daemon

Use the recommended process described below to start snmpd and monitor it using systemctl.

If you intend to run this service within a VRF, including the management VRF, follow these steps for configuring the service.

To start the SNMP daemon:

  1. Start the snmpd daemon:

    cumulus@switch:~$ sudo systemctl start snmpd.service
    
  2. Configure the snmpd daemon to start automatically after reboot:

    cumulus@switch:~$ sudo systemctl enable snmpd.service
    
  3. To enable snmpd to restart automatically after failure, create a file called /etc/systemd/system/snmpd.service.d/restart.conf and add the following lines:

    [Service]
    Restart=always
    RestartSec=60
    
  4. Run the sudo systemctl daemon-reload command.

After the service starts, you can use SNMP to manage various components on the switch.

Set up the Custom MIBs

No changes are required in the /etc/snmp/snmpd.conf file on the switch to support the custom MIBs. The following lines are already included by default and provide support for both the Cumulus Counters and the Cumulus Resource Query MIBs.

sysObjectID 1.3.6.1.4.1.40310
pass_persist .1.3.6.1.4.1.40310.1 /usr/share/snmp/resq_pp.py
pass_persist .1.3.6.1.4.1.40310.2 /usr/share/snmp/cl_drop_cntrs_pp.py

However, you need to copy several files to the NMS server for the custom Cumulus MIB to be recognized on NMS server.

Set the Community String

The snmpd authentication for versions 1 and 2 is disabled by default in Cumulus Linux. You can enable this password (called a community string) by setting rocommunity (for read-only access or rwcommunity (for read-write access). Setting a community string is required.

  1. To enable read-only querying by a client, open the /etc/snmp/snmpd.conf file in a text editor and uncomment the following line:

    rocommunity public default -V systemonly
    
    Keyword Meaning
    rocommunity Read-only community; rwcommunity is for read-write access.
    public Plain text password/community string.

    Note: Change this password to prevent security issues.
    default The default keyword allows connections from any system. The localhost keyword allows requests only from the local host. A restricted source can either be a specific hostname (or address), or a subnet, represented as IP/MASK (like 10.10.10.0/255.255.255.0), or IP/BITS (like 10.10.10.0/24), or the IPv6 equivalents.
    systemonly The name of this particular SNMP view. This is a user-defined value.
  2. Restart snmpd:

    cumulus@switch:~$ systemctl restart snmpd.service
    

Enable SNMP Support for FRRouting

SNMP supports Routing MIBs in FRRouting. To enable SNMP support for FRRouting, you need to:

Enabling FRRouting includes support for BGP. However, if you plan on using the BGP4 MIB, be sure to provide access to the MIB tree 1.3.6.1.2.1.15.

At this time, SNMP does not support monitoring BGP unnumbered neighbors.

If you plan on using the OSPFv2 MIB, provide access to 1.3.6.1.2.1.14 and to 1.3.6.1.2.1.191 for the OSPv3 MIB.

To enable SNMP support for FRRouting:

  1. Configure AgentX access in FRRouting:

    cumulus@switch:~$ net add routing agentx
    cumulus@switch:~$ net pending
    cumulus@switch:~$ net commit
    
  2. Update the SNMP configuration to enable FRRouting to respond to SNMP requests. Open the /etc/snmp/snmpd.conf file in a text editor and verify that the following configuration exists:

    agentxsocket /var/agentx/master
    agentxperms 777 777 snmp snmp
    master agentx
    

    Make sure that the /var/agentx directory is world-readable andworld-searchable (octal mode 755).

  3. Optionally, you might need to expose various MIBs:

    • For the BGP4 MIB, allow access to 1.3.6.1.2.1.15
    • For the OSPF MIB, allow access to 1.3.6.1.2.1.14
    • For the OSPFV3 MIB, allow access to 1.3.6.1.2.1.191

To verify the configuration, run snmpwalk. For example, if you have a running OSPF configuration with routes, you can check this OSPF-MIB first from the switch itself with:

cumulus@switch:~$ sudo snmpwalk -v2c -cpublic localhost 1.3.6.1.2.1.14

Enable the .1.3.6.1.2.1 Range

Some MIBs, including storage information, are not included by default in snmpd.conf in Cumulus Linux. This results in some default views on common network tools (like librenms) to return less than optimal data. You can include more MIBs by enabling all the .1.3.6.1.2.1 range. This simplifies the configuration file, removing concern that any required MIBs will be missed by the monitoring system. Various MIBs were added to version 3.0 and include the following: ENTITY and ENTITY-SENSOR MIB and parts of the BRIDGE-MIB and Q-BRIDGE-MIBs. These are included in the default configuration.

This configuration grants access to a large number of MIBs, including all SNMPv2-MIB, which might reveal more data than expected. In addition to being a security vulnerability, it might consume more CPU resources.

To enable the .1.3.6.1.2.1 range, make sure the view name commands include the required MIB objects.

Configure SNMPv3

SNMPv3 is often used to enable authentication and encryption, as community strings in versions 1 and 2c are sent in plaintext. SNMPv3 usernames are added to the /etc/snmp/snmpd.conf file, along with plaintext authentication and encryption pass phrases.

Configure SNMPv3 usernames and passwords with NCLU. However, if you prefer to edit the /etc/snmp/snmpd.conf manually instead, be aware that snmpd caches SNMPv3 usernames and passwords in the /var/lib/snmp/snmpd.conf file. Make sure you stop snmpd and remove the old entries when making changes. Otherwise, Cumulus Linux uses the old usernames and passwords in the /var/lib/snmp/snmpd.conf file instead of the ones in the /etc/snmp/snmpd.conf file.

The NCLU command structures for configuring SNMP user passwords are:

cumulus@switch:~$ net add snmp-server username <username> [auth-none] | [(auth-md5 | auth-sha) <auth-password>]
cumulus@switch:~$ net add snmp-server username <username> auth-(none | sha | md5)  (oid <OID> | view <view>)

The example below defines five users, each with a different combination of authentication and encryption:

cumulus@switch:~$ net add snmp-server username user1 auth-none
cumulus@switch:~$ net add snmp-server username user2 auth-md5 user2password
cumulus@switch:~$ net add snmp-server username user3 auth-md5 user3password encrypt-des user3encryption
cumulus@switch:~$ net add snmp-server username user666 auth-sha user666password encrypt-aes user666encryption
cumulus@switch:~$ net add snmp-server username user999 auth-md5 user999password encrypt-des user999encryption
cumulus@switch:~$ net add snmp-server username user1 auth-none oid 1.3.6.1.2.1
cumulus@switch:~$ net add snmp-server username user1 auth-none oid system
cumulus@switch:~$ net add snmp-server username user2 auth-md5 test1234 view testview oid 1.3.6.1.2.1
cumulus@switch:~$ net add snmp-server username user3 auth-sha testshax encrypt-aes testaesx oid 1.3.6.1.2.1
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit

# simple no auth user
#createuser user1
     
# user with MD5 authentication
#createuser user2 MD5 user2password
     
# user with MD5 for auth and DES for encryption
#createuser user3 MD5 user3password DES user3encryption
     
# user666 with SHA for authentication and AES for encryption
createuser user666 SHA user666password AES user666encryption
     
# user999 with MD5 for authentication and DES for encryption
createuser user999 MD5 user999password DES user999encryption

# restrict users to certain OIDs
# (Note: creating rouser or rwuser will give
# access regardless of the createUser command above. However,
# createUser without rouser or rwuser will not provide any access).
rouser user1 noauth 1.3.6.1.2.1
rouser user2 auth 1.3.6.1.2.1
rwuser user3 priv 1.3.6.1.2.1
rwuser user666
rwuser user999

After configuring user passwords and restarting the snmpd daemon, you can check user access with a client.

The snmp Debian package contains snmpget, snmpwalk, and other programs that are useful for checking daemon functionality from the switch itself or from another workstation.

The following commands check the access for each user defined above from the localhost:

# check user1 which has no authentication or encryption (NoauthNoPriv)
snmpget -v 3 -u user1 -l NoauthNoPriv localhost 1.3.6.1.2.1.1.1.0
snmpwalk -v 3 -u user1 -l NoauthNoPriv localhost 1.3.6.1.2.1.1
 
# check user2 which has authentication but no encryption (authNoPriv)
snmpget -v 3 -u user2 -l authNoPriv -a MD5 -A user2password localhost 1.3.6.1.2.1.1.1.0
snmpget -v 3 -u user2 -l authNoPriv -a MD5 -A user2password localhost 1.3.6.1.2.1.2.1.0
snmpwalk -v 3 -u user2 -l authNoPriv -a MD5 -A user2password localhost 1.3.6.1.2.1
      
# check user3 which has both authentication and encryption (authPriv)
snmpget -v 3 -u user3 -l authPriv -a MD5 -A user3password -x DES -X user3encryption localhost .1.3.6.1.2.1.1.1.0
snmpwalk -v 3 -u user3 -l authPriv -a MD5 -A user3password -x DES -X user3encryption localhost .1.3.6.1.2.1
snmpwalk -v 3 -u user666 -l authPriv -a SHA -x AES -A user666password -X user666encryption localhost 1.3.6.1.2.1.1
snmpwalk -v 3 -u user999 -l authPriv -a MD5 -x DES -A user999password -X user999encryption localhost 1.3.6.1.2.1.1

The following procedure shows a slightly more secure method of configuring SNMPv3 users without creating cleartext passwords:

  1. Install the net-snmp-config script that is in libsnmp-dev package:

    cumulus@switch:~$ sudo -E apt-get update
    cumulus@switch:~$ sudo -E apt-get install libsnmp-dev
    
  2. Stop the daemon:

    cumulus@switch:~$ sudo systemctl stop snmpd.service
    
  3. Use the net-snmp-config command to create two users, one with MD5 and DES, and the next with SHA and AES.

    The minimum password length is eight characters and the arguments -a and -x have different meanings in net-snmp-config than snmpwalk.

    cumulus@switch:~$ sudo net-snmp-config --create-snmpv3-user -a md5authpass -x desprivpass -A MD5 -X DES userMD5withDES 
    cumulus@switch:~$ sudo net-snmp-config --create-snmpv3-user -a shaauthpass -x aesprivpass -A SHA -X AES userSHAwithAES
    cumulus@switch:~$ sudo systemctl start snmpd.service
    

This adds a createUser command in /var/lib/snmp/snmpd.conf. Do not edit this file by hand unless you are removing usernames. You can edit this file and restrict access to certain parts of the MIB by adding noauth, auth or priv to allow unauthenticated access, require authentication, or to enforce use of encryption.

The snmpd daemon reads the information from the /var/lib/snmp/snpmd.conf file and then the line is removed (eliminating the storage of the master password for that user) and replaced with the key that is derived from it (using the EngineID). This key is a localized key, so that if it is stolen, it cannot be used to access other agents. To remove the two users userMD5withDES and userSHAwithAES, stop the snmpd daemon and edit the /var/lib/snmp/snmpd.conf file. Remove the lines containing the username, then restart the snmpd daemon as in step 3 above.

From a client, you access the MIB with the correct credentials. (The roles of -x, -a and -X and -A are reversed on the client side as compared with the net-snmp-config command used above.)

snmpwalk -v 3 -u userMD5withDES -l authPriv -a MD5 -x DES -A md5authpass -X desprivpass localhost 1.3.6.1.2.1.1.1
snmpwalk -v 3 -u userSHAwithAES -l authPriv -a SHA -x AES -A shaauthpass -X aesprivpass localhost 1.3.6.1.2.1.1.1

Manually Configure SNMP Traps (Non-NCLU)

Generate Event Notification Traps

The Net-SNMP agent provides a method to generate SNMP trap events using the Distributed Management (DisMan) Event MIB for various system events, including:

To enable specific types of traps, you need to create the following configurations in /etc/snmp/snmpd.conf.

Define Access Credentials

An SNMPv3 username is required to authorize the DisMan service even though you are not configuring SNMPv3 here. The example snmpd.conf configuration shown below creates trapusername as the username using the createUser command. iquerySecName defines the default SNMPv3 username to be used when making internal queries to retrieve monitored expressions. rouser specifies which username to use for these SNMPv3 queries. All three are required for snmpd to retrieve information and send traps (even with the monitor command shown below in the examples). Add the following lines to your /etc/snmp/snmpd.conf configuration file:

createuser trapusername
iquerysecname trapusername
rouser trapusername

iquerysecname specifies the default SNMPv3 username to be used when making internal queries to retrieve any necessary information - either for evaluating the monitored expression or building a notification payload. These internal queries always use SNMPv3, even if normal querying of the agent is done using SNMPv1 or SNMPv2c. Note that this user must also be explicitly created via createUser and given appropriate access rights, for rouser, for example. The iquerysecname directive is purely concerned with defining which user should be used, not with actually setting this user up.

Define Trap Receivers

The following configuration defines the trap receiver IP address where SNMPv2 traps are sent:

trap2sink 192.168.1.1 public
# For SNMPv1 Traps, use
# trapsink  192.168.1.1  public 

Although the traps are sent to an SNMPV2 receiver, the SNMPv3 user is still required. Starting with Net-SNMP 5.3, snmptrapd no longer accepts all traps by default. snmptrapd must be configured with authorized SNMPv1/v2c community strings and/or SNMPv3 users. Non-authorized traps/informs are dropped. Refer to the snmptrapd.conf(5) manual page for details.

It is possible to define multiple trap receivers and to use the domain name instead of an IP address in the trap2sink directive.

Restart the snmpd service to apply the changes.

cumulus@switch:~$ sudo systemctl restart snmpd.service

SNMP Version 3 Trap and Inform Messages

You can configure SNMPv3 trap and inform messages with the trapsess configuration command. Inform messages are traps that are acknowledged by the receiving trap daemon. You configure inform messages with the -Ci parameter. You must specify the EngineID of the receiving trap server with the -e field.

trapsess -Ci -e 0x80ccff112233445566778899 -v3 -l authPriv  -u trapuser1 -a MD5 -A trapuser1password -x DES -X trapuser1encryption 192.168.1.1

The SNMP trap receiving daemon must have usernames, authentication passwords, and encryption passwords created with its own EngineID. You must configure this trap server EngineID in the switch snmpd daemon sending the trap and inform messages. You specify the level of authentication and encryption for SNMPv3 trap and inform messages with -l (NoauthNoPriv, authNoPriv, or authPriv).

You can define multiple trap receivers and use the domain name instead of an IP address in the trap2sink directive.

After you complete the configuration, restart the snmpd service to apply the changes:

cumulus@switch:~$ sudo systemctl restart snmpd.service

Source Traps from a Different Source IP Address

When client SNMP programs (such as snmpget, snmpwalk, or snmptrap) are run from the command line, or when snmpd is configured to send a trap (based on snmpd.conf), you can configure a clientaddr in snmp.conf that allows the SNMP client programs or snmpd (for traps) to source requests from a different source IP address.

snmptrap, snmpget, snmpwalk and snmpd itself must be able to bind to this address.

For more information, read snmp.conf man page:

clientaddr [<transport-specifier>:]<transport-address>
  specifies the source address to be used by command-line applica-
  tions when sending SNMP requests. See snmpcmd(1) for more infor-
  mation about the format of addresses.
  This value is also used by snmpd when generating notifications.

Monitor Fans, Power Supplies, and Transformers

An SNMP agent (snmpd) waits for incoming SNMP requests and responds to them. If no requests are received, an agent does not initiate any actions. However, various commands can configure snmpd to send traps based on preconfigured settings (load, file, proc, disk, or swap commands), or customized monitor commands.

From the snmpd.conf man page, the monitor command is defined this way:

monitor [OPTIONS] NAME EXPRESSION

            defines  a  MIB  object to monitor.  If the EXPRESSION condition holds then 
            this will trigger the corresponding event, and either send a notification or
            apply a SET assignment (or both).  Note that the event will only be triggered once,
            when the expression first matches.  This monitor entry will not fire again until the
            monitored condition first becomes false, and then matches again.  NAME is an administrative
            name for this expression, and is used for indexing the mteTriggerTable (and related tables).
            Note also that such monitors use an internal SNMPv3 request to retrieve the values
            being monitored (even  if  normal  agent  queries  typically  use SNMPv1 or SNMPv2c).
            See the iquerySecName token described above.

      EXPRESSION
            There are three types of monitor expression supported by the Event MIB - existence, boolean and threshold tests.

            OID | ! OID | != OID

                    defines  an  existence(0)  monitor  test.  A bare OID specifies a present(0) test,
                    which will fire when (an instance of) the monitored OID is created.  An expression
                    of the form ! OID specifies an absent(1) test, which will fire when the monitored
                    OID is delected.  An expression of the form != OID specifies a changed(2) test,
                    which will fire whenever the monitored value(s) change.  Note that there must be
                    whitespace before the OID token.

            OID OP VALUE

                    defines a boolean(1) monitor test.  OP should be one of the defined comparison operators
                    (!=, ==, <, <=, >, >=) and VALUE should be an integer value to compare against.  Note that
                    there must be whitespace around the OP token.  A comparison such as OID !=0 will not be
                    handled correctly.

            OID MIN MAX [DMIN DMAX]

                    defines a threshold(2) monitor test.  MIN and MAX are integer values, specifying
                    lower and upper thresholds.  If the value of the monitored OID falls below the lower
                    threshold (MIN) or rises above the upper threshold (MAX), then the monitor entry will
                    trigger the corresponding event.

                    Note that the rising threshold event will only be re-armed when the monitored value
                    falls below the lower threshold (MIN).  Similarly, the falling threshold event will
                    be re-armed by the upper threshold (MAX).

                    The optional parameters DMIN and DMAX configure a pair of similar threshold tests,
                    but working with the delta differences between successive sample values.

    OPTIONS

            There are various options to control the behavior of the monitored expression.  These include:
            -D     indicates that the expression should be evaluated using delta differences between sample
                    values (rather than the values themselves).
            -d OID  or  -di OID
                    specifies a discontinuity marker for validating delta differences.  A -di object instance
                    will be used exactly as given.  A -d object will have the instance subidentifiers from
                    the corresponding (wildcarded) expression object appended.  If the -I flag is specified,
                    then there is no difference between these two options. This option also implies -D.
            -e EVENT
                    specifies the event to be invoked when this monitor entry is triggered.  If this option
                    is not given, the monitor entry will generate one of the standard notifications defined
                    in the DISMAN-EVENT-MIB.
            -I     indicates that the monitored expression should be applied to the specified OID as a
                    single instance.  By default, the OID will be treated as a wildcarded object, and the
                    monitor expanded to cover all matching instances.
            -i OID or -o OID
                    define additional varbinds to be added to the notification payload when this monitor
                    trigger fires.  For a wildcarded expression, the suffix of the matched instance will be
                    added to any OIDs specified using -o, while OIDs specified using -i will be treated
                    as exact instances.  If the -I flag is specified,  then  there  is  no difference between
                    these two options.
                    See strictDisman for details of the ordering of notification payloads.
            -r FREQUENCY
                    monitors the given expression every FREQUENCY, where FREQUENCY is in seconds or optionally
                    suffixed by one of s (for seconds), m (for minutes), h (for hours), d (for days),
                    or w (for weeks).  By default, the expression will be evaluated every 600s (10 minutes).
            -S     indicates that the monitor expression should not be evaluated when the agent first starts up.
                    The first evaluation will be done once the first repeat interval has expired.
            -s      indicates that the monitor expression should be evaluated when the agent first starts up.
                    This is the default behavior.
                    Note:  Notifications triggered by this initial evaluation will be sent before the coldStart trap.
             -u SECNAME
                     specifies a security name to use for scanning the local host, instead of the default
                     iquerySecName.  Once again, this user must be explicitly created and given suitable access rights.

You can configurecsnmpd to monitor the operational status of an Entity MIB or Entity-Sensor MIB. You can determine the operational status, given as a value of ok(1), unavailable(2) or nonoperational(3), by adding the following example configuration to /etc/snmp/snmpd.conf and adjusting the values:

Enable MIB to OID Translation

MIB names can be used instead of OIDs, by installing the snmp-mibs-downloader, to download SNMP MIBs to the switch prior to enabling traps. This greatly improves the readability of the snmpd.conf file.

  1. Open /etc/apt/sources.list in a text editor.

  2. Add the non-free repository, then save the file:

    cumulus@switch:~$ sudo deb http://ftp.us.debian.org/debian/ buster main non-free
    
  3. Update the switch:

    cumulus@switch:~$ sudo -E apt-get update
    
  4. Install the snmp-mibs-downloader:

    cumulus@switch:~$ sudo -E apt-get install snmp-mibs-downloader
    
  5. Open the /etc/snmp/snmp.conf file to verify that the mibs : line is commented out:

    #
    # As the snmp packages come without MIB files due to license reasons, loading
    # of MIBs is disabled by default. If you added the MIBs you can reenable
    # loading them by commenting out the following line.
    #mibs :
    
  6. Open the /etc/default/snmpd file to verify that the export MIBS= line is commented out:

    # This file controls the activity of snmpd and snmptrapd
    
    # Don't load any MIBs by default.
    # You might comment this lines once you have the MIBs Downloaded.
    #export MIBS=
    
  7. After you confirm the configuration, remove or comment out the non-free repository in /etc/apt/sources.list.

    #deb http://ftp.us.debian.org/debian/ buster main non-free
    

The linkUpDownNotifications directive is used to configure link up/down notifications when the operational status of the link changes.

    linkUpDownNotifications yes

The default frequency for checking link up/down is 60 seconds. You can change the default frequency using the monitor directive directly instead of the linkUpDownNotifications directive. See man snmpd.conf for details.

Configure Temperature Notifications

Temperature sensor information for each available sensor is maintained in lmSensors MIB. Each platform can contain a different number of temperature sensors. The example below generates a trap event when any temperature sensor exceeds a threshold of 68 degrees (centigrade). It monitors each lmTempSensorsValue. When the threshold value is checked and exceeds the lmTempSensorsValue, a trap is generated. The -o lmTempSenesorsDevice option is used to instruct SNMP to also include the lmTempSensorsDevice MIB in the generated trap. The default frequency for the monitor directive is 600 seconds. You can change the default frequency with the -r option:

monitor lmTemSensor -o lmTempSensorsDevice lmTempSensorsValue > 68000

To monitor the sensors individually, first use the sensors command to determine which sensors are available to be monitored on the platform.

cumulus@switch:~$ sudo sensors
]
CY8C3245-i2c-4-2e
Adapter: i2c-0-mux (chan_id 2)
fan5: 7006 RPM (min = 2500 RPM, max = 23000 RPM)
fan6: 6955 RPM (min = 2500 RPM, max = 23000 RPM)
fan7: 6799 RPM (min = 2500 RPM, max = 23000 RPM)
fan8: 6750 RPM (min = 2500 RPM, max = 23000 RPM)
temp1: +34.0 C (high = +68.0 C)
temp2: +28.0 C (high = +68.0 C)
temp3: +33.0 C (high = +68.0 C)
temp4: +31.0 C (high = +68.0 C)
temp5: +23.0 C (high = +68.0 C)

Configure a monitor command for the specific sensor using the -I option. The -I option indicates that the monitored expression is applied to a single instance. In this example, there are five temperature sensors available. Use the following directive to monitor only temperature sensor 3 at 5 minute intervals.

monitor -I -r 300 lmTemSensor3 -o lmTempSensorsDevice.3 lmTempSensorsValue.3 > 68000

Configure Free Memory Notifications

You can monitor free memory using the following directives. The example below generates a trap when free memory drops below 1,000,000KB. The free memory trap also includes the amount of total real memory:

monitor MemFreeTotal -o memTotalReal memTotalFree <  1000000

Configure Processor Load Notifications

To monitor CPU load for 1, 5, or 15 minute intervals, use the load directive with the monitor directive. The following example generates a trap when the 1 minute interval reaches 12%, the 5 minute interval reaches 10%, or the 15 minute interval reaches 5%.

load 12 10 5

Configure Disk Utilization Notifications

To monitor disk utilization for all disks, use the includeAllDisks directive together with the monitor directive. The example code below generates a trap when a disk is 99% full:

includeAllDisks 1%
monitor -r 60 -o dskPath -o DiskErrMsg "dskTable" diskErrorFlag !=0

Configure Authentication Notifications

To generate authentication failure traps, use the authtrapenable directive:

authtrapenable 1

snmptrapd.conf

Use the Net-SNMP trap daemon to receive SNMP traps. The /etc/snmp/snmptrapd.conf file is used to configure how incoming traps are processed. Starting with Net-SNMP release 5.3, you must specify who is authorized to send traps and informs to the notification receiver (and what types of processing these are allowed to trigger). You can specify three processing types:

Typically, this configuration is log,execute,net to cover any style of processing for a particular category of notification. But it is possible (even desirable) to limit certain notification sources to selected processing only.

authCommunity TYPES COMMUNITY [SOURCE [OID | -v VIEW ]] authorizes traps and SNMPv2c INFORM requests with the specified community to trigger the types of processing listed. By default, this allows any notification using this community to be processed. You can use the SOURCE field to specify that the configuration only applies to notifications received from particular sources. For more information about specific configuration options within the file, look at the snmpd.conf(5) man page with the following command:

cumulus@switch:~$ man 5 snmptrapd.conf

###############################################################################
#
# EXAMPLE-trap.conf:
#   An example configuration file for configuring the Net-SNMP snmptrapd agent.
#
###############################################################################
#
# This file is intended to only be an example.  If, however, you want
# to use it, it should be placed in /etc/snmp/snmptrapd.conf.
# When the snmptrapd agent starts up, this is where it will look for it.
#
# All lines beginning with a '#' are comments and are intended for you
# to read.  All other lines are configuration commands for the agent.

#
# PLEASE: read the snmptrapd.conf(5) manual page as well!
#
# this is the default (port 162) and defines the listening
# protocol and address  (e.g.  udp:10.10.10.10)
snmpTrapdAddr localhost
#
# defines the actions and the community string 
authCommunity log,execute,net public

Supported MIBs

Below are the MIBs supported by Cumulus Linux, as well as suggested uses for them. The overall Cumulus Linux MIB is defined in the /usr/share/snmp/mibs/Cumulus-Snmp-MIB.txt file.

MIB Name Suggested Uses
BGP4-MIB
OSPFv2-MIB
OSPFv3-MIB
RIPv2-MIB
You can enable FRRouting SNMP support to provide support for OSPF-MIB (RFC-1850), OSPFV3-MIB (RFC-5643), and BGP4-MIB (RFC-1657). See the FRRouting section above.
CUMULUS-COUNTERS-MIB Discard counters: Cumulus Linux also includes its own counters MIB, defined in /usr/share/snmp/mibs/Cumulus-Counters-MIB.txt. It has the OID .1.3.6.1.4.1.40310.2
CUMULUS-POE-MIB The custom Power over Ethernet PoE MIB defined in the /usr/share/snmp/mibs/Cumulus-POE-MIB.txt file. For devices that provide PoE, this provides users with the system wide power information in poeSystemValues as well as per interface PoeObjectsEntry values for the poeObjectsTable. Most of this information comes from the poectl command. To enable this MIB, uncomment the following line in /etc/snmp/snmpd.conf
#pass_persist .1.3.6.1.4.1.40310.3 /usr/share/snmp/cl_poe_pp.py
CUMULUS-RESOURCE-QUERY-MIB Cumulus Linux includes its own resource utilization MIB, which is similar to using cl-resource-query. This MIB monitors layer 3 entries by host, route, nexthops, ECMP groups, and layer 2 MAC/BDPU entries. The MIB is defined in /usr/share/snmp/mibs/Cumulus-Resource-Query-MIB.txt and has the OID .1.3.6.1.4.1.40310.1.
CUMULUS-SNMP-MIB SNMP counters. For information on exposing CPU and memory information with SNMP, see this knowledge base article.
DISMAN-EVENT-MIB Trap monitoring
ENTITY-MIB From RFC 4133, the temperature sensors, fan sensors, power sensors, and ports are covered.
ENTITY-SENSOR-MIB Physical sensor information (temperature, fan, and power supply) from RFC 3433.
HOST-RESOURCES-MIB Users, storage, interfaces, process info, run parameters
BRIDGE-MIB
Q-BRIDGE-MIB
The dot1dBasePortEntry and dot1dBasePortIfIndex tables in the BRIDGE-MIB and dot1qBase, dot1qFdbEntry, dot1qTpFdbEntry, dot1qTpFdbStatus, and dot1qVlanStaticName tables in the Q-BRIDGE-MIB tables. You must uncomment the bridge_pp.py pass_persist script in /etc/snmp/snmpd.conf.
IEEE8023-LAG-MIB Implementation of the IEEE 8023-LAG-MIB includes the dot3adAggTable and dot3adAggPortListTable tables. To enable this, edit /etc/snmp/snmpd.conf and uncomment or add the following lines:
view systemonly included .1.2.840.10006.300.43
pass_persist .1.2.840.10006.300.43 /usr/share/snmp/ieee8023_lag_pp.py
IF-MIB Interface description, type, MTU, speed, MAC, admin, operation status, counters

Note: The IF-MIB cache is disabled by default. The non-caching code path in the IF-MIB treats 64-bit counters like 32-bit counters (a 64-bit counter rolls over after the value increments to a value that extends beyond 32 bits). To enable the counter to reflect traffic statistics using 64-bit counters, remove the -y option from the SNMPDOPTS line in the /etc/default/snmpd file. The example below first shows the original line, commented out, then the modified line without the -y option:
cumulus@switch:~$ cat /etc/default/snmpd
# SNMPDOPTS='-y -LS 0-4 d -Lf /dev/null -u snmp -g snmp -I -smux -p /run/snmpd.pid'
SNMPDOPTS='-LS 0-4 d -Lf /dev/null -u snmp -g snmp -I -smux -p /run/snmpd.pid
IP-FORWARD-MIB IP routing table
IP-MIB (includes ICMP) IPv4, IPv4 addresses counters, netmasks
IPv6-MIB IPv6 counters
LLDP-MIB Layer 2 neighbor information from lldpd (you need to enable the SNMP subagent in LLDP). You need to start lldpd with the -x option to enable connectivity to snmpd(AgentX).
LM-SENSORS MIB Fan speed, temperature sensor values, voltages. This is deprecated since the ENTITY-SENSOR MIB has been added.
NET-SNMP-AGENT-MIB Agent timers, user, group config
NET-SNMP-VACM-MIB Agent timers, user, group config.
NOTIFICATION-LOG-MIB Local logging
SNMP-FRAMEWORK-MIB Users, access
SNMP-MPD-MIB Users, access
SNMP-TARGET-MIB SNMP-TARGET-MIB
SNMP-USER-BASED-SM-MIBS Users, access
SNMP-VIEW-BASED-ACM-MIB Users, access
TCP-MIB TCP-related information
UCD-SNMP-MIB System memory, load, CPU, disk IO
UDP-MIB UDP-related information

The ENTITY MIB does not show the chassis information in Cumulus Linux.

Pass Persist Scripts

The pass persist scripts in Cumulus Linux use the pass_persist extension to Net-SNMP. The scripts are stored in /usr/share/snmp and include:

All the scripts are enabled by default in Cumulus Linux, except for:

Troubleshooting

Use the following commands to troubleshoot potential SNMP issues:

cumulus@switch:~$ net show snmp-server status
Simple Network Management Protocol (SNMP) Daemon.
---------------------------------  ------------------------------------------------------------------------------------
Current Status                     failed (failed)
Reload Status                      enabled
Listening IP Addresses             localhost 9.9.9.9
Main snmpd PID                     0
Version 1 and 2c Community String  Configured
Version 3 Usernames                Not Configured
Last Logs (with Errors)            -- Logs begin at Thu 2017-08-03 16:23:05 UTC, end at Fri 2017-08-04 18:17:24 UTC. --
                                   Aug 04 18:17:19 cel-redxp-01 snmpd[8389]: Error opening specified endpoint "9.9.9.9"
                                   Aug 04 18:17:19 cel-redxp-01 snmpd[8389]: Server Exiting with code 1
---------------------------------  ------------------------------------------------------------------------------------
cumulus@switch:~$ net show configuration snmp-server
snmp-server
  listening-address 127.0.0.1
  readonly-community public access default
  readonly-community allpass access any
  readonly-community temp2 access 1.1.1.1
  readonly-community temp2 access 2.2.2.2
  trap-destination 1.1.1.1 community-password public version 2c
  trap-link-up check-frequency 10
  trap-snmp-auth-failures
cumulus@switch:~$ net show configuration commands
...
net add snmp-server listening-address all
net add snmp-server readonly-community allpass access any
net add snmp-server readonly-community temp2 access 1.1.1.1
net add snmp-server readonly-community temp2 access 2.2.2.2
net add snmp-server trap-destination 1.1.1.1 community-password public version 2c
net add snmp-server trap-link-up check-frequency 10
net add snmp-server trap-snmp-auth-failures
...

Using Nutanix Prism as a Monitoring Tool

Nutanix Prism is a graphical user interface (GUI) for managing infrastructure and virtual environments. You need to take special steps within Cumulus Linux before you can configure Prism.

Configure Cumulus Linux

  1. SSH to the Cumulus Linux switch that needs to be configured, replacing [switch] below as appropriate:

    cumulus@switch:~$ ssh cumulus@[switch]
    
  2. Open the /etc/snmp/snmpd.conf file in an editor.

  3. Uncomment the following 3 lines in the /etc/snmp/snmpd.conf file, then save the file:

    • bridge_pp.py
    pass_persist .1.3.6.1.2.1.17 /usr/share/snmp/bridge_pp.py
    
    • Community
    rocommunity public  default    -V systemonly
    
    • Line directly below the Q-BRIDGE-MIB (.1.3.6.1.2.1.17)
    # BRIDGE-MIB and Q-BRIDGE-MIB tables
    view   systemonly  included   .1.3.6.1.2.1.17
    
  4. Restart snmpd:

    cumulus@switch:~$ sudo systemctl restart snmpd.service
    Restarting network management services: snmpd.
    

Configure Nutanix

  1. Log into the Nutanix Prism. Nutanix defaults to the Home menu, referred to as the Dashboard:

  2. Click on the gear icon in the top right corner of the dashboard, then select NetworkSwitch:

  3. Click the +Add Switch Configuration button in the Network Switch Configuration pop up window.

  4. Fill out the Network Switch Configuration for the Top of Rack (ToR) switch configured for snmpd in the previous section:

    Configuration Parameter Description Value Used in Example
    Switch Management IP Address This can be any IP address on the box. In the screenshot above, the eth0 management IP is used. 192.168.0.111
    Host IP Addresses or Host Names IP addresses of Nutanix hosts connected to that particular ToR switch. 192.168.0.171,192.168.0.172,192.168.0.173,192.168.0.174
    SNMP Profile Saved profiles, for easy configuration when hooking up to multiple switches. None
    SNMP Version SNMP v2c or SNMP v3. Cumulus Linux has only been tested with SNMP v2c for Nutanix integration. SNMP v2c
    SNMP Community Name SNMP v2c uses communities to share MIBs. The default community for snmpd is ‘public’. public

    The rest of the values were not touched for this demonstration. They are usually used with SNMP v3.
    

  5. Save the configuration. The switch will now be present in the Network Switch Configuration menu now.

  6. Close the pop up window to return to the dashboard.

  7. Open the Hardware option from the Home dropdown menu:

  8. Click the Table button.

  9. Click the Switch button. Configured switches are shown in the table, as indicated in the screenshot below, and can be selected in order to view interface statistics:

The switch has been added correctly when interfaces hooked up to the Nutanix hosts are visible.

Switch Information Displayed on Nutanix Prism

The Nutanix appliance will use Switch IDs that can also be viewed on the Prism CLI (by SSHing to the box). To view information from the Nutanix CLI, login using the default username nutanix, and the password nutanix/4u.

nutanix@NTNX-14SM15270093-D-CVM:192.168.0.184:~$ ncli network list-switch
    Switch ID                 : 00051a76-f711-89b6-0000-000000003bac::5f13678e-6ffd-4b33-912f-f1aa6e8da982
    Name                      : switch
    Switch Management Address : 192.168.0.111
    Description               : Linux switch 3.2.65-1+deb7u2+cl2.5+2 #3.2.65-1+deb7u2+cl2.5+2 SMP Mon Jun 1 18:26:59 PDT 2015 x86_64
    Object ID                 : enterprises.40310
    Contact Information       : Admin <admin@company.com>
    Location Information      : Raleigh, NC
    Services                  : 72
    Switch Vendor Name        : Unknown
    Port Ids                  : 00051a76-f711-89b6-0000-000000003bac::5f13678e-6ffd-4b33-912f-f1aa6e8da982:52, 00051a76-f711-89b6-0000-000000003bac::5f13678e-6ffd-4b33-912f-f1aa6e8da982:53, 00051a76-f711-89b6-0000-000000003bac::5f13678e-6ffd-4b33-912f-f1aa6e8da982:54, 00051a76-f711-89b6-0000-000000003bac::5f13678e-6ffd-4b33-912f-f1aa6e8da982:55

Troubleshooting

To help visualize the following diagram is provided:

Nutanix Node Physical Port Cumulus Linux Port
Node A (Green) vmnic2 swp49
Node B (Blue) vmnic2 swp50
Node C (Red) vmnic2 swp51
Node D (Yellow) vmnic2 swp52

Enable LLDP/CDP on VMware ESXi (Hypervisor on Nutanix)

  1. Follow the directions on one of the following websites to enable CDP:

    For example, switch CDP on:

    root@NX-1050-A:~] esxcli network vswitch standard set -c both -v vSwitch0
    

    Then confirm it is running:

    root@NX-1050-A:~] esxcli network vswitch standard list -v vSwitch0
    vSwitch0
        Name: vSwitch0
        Class: etherswitch
        Num Ports: 4082
        Used Ports: 12
        Configured Ports: 128
        MTU: 1500
        CDP Status: both
        Beacon Enabled: false
        Beacon Interval: 1
        Beacon Threshold: 3
        Beacon Required By:
        Uplinks: vmnic3, vmnic2, vmnic1, vmnic0
        Portgroups: VM Network, Management Network
    

    both means CDP is now running and the lldp dameon on Cumulus Linux is capable of seeing CDP devices.

  2. After the next CDP interval, the Cumulus Linux box will pick up the interface via the lldp daemon:

    cumulus@switch:~$ lldpctl show neighbor swp49
    -------------------------------------------------------------------------------
    LLDP neighbors:
    -------------------------------------------------------------------------------
    Interface:    swp49, via: CDPv2, RID: 6, Time: 0 day, 00:34:58
    Chassis:
        ChassisID:    local NX-1050-A
        SysName:      NX-1050-A
        SysDescr:     Releasebuild-2494585 running on VMware ESX
        MgmtIP:       0.0.0.0
        Capability:   Bridge, on
    Port:
        PortID:       ifname vmnic2
        PortDescr:    vmnic2
    -------------------------------------------------------------------------------
    
  3. Use net show to look at lldp information:

    cumulus@switch:~$ net show lldp
    
    Local Port    Speed    Mode                 Remote Port        Remote  Host     Summary
    ------------  -------  -------------  ----  -----------------  ---------------  -------------------------
    eth0          1G       Mgmt           ====  swp6               oob-mgmt-switch  IP: 192.168.0.11/24(DHCP)
    swp1          1G       Access/L2      ====  44:38:39:00:00:03  server01         Untagged: br0
    swp51         1G       NotConfigured  ====  swp1               spine01
    swp52         1G       NotConfigured  ====  swp1               spine02
    

Nutanix Acropolis is an alternate hypervisor that Nutanix supports. Acropolis Hypervisor uses the yum packaging system and is capable of installing normal Linux lldp daemons to operating just like Cumulus Linux. LLDP should be enabled for each interface on the host. Refer to this article from Mellanox, https://portal.nutanix.com/page/documents/kbs/details/?targetId=kA032000000TVfiCAG, for setup instructions.

Troubleshoot Connections without LLDP or CDP

  1. Find the MAC address information in the Prism GUI, located in: Hardware > Table > Host > Host NICs

  2. Select a MAC address to troubleshoot (e.g. 0c:c4:7a:09:a2:43 represents vmnic0 which is tied to NX-1050-A).

  3. List out all the MAC addresses associated to the bridge:

    cumulus@switch:~$ brctl showmacs br-ntnx
    port name mac addr        vlan    is local?   ageing timer
    swp9      00:02:00:00:00:06   0   no        66.94
    swp52     00:0c:29:3e:32:12   0   no         2.73
    swp49     00:0c:29:5a:f4:7f   0   no         2.73
    swp51     00:0c:29:6f:e1:e4   0   no         2.73
    swp49     00:0c:29:74:0c:ee   0   no         2.73
    swp50     00:0c:29:a9:36:91   0   no         2.73
    swp9      08:9e:01:f8:8f:0c   0   no        13.56
    swp9      08:9e:01:f8:8f:35   0   no         2.73
    swp4      0c:c4:7a:09:9e:d4   0   no        24.05
    swp1      0c:c4:7a:09:9f:8e   0   no        13.56
    swp3      0c:c4:7a:09:9f:93   0   no        13.56
    swp2      0c:c4:7a:09:9f:95   0   no        24.05
    swp52     0c:c4:7a:09:a0:c1   0   no         2.73
    swp51     0c:c4:7a:09:a2:35   0   no         2.73
    swp49     0c:c4:7a:09:a2:43   0   no         2.73
    swp9      44:38:39:00:82:04   0   no         2.73
    swp9      74:e6:e2:f5:a2:80   0   no         2.73
    swp1      74:e6:e2:f5:a2:81   0   yes        0.00
    swp2      74:e6:e2:f5:a2:82   0   yes        0.00
    swp3      74:e6:e2:f5:a2:83   0   yes        0.00
    swp4      74:e6:e2:f5:a2:84   0   yes        0.00
    swp5      74:e6:e2:f5:a2:85   0   yes        0.00
    swp6      74:e6:e2:f5:a2:86   0   yes        0.00
    swp7      74:e6:e2:f5:a2:87   0   yes        0.00
    swp8      74:e6:e2:f5:a2:88   0   yes        0.00
    swp9      74:e6:e2:f5:a2:89   0   yes        0.00
    swp10     74:e6:e2:f5:a2:8a   0   yes        0.00
    swp49     74:e6:e2:f5:a2:b1   0   yes        0.00
    swp50     74:e6:e2:f5:a2:b2   0   yes        0.00
    swp51     74:e6:e2:f5:a2:b3   0   yes        0.00
    swp52     74:e6:e2:f5:a2:b4   0   yes        0.00
    swp9      8e:0f:73:1b:f8:24   0   no         2.73
    swp9      c8:1f:66:ba:60:cf   0   no        66.94
    

    Alternatively, you can use grep:

    cumulus@switch:~$ brctl showmacs br-ntnx | grep 0c:c4:7a:09:a2:43
    swp49     0c:c4:7a:09:a2:43   0   no         4.58
    

    vmnic1 is now hooked up to swp49. This matches what is seen in lldp:

    cumulus@switch:~$ lldpctl show neighbor swp49
    -------------------------------------------------------------------------------
    LLDP neighbors:
    -------------------------------------------------------------------------------
    Interface:    swp49, via: CDPv2, RID: 6, Time: 0 day, 01:11:12
        Chassis:
        ChassisID:      local NX-1050-A
        SysName:        NX-1050-A
        SysDescr:       Releasebuild-2494585 running on VMware ESX
        MgmtIP:         0.0.0.0
        Capability:     Bridge, on
        Port:
        PortID:         ifname vmnic2
        PortDescr:      vmnic2
    -------------------------------------------------------------------------------
    

Monitoring Best Practices

The following monitoring processes are considered best practices for reviewing and troubleshooting potential issues with Cumulus Linux environments. In addition, several of the more common issues have been listed, with potential solutions included.

Overview

This document describes:

Trend Analysis Using Metrics

A metric is a quantifiable measure that is used to track and assess the status of a specific infrastructure component. It is a check collectedover time. Examples of metrics include bytes on an interface, CPU utilization, and total number of routes.

Metrics are more valuable when used for trend analysis.

Generate Alerts with Triggered Logging

Triggered issues are normally sent to syslog, but can go to another log file depending on the feature. In Cumulus Linux, rsyslog handles all logging, including local and remote logging. Logs are the best method to use for generating alerts when the system transitions from a stable steady state.

Sending logs to a centralized collector, then creating alerts based on critical logs is an optimal solution for alerting.

Log Formatting

Most log files in Cumulus Linux use a standard presentation format. For example, consider this syslog entry:

2017-03-08T06:26:43.569681+00:00 leaf01 sysmonitor: Critically high CPU use: 99%

For brevity and legibility, the timestamp and hostname have been omitted from the examples in this chapter.

Hardware

The smond process provides monitoring functionality for various switch hardware elements. Minimum or maximum values are output depending on the flags applied to the basic command. The hardware elements and applicable commands and flags are listed in the table below.

Hardware Element Monitoring Commands Interval Poll
Temperature
cumulus@switch:~$ smonctl -j
cumulus@switch:~$ smonctl -j -s TEMP[X]
10 seconds
Fan
cumulus@switch:~$ smonctl -j
cumulus@switch:~$ smonctl -j -s FAN[X]
10 seconds
PSU
cumulus@switch:~$ smonctl -j
cumulus@switch:~$ smonctl -j -s PSU[X]
10 seconds
PSU Fan
cumulus@switch:~$ smonctl -j
cumulus@switch:~$ smonctl -j -s PSU[X]Fan[X]
10 seconds
PSU Temperature
cumulus@switch:~$ smonctl -j
cumulus@switch:~$ smonctl -j -s PSU[X]Temp[X]
10 seconds
Voltage
cumulus@switch:~$ smonctl -j
cumulus@switch:~$ smonctl -j -s Volt[X]
10 seconds
Front Panel LED
cumulus@switch:~$ ledmgrd -d
cumulus@switch:~$ ledmgrd -j
5 seconds

Not all switch models include a sensor for monitoring power consumption and voltage. See this note for details.

Hardware Logs Log Location Log Entries
High temperature
/var/log/syslog
/usr/sbin/smond : : Temp1(Board Sensor near CPU): state changed from UNKNOWN to OK
/usr/sbin/smond : : Temp2(Board Sensor Near Virtual Switch): state changed from UNKNOWN to OK
/usr/sbin/smond : : Temp3(Board Sensor at Front Left Corner): state changed from UNKNOWN to OK
/usr/sbin/smond : : Temp4(Board Sensor at Front Right Corner): state changed from UNKNOWN to OK
/usr/sbin/smond : : Temp5(Board Sensor near Fan): state changed from UNKNOWN to OK
Fan speed issues
/var/log/syslog
/usr/sbin/smond : : Fan1(Fan Tray 1, Fan 1): state changed from UNKNOWN to OK
/usr/sbin/smond : : Fan2(Fan Tray 1, Fan 2): state changed from UNKNOWN to OK
/usr/sbin/smond : : Fan3(Fan Tray 2, Fan 1): state changed from UNKNOWN to OK
/usr/sbin/smond : : Fan4(Fan Tray 2, Fan 2): state changed from UNKNOWN to OK
/usr/sbin/smond : : Fan5(Fan Tray 3, Fan 1): state changed from UNKNOWN to OK
/usr/sbin/smond : : Fan6(Fan Tray 3, Fan 2): state changed from UNKNOWN to OK
PSU failure
/var/log/syslog
/usr/sbin/smond : : PSU1Fan1(PSU1 Fan): state changed from UNKNOWN to OK
/usr/sbin/smond : : PSU2Fan1(PSU2 Fan): state changed from UNKNOWN to BAD

System Data

Cumulus Linux includes a number of ways to monitor various aspects of system data. In addition, alerts are issued in high risk situations.

CPU Idle Time

When a CPU reports five high CPU alerts within a span of five minutes, an alert is logged.

Short bursts of high CPU can occur during switchd churn or routing protocol startup. Do not set alerts for these short bursts.

System Element Monitoring Commands Interval Poll
CPU utilization
cumulus@switch:~$ cat /proc/stat
cumulus@switch:~$ top -b -n 1
30 seconds
CPU Logs Log Location Log Entries
——— ————- ————
High CPU
/var/log/syslog
sysmonitor: Critically high CPU use: 99%
systemd[1]: Starting Monitor system resources (cpu, memory, disk)…
systemd[1]: Started Monitor system resources (cpu, memory, disk).
sysmonitor: High CPU use: 89%
systemd[1]: Starting Monitor system resources (cpu, memory, disk)…
systemd[1]: Started Monitor system resources (cpu, memory, disk).
sysmonitor: CPU use no longer high: 77%

Cumulus Linux 3.0 and later monitors CPU, memory, and disk space via sysmonitor. The configurations for the thresholds are stored in /etc/cumulus/sysmonitor.conf. More information is available with man sysmonitor.

CPU measure Thresholds
Use Alert: 90% Crit: 95%
Process Load Alarm: 95% Crit: 125%

Disk Usage

When monitoring disk utilization, you can exclude tmpfs from monitoring.

System Element Monitoring Commands Interval Poll
Disk utilization
cumulus@switch:~$ /bin/df -x tmpfs
300 seconds

Process Restart

In Cumulus Linux, systemd is responsible for monitoring and restarting processes.

Process Element Monitoring Commands
View processes monitored by systemd
cumulus@switch:~$ systemctl status

Layer 1 Protocols and Interfaces

Link and port state interface transitions are logged to /var/log/syslog and /var/log/switchd.log.

Interface Element Monitoring Commands
Link state
cumulus@switch:~$ cat /sys/class/net/[iface]/operstate
cumulus@switch:~$ net show interface all json
Link speed
cumulus@switch:~$ cat /sys/class/net/[iface]/speed
cumulus@switch:~$ net show interface all json
Port state
cumulus@switch:~$ ip link show
cumulus@switch:~$ net show interface all json
Bond state
cumulus@switch:~$ cat /proc/net/bonding/[bond]
cumulus@switch:~$ net show interface all json

Interface counters are obtained from either querying the hardware or the Linux kernel. The two outputs should align, but the Linux kernel aggregates the output from the hardware.

Interface Counter Element Monitoring Commands Interval Poll
Interface counters
cumulus@switch:~$ cat /sys/class/net/[iface]/statistics/[stat_name]
cumulus@switch:~$ net show counters json
cumulus@switch:~$ cl-netstat -j
cumulus@switch:~$ ethtool -S [ iface]
10 seconds
Layer 1 Logs L og Location Log Entries
Link failure/Link flap
/var/log/switchd.log
switchd[5692]: nic.c:213 nic_set_carrier: swp17: setting kernel carrier: down
switchd[5692]: netlink.c:291 libnl: swp1, family 0, ifi 20, oper down
switchd[5692]: nic.c:213 nic_set_carrier: swp1: setting kernel carrier: up
switchd[5692]: netlink.c:291 libnl: swp17, family 0, ifi 20, oper up
Unidirectional link
/var/log/switchd.log
/var/log/ptm.log
ptmd[7146]: ptm_bfd.c:2471 Created new session 0x1 with peer 10.255.255.11 port swp1
ptmd[7146]: ptm_bfd.c:2471 Created new session 0x2 with peer fe80::4638:39ff:fe00:5b port swp1
ptmd[7146]: ptm_bfd.c:2471 Session 0x1 down to peer 10.255.255.11, Reason 8
ptmd[7146]: ptm_bfd.c:2471 Detect timeout on session 0x1 with peer 10.255.255.11, in state 1
Bond Negotiation Working
/var/log/syslog
kernel: [85412.763193] bonding: bond0 is being created…
kernel: [85412.770014] bond0: Enslaving swp2 as a backup interface with an up link
kernel: [85412.775216] bond0: Enslaving swp1 as a backup interface with an up link
kernel: [85412.797393] IPv6: ADDRCONF(NETDEV_UP): bond0: link is not ready
kernel: [85412.799425] IPv6: ADDRCONF(NETDEV_CHANGE): bond0: link becomes ready
Bond Negotiation Failing
/var/log/syslog
kernel: [85412.763193] bonding: bond0 is being created…
kernel: [85412.770014] bond0: Enslaving swp2 as a backup interface with an up link
kernel: [85412.775216] bond0: Enslaving swp1 as a backup interface with an up link
kernel: [85412.797393] IPv6: ADDRCONF(NETDEV_UP): bond0: link is not ready
MLAG peerlink negotiation Working
/var/log/syslog
lldpd[998]: error while receiving frame on swp50: Network is down
lldpd[998]: error while receiving frame on swp49: Network is down
kernel: [76174.262893] peerlink: Setting ad_actor_system to 44:38:39:00:00:11
kernel: [76174.264205] 8021q: adding VLAN 0 to HW filter on device peerlink
mstpd: one_clag_cmd: setting (1) peer link: peerlink
mstpd: one_clag_cmd: setting (1) clag state: up
mstpd: one_clag_cmd: setting system-mac 44:38:39:ff:40:94
mstpd: one_clag_cmd: setting clag-role secondary
/var/log/clagd.log
clagd[14003]: Cleanup is executing.
clagd[14003]: Cannot open file “/tmp/pre-clagd.q7XiO
clagd[14003]: Cleanup is finished
clagd[14003]: Beginning execution of clagd version 1
clagd[14003]: Invoked with: /usr/sbin/clagd –daemon
clagd[14003]: Role is now secondary
clagd[14003]: HealthCheck: role via backup is second
clagd[14003]: HealthCheck: backup active
clagd[14003]: Initial config loaded
clagd[14003]: The peer switch is active.
clagd[14003]: Initial data sync from peer done.
clagd[14003]: Initial handshake done.
clagd[14003]: Initial data sync to peer done.
MLAG peerlink negotiation Failing
/var/log/syslog
lldpd[998]: error while receiving frame on swp50: Network is down
lldpd[998]: error while receiving frame on swp49: Network is down
kernel: [76174.262893] peerlink: Setting ad_actor_system to 44:38:39:00:00:11
kernel: [76174.264205] 8021q: adding VLAN 0 to HW filter on device peerlink
mstpd: one_clag_cmd: setting (1) peer link: peerlink
mstpd: one_clag_cmd: setting (1) clag state: down
mstpd: one_clag_cmd: setting system-mac 44:38:39:ff:40:94
mstpd: one_clag_cmd: setting clag-role secondary
/var/log/clagd.log
clagd[26916]: Cleanup is executing.
clagd[26916]: Cannot open file “/tmp/pre-clagd.6M527vvGX0/brbatch” for reading: No such file or directory
clagd[26916]: Cleanup is finished
clagd[26916]: Beginning execution of clagd version 1.3.0
clagd[26916]: Invoked with: /usr/sbin/clagd –daemon 169.254.1.2 peerlink.4094 44:38:39:FF:01:01 –priority 1000 –backupIp 10.0.0.2
clagd[26916]: Role is now secondary
clagd[26916]: Initial config loaded
MLAG port negotiation Working
/var/log/syslog
kernel: [77419.112195] bonding: server01 is being created…
lldpd[998]: error while receiving frame on swp1: Network is down
kernel: [77419.122707] 8021q: adding VLAN 0 to HW filter on device swp1
kernel: [77419.126408] server01: Enslaving swp1 as a backup interface with a down link
kernel: [77419.177175] server01: Setting ad_actor_system to 44:38:39:ff:40:94
kernel: [77419.190874] server01: Warning: No 802.3ad response from the link partner for any adapters in the bond
kernel: [77419.191448] IPv6: ADDRCONF(NETDEV_UP): server01: link is not ready
kernel: [77419.191452] 8021q: adding VLAN 0 to HW filter on device server01
kernel: [77419.192060] server01: link status definitely up for interface swp1, 1000 Mbps full duplex
kernel: [77419.192065] server01: now running without any active interface!
kernel: [77421.491811] IPv6: ADDRCONF(NETDEV_CHANGE): server01: link becomes ready
mstpd: one_clag_cmd: setting (1) mac 44:38:39:00:00:17 <server01, None>
/var/log/clagd.log
clagd[14003]: server01 is now dual connected.
MLAG port negotiation Failing
/var/log/syslog
kernel: [79290.290999] bonding: server01 is being created…
kernel: [79290.299645] 8021q: adding VLAN 0 to HW filter on device swp1
kernel: [79290.301790] server01: Enslaving swp1 as a backup interface with a down link
kernel: [79290.358294] server01: Setting ad_actor_system to 44:38:39:ff:40:94
kernel: [79290.373590] server01: Warning: No 802.3ad response from the link partner for any adapters in the bond
kernel: [79290.374024] IPv6: ADDRCONF(NETDEV_UP): server01: link is not ready
kernel: [79290.374028] 8021q: adding VLAN 0 to HW filter on device server01
kernel: [79290.375033] server01: link status definitely up for interface swp1, 1000 Mbps full duplex
kernel: [79290.375037] server01: now running without any active interface!
/var/log/clagd.log
clagd[14291]: Conflict (server01): matching clag-id (1) not configured on peer…
clagd[14291]: Conflict cleared (server01): matching clag-id (1) detected on peer
MLAG port negotiation Flapping
/var/log/syslog
mstpd: one_clag_cmd: setting (0) mac 00:00:00:00:00:00 <server01, None>
mstpd: one_clag_cmd: setting (1) mac 44:38:39:00:00:03 <server01, None>
/var/log/clagd.log
clagd[14291]: server01 is no longer dual connected
clagd[14291]: server01 is now dual connected.

Prescriptive Topology Manager (PTM) uses LLDP information to compare against a topology.dot file that describes the network. It has built in alerting capabilities, so it is preferable to use PTM on box rather than polling LLDP information regularly. The PTM code is available in the Cumulus Networks GitHub repository. Additional PTM, BFD, and associated logs are documented in the code.

Tracking peering information through PTM is highly recommended. For more information, refer to the Prescriptive Topology Manager documentation.

Neighbor Element Monitoring Commands Interval Poll
LLDP Neighbor
cumulus@switch:~$ lldpctl -f json
300 seconds
Prescriptive Topology Manager
cumulus@switch:~$ ptmctl -j [-d]
Triggered

Layer 2 Protocols

Spanning tree is a protocol that prevents loops in a layer 2 infrastructure. In a stable state, the spanning tree protocol should stably converge. Monitoring the Topology Change Notifications (TCN) in STP helps identify when new BPDUs are received.

Interface Counter Element Monitoring Commands Interval Poll
STP TCN Transitions
cumulus@switch:~$ mstpctl showbridge json
cumulus@switch:~$ mstpctl showport json
60 seconds
MLAG peer state
cumulus@switch:~$ clagctl status
cumulus@switch:~$ clagd -j
cumulus@switch:~$ cat /var/log/clagd.log
60 seconds
MLAG peer MACs
cumulus@switch:~$ clagctl dumppeermacs
cumulus@switch:~$ clagctl dumpourmacs
300 seconds
Layer 2 Logs Log Location Log Entries
Spanning Tree Working
/var/log/syslog
kernel: [1653877.190724] device swp1 entered promiscuous mode
kernel: [1653877.190796] device swp2 entered promiscuous mode
mstpd: create_br: Add bridge bridge
mstpd: clag_set_sys_mac_br: set bridge mac 00:00:00:00:00:00
mstpd: create_if: Add iface swp1 as port#2 to bridge bridge
mstpd: set_if_up: Port swp1 : up
mstpd: create_if: Add iface swp2 as port#1 to bridge bridge
mstpd: set_if_up: Port swp2 : up
mstpd: set_br_up: Set bridge bridge up
mstpd: MSTP_OUT_set_state: bridge:swp1:0 entering blocking state(Disabled)
mstpd: MSTP_OUT_set_state: bridge:swp2:0 entering blocking state(Disabled)
mstpd: MSTP_OUT_flush_all_fids: bridge:swp1:0 Flushing forwarding database
mstpd: MSTP_OUT_flush_all_fids: bridge:swp2:0 Flushing forwarding database
mstpd: MSTP_OUT_set_state: bridge:swp1:0 entering learning state(Designated)
mstpd: MSTP_OUT_set_state: bridge:swp2:0 entering learning state(Designated)
sudo: pam_unix(sudo:session): session closed for user root
mstpd: MSTP_OUT_set_state: bridge:swp1:0 entering forwarding state(Designated)
mstpd: MSTP_OUT_set_state: bridge:swp2:0 entering forwarding state(Designated)
mstpd: MSTP_OUT_flush_all_fids: bridge:swp2:0 Flushing forwarding database
mstpd: MSTP_OUT_flush_all_fids: bridge:swp1:0 Flushing forwarding database
Spanning Tree Blocking
/var/log/syslog
mstpd: MSTP_OUT_set_state: bridge:swp2:0 entering blocking state(Designated)
mstpd: MSTP_OUT_set_state: bridge:swp2:0 entering learning state(Designated)mstpd: MSTP_OUT_set_state: bridge:swp2:0 entering forwarding state(Designated)mstpd: MSTP_OUT_flush_all_fids: bridge:swp2:0 Flushing forwarding databasemstpd: MSTP_OUT_flush_all_fids: bridge:swp2:0 Flushing forwarding databasemstpd: MSTP_OUT_set_state: bridge:swp2:0 entering blocking state(Alternate)
mstpd: MSTP_OUT_flush_all_fids: bridge:swp2:0 Flushing forwarding database

Layer 3 Protocols

When FRRouting boots up for the first time, there is a different log file for each daemon that is activated. If the log file is ever edited (for example, through vtysh or frr.conf), the integrated configuration sends all logs to the same file.

To send FRRouting logs to syslog, apply the configuration log syslog in vtysh.

BGP

When monitoring BGP, check if BGP peers are operational. There is not much value in alerting on the current operational state of the peer; monitoring the transition is more valuable, which you can do by monitoring syslog.

Monitoring the routing table provides trending on the size of the infrastructure. This is especially useful when integrated with host-based solutions (such as Routing on the Host) when the routes track with the number of applications available.

BGP Element Monitoring Commands Interval Poll
BGP peer failure
cumulus@switch:~$ vtysh -c “show ip bgp summary json”
cumulus@switch:~$ net show bgp summary json
60 seconds
BGP route table
cumulus@switch:~$ vtysh -c “show ip bgp json”
cumulus@switch:~$ net show route bgp json
600 seconds
BGP Logs Log Location Log Entries
BGP peer down
/var/log/syslog
/var/log/frr/*.log
bgpd[3000]: %NOTIFICATION: sent to neighbor swp1 4/0 (Hold Timer Expired) 0 bytes
bgpd[3000]: %ADJCHANGE: neighbor swp1 Down BGP Notification send

OSPF

When monitoring OSPF, check if OSPF peers are operational. There is not much value in alerting on the current operational state of the peer; monitoring the transition is more valuable, which you can do by monitoring syslog.

Monitoring the routing table provides trending on the size of the infrastructure. This is especially useful when integrated with host-based solutions (such as Routing on the Host) when the routes track with the number of applications available.

OSPF Element Monitoring Commands Interval Poll
OSPF protocol peer failure
cumulus@switch:~$ vtysh -c “show ip ospf neighbor all json”
cumulus@switch:~$ cl-ospf summary show json
60 seconds
OSPF link state database
cumulus@switch:~$ vtysh - c “show ip ospf database”
600 seconds

Route and Host Entries

Route Element Monitoring Commands Interval Poll
Host Entries
cumulus@switch:~$ cl-resource-query
cumulus@switch:~$ cl-resource-query -k
600 seconds
Route Entries
cumulus@switch:~$ cl-resource-query
cumulus@switch:~$ cl-resource-query -k
600 seconds

Routing Logs

Layer 3 Logs Log Location Log Entries
Routing protocol process crash
/var/log/syslog
frrouting[1824]: Starting FRRouting daemons (prio:10):. zebra. bgpd.
bgpd[1847]: BGPd 1.0.0+cl3u7 starting: vty@2605, bgp@:179
zebra[1840]: client 12 says hello and bids fair to announce only bgp routes
watchfrr[1853]: watchfrr 1.0.0+cl3u7 watching [zebra bgpd], mode [phased zebra restart]
watchfrr[1853]: bgpd state -> up : connect succeeded
watchfrr[1853]: bgpd state -> down : read returned EOF
cumulus-core: Running cl-support for core files bgpd.3030.1470341944.core.core_helper
core_check.sh[4992]: Please send /var/support/cl_support__spine01_20160804_201905.tar.xz to Cumulus support
watchfrr[1853]: Forked background command [pid 6665]: /usr/sbin/service frr restart bgpd
watchfrr[1853]: watchfrr 0.99.24+cl3u2 watching [zebra bgpd ospfd], mode [phased zebra restart]
watchfrr[1853]: zebra state -> up : connect succeeded
watchfrr[1853]: bgpd state -> up : connect succeeded
watchfrr[1853]: watchfrr: Notifying Systemd we are up and running

Logging

The table below describes the various log files.

Logging Element Monitoring Commands Log Location
syslog Catch all log file. Identifies memory leaks and CPU spikes.
/var/log/syslog
switchd functionality Hardware Abstraction Layer (HAL).
/var/log/switchd.log
Routing daemons FRRouting zebra daemon details.
/var/log/daemon.log
Routing protocol The log file is configurable in FRRouting. When FRRouting first boots, it uses the non-integrated configuration so each routing protocol has its own log file. After booting up, FRRouting switches over to using the integrated configuration, so that all logs go to a single place.
To edit the location of the log files, use the log file command. By default, FRRouting logs are not sent to syslog. Use the log syslog command to send logs through rsyslog and into /var/log/syslog.

Note: To write syslog debug messages to the log file, you must run the log syslog debug command to configure FRR with syslog severity 7 (debug); otherwise, when you issue a debug command such as, debug bgp neighbor-events, no output is sent to /var/log/frr/frr.log.
However, when you manually define a log target with the log file /var/log/frr/debug.log command, FRR automatically defaults to severity 7 (debug) logging and the output is logged to /var/log/frr/frr.log.
/var/log/frr/zebra.log
/var/log/frr/{protocol}.log
/var/log/frr/frr.log

Protocols and Services

Run the following command to confirm that the NTP process is working correctly and that the switch clock is in sync with NTP:

cumulus@switch:~$ /usr/bin/ntpq -p

Device Management

Device Access Logs

Access Logs Log Location Log Entries
User Authentication and Remote Login
/var/log/syslog
sshd[31830]: Accepted publickey for cumulus from 192.168.0.254 port 45582 ssh2: RSA 38:e6:3b:cc:04:ac:41:5e:c9:e3:93:9d:cc:9e:48:25
sshd[31830]: pam_unix(sshd:session): session opened for user cumulus by (uid=0)

Device Super User Command Logs

Super User Command Logs Log Location Log Entries
Executing commands using sudo
/var/log/syslog
sudo: cumulus: TTY=unknown ; PWD=/home/cumulus ; USER=root ; COMMAND=/tmp/script_9938.sh -v
sudo: pam_unix(sudo:session): session opened for user root by (uid=0)
sudo: pam_unix(sudo:session): session closed for user root

Network Solutions

This section discusses the various architectures and strategies available with Cumulus Linux and describes different solutions.

Data Center Host to ToR Architecture

This chapter discusses the various architectures and strategies available from the top of rack (ToR) switches all the way down to the server hosts.

Layer 2 - Traditional Spanning Tree - Single Attached

Example
Summary
Bond and Etherchannel are not configured on host to multiple switches (bonds can still occur but only to one switch at a time), so leaf01 and leaf02 see two different MAC addresses.
Benefits
Caveats
  • Established technology: Interoperability with other vendors, easy configuration, a lot of documentation from multiple vendors and the industry
  • Ability to use spanning tree commands: PortAdminEdge and BPDU guard
  • Layer 2 reachability to all VMs
  • The load balancing mechanism on the host can cause problems. If there is only host pinning to each NIC, there are no problems, but if you have a bond, you need to look at an MLAG solution.
  • No active-active host links. Some operating systems allow HA (NIC failover), but this still does not utilize all the bandwidth. VMs use one NIC, not two.
Active-Active Mode
Active-Passive Mode
L2 to L3 Demarcation
None (not possible with traditional spanning tree) VRR
  • ToR layer (recommended)
  • Spine layer
  • Core/edge/exit

You can configure VRR on a pair of switches at any level in the network. However, the higher up the network, the larger the layer 2 domain becomes. The benefit is layer 2 reachability. The drawback is that the layer 2 domain is more difficult to troubleshoot, does not scale as well, and the pair of switches running VRR needs to carry the entire MAC address table of everything below it in the network. Cumulus Professional Services recommends minimizing the layer 2 domain as much as possible. For more information, see this presentation.

Example Configuration

auto bridge
iface bridge
  bridge-vlan-aware yes
  bridge-ports swp1 peerlink
  bridge-vids 1-2000
  bridge-stp on

auto bridge.10
iface bridge.10
  address 10.1.10.2/24

auto peerlink
iface peerlink
    bond-slaves glob swp49-50

auto swp1
iface swp1
  mstpctl-portadminedge yes
  mstpctl-bpduguard yes
auto eth1
iface eth1 inet manual

auto eth1.10
iface eth1.10 inet manual

auto eth2
iface eth1 inet manual

auto eth2.20
iface eth2.20 inet manual

auto br-10
iface br-10 inet manual
  bridge-ports eth1.10 vnet0

auto br-20
iface br-20 inet manual
  bridge-ports eth2.20 vnet1

Layer 2 - MLAG

Example
Summary
MLAG (multi-chassis link aggregation) uses both uplinks at the same time. VRR enables both spines to act as gateways simultaneously for HA (high availability) and active-active mode (both are used at the same time).
Benefits
Caveats
100% of links utilized
  • More complicated (more moving parts)
  • More configuration
  • No interoperability between vendors
  • ISL (inter-switch link) required
Active-Active Mode Active-Passive Mode L2 to L3 Demarcation More Information
VRR None
  • ToR layer (recommended)
  • Spine layer
  • Core/edge/exit

    Example Configuration

    auto bridge
    iface bridge
      bridge-vlan-aware yes
      bridge-ports host-01 peerlink
      bridge-vids 1-2000
      bridge-stp on
    
    auto bridge.10
    iface bridge.10
      address 172.16.1.2/24
      address-virtual 44:38:39:00:00:10 172.16.1.1/24
    
    auto peerlink
    iface peerlink
        bond-slaves glob swp49-50
    
    auto peerlink.4094
    iface peerlink.4094
        address 169.254.1.1/30
        clagd-enable yes
        clagd-peer-ip 169.254.1.2
        clagd-system-mac 44:38:39:FF:40:94
    
    auto host-01
    iface host-01
      bond-slaves swp1
      clag-id 1
      {bond-defaults removed for brevity}
    
    auto bond0
    iface bond0 inet manual
      bond-slaves eth0 eth1
      {bond-defaults removed for brevity}
    
    auto bond0.10
    iface bond0.10 inet manual
    
    auto vm-br10
    iface vm-br10 inet manual
      bridge-ports bond0.10 vnet0
    

    Layer 3 - Single-attached Hosts

    Example
    Summary
    The server (physical host) has only has one link to one ToR switch.
    Benefits
    Caveats
    • Relatively simple network configuration
    • No STP
    • No MLAG
    • No layer 2 loops
    • No crosslink between leafs
    • Greater route scaling and flexibility
    • No redundancy for ToR, upgrades can cause downtime
    • There is often no software to support application layer redundancy
      FHR (First Hop Redundancy)
      More Information
      No redundancy for ToR, uses single ToR as gateway. For additional bandwidth, links between host and leaf can be bonded.

      Example Configuration

      /etc/network/interfaces file

      auto swp1
      iface swp1
        address 172.16.1.1/30
      

      /etc/frr/frr.conf file

      router ospf
        router-id 10.0.0.11
      interface swp1
        ip ospf area 0
      

      /etc/network/interfaces file

      auto swp1
      iface swp1
        address 172.16.2.1/30
      

      /etc/frr/frr.conf file

      router ospf
        router-id 10.0.0.12
      interface swp1
        ip ospf area 0
      
      auto eth1
      iface eth1 inet static
        address 172.16.1.2/30
        up ip route add 0.0.0.0/0 nexthop via 172.16.1.1
      
      auto eth1
      iface eth1 inet static
        address 172.16.2.2/30
        up ip route add 0.0.0.0/0 nexthop via 172.16.2.1
      

      Layer 3 - Redistribute Neighbor

      Example
      Summary
      The Redistribute neighbor daemon grabs ARP entries dynamically and uses the redistribute table for FRRouting to take these dynamic entries and redistribute them into the fabric.
      Benefits
      Caveats
      Configuration in FRRouting is simple (route map plus redistribute table)
      • Silent hosts do not receive traffic (depending on ARP)
      • IPv4 only
      • If two VMs are on the same layer 2 domain, they can learn about each other directly instead of using the gateway, which causes problems (such as VM migration or getting the network routed). Put hosts on /32 (no other layer 2 adjacency).
      • VM moves do not trigger a route withdrawal from the original leaf (four hour timeout).
      • Clearing ARP impacts routing.
      • No layer 2 adjacency between servers without VXLAN.
      FHR (First Hop Redundancy) More Information
      • Equal cost route installed on server, host, or hypervisor to both ToRs to load balance evenly.
      • For host/VM/container mobility, use the same default route on all hosts (such as x.x.x.1) but do not distribute or advertise the .1 on the ToR into the fabric. This allows the VM to use the same gateway no matter to which pair of leafs it is cabled.

      Layer 3 - Routing on the Host

      Example
      Summary
      Routing on the host means there is a routing application (such as FRRouting, either on the bare metal host (no VMs or containers) or the hypervisor (for example, Ubuntu with KVM). This is highly recommended by the our Professional Services team.
      Benefits
      Caveats
      • No requirement for MLAG
      • No spanning tree or layer 2 domain
      • No loops
      • You can use three or more ToRs instead of the usual two
      • Host and VM mobility
      • You can use traffic engineering to migrate traffic from one ToR to another when upgrading both hardware and software
      • The hypervisor or host OS might not support a routing application like FRRouting and requires a virtual router on the hypervisor
      • No layer 2 adjacnecy between servers without VXLAN
      FHR (First Hop Redundancy)
      More Information
      • The first hop is still the ToR, just like redistribute neighbor
      • A default route can be advertised by all leaf/ToRs for dynamic ECMP paths

      Layer 3 - Routing on the VM

      Example
      Summary
      Instead of routing on the hypervisor, each virtual machine uses its own routing stack.
      Benefits
      Caveats
      In addition to routing on host:
      • The hypervisor/base OS does not need to be able to do routing.
      • VMs can be authenticated into routing fabric.
      • All VMs must be capable of routing
      • You need to take scale considerations into an account; instead of one routing process, there are as many as there are VMs
      • No layer 2 adjacency between servers without VXLAN
      FHR (First Hop Redundancy)
      More Information
      • The first hop is still the ToR, just like redistribute neighbor
      • You can use multiple ToRs (two or more)

        Layer 3 - Virtual Router

        Example
        Summary
        Virtual router (vRouter) runs as a VM on the hypervisor or host and sends routes to the ToR using BGP or OSPF.
        Benefits
        Caveats
        In addition to routing on a host:
        • Multi-tenancy can work, where multiple customers share the same racks
        • The base OS does not need to be routing capable
        • ECMP might not work correctly (load balancing to multiple ToRs); the Linux kernel in older versions is not capable of ECMP per flow (it does it per packet)
        • No layer 2 adjacency between servers without VXLAN
        FHR (First Hop Redundancy)
        More Information
        • The gateway is the vRouter, which has two routes out (two ToRs)
        • You can use multiple vRouters

        Layer 3 - Anycast with Manual Redistribution

        Example
        Summary
        In contrast to routing on the host (preferred), this method allows you to route to the host. The ToRs are the gateway, as with redistribute neighbor, except because there is no daemon running, you must manually configure the networks under the routing process. There is a potential to black hole unless you run a script to remove the routes when the host no longer responds.
        Benefits
        Caveats
        • Most benefits of routing on the host
        • No requirement for host to run routing
        • No requirement for redistribute neighbor
        • Removing a subnet from one ToR and re-adding it to another (network statements from your router process) is a manual process
        • Network team and server team have to be in sync, or the server team controls the ToR, or automation is used used whenever VM migration occurs
        • When using VMs or containers it is very easy to black hole traffic, as the leafs continue to advertise prefixes even when the VM is down
        • No layer 2 adjacency between servers without VXLAN
        FHR (First Hop Redundancy)
        The gateways are the ToRs, exactly like redistribute neighbor with an equal cost route installed.

        Example Configuration

        /etc/network/interfaces file

        auto swp1
        iface swp1
          address 172.16.1.1/30
        

        /etc/frr/frr.conf file

        router ospf
          router-id 10.0.0.11
        interface swp1
          ip ospf area 0
        

        /etc/network/interfaces file

        auto swp2
        iface swp2
          address 172.16.1.1/30
        

        /etc/frr/frr.conf file

        router ospf
          router-id 10.0.0.12
        interface swp1
          ip ospf area 0
        
        auto lo
        iface lo inet loopback
        
        auto lo:1
        iface lo:1 inet static
          address 172.16.1.2/32
          up ip route add 0.0.0.0/0 nexthop via 172.16.1.1 dev eth0 onlink nexthop via 172.16.1.1 dev eth1 onlink
        
        auto eth1
        iface eth2 inet static
          address 172.16.1.2/32
        
        auto eth2
        iface eth2 inet static
          address 172.16.1.2/32
        

        Layer 3 - EVPN with Symmetric VXLAN Routing

        Symmetric VXLAN routing is configured directly on the ToR, using EVPN for both VLAN and VXLAN bridging as well as VXLAN and external routing.

        Each server is configured on a VLAN, with a total of two VLANs for the setup. MLAG is also set up between servers and the leafs. Each leaf is configured with an anycast gateway and the servers default gateways are pointing towards the corresponding leaf switch IP gateway address. Two tenant VNIs (corresponding to two VLANs/VXLANs) are bridged to corresponding VLANs.

        Benefits
        Caveats
        • Layer 2 domain is reduced to the pair of ToRs
        • Aggregation layer is all layer 3 (VLANs do not have to exist on spine switches)
        • Greater route scaling and flexibility
        • High availability
        Needs MLAG (with the same caveats as the MLAG section above)
        Active-Active Mode Active-Passive Mode Demarcation More Information
        VRR None ToR layer

        Example Configuration

        # Loopback interface
        auto lo
        iface lo inet loopback
          address 10.0.0.11/32
          clagd-vxlan-anycast-ip 10.0.0.112
          alias loopback interface
        
        # Management interface
         auto eth0
         iface eth0 inet dhcp
            vrf mgmt
        
        auto mgmt
        iface mgmt
            address 127.0.0.1/8
            address ::1/128
            vrf-table auto
        
        # Port to Server01
        auto swp1
        iface swp1
          alias to Server01
          # This is required for Vagrant only
          post-up ip link set swp1 promisc on
        
        # Port to Server02
        auto swp2
        iface swp2
          alias to Server02
          # This is required for Vagrant only
          post-up ip link set swp2 promisc on
        
        # Port to Leaf02
        auto swp49
        iface swp49
          alias to Leaf02
          # This is required for Vagrant only
          post-up ip link set swp49 promisc on
        
        # Port to Leaf02
        auto swp50
        iface swp50
          alias to Leaf02
          # This is required for Vagrant only
          post-up ip link set swp50 promisc on
        
        # Port to Spine01
        auto swp51
        iface swp51
          mtu 9216
          alias to Spine01
        
        # Port to Spine02
        auto swp52
        iface swp52
          mtu 9216
          alias to Spine02
        
        # MLAG Peerlink bond
        auto peerlink
        iface peerlink
          mtu 9000
          bond-slaves swp49 swp50
        
        # MLAG Peerlink L2 interface.
        # This creates VLAN 4094 that only lives on the peerlink bond
        # No other interface will be aware of VLAN 4094
        auto peerlink.4094
        iface peerlink.4094
          address 169.254.1.1/30
          clagd-peer-ip 169.254.1.2
          clagd-backup-ip 10.0.0.12
          clagd-sys-mac 44:39:39:ff:40:94
          clagd-priority 100
        
        # Bond to Server01
        auto bond01
        iface bond01
          mtu 9000
          bond-slaves swp1
          bridge-access 13
          clag-id 1
        
        # Bond to Server02
        auto bond02
        iface bond02
          mtu 9000
          bond-slaves swp2
          bridge-access 24
          clag-id 2
        
        # Define the bridge for STP
        auto bridge
        iface bridge
          bridge-vlan-aware yes
          # bridge-ports includes all ports related to VxLAN and CLAG.
          # does not include the Peerlink.4094 subinterface
          bridge-ports bond01 bond02 peerlink vni13 vni24 vxlan4001
          bridge-vids 13 24
          bridge-pvid 1
        
        # VXLAN Tunnel for Server1-Server3 (Vlan 13)
        auto vni13
        iface vni13
          mtu 9000
          vxlan-id 13
          vxlan-local-tunnelip 10.0.0.11
          bridge-access 13
          mstpctl-bpduguard yes
          mstpctl-portbpdufilter yes
        
        #VXLAN Tunnel for Server2-Server4 (Vlan 24)
        auto vni24
        iface vni24
          mtu 9000
          vxlan-id 24
          vxlan-local-tunnelip 10.0.0.11
          bridge-access 24
          mstpctl-bpduguard yes
          mstpctl-portbpdufilter yes
        
        auto vxlan4001
        iface vxlan4001
            vxlan-id 104001
            vxlan-local-tunnelip 10.0.0.11
            bridge-access 4001
        
        auto vrf1
        iface vrf1
           vrf-table auto
        
        #Tenant SVIs - anycast GW
        auto vlan13
        iface vlan13
            address 10.1.3.11/24
            address-virtual 44:39:39:ff:00:13 10.1.3.1/24
            vlan-id 13
            vlan-raw-device bridge
            vrf vrf1
        
        auto vlan24
        iface vlan24
            address 10.2.4.11/24
            address-virtual 44:39:39:ff:00:24 10.2.4.1/24
            vlan-id 24
            vlan-raw-device bridge
            vrf vrf1
        
        #L3 VLAN interface per tenant (for L3 VNI)
        auto vlan4001
        iface vlan4001
            hwaddress 44:39:39:FF:40:94
            vlan-id 4001
            vlan-raw-device bridge
            vrf vrf1
        
        # Loopback interface
        auto lo
        iface lo inet loopback
          address 10.0.0.12/32
          clagd-vxlan-anycast-ip 10.0.0.112
          alias loopback interface
        
        # Management interface
        auto eth0
        iface eth0 inet dhcp
            vrf mgmt
        
        auto mgmt
        iface mgmt
            address 127.0.0.1/8
            address ::1/128
            vrf-table auto
        
        # Port to Server01
        auto swp1
        iface swp1
          alias to Server01
          # This is required for Vagrant only
          post-up ip link set swp1 promisc on
        
        # Port to Server02
        auto swp2
        iface swp2
          alias to Server02
          # This is required for Vagrant only
          post-up ip link set swp2 promisc on
        
        # Port to Leaf01
        auto swp49
        iface swp49
          alias to Leaf01
          # This is required for Vagrant only
          post-up ip link set swp49 promisc on
        
        # Port to Leaf01
        auto swp50
        iface swp50
          alias to Leaf01
          # This is required for Vagrant only
          post-up ip link set swp50 promisc on
        
        # Port to Spine01
        auto swp51
        iface swp51
          mtu 9216
          alias to Spine01
        
        # Port to Spine02
        auto swp52
        iface swp52
          mtu 9216
          alias to Spine02
        
        # MLAG Peerlink bond
        auto peerlink
        iface peerlink
          mtu 9000
          bond-slaves swp49 swp50
        
        # MLAG Peerlink L2 interface.
        # This creates VLAN 4094 that only lives on the peerlink bond
        # No other interface will be aware of VLAN 4094
        auto peerlink.4094
        iface peerlink.4094
          address 169.254.1.2/30
          clagd-peer-ip 169.254.1.1
          clagd-backup-ip 10.0.0.11
          clagd-sys-mac 44:39:39:ff:40:94
          clagd-priority 200
        
        # Bond to Server01
        auto bond01
        iface bond01
          mtu 9000
          bond-slaves swp1
          bridge-access 13
          clag-id 1
        
        # Bond to Server02
        auto bond02
        iface bond02
          mtu 9000
          bond-slaves swp2
          bridge-access 24
          clag-id 2
        
        # Define the bridge for STP
        auto bridge
        iface bridge
          bridge-vlan-aware yes
          # bridge-ports includes all ports related to VxLAN and CLAG.
          # does not include the Peerlink.4094 subinterface
          bridge-ports bond01 bond02 peerlink vni13 vni24 vxlan4001
          bridge-vids 13 24
          bridge-pvid 1
        
        auto vxlan4001
        iface vxlan4001
             vxlan-id 104001
             vxlan-local-tunnelip 10.0.0.12
             bridge-access 4001
        
        # VXLAN Tunnel for Server1-Server3 (Vlan 13)
        auto vni13
        iface vni13
          mtu 9000
          vxlan-id 13
          vxlan-local-tunnelip 10.0.0.12
          bridge-access 13
          mstpctl-bpduguard yes
          mstpctl-portbpdufilter yes
        
        #VXLAN Tunnel for Server2-Server4 (Vlan 24)
        auto vni24
        iface vni24
          mtu 9000
          vxlan-id 24
          vxlan-local-tunnelip 10.0.0.12
          bridge-access 24
          mstpctl-bpduguard yes
          mstpctl-portbpdufilter yes
        
        auto vrf1
        iface vrf1
           vrf-table auto
        
        auto vlan13
        iface vlan13
            address 10.1.3.12/24
            address-virtual 44:39:39:ff:00:13 10.1.3.1/24
            vlan-id 13
            vlan-raw-device bridge
            vrf vrf1
        
        auto vlan24
        iface vlan24
            address 10.2.4.12/24
            address-virtual 44:39:39:ff:00:24 10.2.4.1/24
            vlan-id 24
            vlan-raw-device bridge
            vrf vrf1
        
        #L3 VLAN interface per tenant (for L3 VNI)
        auto vlan4001
        iface vlan4001
            hwaddress 44:39:39:FF:40:94
            vlan-id 4001
            vlan-raw-device bridge
            vrf vrf1
        
        auto lo
        iface lo inet loopback
        
        auto eth0
        iface eth0 inet dhcp
        
        auto eth1
        iface eth1 inet manual
          bond-master uplink
          # Required for Vagrant
          post-up ip link set promisc on dev eth1
        
        auto eth2
        iface eth2 inet manual
          bond-master uplink
          # Required for Vagrant
          post-up ip link set promisc on dev eth2
        
        auto uplink
        iface uplink inet static
          mtu 9000
          bond-slaves none
          bond-mode 802.3ad
          bond-miimon 100
          bond-lacp-rate 1
          bond-min-links 1
          bond-xmit-hash-policy layer3+4
          address 10.1.3.101
          netmask 255.255.255.0
          post-up ip route add default via 10.1.3.1
        
        auto lo
        iface lo inet loopback
        
        auto eth0
        iface eth0 inet dhcp
        
        auto eth1
        iface eth1 inet manual
          bond-master uplink
          # Required for Vagrant
          post-up ip link set promisc on dev eth1
        
        auto eth2
        iface eth2 inet manual
          bond-master uplink
          # Required for Vagrant
          post-up ip link set promisc on dev eth2
        
        auto uplink
        iface uplink inet static
          mtu 9000
          bond-slaves none
          bond-mode 802.3ad
          bond-miimon 100
          bond-lacp-rate 1
          bond-min-links 1
          bond-xmit-hash-policy layer3+4
          address 10.2.4.102
          netmask 255.255.255.0
          post-up ip route add default via 10.2.4.1
        

        Cumulus Networks Services Demos

        The Services team demos provide a virtual environment built using either VirtualBox or libvirt using Vagrant to manage the VMs. This environment utilizes the reference topology shown below. Vagrant and Cumulus VX can be used together to build virtual simulations of production networks to validate configurations, develop automation code and simulate failure scenarios.

        Reference Topology

        The reference topology includes cabling (in DOT format for dual use with PTM), MAC addressing, IP addressing, switches and servers. This topology is blessed by the our Professional Services Team to fit a majority of designs seen in the field.

        IP and MAC Addressing

        Hostname eth0 IP eth0 MAC Interface Count
        oob-mgmt-server 192.168.0.254 any
        oob-mgmt-switch 192.168.0.1 any
        leaf01 192.168.0.11 A0:00:00:00:00:11 48x10g w/ 6x40g uplink
        leaf02 192.168.0.12 A0:00:00:00:00:12 48x10g w/ 6x40g uplink
        leaf03 192.168.0.13 A0:00:00:00:00:13 48x10g w/ 6x40g uplink
        leaf04 192.168.0.14 A0:00:00:00:00:14 48x10g w/ 6x40g uplink
        spine01 192.168.0.21 A0:00:00:00:00:21 32x40g
        spine02 192.168.0.22 A0:00:00:00:00:22 32x40g
        server01 192.168.0.31 A0:00:00:00:00:31 10g NICs
        server02 192.168.0.32 A0:00:00:00:00:32 10g NICs
        server03 192.168.0.33 A0:00:00:00:00:33 10g NICs
        server04 192.168.0.34 A0:00:00:00:00:34 10g NICs
        exit01 192.168.0.41 A0:00:00:00:00:41 48x10g w/ 6x40g uplink (exit leaf)
        exit02 192.168.0.42 A0:00:00:00:00:42 48x10g w/ 6x40g uplink (exit leaf)
        edge01 192.168.0.51 A0:00:00:00:00:51 10g NICs (customer edge device, firewall, load balancer, etc.)
        internet 192.168.0.253 any (represents internet provider edge device)

        Build the Topology

        Virtual Appliance

        You can build out the reference topology in hardware or using Cumulus VX. The Cumulus Reference Topology using Vagrant is essentially the reference topology built out inside Vagrant with VirtualBox or KVM. The installation and setup instructions for bringing up the entire reference topology on a laptop or server are on the cldemo-vagrant GitHub repo.

        Demos

        You can find an up to date list of all the demos in the cldemo-vagrant GitHub repository, which is available to anyone free of charge.

        Docker on Cumulus Linux

        Cumulus Linux can be used to run the Docker container platform. You can install Docker Engine directly on a Cumulus Linux switch and run Docker containers natively on the switch.

        To set up Docker on Cumulus Linux, run the following commands as root.

        1. Install the authentication key for Docker:

          root@switch:~# curl -fsSL https://download.docker.com/linux/debian/gpg | apt-key add -
          
        2. Configure the repositories for Docker:

          root@switch:~# echo "deb [arch=amd64] https://download.docker.com/linux/debian buster stable" >/etc/apt/sources.list.d/docker.list
          
        3. Install the Docker package:

          root@switch:~# apt update
          root@switch:~# apt install -y docker-ce
          
        4. Configure Docker to minimize impact on the system’s firewall and forwarding configuration:

          root@switch:~# cat >/etc/docker/daemon.json <<EOD
          {
             "iptables": false,
             "ip-forward": false,
             "ip-masq": false
          }
          EOD
          
        5. Configure Docker to run in the management VRF:

          root@switch:~# cp /lib/systemd/system/docker.service /lib/systemd/system/docker@.service
          root@switch:~# sed -i -re '
                /^Requires=docker.socket$/ d;
                /^ExecStart\>/ s/-H fd:\/\/ //
             ' /lib/systemd/system/docker@.service
          
          root@switch:~# echo "docker" >>/etc/vrf/systemd.conf
          
          root@switch:~# systemctl daemon-reload
          root@switch:~# systemctl mask docker.socket
          root@switch:~# systemctl disable --now docker.service
          root@switch:~# systemctl enable --now docker@mgmt
          
        6. Test your installation by running the hello-world container:

          root@switch:~# docker run hello-world
          

        Be mindful of the types of applications you want to run in containers on a Cumulus Linux switch. Depending on the configuration of the container, DHCP servers, custom scripts, and other lightweight services run well. However, VPN, NAT and encryption-type services are CPU-intensive and might lead to undesirable effects on critical applications. Resource-intensive services are not supported.

        Anycast Design Guide

        Routing on the Host enables you to run OSPF or BGP directly on server hosts. This can enable a network architecture known as anycast, where many servers can provide the same service without needing layer 2 extensions or load balancer appliances.

        Anycast is not a new protocol or protocol implementation and does not require any additional network configuration. Anycast leverages the equal cost multipath (ECMP) capabilities inherent in layer 3 networks to provide stateless load sharing services.

        The following image depicts an example anycast network. Each server is advertising the 172.16.255.66/32 anycast IP address.

        Anycast Architecture

        Anycast relies on layer 3 equal cost multipath functionality to provide load sharing throughout the network. Each server announces a route for a service. As the route is propagated through the network, each network device sees the route as originating from multiple places. As an end user connects to the anycast IP, each network device performs a hardware hash of the layer 3 and layer 4 headers to determine which path to use.

        Every packet in a flow from an end user has the same source and destination IP address as well as source and destination port numbers. The hash performed by the network devices results in the same answer for every packet, ensuring all packets in a flow are sent to the same destination.

        In the following image, the client initiates two flows: the blue, dotted flow and the red dashed flow. Each flow has the same source IP address (the client’s IP address), destination IP address (172.16.255.66) and same destination port (depending on the service; for example, DNS is port 53). Each flow has a unique source port generated by the client.

        In this example, each flow hashes to different servers based on this source port, which you can see when you run ip route show to the destination IP address:

        cumulus@spine02$ ip route show 172.16.255.66
        172.16.255.66  proto zebra  metric 20
            nexthop via 169.254.64.0  dev swp1 weight 1
            nexthop via 169.254.64.2  dev swp2 weight 1
            nexthop via 169.254.64.2  dev swp3 weight 1
            nexthop via 169.254.64.0  dev swp4 weight 1
        

        On a Cumulus Linux switch, you can see the hardware hash with the cl-ecmpcalc command. In Figure 2, two flows originate from a remote user destined to the anycast IP address. Each session has a different source port. Using the cl-ecmpcalc command, you can see that the sessions were hashed to different egress ports.

        cumulus@spine02$ sudo cl-ecmpcalc -p udp -s 10.2.0.100 --sport 32700 -d 172.31.255.66 --dport 53 -i swp51
        ecmpcalc: will query hardware
        swp2
        
        cumulus@spine02$ sudo cl-ecmpcalc -p udp -s 10.2.0.100 --sport 31884 -d 172.31.255.66 --dport 53 -i swp51
        ecmpcalc: will query hardware
        swp3
        

        Anycast with TCP and UDP

        A key component to the functionality and cost effective nature of anycast is that the network does not maintain state for flows. Every packet is handled individually through the routing table, saving memory and resources that would be required to track individual flows, similar to the functionality of a load balancing appliance.

        As previously described, every packet in a flow hashes to the same next hop. However, if that next hop is no longer valid, the traffic flows to another anycast next hop instead. For example, in the image below, if leaf03 fails, traffic flows to a different anycast address; in this case, server04:

        For stateless applications that rely on UDP, like DNS, this does not present a problem. However, for stateful applications that rely on TCP, like HTTP, this breaks any existing traffic flows, such as a file download. If the TCP three-way handshake was established on server03, after the failure, server04 would have no connection built and would send a TCP reset message back to the client, restarting the session.

        This is not to say that it is not possible to use TCP-based applications for anycast. However, TCP applications in an anycast environment should have short-lived flows (measured in seconds or less) to reduce the impact of network changes or failures.

        Resilient Hashing

        Resilient hashing provides a method to prevent failures from impacting the hash result of unrelated flows. However, resilient hashing does not prevent rehashing when new next hops are added.

        As previously mentioned, the hardware hashing function determines which path gets used for a given flow. The simplified version of that hash is the combination of protocol, source IP address, destination IP address, source layer 4 port and destination layer 4 port. The full hashing function includes not only these fields but also the list of possible layer 3 next hop addresses. The hash result is passed through a modulo of the number of next hop addresses. If the number of next hop addresses changes, through either addition or subtraction of the next hops, this changes the hash result for all traffic, including flows that have already established.

        Continuing with the example in Figure 3, leaf03 is in a failed state, so traffic is hashing to server04. This is a result of the hash considering three possible next hop IPs (leaf01, leaf02, leaf04). When leaf03 is brought back online, the number of possible next hop IPs grows to four. This changes the modulo value that is part of the hashing function, which may result in traffic being sent to a different server, even if previously unaffected by the change.

        As you can see below, leaf03 is in a failed state. The blue dotted flow uses leaf02 to reach server02.

        As leaf03 is brought back into service, the hashing function on spine02 changes, impacting the blue dotted flow:

        Just as the addition of a device can impact unrelated traffic, the removal of a device can also impact unrelated traffic, since again, the modulo of the hash function is changed. You can see this below, where the blue dotted flow goes through leaf01 and the red dashed line goes through leaf04.

        Now, leaf02 has failed. As a result, the modulo on spine02 has changed from four possible next hops to only three next hops. In this example, the red dashed line has rehashed to leaf03:

        To help solve this issue, resilient hashing can prevent traffic flows from shifting on unrelated failure scenarios. With resilient hashing enabled, the failure of leaf02 does not impact both existing flows, since they do not currently flow through leaf02:

        Although resilient hashing can prevent rehashing on next hop failure, it cannot prevent rehashing on next hop addition.

        You can read more information on resilient hashing in the ECMP chapter.

        Applications for Anycast

        As previously mentioned, UDP-based applications are great candidates for anycast architectures, such as NTP or DNS.

        When considering applications to be deployed in an anycast scenario, the first two questions to answer are:

        Applications with Multiple Connections

        The network has no knowledge of any sessions or relationships between different sessions for the same application. This affects protocols that rely on more than one TCP or UDP connection to function properly - one example being FTP.

        FTP data transfers require two connections: one for control and one for the file transfer. These two connections are independent, with their own TCP ports. Consider the scenario where an FTP server was deployed in an anycast architecture. When the secondary data connection is initiated, the traffic is destined initially to the same FTP server IP address, but the network hashes this traffic as a new, unique flow because the ports are different. This may result in the new session ending up on a new server. The new server would only accept that data connection if the FTP server application was capable of robust information sharing, as it has no history of the original request in the control session.

        Initiating Traffic vs. Receiving Traffic

        It is also important to understand that an outbound TCP session should never be initiated over an anycast IP address, as traffic that originates from an anycast IP address may not return to the same anycast server after the network hash. Contrast this with inbound sessions, where the network hash is the same for all packets in a flow, so the inbound traffic will hash to the same anycast server.

        TCP and Anycast

        TCP-based applications can be used with anycast, with the following recommendations:

        TCP applications that have longer-lived flows should not be used as anycast services. For example:

        It should be noted that anycast TCP is possible and has been implemented by a number of organizations, one notable example being LinkedIn.

        Conclusion

        Anycast can provide a low cost, highly scalable implementation for services. However, the limitations inherent in network-based ECMP makes anycast challenging to integrate with some applications. An anycast architecture is best suited for stateless applications or applications that are able to share session state at the application layer.

        RDMA over Converged Ethernet - RoCE

        RDMA over Converged Ethernet (RoCE) provides the ability to write to compute or storage elements using remote direct memory access (RDMA) over an Ethernet network instead of using host CPUs. RoCE relies on congestion control and lossless Ethernet to operate. Cumulus Linux supports features that can enable lossless Ethernet for RoCE environments.

        While Cumulus Linux can support RoCE environments, the hosts send and receive the RoCE packets.

        RoCE helps you obtain a converged network, where all services run over the Ethernet infrastructure, including Infiniband apps.

        There are two versions of RoCE, which run at separate layers of the stack:

        Enable RDMA over Converged Ethernet with PFC

        RoCEv1 uses the Infiniband (IB) Protocol over converged Ethernet. The IB global route header rides directly on top of the Ethernet header. The lossless Ethernet layer handles congestion hop by hop.

        To learn the Cumulus Linux settings, you need to configure support for RoCEv1, see the example configuration in the PFC section of the Buffer and Queue Management chapter.

        On switches with Spectrum ASICs, you can use NCLU to configure RoCE with PFC:

        cumulus@switch:~$ net add interface swp1 storage-optimized pfc
        cumulus@switch:~$ net pending
        cumulus@switch:~$ net commit
        

        These commands create the following configuration in the /etc/cumulus/datapath/traffic.conf file. They configure PFC on cos 1, ECN on cos 0 and 1 in /etc/cumulus/datapath/traffic.conf file. They also add a flow control buffer pool for lossless traffic and change the buffer limits in the /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf file.

        cumulus@switch:~$ sudo cat /etc/cumulus/datapath/traffic.conf
        ...
        ecn_red.port_group_list = [ROCE_ECN]
        pfc.ROCE_PFC.port_set = swp1
        pfc.ROCE_PFC.cos_list = [1]
        pfc.ROCE_PFC.xoff_size = 18000
        pfc.ROCE_PFC.xon_delta = 18000
        pfc.ROCE_PFC.tx_enable = true
        pfc.ROCE_PFC.rx_enable = true
        pfc.ROCE_PFC.port_buffer_bytes = 70000
        ecn_red.ROCE_ECN.port_set = swp1
        ecn_red.ROCE_ECN.cos_list = [0,1]
        ecn_red.ROCE_ECN.min_threshold_bytes = 150000
        ecn_red.ROCE_ECN.max_threshold_bytes = 1500000
        ecn_red.ROCE_ECN.ecn_enable = true
        ecn_red.ROCE_ECN.red_enable = true
        ecn_red.ROCE_ECN.probability = 100
        
        ...
        

        • While link pause is another way to provide lossless ethernet, PFC is the preferred method. PFC allows more granular control by pausing the traffic flow for a given CoS group, rather than the entire link.
        • RoCEv1 depends on 802.1p fields for traffic classification; therefore it is not supported with access ports. Use trunk ports with RoCEv1.

        Enable RDMA over Converged Ethernet with ECN

        RoCEv2 requires flow control for lossless Ethernet. RoCEv2 uses the Infiniband (IB) Transport Protocol over UDP. The IB transport protocol includes an end-to-end reliable delivery mechanism and has its own sender notification mechanism.

        RoCEv2 congestion management uses RFC 3168 to signal congestion experienced to the receiver. The receiver generates an RoCEv2 congestion notification packet directed to the source of the packet.

        To learn the Cumulus Linux settings you need to configure support for RoCEv2, see the example configuration in the ECN section of the Buffer and Queue Management chapter.

        On switches with Spectrum ASICs, you can use NCLU to configure RoCE with ECN:

        cumulus@switch:~$ net add interface swp1 storage-optimized
        cumulus@switch:~$ net pending
        cumulus@switch:~$ net commit
        

        These commands create the following configuration in the /etc/cumulus/datapath/traffic.conf file:

        cumulus@switch:~$ sudo cat /etc/cumulus/datapath/traffic.conf
        ...
        ecn_red.port_group_list = [ROCE_ECN]
        ecn_red.ROCE_ECN.port_set = swp1
        ecn_red.ROCE_ECN.cos_list = [0,1]
        ecn_red.ROCE_ECN.min_threshold_bytes = 150000
        ecn_red.ROCE_ECN.max_threshold_bytes = 1500000
        ecn_red.ROCE_ECN.ecn_enable = true
        ecn_red.ROCE_ECN.red_enable = true
        ecn_red.ROCE_ECN.probability = 100
        ...
        

        The storage-optimized command changes the buffer limits in the /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf file.

        The storage-optimized command also enables drop behaviors and Random Early Detection (RED). RED identifies packets that have been added to a long egress queue. The ECN action marks the packet and forwards it, requiring the packet to be ECT-capable. However, the drop action drops the packet, requiring the packet to not be ECT-capable.