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.
For complete details on the differences between Cumulus Linux 4.0 and Cumulus Linux 3.7, see this article.
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
Dell S4128F-ON
Dell S4128T-ON
Dell S4148F-ON
Dell S4148T-ON
Dell S5048F-ON
Dell Z9100-ON
Delta Platforms
Delta AG7648
Delta AG9032v1
Delta AG9032v2
Edgecore Platforms
Edgecore AS4610-54P
Edgecore AS4610-54T
Edgecore AS4610-54T-B
Edgecore AS5712-54X
Edgecore AS7312-54XS
Edgecore AS7712-32X
Mellanox Platforms
Mellanox SN2010
Mellanox SN2100
Penguin Platforms
Penguin Arctica 3200xlp
Penguin Arctica 4804ip
Penguin Arctica 4804iq
Penguin Arctica 4806xp
Quanta Platforms
QCT QuantaMesh BMS T4048-IX2
QCT QuantaMesh T1048-LY4R
QCT QuantaMesh BMS T5032-LY6-x86
QCT QuantaMesh BMS T3048-LY7
QCT QuantaMesh BMS T3048-LY8
QCT QuantaMesh BMS T3048-LY9
Supermicro Platforms
SuperMicro SSE-C3632S
SuperMicro SSE-G3648B
SuperMicro SSE-X3648S
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:
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.
Download the Cumulus Linux installation file to the root directory of the web server. Rename this file onie-installer.
Connect your host using an Ethernet cable to the management Ethernet port of the switch.
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:
Log in to Cumulus Linux on the switch.
Install the Cumulus Linux license.
Configure Cumulus Linux. This quick start guide provides instructions on configuring switch ports and a loopback interface.
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.
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:
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
Change the hostname with the hostnamectl command; for example:
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:
Run the following command in a terminal.
cumulus@switch:~$ sudo dpkg-reconfigure tzdata
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:
Copy the license from a local server. Create a text file with the license and copy it to a server accessible from the switch. On the switch, use the following command to transfer the file directly on the switch, then install the license file:
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.
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 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:
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:
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.
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:
No image is installed on the switch (the switch is only running ONIE).
Cumulus Linux is already installed on the switch but you want to use ONIE to reinstall Cumulus Linux or upgrade to a newer version.
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.
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:
You can name your Cumulus Linux installer disk image using any of the ONIE naming schemes mentioned here.
In the example commands, [PLATFORM] can be any supported Cumulus Linux platform, such as x86_64, or arm.
Run the sudo onie-install -h command to show the ONIE installer options.
After you install the Cumulus Linux disk image, you need to install the license file. Refer to Install the License.
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:
The bare metal switch boots up and requests an IP address (DHCP request).
The DHCP server acknowledges and responds with DHCP option 114 and the location of the installation image.
ONIE downloads the Cumulus Linux disk image, installs, and reboots.
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:
Place the Cumulus Linux disk image in a directory on the web server.
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.
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
Assign a static address to eth0 with the ip addr add command:
ONIE:/ #ip addr add 10.0.1.252/24 dev eth0
Place the Cumulus Linux disk image in a directory on your web server.
Run the installer manually (because there are no DHCP options):
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.
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.
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.
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
Create a new partition on the USB drive:
sudo parted /dev/sdb -a optimal mkpart primary 0% 100%
Format the partition to your filesystem of choice using one of the examples below:
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.
To continue installing Cumulus Linux, mount the USB drive to move files
sudo mkdir /mnt/usb
sudo mount /dev/sdb1 /mnt/usb
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.
Insert the USB drive into the switch, then continue with the appropriate instructions below for your x86 or ARM platform.
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.
Monitor the console and select the ONIE option from the first GRUB screen shown below.
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.
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/
After installation completes, the switch automatically reboots into the newly installed instance of Cumulus Linux.
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.
Interrupt the normal boot process before the countdown (shown below) completes. Press any key to stop the autoboot.
A command prompt appears so that you can run commands. Execute the following command:
run onie_bootcmd
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/
After installation completes, the switch automatically reboots into the newly installed instance of 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.
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/
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.
Create the cl-support archive file with the cl-support command:
cumulus@switch:~$ sudo cl-support
Copy the cl-support file off the switch to a different location.
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:
Installing a disk image is destructive; any configuration files on the switch are not saved; copy them to a different server before you start installation.
You must move configuration data to the new OS using ZTP or automation while the OS is first booted, or soon afterwards using out-of-band management.
Moving a configuration file might cause issues:
Identifying all the locations of configuration data is not always an easy task. See Before You Upgrade above.
Merge conflicts with configuration file changes in the new release might go undetected.
If configuration files are not restored correctly, you might be unable to ssh to the switch from in-band management. Out-of-band connectivity (eth0 or console) is recommended.
You must reinstall and reconfigure third-party applications after upgrade.
To upgrade the switch:
Back up the configurations off the switch.
Download the Cumulus Linux image.
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
Restore the configuration files to the new release - ideally with automation.
Verify correct operation with the old configurations on the new release.
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.
Verify the switch is in the secondary role:
cumulus@switch:~$ clagctl status
Shut down the core uplink layer 3 interfaces:
cumulus@switch:~$ sudo ip link set swpX down
Shut down the peer link:
cumulus@switch:~$ sudo ip link set peerlink down
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.
Reboot the switch:
cumulus@switch:~$ sudo reboot
If you installed a new image on the switch, restore the configuration files to the new release.
Verify STP convergence across both switches:
cumulus@switch:~$ mstpctl showall
Verify core uplinks and peer links are UP:
cumulus@switch:~$ net show interface
Verify MLAG convergence:
cumulus@switch:~$ clagctl status
Make this secondary switch the primary:
cumulus@switch:~$ clagctl priority 2048
Verify the other switch is now in the secondary role.
Repeat steps 2-9 on the new secondary switch.
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:
Flatten and rebuild: If the OS becomes unusable, you can use orchestration tools to reinstall the previous OS release from scratch and then rebuild the configuration automatically.
Backup and restore: Another common strategy is to restore to a previous state using a backup captured before the upgrade. See Back up and Restore.
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.
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:
It is not possible to reconcile the bridge-learning configuration on all of the VTEP interfaces if both LNV and EVPN are enabled at the same time. LNV requires MAC learning to be enabled on the VXLAN VTEP interfaces. EVPN requires MAC learning to be disabled on the VXLAN VTEP interfaces.
The Linux bridge installs MAC address entries differently when LNV is enabled than when EVPN is enabled. Different flags are set on the MAC addresses in the Linux kernel depending on how the address is learned. Duplicate and/or conflicting bridge entries and race conditions become a possibility when both are enabled at the same time. Because the kernel bridging table is the basis for programming the forwarding ASICs, this might lead to downstream inconsistencies in the hardware forwarding tables.
The standard IPv4 unicast address family is commonly used to route inside the fabric for spine and leaf Clos networks. Because FRRouting does not currently support BGP dynamic capability negotiation, enabling the EVPN address family requires all of the neighbors to restart for the changes to take effect. This results in a brief disruption to traffic forwarding.
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:
NCLU restarts services and reloads interfaces automatically so the changes can take effect.
With the transactional commit model of NCLU, the order in which the NCLU commands are entered is of no consequence. This further reduces complexity and hidden dependencies.
The BGP EVPN configuration for a centralized routing topology is slightly different on the exit/routing leafs compared to the other ToR leaf switches.
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
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.
To disable and stop the LNV registration daemon, run the following commands on the leaf and exit nodes:
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.
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).
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.
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:
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:
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:
Run the dpkg command to ensure that the package is not already installed on the system:
cumulus@switch:~$ dpkg -l | grep {name of package}
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:
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:
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:
audisp-tacplus
ifplugd
libdaemon0
libnss-ldapd
libnss-mapuser
libnss-tacplus
libpam-ldapd
libpam-radius-auth
libpam-tacplus
libtac2
libtacplus-map1
nslcd
You add these packages normally with apt-get update && apt-get install, as described above.
man pages for apt-get, dpkg, sources.list, apt_preferences
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:
Through a local file
Using a USB drive inserted into the switch (ZTP-USB)
Through DHCP
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:
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:
Install the Cumulus Linux operating system and license.
Copy over a basic configuration to the switch.
Restart the switch or the relevant services to get switchd up and running with that configuration.
Follow these steps to perform ZTP using a USB drive:
Copy the Cumulus Linux license and installation image to the USB drive.
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.
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:
The first time you boot Cumulus Linux, eth0 is configured for DHCP and makes a DHCP request.
The DHCP server offers a lease to the switch.
If option 239 is present in the response, the ZTP process starts.
The ZTP process requests the contents of the script from the URL, sending additional HTTP headers containing details about the switch.
The contents of the script are parsed to ensure it contains the CUMULUS-AUTOPROVISIONING flag (see example scripts).
If provisioning is necessary, the script executes locally on the switch with root privileges.
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:
The switch boots.
You plug a cable into or unplug a cable from the eth0 port.
You disconnect, then reconnect the switch power cord.
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:
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:
Perl
Python
Ruby
Shell
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.
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:
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:
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
During the development of a provisioning script, the switch might need to be rebooted.
You can use the Cumulus Linux onie-select -i command to cause the switch to reprovision itself and install a network operating system again using ONIE.
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:
Embeds help, examples, and automatic command checking with suggestions in case you enter a typo.
Runs directly from and integrates with bash, while being interoperable with the regular way of accessing underlying configuration files.
Configures dependent features automatically so that you don’t have to.
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:
Use the net add and net del commands to stage and remove configuration changes.
Use the net pending command to review staged changes.
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:
net show is a series of commands for viewing various parts of the network configuration. For example, use net show configuration to view the complete network configuration, net show commit history to view a history of commits using NCLU, and net show bgp to view BGP status.
net clear provides a way to clear net show counters, BGP and OSPF neighbor content, and more.
net rollback provides a mechanism to revert back to an earlier configuration.
net commit confirm requires you to press Enter to commit changes using NCLU. If you run net commit confirm but do not press Enter within 10 seconds, the commit automatically reverts and no changes are made.
net commit description <description> enables you to provide a descriptive summary of the changes you are about to commit.
net commit permanent retains the backup file taken when committing the change. Otherwise, the backup files created from NCLU commands are cleaned up periodically.
net del all deletes all configurations.
The net del all command does not remove management VRF configurations; NCLU does not interact with eth0 interfaces and management VRF.
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:
You create user accounts with read-only permissions for NCLU by adding them to the netshow group. A user in the netshow group can run NCLU net show commands, such as net show interface or net show config, and certain general Linux commands, such as ls, cd or man, but cannot run net add, net del or net commit commands.
You create user accounts with edit permissions for NCLU by adding them to the netedit group. A user in the netedit group can run NCLU configuration commands, such net add, net del or net commit in addition to NCLU net show commands.
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:
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.
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.
Use the guided wizard.
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.
To set the time zone using the guided wizard, run dpkg-reconfigure tzdata as root:
cumulus@switch:~$ sudo dpkg-reconfigure tzdata
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:
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
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.
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:
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.
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:
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:
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:
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!
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:
Restart NTP with the sudo systemctl restart ntp command.
Configure the NTP client (the Cumulus Linux switch):
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!
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
...
Restart NTP in the active VRF (default or management). For example:
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:
Open the /etc/cumulus/switchd.conf file in a text editor and add the following line:
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
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.
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:
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:
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.
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
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 |
| |
| |
+-----------------+
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
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:
Uses the default password CumulusLinux!
Is a user account in the sudo group with sudo privileges.
Can log in to the system through all the usual channels, such as console and SSH.
Along with the cumulus group, has both show and edit rights for NCLU.
The root account:
Has the default password disabled by default.
Has the standard Linux root user access to everything on the switch.
Disabled password prohibits login to the switch by SSH, telnet, FTP, and so on.
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:
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
Set a password
Generate an SSH Key for the root Account
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.
If a key does not exist, generate a new one by first creating the RSA key pair:
root@host:~# ssh-keygen -t rsa
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.
You are prompted to enter a passphrase (empty for no passphrase). This is optional but it does provide an extra layer of security.
The public key is now located in /root/.ssh/id_rsa.pub. The private key (identification) is now located in /root/.ssh/id_rsa.
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
Run the following command:
cumulus@switch:~$ sudo passwd root
Change the PermitRootLogin setting in the /etc/ssh/sshd_config file from without-password to yes.
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 manvisudo(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.
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.
NSS specifies the order of the information sources that are used to resolve names for each service. Using NSS with authentication and authorization provides the order and location for user lookup and group mapping on the system.
PAM handles the interaction between the user and the system, providing login handling, session setup, authentication of users, and authorization of user actions.
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:
libnss-ldapd
libpam-ldapd
ldap-utils
To install the additional packages, run the following command:
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.
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.
Edit the /etc/nslcd.conf file to update the LDAP URI and search base DN (see Update the nslcd.conf File, below).
Edit the /etc/nssswitch.conf file to update the service selections.
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.
Run apt-get install debconf-utils and create the pre-seeded parameters using debconf-set-selections. Provide the appropriate answers.
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:
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).
The FQDN of the LDAP server URI does not match the FQDN in the CA-signed server certificate exactly.
nslcd cannot read the SSL certificate and reports a Permission denied error in the debug during server connection negotiation. Check the permission on each directory in the path of the root SSL certificate. Ensure that it is readable by the nslcd user.
NSCD
If the nscd cache daemon is also enabled and you make some changes to the user from LDAP, you can clear the cache using the following commands:
nscd --invalidate = passwd
nscd --invalidate = group
The nscd package works with nslcd to cache name entries returned from the LDAP server. This might cause authentication failures. To work around these issues, disable nscd, restart the nslcd service, then retry authentication:
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:
When a local username also exists in the LDAP database, the order of the information sources in /etc/nsswitch can be updated to query LDAP before the local user database. This is generally not recommended. For example, the configuration below ensures that LDAP is queried before the local database.
# /etc/nsswitch.conf
passwd: ldap compat
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.
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.
LDAP search
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.
# 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:
Add a user or one of their groups to the /etc/netd.conf file manually.
Add a user to the local /etc/group file as a member of the netshow or netedit groups.
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.
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
Authentication using PAM; includes login, ssh, sudo and su
TACACS+ privilege 15 users can run any command with sudo using the /etc/sudoers.d/tacplus file that is installed by the libtacplus-map1 package
Up to seven TACACS+ servers
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:
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:
Whether the user is a valid TACACS+ user
The user’s privilege level
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:
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
...
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.
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
...
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.
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:
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:
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:
/etc/tacplus_servers
/etc/tacplus_nss.conf
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:
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:
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.
For commands that do not execute other commands (for example, changes to configurations in an editor, or actions with tools like clagctl and vtysh), no additional accounting is done.
Per-command authorization is implemented at the most basic level (commands are permitted or denied based on the standard Linux user permissions for the local TACACS users and only privilege level 15 users can run sudo commands by default).
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.
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:
The PAM configuration is modified automatically using pam-auth-update (8), and the NSS configuration file /etc/nsswitch.conf is modified to add the mapuser and mapuid plugins. If you remove or purge the packages, these files are modified to remove the configuration for these plugins.
The radius_shell package is added, which installs the /sbin/radius_shell and setcap cap_setuid program used as the login shell for RADIUS accounts. The package adjusts the UID when needed, then runs the bash shell with the same arguments. When installed, the package changes the shell of the RADIUS accounts to /sbin//radius_shell, and to /bin/shell if the package is removed. This package is required for privileged RADIUS users to be enabled. It is not required for regular RADIUS client use.
The radius_user account is added to the netshow group and the radius_priv_user account to the netedit and sudo groups. This change enables all RADUS logins to run NCLU net show commands and all privileged RADIUS users to also run net add, net del, and net commit commands, and to use sudo.
Configure the RADIUS Client
To configure the RADIUS client, edit the /etc/pam_radius_auth.conf file:
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.
If the server is slow or latencies are high, change the timeout setting. The setting defaults to 3 seconds.
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.
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.
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:
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:
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:
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:
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.
If two or more RADIUS users are logged in simultaneously, a UID lookup only returns the user that logged in first. Any processes run by either user get attributed to both, and all files created by either user get 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 fixed user from the password file. The current algorithm returns the first name matching the UID from the mapping file; this might be the first or second user that logged in.
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.
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:
iptables, ip6tables, and ebtables are Linux userspace tools used to administer filtering rules for IPv4 packets, IPv6 packets, and Ethernet frames (layer 2 using MAC addresses).
NCLU is a Cumulus Linux-specific userspace tool used to configure custom ACLs.
cl-acltool is a Cumulus Linux-specific userspace tool used to administer filtering rules and configure default ACLs.
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:
PREROUTING touches packets before they are routed
INPUT touches packets after they are determined to be destined for the local system but before they are received by the control plane software
FORWARD touches transit traffic as it moves through the box
OUTPUT touches packets that are sourced by the control plane software before they are put on the wire
POSTROUTING touches packets immediately before they are put on the wire but after the routing decision has been made
Tables
When building rules to affect the flow of traffic, the individual chains can be accessed by tables. Linux provides three tables by default:
Filter classifies traffic or filters traffic
NAT applies Network Address Translation rules
Cumulus Linux does not support NAT.
Mangle alters packets as they move through the switch
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.
Table: The first argument is the table. Notice the second example does not specify a table, that is because the filter table is implied if a table is not specified.
Chain: The second argument is the chain. Each table supports several different chains. See Understanding Tables above.
Matches: The third argument(s) are called the matches. You can specify multiple matches in a single rule. However, the more matches you use in a rule, the more memory that rule consumes.
Jump: The jump specifies the target of the rule; that is, what action to take if the packet matches the rule. If this option is omitted in a rule, then matching the rule will have no effect on the packet’s fate, but the counters on the rule will be incremented.
Target(s): The target can be a user-defined chain (other than the one this rule is in), one of the special built-in targets that decides the fate of the packet immediately (like DROP), or an extended target. See the Supported Rule Types section below for examples of different targets.
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:
IPv6 (ip6tables)
IPv4 (iptables)
ebtables
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:
The order of operations for how rules are processed is not perfectly maintained when you compare how iptables and the switch silicon process packets. The switch silicon reorders rules when switchd writes to the ASIC, whereas traditional iptables execute the list of rules in order.
All rules are terminating; after a rule matches, the action is carried out and no more rules are processed. However, as an exception, when a SETCLASS rule is placed immediately before another rule, it exists multiple times in the default ACL configuration. In the example below, the SETCLASS action applied with the --in-interface option, creates the internal ASIC classification, and continues to process the next rule, which does the rate-limiting for the matched protocol:
If multiple contiguous rules with the same match criteria are applied to --in-interface, only the first rule gets processeand then terminates processing. This is a misconfiguration; there is no reason to have duplicate rules with different actions.
When processing traffic, rules affecting the FORWARD chain that specify an ingress interface are performed prior to rules that match on an egress interface. As a workaround, rules that only affect the egress interface can have an ingress interface wildcard (currently, only swp+ and bond+ are supported as wildcard names; see below) that matches any interface applied so that you can maintain order of operations with other input interface rules. For example, with the following rules:
-A FORWARD -i $PORTA -j ACCEPT
-A FORWARD -o $PORTA -j ACCEPT <-- This rule is performed LAST (because of egress interface matching)
-A FORWARD -i $PORTB -j DROP
If you modify the rules like this, they are performed in order:
-A FORWARD -i $PORTA -j ACCEPT
-A FORWARD -i swp+ -o $PORTA -j ACCEPT <-- These rules are performed in order (because of wildcard match on ingress interface)
-A FORWARD -i $PORTB -j DROP
When using rules that do a mangle and a filter lookup for a packet, Cumulus Linux processes them in parallel and combines the action.
If a switch port is assigned to a bond, any egress rules must be assigned to the bond.
When using the OUTPUT chain, rules must be assigned to the source. For example, if a rule is assigned to the switch port in the direction of traffic but the source is a bridge (VLAN), the traffic is not affected by the rule and must be applied to the bridge.
If all transit traffic needs to have a rule applied, use the FORWARD chain, not the OUTPUT chain.
ebtable rules are put into either the IPv4 or IPv6 memory space depending on whether the rule utilizes IPv4 or IPv6 to make a decision. Layer 2-only rules that match the MAC address are put into the IPv4 memory space.
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:
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:
mirror (ingress only)
ipv4-mac (can be both ingress and egress)
ipv6 (ingress only)
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:
Updates are performed incrementally, one table at a time without stopping traffic.
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.
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.
Finally, old resources for that table are freed. This process is repeated for each of the tables listed above.
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.
If the regular nonatomic update fails, Cumulus Linux reverts back to the previous rules.
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:
An entry with multiple comma-separated input interfaces is split into one rule for each input interface (listed after --in-interface below). For example, this entry splits into two rules:
-A FORWARD –in-interface swp1s0,swp1s1 -p icmp -j ACCEPT
An entry with multiple comma-separated output interfaces is split into one rule for each output interface (listed after --out-interface below). This entry splits into two rules:
-A FORWARD --in-interface swp+ --out-interface swp1s0,swp1s1 -p icmp -j ACCEPT
An entry with both input and output comma-separated interfaces is split into one rule for each combination of input and output interface (listed after --in-interface and --out-interface below). This entry splits into four rules:
-A FORWARD --in-interface swp1s0,swp1s1 --out-interface swp1s2,swp1s3 -p icmp -j ACCEPT
An entry with multiple layer 4 port ranges is split into one rule for each range (listed after --dports below). For example, this entry splits into two 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:
If a traditional mode bridge has a mix of different VLANs, or has both access and trunk members, output interface matching is not supported.
For iptables rules, all IP packets in a bridge are matched, not just routed packets.
You cannot match both input and output interfaces in a rule.
For routed packets, Cumulus Linux cannot match the output bridge for SPAN/ERSPAN.
Matching SVI interfaces in ebtable rules is supported on switches based on Broadcom ASICs. This feature is not currently supported on switches with Mellanox Spectrum ASICs.
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:
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:
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:
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.
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 $INGRESS_INTF -s 192.0.2.2 -d 192.0.2.8 -j DROP
Apply all rules and policies included in /etc/cumulus/acl/policy.conf:
cumulus@switch:~$ 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:
The platform type (switch silicon, like Tomahawk or Spectrum.
The mix of IPv4 and IPv6 rules; Cumulus Linux does not support the maximum number of rules for both IPv4 and IPv6 simultaneously.
The number of default rules provided by Cumulus Linux.
Whether the rules are applied on ingress or egress.
Whether the rules are in atomic or nonatomic mode; nonatomic mode rules are used when nonatomic updates are enabled (see above).
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
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
Rules that have no matches and accept all packets in a chain are currently ignored.
Chain default rules (that are ACCEPT) are also ignored.
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:
Cumulus Linux compares all the match fields in the IPv6 ingress slice, except the --out-interface field, and marks the packet with a classid.
The egress IPv4 MAC slice matches on the classid and the out-interface, and performs the actions.
For example, the -A FORWARD --out-interface vlan100 -p icmp6 -j ACCEPT rule is split into the following:
IPv6 ingress: -A FORWARD -p icmp6 → action mark (for example, classid 4)
IPv4 MAC egress: <match mark 4> and --out-interface vlan100 -j ACCEPT
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 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 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:
--set-class value sets the system internal class of service queue configuration to value.
--set-rate value specifies the maximum rate in kilobytes (KB) or packets.
--set-burst value specifies the number of packets or kilobytes (KB) allowed to arrive sequentially.
--set-mode string sets the mode in KB (kilobytes) or pkt (packets) for rate and burst size.
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:
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
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:
Without using cl-acltool, rules are not installed into hardware.
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, 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:
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
If a switch port is assigned to a bond, any egress rules must be assigned to the bond.
When using the OUTPUT chain, rules must be assigned to the source. For example, if a rule is assigned to the switch port in the direction of traffic but the source is a bridge (VLAN), the traffic is not affected by the rule and must be applied to the bridge.
If all transit traffic needs to have a rule applied, use the FORWARD chain, not the OUTPUT chain.
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
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.
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:~$ 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:
Identify currently active or stopped services
Identify boot time state of a specific service
Disable or enable a specific service
Identify active listener ports
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.
systemctl has a number of subcommands that perform a specific operation on a given service.
status returns the status of the specified service.
start starts the service.
stop stops the service.
restart stops, then starts the service, all the while maintaining state. If there are dependent services or services that mark the restarted service as Required, the other services also restart. For example, running systemctl restart frr.service restarts any of the routing protocol services that are enabled and running, such as bgpd or ospfd.
reload reloads the configuration for the service.
enable enables the service to start when the system boots, but does not start it unless you use the systemctl start SERVICENAME.service command or reboot the switch.
disable disables the service, but does not stop it unless you use the systemctl stop SERVICENAME.service command or reboot the switch. You can start or stop a disabled service.
reenable disables, then enables a service. You might need to do this so that any new Wants or WantedBy lines create the symlinks necessary for ordering. This has no side effects on other services.
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:
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:
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.
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:
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:
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.
PoE functionality is provided by the cumulus-poe package. When a powered device is connected to the switch via an Ethernet cable:
If the available power is greater than the power required by the connected device, power is supplied to the switch port, and the device powers on
If available power is less than the power required by the connected device and the switch port’s priority is less than the port priority set on all powered ports, power is not supplied to the port
If available power is less than the power required by the connected device and the switch port’s priority is greater than the priority of a currently powered port, power is removed from lower priority port(s) and power is supplied to the port
If the total consumed power exceeds the configured power limit of the power source, low priority ports are turned off. In the case of a tie, the port with the lower port number gets priority
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:
Green: The poed daemon is running and no errors are detected
Yellow: One or more errors are detected or the poed daemon is not running
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:
Enable or disable PoE for a given switch port
Set a switch port’s PoE priority to one of three values: low, high or critical
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.
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:
searching: PoE is enabled but no device has been detected.
disabled: The PoE port has been configured as disabled.
connected: A powered device is connected and receiving power.
power-denied: There is insufficient PoE power available to enable the connected device.
The Allocated column displays how much PoE power has been allocated to the port, which can be one of the following:
n/a: No device is connected or the connected device does not support LLDP negotiation.
negotiating: An LLDP-capable device is connected and is negotiating for PoE power.
XX.X W: An LLDP-capable device has negotiated for XX.X watts of power (for example, 51.0 watts for swp13 above).
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:
poectl -s, as described above.
The Cumulus Linux cl-support script, which includes PoE-related output from poed.conf, syslog, poectl --diag-info and lldpctl.
lldpcli show neighbors ports <swp> protocol lldp hidden details
tcpdump -v -v -i <swp> ether proto 0x88cc
The contents of the PoE/PoE+ /etc/lldpd.d/poed.conf configuration file, as described above.
Verify the Link Is Up
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:
A switch provides power to a powered device.
A device that was receiving power is removed.
The power available to the switch changes.
Errors are detected.
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.
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.
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 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:
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.
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:
Username: user
Password: pw
IP: 192.168.0.32
Port: 8080
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:
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.
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 admindown 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.
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.
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:
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:
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:
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
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
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${i}
## % endfor
##
Run ifupdown Scripts under /etc/network/ with ifupdown2
Unlike the traditional ifupdown system, ifupdown2 does not run scripts installed in /etc/network/*/ automatically to configure network interfaces.
To enable or disable ifupdown2 scripting, edit the addon_scripts_support line in the /etc/network/ifupdown2/ifupdown2.conf file. 1 enables scripting and 2 disables scripting. The following example enables scripting.
cumulus@switch:~$ 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:
$IFACE represents the physical name of the interface being processed; for example, br0 or vxlan42. The name is obtained from the /etc/network/interfaces file.
$LOGICAL represents the logical name (configuration name) of the interface being processed.
$METHOD represents the address method; for example, loopback, DHCP, DHCP6, manual, static, and so on.
$ADDRFAM represents the address families associated with the interface, formatted in a comma-separated list for example, "inet,inet6".
Add Descriptions to Interfaces
You can add descriptions to interfaces configured in the /etc/network/interfaces file by using the alias keyword.
The following commands create an alias for swp1:
cumulus@switch:~$ 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
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.
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
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
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:
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
```
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
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
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:
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:
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:
Reed Solomon (RS), IEEE 802.3 Clause 108 (CL108) on individual 25G channels and Clause 91 on 100G (4channels). This is the highest FEC algorithm, providing the best bit-error correction.
Base-R (BaseR), Fire Code (FC), IEEE 802.3 Clause 74 (CL74). Base-R provides less protection from bit errors than RS FEC but adds less latency.
Cumulus Linux includes additional FEC options:
Auto FEC instructs the hardware to select the best FEC. For copper DAC, FEC can be negotiated with the remote end. However, optical modules do not have auto-negotiation capability; if the device chooses a preferred mode, it might not match the remote end. This is the current default on a Spectrum switch.
No FEC (no error correction is done). This is the current default on a Broadcom switch.
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:
CA-25G-L (long cables - achievable cable length of at least 5m) dB loss less or equal to 22.48. Requires RS FEC and expects BER of 10-5 or better with RS FEC enabled.
CA-25G-S (short cables - achievable cable length of at least 3m) dB loss less or equal to 16.48. Requires Base-R FEC and expects BER of 10-8 or better with Base-R FEC enabled.
CA-25G-N (no FEC - achievable cable length of at least 3m) dB loss less or equal to 12.98. Does not require FEC. Expects BER 10-12 or better with no FEC.
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.
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:
For 25G optical modules, the Spectrum ASIC firmware chooses Base-R/FC-FEC.
For 25G DAC cables with attenuation less or equal to 16db, the firmware chooses Base-R/FC-FEC.
For 25G DAC cables with attenuation higher than 16db, the firmware chooses RS-FEC.
For 100G cables/modules, the firmware chooses RS-FEC.
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
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
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:
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
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
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.
$ 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.
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:
Break out 100G switch ports into 2x50G, 4x25G, or 4x10G with breakout cables.
Break out 40G switch ports into four separate 10G ports for use with breakout cables.
Combine (aggregate or gang) four 10G switch ports into one 40G port for use with a breakout cable (not to be confused with a bond).
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.
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.
The /etc/cumulus/ports.conf file varies across different hardware platforms.
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
...
Restart switchd with the sudo systemctl restart switchd.service command. The restart interrupts network services.
Remove a Breakout Port
To remove a breakout port:
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
Manually edit the /etc/cumulus/ports.conf file to configure the interface for the original speed. For example:
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:
You must gang four 10G ports in sequential order. For example, you cannot gang swp1, swp10, swp20 and swp40 together.
The ports must be in increments of four, with the starting port being swp1 (or swp5, swp9, or so forth); so you cannot gang swp2, swp3, swp4 and swp5 together.
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:
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:
Mellanox SN2700, SN2700B, SN2410, and SN2410B switches
Switches with Broadcom Tomahawk, Trident II, Trident II+, and Trident3 chipsets
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:
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:
If you configure, or configure then remove, the port speed in the /etc/cumulus/ports.conf file and you also set or remove the speed on the same physical port or breakouts of that port in the /etc/network/interfaces file since the last time you restarted switchd.
If you break out a switch port or remove a break out port and the port speed is set in both the /etc/cumulus/ports.conf file and the /etc/network/interfaces file.
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.
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.
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.
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.
The front SFP+ ports (swp33 and swp34) are disabled in Cumulus Linux on the following switches:
Dell Z9100-ON
Penguin Arctica 3200-series switches (the 3200C, 3200XL and 3200XLP)
Supermicro SSE-C3632S
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:
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:
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:
Cumulus Express CX-5148-S
Cumulus Express CX-8132-S
Edgecore AS7326-56X
Edgecore AS7726-32X
Mellanox SN2100 Switch and eth0 Link Speed
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
Link Speed on the EdgeCore AS7326-56X Switch
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:
1 2 3 6*
4 5 7* 9
8 10 11* 12
13 14 15 18*
16 17 19* 21
20 22 23* 24
25 26 27 30*
28 29 31* 33
32 34 35* 36
37 38 39 42*
40* 41 43 45
44* 46 47 48
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.
Link Speed on the Lenovo NE2572O Switch
The Lenovo NE2572O switch has external retimers on swp1 through swp8. Currently, these ports only support a speed of 25G.
Link Speed and Auto-negotiation on Switches with SOL
The following switches that use Serial over LAN technology (SOL) do not support eth0 speed or auto-negotiation changes:
EdgeCore AS7816-64X
Penguin Arctica 4804ip
Penguin Arctica NX3200c
Penguin Arctica NX4808xxv
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 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:
Update the switch before installing the daemon:
cumulus@switch:~$ sudo -E apt-get update
Install the ifplugd package:
cumulus@switch:~$ sudo -E apt-get install ifplugd
Configure ifplugd
After you install ifplugd, you must edit two configuration files:
/etc/default/ifplugd
/etc/ifplugd/action.d/ifupdown
The example configuration below configures ifplugd to bring down all uplinks when the peer bond goes down in an MLAG environment.
Open /etc/default/ifplugd in a text editor and configure the file as appropriate. Add the peerbond name before you save the file.
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
Restart the ifplugd daemon to implement the changes:
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:
Control: Highest priority traffic
Service: Second-highest priority traffic
Bulk: All remaining traffic
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.
For the default source packet fields and mapping, each selected packet field must have a block of mapped values. Any packet field value that is not specified in the configuration is assigned to a default internal switch priority. The configuration applies to every forwarding port unless a custom remark configuration is defined for that port (see below).
For the default remark packet fields and mapping, each selected packet field should have a block of mapped values. Any internal switch priority value that is not specified in the configuration is assigned to a default packet field value. The configuration applies to every forwarding port unless a custom remark configuration is defined for that port (see below).
Per-port source packet fields and mapping apply to the designated set of ports.
Per-port remark packet fields and mapping apply to the designated set of ports.
▼
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:
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.
You can mark traffic for egress packets through iptables or ip6tables rule classifications. To enable these rules, you do one of the following:
Mark DSCP values in egress packets.
Mark 802.1p CoS values in egress packets.
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.
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:
Specify the name of the port group in pfc.port_group_list in brackets; for example, pfc.port_group_list = [pfc_port_group].
Assign a CoS value to the port group in pfc.pfc_port_group.cos_list setting. pfc_port_group is the name of a port group you specified above and is used throughout the following settings.
Populate the port group with its member ports in pfc.pfc_port_group.port_set.
Set a PFC buffer size in pfc.pfc_port_group.port_buffer_bytes. This is the maximum number of bytes allocated for storing bursts of packets, guaranteed at the ingress port. The default is 25000 bytes.
Set the xoff byte limit in pfc.pfc_port_group.xoff_size. This is a threshold for the PFC buffer; when this limit is reached, an xoff transition is initiated, signaling the upstream port to stop sending traffic, during which time packets continue to arrive due to the latency of the communication. The default is 10000 bytes.
Set the xon delta limit in pfc.pfc_port_group.xon_delta. This is the number of bytes to subtract from the xoff limit, which results in a second threshold at which the egress port resumes sending traffic. After the xoff limit is reached and the upstream port stops sending traffic, the buffer begins to drain. When the buffer reaches 8000 bytes (assuming default xoff and xon settings), the egress port signals that it can start receiving traffic again. The default is 2000 bytes.
Enable the egress port to signal the upstream port to stop sending traffic (pfc.pfc_port_group.tx_enable). The default is true.
Enable the egress port to receive notifications and act on them (pfc.pfc_port_group.rx_enable). The default is true.
The switch priority value(s) are mapped to the specific ingress buffer for each targeted switch port. Cumulus Linux looks at either the 802.1p bits or the IP layer DSCP bits depending on which is configured in the traffic.conf file to map packets to internal switch priority values.
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:
A comma-separated list of port group names to the port_group_list.
The port_set, rx_enable, and tx_enable configuration lines for each port group.
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:
A single port (swp1s0 or swp5)
A sequence of regular swp ports (swp2-swp5)
A sequence within a breakout swp port (swp6s0-swp6s3)
A sequence of regular and breakout ports, provided they are all in a contiguous range. For example:
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.
Link Pause
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:
Transmitting pause frames when its ingress buffers become congested (TX pause enable)
Responding to received pause frames (RX pause enable).
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.
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
On switches with
ASICs, you can collect a fine-grained history of queue lengths using histograms maintained by the ASIC; see the ASIC Monitoring for details.
On Broadcom switches, the buffer status is not visible currently.
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:
Source IP address matches the destination address for IPv4 and IPv6 packets
Source MAC address matches the destination MAC address
Unfragmented or first fragment SYN packets with a source port of 0-1023
TCP packets with control flags =0 and seq number == 0
TCP packets with FIN, URG and PSH bits set and seq number == 0
TCP packets with both SYN and FIN bits set
TCP source PORT matches the destination port
UDP source PORT matches the destination port
First TCP fragment with partial TCP header
TCP header has fragment offset value of 1
ICMPv6 ping packets payload larger than programmed value of ICMP max size
ICMPv4 ping packets payload larger than programmed value of ICMP max size
Fragmented ICMP packet
IPv6 fragment lower than programmed minimum IPv6 packet size
DDOS protection is not supported on Broadcom Hurricane2 and Mellanox Spectrum ASICs.
Configure DDOS Protection
Open the /etc/cumulus/datapath/traffic.conf file in a text editor.
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
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:
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.
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:
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).
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:
The Circuit ID sub-option includes information about the circuit on which the request comes in, such as the SVI or physical port.
The Remote ID sub-option includes information that identifies the relay agent, such as the MAC address.
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.
To configure the DHCP relay to inject the ingress SVI interface against which the relayed DHCP discover packet is processed, edit /etc/default/isc-dhcp-relay file and add -a to the OPTIONS line. For example:
cumulus@switch:~$ sudo nano /etc/default/isc-dhcp-relay
...
# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-a"
To configure the DHCP relay to inject the physical switch port on which the relayed DHCP discover packet arrives instead of the SVI, edit the /etc/default/isc-dhcp-relay file and add -a --use-pif-circuit-id to the OPTIONS line. For example:
cumulus@switch:~$ sudo nano /etc/default/isc-dhcp-relay
...
# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-a --use-pif-circuit-id"
To customize the Remote ID sub-option, edit /etc/default/isc-dhcp-relay file and add -a -r to the OPTIONS line followed by a custom string (up to 255 characters that is used for the Remote ID. For example:
cumulus@switch:~$ sudo nano /etc/default/isc-dhcp-relay
...
# Additional options that are passed to the DHCP relay daemon?
OPTIONS="-a -r CUSTOMVALUE"
Make sure to restart the dhcrelay service to apply the new configuration:
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.
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"
Restart the dhcrelay service to apply the configuration change:
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"
Restart the dhcrelay service to apply the configuration change :
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:
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
Edit the /etc/default/isc-dhcp-relay file to add --giaddr-src to the OPTIONS line. An example is shown below.
NCLU commands are not currently available to configure IPv6 relays.
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.
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:
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=""
Run the following command to start a dhcrelay instance, where <dhcp-name> is the instance name or number.
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:
Pool 1 is the subnet that includes the IP addresses of the interfaces on the DHCP server
Pool 2 is the subnet that includes the IP addresses being assigned
Configure the IPv4 DHCP Server
In a text editor, edit the /etc/dhcp/dhcpd.conf file. Use following configuration as an example:
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:
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
802.1X is supported on Broadcom-based switches (except the Hurricane2 switch). The Tomahawk, Tomahawk2, and Trident3 switch must be running in nonatomic mode.
802.1X is supported on physical interfaces only, such as swp1 or swp2s0 (bridged/access only and routed interfaces).
MAB, parking VLAN, and dynamic VLAN all require a bridge access port.
In traditional bridge mode, parking VLANs and dynamic VLANs both require the destination bridge to have a parking VLAN ID or dynamic VLAN ID tagged subinterface.
When you enable or disable 802.1X on ports, hostapd reloads; however, existing authorized sessions do not reset.
Changing the 802.1X interface, MAB, or parking VLAN settings do not reset existing authorized user ports. However, removing all 802.1X interfaces or changing any of the following RADIUS parameters restarts hostapd, which forces existing, authorized users to re-authenticate:
RADIUS server IP address, shared secret, authentication port or accounting port
Parking VLAN ID
MAB activation delay
EAP reauthentication period
You can configure up to three RADIUS servers (in case of failover). However, do not use a Cumulus Linux switch as the RADIUS server.
802.1X on Cumulus Linux has been tested with only a few wpa_supplicant (Debian), Windows 10 and Windows 7 supplicants.
RADIUS authentication is supported with FreeRADIUS and Cisco ACS.
802.1X supports simple login and password, PEAP/MSCHAPv2 (Win7) and EAP-TLS (Debian).
Mako template-based configurations are not supported.
Cumulus Linux supports Multi Domain Authentication (MDA), where 802.1X is extended to allow authorization of multiple devices (a data and a voice device) on a single port and assign different VLANs to the devices based on authorization.
A maximum of four authorized devices (MAB + EAPOL) per port are supported.
The 802.1X enabled port must be a trunk port to allow tagged voice traffic from a phone; you cannot enable 802.1X on an access port.
Only one untagged VLAN and one tagged VLAN is supported on the 802.1X enabled ports.
Multiple MAB (non voice) devices on a port are supported for VLAN-aware bridges only. Authorization of multiple MAB devices for different VLANs is not supported.
Cumulus Linux does not support 802.1X with MLAG; the switch cannot synchronize 802.1X authenticated MAC addresses over the peerlink.
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:
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:
The RADIUS accounting port, which defaults to 1813.
The RADIUS Server IPv4 or IPv6 address, which has no default, but is required. You can also specify a VRF.
The RADIUS shared secret, which has no default, but is required.
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.
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
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
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
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.
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).
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.
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
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
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
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
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
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
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).
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)
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.
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)
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:
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 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:
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:
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).
The Message-Authenticator attribute is required.
If the packet comes from a different source IP address than the one defined by das-client-ip, the session is not disconnected and the hostapd logs the debug message: DAS: Drop message from unknown client.
The Event-Timestamp attribute is required. If Event-Timestamp in the packet is outside the time window, a debug message is shown in the hostapd logs: DAS: Unacceptable Event-Timestamp (1532978602; local time 1532979367) in packet from 10.10.0.21:45263 - drop
If the Acct-Session-Id attribute is omitted, the User-Nameattribute is used to find the session. If the User-Name attribute is omitted, the Acct-Session-Id attribute is used. If both the User-Name and the Acct-Session-Id attributes are supplied, they must match the username provided by the supplicant with the Acct-Session-Id provided. If neither are given or there is no match, a Disconnect-NAK message is returned to the RADIUS server with Error-Cause "Session-Context-Not-Found" and the following debug message is shown in the log:
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:
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:
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:
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:
json prints the command output in JSON format.
macs displays MAC address information.
port-details shows counters from the IEEE8021-PAE-MIB for ports.
radius-details shows counters from the RADIUS-CLIENT MIB (RFC 2618) for ports.
status displays the status of the daemon.
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
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:
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
Topology verification using LLDP. ptmd creates a client connection to the LLDP daemon, lldpd, and retrieves the neighbor relationship between the nodes/ports in the network and compares them against the prescribed topology specified in the topology.dot file.
Only physical interfaces, such as swp1 or eth0, are currently supported. Cumulus Linux does not support specifying virtual interfaces, such as bonds or subinterfaces, such as eth0.200 in the topology file.
Integration with FRRouting (PTM to FRRouting notification).
Client management: ptmd creates an abstract named socket /var/run/ptmd.socket on startup. Other applications can connect to this socket to receive notifications and send commands.
Event notifications: see Scripts below.
User configuration via a topology.dot file; see below.
Configure PTM
ptmd verifies the physical network topology against a DOT-specified network graph file, /etc/ptm.d/topology.dot.
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.
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.
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:
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:
bfdtmpl specifies a custom parameter tuple for BFD.
lldptmpl specifies a custom parameter tuple for LLDP.
match_type, which defaults to the interface name (ifname), but can accept a port description (portdescr) instead if you want lldpd to compare the topology against the port description instead of the interface name. You can set this parameter globally or at the per-port level.
match_hostname, which defaults to the host name (hostname), but enables PTM to match the topology using the fully-qualified domain name (fqdn) supplied by LLDP.
The following is an example of a topology with LLDP applied at the port level:
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:
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.
Check Link State with FRRouting
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:
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 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 is a layer 2 traffic control feature that enables you to manage network access from end-users. Use port security to:
Limit port access to specific MAC addresses so that the port does not forward ingress traffic from source addresses that are not defined.
Limit port access to only the first learned MAC address on the port (sticky MAC) so that the device with that MAC address has full bandwidth. You can provide a timeout so that the MAC address on that port no longer has access after a specified time.
Limit port access to a specific number of MAC addresses.
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:
shutdown puts a port into ADMIN down state
restrict drops packets. When packets are dropped, Cumulus Linux sends a log message.
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:~$ 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
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:
Traditional bridges operate in both PVST and PVRST mode. The default is set to PVRST. Each traditional bridge has its own separate STP instance.
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.
To enable proper BPDU exchange across the network, be sure to allow all VLANs participating in the PVST domain on the link between the RSTP and PVST domains.
When using RSTP together with an existing PVST network, you need to define the root bridge on the PVST domain. Either lower the priority on the PVST domain or change the priority of the RSTP switches to a higher number.
When connecting a VLAN-aware bridge to a proprietary PVST+ switch using STP, you must allow VLAN 1 on all 802.1Q trunks that interconnect them, regardless of the configured native VLAN. Only VLAN 1 enables the switches to address the BPDU frames to the IEEE multicast MAC address. The proprietary switch might be configured like this:
switchport trunk allowed vlan 1-100
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.
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:
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:
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:
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:
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/.
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:
The first timer catches any port-related changes.
The second is a system-based refresh timer on each port that looks for other changes like hostname. This timer uses the tx-interval value multiplied by 20.
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
-------------------------------------------------------------------------------
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:
You must restart the lldpd service for the changes to take effect.
cumulus@switch:~$ sudo systemctl restart lldpd
Caveats and Errata
Annex E (and hence Annex D) of IEEE802.1AB (lldp) is not supported.
If you configure both an eth0 IP address and a loopback IP address on the switch, LLDP advertises the loopback IP address as the management IP address. In this case, the Cumulus Linux switch behaves more like a typical Linux host than a networking appliance.
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.
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:
Native VLAN, which carries both data and voice traffic
Voice VLAN, which carries the voice traffic, and a data or native VLAN, which carries the data traffic in a trunk port.
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).
To capture LLDP information, check syslog or use tcpdump on an interface.
Considerations
A static voice VLAN configuration overwrites the existing configuration for the switch port.
Removing the bridge-vids or bridge-pvid configuration from a voice VLAN does not remove the VLAN from the bridge.
Configuring voice VLAN with NCLU does not configure lldpd in Cumulus Linux; LLDP-MED does not provide data and voice VLAN information. You can configure LLDP-MED for each interface in a new file in /etc/lldp.d. In the following example, the file is called /etc/lldpd.d/voice_vlan.conf:
You can also use the lldpcli command to configure an LLDP-MED network policy. However, lldpcli commands do not persist across switch reboots.
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:
IEEE 802.3ad link aggregation mode that allows one or more links to be aggregated together to form a link aggregation group (LAG) so that a media access control (MAC) client can treat the group as if it were a single link. IEEE 802.3ad link aggregation is the default mode.
Balance-xor mode, where the bonding of slave interfaces are static and all slave interfaces are active for load balancing and fault tolerance purposes. This is useful for MLAG deployments.
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:
For IP traffic, IP header source and destination fields are used in the calculation.
For IP + TCP/UDP traffic, source and destination ports are included in the hash calculation.
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:
Source MAC
Destination
Source IP
Destination IP
Ether type
VLAN ID
Source port
Destination port
Layer 3 protocol
To configure custom hash, edit the /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf file:
To enable custom hashing, uncomment the lag_hash_config.enable = true line.
To enable a field, set the field to true. To disable a field, set the field to false.
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.
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:
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:
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
An interface cannot belong to multiple bonds.
A bond can have subinterfaces, but subinterfaces cannot have a bond.
A bond cannot enslave VLAN subinterfaces.
Set all slave ports within a bond to the same speed/duplex and make sure they match the link partner’s slave ports.
On a Cumulus RMP switch, if you create a bond with multiple 10G member ports, traffic gets dropped when the bond uses members of the same unit listed in the /var/lib/cumulus/porttab file. For example, traffic gets dropped if both swp49 and swp52 are in the bond because they both are in xe0 (or if both swp50 and swp51 are in the same bond because they are both in xe1):
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 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.
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.
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.
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:
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:
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
...
Add the dummy interface to the bridge-ports line in the bridge configuration:
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
IPv6 Link-local Address Generation
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
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.
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
A bridge cannot contain multiple subinterfaces of the same port. Attempting this configuration results in an error.
In environments where both VLAN-aware and traditional bridges are used, if a traditional bridge has a subinterface of a bond that is a normal interface in a VLAN-aware bridge, the bridge is flapped when the traditional bridge’s bond subinterface is brought down.
You cannot enslave a VLAN raw device to a different master interface (you cannot edit the vlan-raw-device setting in the /etc/network/interfaces file). You need to delete the VLAN and recreate it.
Cumulus Linux supports up to 2000 VLANs. This includes the internal interfaces, bridge interfaces, logical interfaces, and so on.
In Cumulus Linux, MAC learning is enabled by default on traditional or VLAN-aware bridge interfaces. Do not disable MAC learning unless you are using EVPN. See Ethernet Virtual Private Network - EVPN.
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:
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:
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:
Open /etc/cumulus/switchd.conf in a text editor.
Uncomment the following line, specify a new range, and save the file:
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
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.
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.
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.
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)
Because STP is enabled on a per-bridge basis, VLAN-aware mode supports a single instance of STP across all VLANs. A common practice when using a single STP instance for all VLANs is to define every VLAN on every switch in the spanning tree instance.
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:
You can add an IP address to provide IP access to the bridge interface.
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:
host-1 and host-2 can communicate with each other
host-3 and host-4 can communicate with each other
host-1 and host-2 cannot communicate with host-3 and host-4
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 trunk port is a switch port configured to send and receive 802.1Q tagged frames.
A switch sending an untagged (bare Ethernet) frame on a trunk port is sending from the native VLAN defined on the trunk port.
A switch sending a tagged frame on a trunk port is sending to the VLAN identified by the 802.1Q tag.
A switch receiving an untagged (bare Ethernet) frame on a trunk port places that frame in the native VLAN defined on the trunk port.
A switch receiving a tagged frame on a trunk port places that frame in the VLAN identified by the 802.1Q tag.
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
...
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.
host1 connects to swp1 with both untagged frames and with 802.1Q frames tagged for vlan100.
host2 connects to swp2 with 802.1Q frames tagged for vlan120 and vlan130.
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.
host1 connects to bridge br-untagged with bare Ethernet frames and to bridge br-tag100 with 802.1q frames tagged for vlan100.
host2 connects to bridge br-tag100 with 802.1q frames tagged for vlan100 and to bridge br-vlan120 with 802.1q frames tagged for vlan120.
host3 connects to bridge br-vlan120 with 802.1q frames tagged for vlan120 and to bridge v130 with 802.1q frames tagged for vlan130.
bond2 carries tagged and untagged frames in this example.
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:
swp1 is equivalent to a trunk port with untagged and vlan100.
swp2 is equivalent to a trunk port with vlan100 and vlan120.
swp3 is equivalent to a trunk port with vlan120 and vlan130.
bond2 is equivalent to an EtherChannel in trunk mode with untagged, vlan100, vlan120, and vlan130.
Bridges br-untagged, br-tag100, br-vlan120, and v130 are equivalent to SVIs (switched virtual interfaces).
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/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:
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.
LACP and Dual-connected Links
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:
There must be a direct connection between the two peer switches configured with MLAG. This is typically a bond for increased reliability and bandwidth.
There must be only two peer switches in one MLAG configuration, but you can have multiple configurations in a network for switch-to-switch MLAG.
Both switches in the MLAG pair must be identical; they must both be the same model of switch and run the same Cumulus Linux release. See Upgrading Cumulus Linux.
The dual-connected devices (servers or switches) can use LACP (IEEE 802.3ad or 802.1ax) to form the bond. In this case, the peer switches must also use LACP.
Cumulus Linux does not support MLAG with 802.1X; the switch cannot synchronize 802.1X authenticated MAC addresses over the peerlink.
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:
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.
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
...
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
...
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:
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).
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:
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:
Port configuration, such as VLAN membership, MTU and bonding parameters.
Bridge configuration, such as spanning tree parameters or bridge properties.
Static address entries, such as static FDB entries and static IGMP entries.
QoS configuration, such as ACL entries.
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.
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:
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:
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 STP global configuration must be the same on both peer switches.
The STP configuration for dual-connected ports must be the same on both peer switches.
The STP priority must be the same on both peer switches.
To minimize convergence times when a link transitions to the forwarding state, configure the edge ports (for tagged and untagged frames) with PortAdminEdge and BPDU guard enabled.
Do not use a multicast MAC address for the LACP ID on systems connected to MLAG bonds; the switch drops STP BPDUs from a multicast MAC address.
Peer Link Sizing
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:
You have a hardware limitation on the host where there is only one PCIE slot, and therefore, one NIC on the system, so the host is only single-connected across that interface.
The host does not support 802.3ad and you cannot create a bond on it.
You are accounting for a link failure, where the host becomes single connected until the failure is resolved.
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.
Peer Link Routing
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 must physically attach to a single interface of a switch.
The attached router must peer directly to a local address on the physically connected switch.
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:
leaf01 and leaf02 are MLAG peers
Three bonds are configured for MLAG, each with a single port, a peer link that is a bond with two member ports, and three VLANs on each port
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:
leaf01 and leaf02 are MLAG peers, and leaf03 and leaf04 are are MLAG peers
Three bonds are configured for MLAG, each with a single port, a peer link that is a bond with two member ports, and three VLANs on each port
BGP unnumbered is configured on the leafs and spines with a routed adjacency across the peerlink.4094 interface
/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
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
...
Large Packet Drops on the Peer Link Interface
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.
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.
Peer Link Interfaces and the protodown State
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 the peer link goes down but the peer switch is up (the backup link is active).
When the bond is configured with an MLAG ID but the clagd service is not running (either deliberately stopped or crashes).
When an MLAG-enabled node is booted or rebooted, the MLAG bonds are placed in a protodown state until the node establishes a connection to its peer switch, or five minutes have elapsed.
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
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:
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 Linux provides the option of using Virtual Router Redundancy (VRR) or Virtual Router Redundancy Protocol (VRRP).
VRR enables hosts to communicate with any redundant router without reconfiguration, by running dynamic router protocols or router redundancy protocols. Redundant routers respond to Address Resolution Protocol (ARP) requests from hosts. Routers are configured to respond in an identical manner, but if one fails, the other redundant routers continue to respond, leaving the hosts with the impression that nothing has changed. VRR is typically used in an MLAG configuration.
Use VRR when you have multiple devices connected to a single logical connection, such as an MLAG bond. A device connected to an MLAG bond believes there is a single device on the other end of the bond and only forwards one copy of the transit frames. If this frame is destined to the virtual MAC address and you are running VRRP, it is possible that the frame is sent to the link connected to the VRRP standby device, which will not forward the frame appropriately. By having the virtual MAC active on both MLAG devices, it ensures either MLAG device handles the frame it receives correctly.
VRRP allows a single virtual default gateway to be shared between two or more network devices in an active/standby configuration. The physical 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. VRRP is used in a non-MLAG configuration.
Use VRRP when you have multiple distinct devices that connect to a layer 2 segment through multiple logical connections (not through a single bond). VRRP elects a single active forwarder that owns the virtual MAC address while it is active. This prevents the forwarding database of the layer 2 domain from continuously updating in response to MAC flaps as frames sourced from the virtual MAC address are received from discrete logical connections.
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).
As the bridges in each of the redundant routers are connected, they each receive and reply to ARP requests for the virtual router IP address.
Each ARP request made by a host receives replies from each switch; these replies are identical, and the host receiving the replies either ignores replies after the first, or accepts them and overwrites the previous identical reply.
A range of MAC addresses is reserved for use with VRR to prevent MAC address conflicts with other interfaces in the same bridged network. The reserved range is 00:00:5E:00:01:00 to 00:00:5E:00:01:ff.
Use MAC addresses from the reserved range when configuring VRR. The reserved MAC address range for VRR is the same as for the Virtual Router Redundancy Protocol (VRRP).
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:
One bond interface or switch port interface to each host. For networks using MLAG, use bond interfaces. Otherwise, use switch port interfaces.
One or more interfaces to each peer router. To accommodate higher bandwidth between the routers and to offer link redundancy, multiple inter-peer links are typically bonded interfaces. The VLAN interface must have unique IP addresses for both the physical (the address option below) and virtual (the address-virtual option below) interfaces; the unique address is used when the switch initiates an ARP request.
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:
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.
The following example illustrates a basic VRRP configuration.
Configure VRRP
To configure VRRP, specify the following information on each switch:
A virtual router ID (VRID) that identifies the group of VRRP routers. You must specify the same ID across all virtual routers in the group.
One or more virtual IP addresses that are assigned to the virtual router group. These are IP addresses that do not directly connect to a specific interface. Inbound packets sent to a virtual IP address are redirected to a physical network interface.
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
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
Enable the vrrpd daemon, then start the FRRouting service with the sudo systemctl start frr.service command.
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
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, 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:
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).
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
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:
VNI membership exchange between VTEPs using EVPN type-3 (Inclusive multicast Ethernet tag) routes.
Host MAC and IP address exchange using EVPN type-2 (MAC/IP advertisement) routes.
Host/VM mobility support (MAC and IP moves) through exchange of the MAC Mobility Extended community.
Dual-attached hosts via VXLAN active-active mode. MAC synchronization between the peer switches is done using MLAG.
ARP/ND suppression, which enables VTEPs to suppress ARP flooding over VXLAN tunnels is enabled by default on VNIs in Cumulus Linux.
Inter-subnet routing for both IPv4 and IPv6 hosts: Distributed symmetric routing between different subnets, distributed asymmetric routing between different subnets, and centralized routing.
ECMP for overlay networks on RIOT-capable Broadcom ASICs (Trident 3, Maverick, Trident 2+) in addition to Tomahawk and Mellanox Spectrum-A1 ASICs. No configuration is needed, ECMP occurs in the overlay when there are multiple next hops.
Head end replication is enabled by default in Cumulus Linux on Broadcom Tomahawk, Maverick, Trident3, Trident II+, and Trident II ASICs and switches with Mellanox Spectrum ASICs. Cumulus Linux supports up to 128 VTEPs with head end replication.
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
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.
Advertise All VNIs
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
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:
The clagd-vxlan-anycast-ip and vxlan-local-tunnelip parameters are under the loopback stanza on both peers.
The anycast address is advertised to the routed fabric from both peers.
The VNIs are configured identically on both peers.
The peerlink must belong to the bridge.
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
When EVPN is enabled on a VTEP, all locally defined VNIs on that switch and other information (such as MAC addresses) are advertised to EVPN peers. There is no provision to only announce certain VNIs.
On switches with Spectrum ASICs, ND suppression only works with the Spectrum-A1 chip.
ARP suppression is enabled by default in Cumulus Linux. However, in a VXLAN active-active configuration, ARPs are sometimes not suppressed. This is because the neighbor entries are not synchronized between the two switches operating in active-active mode by a control plane. This has no impact on forwarding.
You must configure the overlay (tenants) in a specific VRF and separate from the underlay, which resides in the default VRF. Layer 3 VNI mapping for the default VRF is not supported.
In an EVPN deployment, Cumulus Linux supports a single BGP ASN which represents the ASN of the core as well as the ASN for any tenant VRFs if they have BGP peerings. If you need to change the ASN, you must first remove the layer 3 VNI in the /etc/frr/frr.conf file, modify the BGP ASN, then add back the layer 3 VNI in the /etc/frr/frr.conf file.
EVPN is not supported when Redistribute Neighbor is also configured. Enabling both features simultaneously causes instability in IPv4 and IPv6 neighbor entries.
Cumulus Linux implements a stricter check on a received type-3 route to ensure that it has the PMSI attribute with the replication type set to ingress-replication in order to conform to RFC 6514.
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
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
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
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.
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:
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
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
You can only match type-2 and type-5 routes based on VNI.
Advertise SVI IP Addresses
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.
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:
Two hosts have the same MAC address (the host IP addresses might be the same or different)
Two hosts have the same IP address but different MAC addresses
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
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:
If the MAC or IP address is learned from a remote VTEP at the time it is frozen, the forwarding information in the kernel and hardware is not updated, leaving it in the prior state. Any future remote updates are processed but they are not reflected in the kernel entry. If the remote VTEP sends a MAC-IP route withdrawal, the local VTEP removes the frozen remote entry. Then, if the local VTEP has a locally-learned entry already present in its kernel, FRR will originate a corresponding MAC-IP route and advertise it to all remote VTEPs.
If the MAC or IP address is locally learned on this VTEP at the time it is frozen, the address is not advertised to remote VTEPs. Future local updates are processed but are not advertised to remote VTEPs. If FRR receives a local entry delete event, the frozen entry is removed from the FRR database. Any remote updates (from other VTEPs) change the state of the entry to remote but the entry is not installed in the kernel (until cleared).
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
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
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
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:
Centralized routing: Specific VTEPs act as designated layer 3 gateways and perform routing between subnets; other VTEPs just perform bridging.
Distributed asymmetric routing: Every VTEP participates in routing, but all routing is done at the ingress VTEP; the egress VTEP only performs bridging.
Distributed symmetric routing: Every VTEP participates in routing and routing is done at both the ingress VTEP and the egress VTEP.
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
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:
Configure a per-tenant VXLAN interface that specifies the layer 3 VNI for the tenant. This VXLAN interface is part of the bridge and the router MAC address of the remote VTEP is installed over this interface.
Configure an SVI (layer 3 interface) corresponding to the per-tenant VXLAN interface. This is attached to the VRF of the tenant. Remote host routes for symmetric routing are installed over this SVI.
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
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
The tenant VRF RD and RTs are different from the RD and RTs for the layer 2 VNI. See Define RDs and RTs.
Advertise Locally-attached Subnets
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.
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:
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.
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.
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
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.
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 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:
Advertise Primary IP address (VXLAN Active-Active Mode)
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).
For host type-2 routes, the anycast IP address is used as the next hop IP address and the anycast MAC address is used as the router MAC address.
For type-5 routes, the system IP address (the primary IP address of the VTEP) is used as the next hop IP address and the system MAC address of the VTEP is used as the router MAC 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:
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
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:
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:
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:
You cannot use ping between SVI IP addresses to verify connectivity between VTEPs because either the local rack itself uses the ping destination IP address or many remote racks use the ping destination IP address.
If you use ping from a host to the SVI IP address, the local VTEP (gateway) might not reply if the host has an ARP entry from a remote gateway.
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:
Enable PIM-SM on the appropriate layer 3 interfaces.
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:
PIM is enabled on swp1, swp2, and the loopback interface (shown in the example /etc/frr/frr.conf file below).
The group mapping 192.168.0.1 is configured for a static RP (shown at the top of the /etc/frr/frr.conf file example below).
Multicast group 239.1.1.111 is mapped to VXLAN1000111. Multicast group 239.1.1.112 is mapped to VXLAN1000112 (shown in the example /etc/network/interfaces file below).
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.
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:
Layer 2 EVPN with external routing
EVPN centralized routing
EVPN symmetric routing
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.
MLAG is configured between leaf01 and leaf02, and leaf03 and leaf04
BGP unnumbered is in the underlay (configured on all leafs and spines)
Server gateways are outside the VXLAN fabric
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.
server01 makes a LACP hash decision and forwards traffic to leaf01.
leaf01 does a layer 2 lookup, has the MAC address for server04, and forwards the packet out VNI10, towards leaf04.
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
The following example shows an EVPN centralized routing configuration:
MLAG is configured between leaf01 and leaf02, leaf03 and leaf04, and border01 and border02
BGP unnumbered is in the underlay (configured on all leafs and spines)
SVIs are configured as gateways on the border leafs
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.
server01 makes a LACP hash decision and forwards traffic to leaf01.
leaf01 does a layer 2 lookup and forwards traffic to server01’s default gateway (border01) out VNI10.
border01 does a layer 3 lookup and routes the packet out VNI20 towards leaf04.
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
The following example shows an EVPN symmetric routing configuration, where:
MLAG is configured between leaf01 and leaf02, leaf03 and leaf04, and border01 and border02
BGP unnumbered is in the underlay (configured on all leafs and spines)
VRF BLUE and VRF RED are configured on the leafs for traffic flow between tenants for traffic isolation
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.
server01 makes a LACP hash decision and forwards traffic to leaf01.
leaf01 does a layer 2 lookup and has the MAC address for server04, it then forwards the packet out VNI10, through leaf04.
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.
server01 makes an LACP hash decision to reach the default gateway and forwards traffic to leaf01.
leaf01 does a layer 3 lookup in VRF RED and has a route out VNIRED through leaf04.
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.
server01 makes an LACP hash decision to reach the default gateway and forwards traffic to leaf01.
leaf01 does a layer 3 lookup in VRF RED and has a route out VNIRED through border01.
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).
fw01 does a layer 3 lookup (without any VRFs) and has a route in VLAN40, through border02.
border02 does a layer 3 lookup in VRF BLUE and has a route out VNIBLUE, through leaf04.
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
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:
ip [-d] link show
bridge link show
bridge vlan show
bridge [-s] fdb show
ip neighbor show
ip route show [table <vrf-name>]
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:
swp3 and swp4 are access ports with VLAN ID 100. This is mapped to VXLAN interface vni100.
00:02:00:00:00:01 is a local host MAC learned on swp3.
The remote VTEPs that participate in VLAN ID 100 are 10.0.0.3, 10.0.0.4, and 10.0.0.2 (the FDB entries have a MAC address of 00:00:00:00:00:00). These entries are used for BUM traffic replication.
00:02:00:00:00:06 is a remote host MAC reachable over the VXLAN tunnel to 10.0.0.2.
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:
172.16.120.11 is a locally-attached host on VLAN 100. It is shown twice because of the configuration of the anycast IP/MAC on the switch.
172.16.120.42 is a remote host on VLAN 100 and 172.16.130.23 is a remote host on VLAN 200. You can examine the MAC address for these hosts with the bridge fdb show command to determine the VTEPs behind which these hosts are located.
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:
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 vniall command or the vtysh show evpn next-hops vniall 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:
A centralized VXLAN routing configuration with a gateway router.
A layer 2 switch deployment with ARP/ND suppression.
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.
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:
When the switches boot up, ifupdown2 places all VXLAN interfaces in a PROTO_DOWN state. The configured anycast addresses are not configured yet.
MLAG peering takes place and a successful VXLAN interface consistency check between the switches occurs.
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:
The anycast virtual IP address for VXLAN termination must be the same on each pair of switches.
A VXLAN interface with the same VXLAN ID must be configured and administratively up on both switches.
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.
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.
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
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:
Broadcom Trident II+, Trident3, and Maverick
Broadcom Tomahawk and Tomahawk+, using an internal loopback on one or more switch ports
Mellanox Spectrum
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.
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:
default: 15% of the underlay next hops are set apart for overlay (8k next hops are reserved)
mode-1: 25% of the underlay next hops are set apart for overlay
mode-2: 50% of the underlay next hops are set apart for overlay
mode-3: 80% of the underlay next hops are set apart for overlay
disable: disables VXLAN routing
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:
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:
Layer 2 protocol tunneling is not a full-featured pseudo-wire solution; there is no end-to-end link status tracking or feedback.
Layer 2 protocols typically run on a link local scope. Running the protocols through a tunnel across a layer 3 fabric incurs significantly higher latency, which might require you to tune protocol timers.
The lack of end to end link/tunnel status feedback and the higher protocol timeout values make for a higher protocol convergence time in case of change.
If the remote endpoint is a Cisco endpoint using LACP, you must configure etherchannel misconfig guard on the Cisco device.
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:
The VXLAN has a network identifier (VNI). Do not use VNI ID 0 or 16777215; these are reserved values under Cumulus Linux.
Bridge learning must be enabled on the VNI (bridge learning is disabled by default).
The VXLAN link and local interfaces are added to the bridge to create the association between the port, VLAN, and VXLAN instance.
Each traditional bridge on the switch has only one VXLAN interface. Cumulus Linux does not support more than one VXLAN ID per traditional bridge.
This limitation only affects a traditional bridge configuration. Cumulus Linux supports more than one VXLAN ID per VLAN-aware bridge.
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:
Specify an IP address for the loopback.
Create a VXLAN interface using the loopback address for the local tunnel IP address.
Enable bridge learning on the VNI.
Create the tunnels by configuring the remote IP address to each other leaf switch’s loopback address.
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:
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:
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:
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 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:
Single tag translation, where you map a customer to a VNI and preserve the service as an inner VLAN inside a VXLAN packet.
Double tag translation, where you map a customer and service to a VNI.
QinQ is available on switches with the following ASICs:
Broadcom Tomahawk 2, Tomahawk+, Tomahawk, Trident3, Trident II+ and Trident II.
Mellanox Spectrum 1 and Spectrum 2, only with VLAN-aware bridges with 802.1ad and only with single tag translation.
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.
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:
Configure the bridge with vlan_protocol set to 802.1ad.
The VNI maps back to S-tag (customer).
A trunk port connected to the public cloud is the QinQ trunk and packets are double tagged, where the S-tag is for the customer and the C-tag is for the service.
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:
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
iptables match on double-tagged interfaces is not supported.
MLAG is only supported with single-tagged translation.
Mixing 802.1Q and 802.1ad subinterfaces on the same switch port is not supported.
When configuring bridges in traditional mode, all VLANs that are members of the same switch port must use the same vlan_protocol.
When using switches with Mellanox Spectrum ASICs in an MLAG pair:
Configure the peerlink (peerlink.4094) between the MLAG pair for VLAN protocol 802.1ad.
You cannot use the peerlink as a backup datapath in case one of the MLAG peers loses all uplinks.
For switches with any type of Spectrum ASIC, when the bridge VLAN protocol is 802.1ad and is VXLAN-enabled, either:
All bridge ports are access ports, except for the MLAG peerlink.
All bridge ports are VLAN trunks. This means the switch terminating the cloud provider connections (double-tagged) cannot have local clients; these clients must be on a separate switch.
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:
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
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
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
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
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
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:
Layer 3 IPv4 LPM (longest prefix match) entries that have a mask less than /32
Layer 3 IPv6 LPM entries that have a mask of /64 or less
Layer 3 IPv6 LPM entries that have a mask greater than /64
Layer 3 IPv4 neighbor (or host) entries that are the next hops seen in ip neighbor
Layer 3 IPv6 neighbor entries that are the next hops seen in ip -6 neighbor
ECMP next hops, which are IP address entries in a router’s routing table that specify the next closest/most optimal router in its routing path
MAC addresses
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, l2-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.
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.
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:
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:
Add a delay to the eth0 interface:
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
Exclude the src parameter to the ip route add that causes the need for the delay. If the src parameter is removed, the route is added correctly.
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:
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:
Who am I (my identity)
Where to disseminate information
What to disseminate
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:
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.”
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:
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.
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.
Confirm that service integrated-vtysh-config is enabled:
cumulus@switch:~$ net show configuration | grep integrated
service integrated-vtysh-config
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.
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:
? 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
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:
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:
The current running configuration (run net show configuration and output the contents to a file)
The contents of /etc/frr/frr.conf
The contents of /var/log/frr/frr-reload.log
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.
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:
arp_accept
arp_announce
arp_filter
arp_ignore
arp_notify
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:
/proc/sys/net/ipv4/conf/all/arp* (all interfaces)
/proc/sys/net/ipv4/conf/default/arp* (default for future interfaces)
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:
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.
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:
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:
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:
Create a new file called /etc/cumulus/neighmgr.conf and add the setsrcipv4 <ipaddress> option; for example:
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).
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.
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:
Which router has the router ID
With which device the router communicates
What information to advertise (the prefix reachability)
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:
Set the router ID to 0.0.0.1
Put all the interfaces on the router whose IP address matches subnet 10.0.0/16 into area 0.0.0.0.
Put all interfaces on the router whose IP address matches subnet 192.0.2.0/16 into area 0.0.0.1.
Set swp10 and swp11 as passive interfaces.
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 ospfnetwork 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 ospfpassive-interface default command to set all interfaces as passive and the net del ospfpassive-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
Enable the ospf daemon, then start the FRRouting service. See Configuring FRRouting.
Instead of configuring the IP subnet prefix and area address per network with the router ospfnetwork 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:
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
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:
0 milliseconds from the initial event until SPF runs
50 milliseconds between consecutive SPF runs (the number doubles with each SPF, until it reaches the value of C)
5000 milliseconds maximum between SPFs
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
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
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
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:
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:
Restarting FRR restarts all the routing protocol daemons that are enabled and running.
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:
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
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
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
...
Run the ifreload -a command to load the new configuration:
cumulus@switch:~$ ifreload -a
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:
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.
Cumulus Linux provides the following troubleshooting commands for OSPF:
To show neighbor states, run the NCLU net show ospf neighbor command or the vtysh show ip ospf neighbor command.
To verify that the LSDB is synchronized across all routers in the network, run the NCLU net show ospf database command or the vtysh show ip ospf database command.
To determine why an OSPF route is not being forwarded correctly, run the NCLU net show route ospf command or the vtysh show ip route ospf command. These commands show the outcome of the SPF computation downloaded to the forwarding table.
To capture OSPF packets, run the Linux sudo tcpdump -v -i swp1 ip proto ospf command.
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.
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
Enable the ospf6 daemon, then start the FRRouting service. See Configuring FRRouting.
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
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:
Limit an OSPFv3 area from reaching another area.
Manage the size of the routing table by creating a summary route for all the routes in a particular address range.
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.
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:
To show neighbor states, run the NCLU net show ospf6 neighbor command or the vtysh show ip ospf6 neighbor command.
To verify that the LSDB is synchronized across all routers in the network, run the NCLU net show ospf6 database command or the vtysh show ip ospf6 database command.
To determine why an OSPF route is not being forwarded correctly, run the NCLU net show route ospf6 command or the vtysh show ip route ospf6 command. These commands show the outcome of the SPF computation downloaded to the forwarding table.
To help visualize the network view, run the NCLU net show ospf6 spf tree command or the show ip ospf6 spf tree command. These commands show the node topology as computed by SPF.
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.
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:
Highest Weight: Weight is a value from 0 to 65535. Weight is not carried in a BGP update but is used locally to influence the best path selection. Locally generated routes have a weight of 32768.
Highest Local Preference: Local preference is exchanged between iBGP neighbors only. Routes received from eBGP peers are assigned a local preference of 0. Whereas weight is used to make route selections without sending additional information to peers, local preference can be used to influence routing to iBGP peers.
Locally Originated Routes: Any route that the local switch is responsible for placing into BGP is selected as best. This includes static routes, aggregate routes and redistributed routes.
Shortest AS Path: The path received with the fewest number of ASN hops is selected.
Origin Check: Preference is given to routes with an IGP origin (routes placed into BGP with a network statement) over incomplete origins (routes places into BGP through redistribution). The EGP origin attribute is no longer used.
Lowest MED: The Multi-Exit Discriminator or MED is sent to eBGP peers to indicate a preference on how traffic enters an AS. A MED received from an eBGP peer is exchanged with iBGP peers but is reset to a value of 0 before advertising a prefix to another AS.
eBGP Routes: A route received from an eBGP peer is preferred over a route learned from an iBGP peer.
Lowest IGP Cost to the Next Hop: The route with the lowest IGP metric to reach the BGP next hop.
iBGP ECMP over eBGP ECMP: If BGP multipath is configured, prefer equal iBGP routes over equal eBGP routes, unless as-path multipath-relax is also configured.
Oldest Route: Preference is given to the oldest route in the BGP table.
Lowest Router ID: Preference is given to the route received from the peer with the lowest Router ID attribute. If the route is received from a route reflector, the ORIGINATOR_ID attribute is used for comparison.
Shortest Route Reflector Cluster List: If a route passes through multiple route reflectors, prefer the route with the shortest route reflector cluster list.
Highest Peer IP Address: Preference is given to the route received from the peer with the highest IP address.
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.
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:
Assign an ASN to identify this BGP node. In a two-tier leaf and spine configuration, you can use auto BGP, where Cumulus Linux assigns an ASN automatically.
Assign a router ID, which is a 32-bit value and is typically the address of the loopback interface on the switch.
Specify where to distribute routing information by providing the IP address and ASN of the neighbor.
For BGP numbered, this is the IP address of the interface between the two peers; the interface must be a layer 3 access port.
The ASN can be a number, or internal for a neighbor in the same AS or external for a neighbor in a different AS.
Specify which prefixes to originate from this BGP node.
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.
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.
Assign the router ID.
cumulus@leaf01:~$ net add bgp router-id 10.10.10.1
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
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
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.
Assign the router ID.
cumulus@spine01:~$ net add bgp router-id 10.10.10.101
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 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.
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.
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
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.
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.
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
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.
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
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
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
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
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.
Advertise IPv4 Prefixes with IPv6 Next Hops
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
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
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:
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:
addpath-tx-all-paths advertises all known paths to a neighbor
addpath-tx-bestpath-per-AS advertises only the best path learned from each AS to a neighbor
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
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
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
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
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
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
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:
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:
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
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:
All the configured peers (except the shutdown peers) have sent an explicit EOR (End-Of-RIB) or an implicit EOR. The first keep-alive after BGP reaches the established state is considered an implicit EOR. If you specify the establish-wait option, BGP only considers peers that have reached the established state from the moment the max-delay timer starts until the establish-wait period ends. The minimum set of established peers for which EOR is expected are the peers that are established during the establish-wait window, not necessarily all the configured neighbors.
The timer reaches the configured max-delay.
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
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:
Filter routes from BGP into Zebra
Filter routes from Zebra into the Linux kernel
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
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:
internet: a BGP community that matches all routes
local-AS: a BGP community that restricts routes to your confederation’s sub-AS
no-advertise: a BGP community that is not advertised to anyone
no-export: a BGP community that is not advertised to the eBGP peer
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
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
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:
Is identified with a unique map name and sequence number. The sequence number is used to determine the relative order of the map within the policy.
Contains a match source IP rule or a match destination IP rule, and a set rule.
To match on a source and destination address, a policy map can contain both match source and match destination IP rules.
A set rule determines the PBR next hop for the policy. The set rule can contain a single next hop IP address or it can contain a next hop group. A next hop group has more than one next hop IP address so that you can use multiple interfaces to forward traffic. To use ECMP, you configure a next hop group.
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.
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
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
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.
Enable the pbrd service in the /etc/frr/daemons file:
Restarting FRR restarts all the routing protocol daemons that are enabled and running.
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.
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.
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
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.
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.
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.
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:
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:
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.
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:
To avoid spoofing with multihop paths, configure the maximum hop count (max_hop_cnt) for each peer, which limits the number of hops for a BFD session. All BFD packets exceeding the maximum hop count are dropped.
Because multihop BFD sessions can take arbitrary paths, demultiplex the initial BFD packet based on the source/destination IP address pair. Use FRRouting, which monitors connectivity to the peer, to determine the source/destination IP address pairs.
Cumulus Linux supports multihop BFD sessions for both IPv4 and IPv6 peers.
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:
The topology file supports BFD IPv4 and IPv6 single hop sessions only; you cannot specify IPv4 or IPv6 multihop sessions in the topology file.
The topology file supports BFD sessions for only link-local IPv6 peers; BFD sessions for global IPv6 peers discovered on the link are not created.
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.
The required minimum interval between the received BFD control packets. The default value is 300ms.
The minimum interval for transmitting BFD control packets. The default value is 300ms.
The detection time multiplier. The default value is 3.
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:
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.
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.
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.
To show IPv6 OSPF interface information, run the NCLU net show ospf6 interface <interface> command or the vtysh show ip ospf6 interface <interface> command.
To show IPv4 OSPF interface information, run the NCLU net show ospf interface <interface> command or the vtysh show ip ospf interface <interface> command.
The following example shows IPv6 OSPF interface information.
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
To show IPv6 OSPF neighbor details, run the NCLU net show ospf6 neighbor detail command or the vtysh show ip ospf6 neighbor detail command.
To show IPv4 OSPF interface information, run the NCLU net show ospf neighbor detail command or the vtysh show ip ospf neighbor detail command.
The following example shows IPv6 OSPF neighbor details.
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:
Version is the version of the BFD echo packet.
Length is the length of the BFD echo packet.
My Discriminator is a non-zero value that uniquely identifies a BFD session on the transmitting side. When the originating node receives the packet after being looped back by the receiving system, this value uniquely identifies the BFD session.
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:
echoSupport enables and disables echo mode. Set to 1 to enable the echo function. It defaults to 0 (disable).
echoMinRx is the minimum interval between echo packets the local system is capable of receiving. This is advertised in the BFD control packet. When the echo function is enabled, it defaults to 50. If you disable the echo function, this parameter is automatically set to 0, which indicates the port or the node cannot process or receive echo packets.
slowMinTx is the minimum interval between transmitting BFD control packets when the echo packets are being exchanged.
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
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:
Originate from the same routing protocol. Routes from different sources are not considered equal. For example, a static route and an OSPF route are not considered for ECMP load sharing.
Have equal cost. If two routes from the same protocol are unequal, only the best route is installed in the routing table.
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:
IP protocol
Ingress interface
Source IPv4 or IPv6 address
Destination IPv4 or IPv6 address
Further, on switches with Spectrum ASICs, Cumulus Linux hashes on these additional fields:
Source MAC address
Destination MAC address
Ethertype
VLAN ID
For TCP/UDP frames, Cumulus Linux also hashes on:
Source port
Destination port
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.
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
...
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:
IP Protocol
Source IP
Destination IP
Source port
Destination port
IPv6 flow label
Ingress interface
You can also enable/disable these Inner header fields:
Inner IP protocol
Inner source IP
Inner destination IP
Inner source port
Inner destination port
Inner IPv6 flow label
To configure custom hashing, edit the /usr/lib/python2.7/dist-packages/cumulus/__chip_config/mlx/datapath.conf file:
To enable custom hashing, uncomment the hash_config.enable = true line.
To enable a field, set the field to true. To disable a field, set the field to false.
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 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:
When a next hop is removed, the assigned buckets are distributed to the remaining next hops.
When a next hop is added, some buckets assigned to other next hops are migrated to the new next hop.
The algorithm assigns buckets to next hops so as to make the number of buckets per next hop as close to equal as possible.
The assignment of buckets to next hops is not changed in any other case. In particular, this assignment is not changed due to traffic loading or imbalance.
Next hops are assigned to buckets randomly, to minimize the chance of systemic imbalance.
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.
resilient_hash_active_timer: A timer that protects TCP sessions from being
disrupted while attempting to populate new next hops. You specify the number of
seconds when at least one hash bucket consistently sees no traffic before
Cumulus Linux rebalances the flows; the default is 120 seconds. If any
one bucket is idle; that is, it sees no traffic for the defined period, the next
new flow utilizes that bucket and flows to the new link. Thus, if the network is
experiencing a large number of flows or very consistent or persistent flows, there
may not be any buckets remaining idle for a consistent 120 second period, and the
imbalance remains until that timer has been met. If a new link is brought up and
added back to a group during this time, traffic does not get allocated to utilize
it until a bucket qualifies as empty, meaning it has been idle for 120 seconds.
This is when a rebalance can occur.
resilient_hash_max_unbalanced_timer: You can force a rebalance every N seconds
with this option. However, while this could correct the persistent imbalance that
is expected with resilient hashing, this rebalance would result in the movement of
all flows and thus a break in any TCP sessions that are active at that time.
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.
When a next hop is removed, the assigned buckets are distributed to the remaining next hops.
When a next hop is added, no buckets are assigned to the new next hop until the background thread rebalances the load.
The load gets rebalanced when the active flow timer specified by the resilient_hash_active_timer setting expires if, and only if, there are inactive hash buckets available; the new next hop may remain unpopulated until the period set in resilient_hash_active_timer expires
When the resilient_hash_max_unbalanced_timer setting expires and the load is not balanced, the thread migrates any bucket(s) to different 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:
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:
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"
...
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.
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:
Virtualized clusters
Hosts with service IP addresses that migrate between racks
Hosts that are dual connected to two leaf nodes without using proprietary protocols such as MLAG
Anycast services that need dynamic advertisement from multiple hosts
Follow these guidelines:
You can connect a host to one or more leafs. Each leaf advertises the /32 it sees in its neighbor table.
Make sure that a host-bound bridge/VLAN is local to each switch.
Connect leaf switches with redistribute neighbor enabled directly to the hosts.
Make sure that IP addressing is non-overlapping, as the host IP addresses are directly advertised into the routed fabric.
Run redistribute neighbor on Linux-based hosts. NVIDIA has not actively tested other host operating systems.
How It Works
Redistribute neighbor works as follows:
The leaf/ToR switches learn about connected hosts when the host sends an ARP request or ARP reply.
An entry for the host is added to the kernel neighbor table of each leaf switch.
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.
FRRouting is configured to import routes from kernel table 10.
A route-map controls which routes from table 10 are imported.
In FRRouting these routes are imported as table routes.
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.
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
Enable the daemon so it starts at bootup, then start the daemon:
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
Import routing table 10 and apply the route-map:
cumulus@leaf01:~$ net add routing import-table 10 route-map REDIST_NEIGHBOR
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
Save the configuration by committing your changes.
cumulus@leaf01:~$ net pending
cumulus@leaf01:~$ net commit
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
...
Enable the daemon so it starts at bootup, then start the daemon:
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:
The loopback IP is assigned to lo, eth1 and eth2.
The post-up ARPing is used to force the host to ARP as soon as its interface comes up. This allows the leaf to learn about the host as soon as possible.
The post-up ip route replace is used to install a default route via one or both leaf nodes if both swp1 and swp2 are up.
▼
Click to expand
```
# The loopback network interface
auto lo
iface lo inet loopback
auto lo:1
iface lo:1
address 10.1.0.101/32
auto eth1
iface eth1
address 10.1.0.101/32
post-up for i in {1..3}; do arping -q -c 1 -w 0 -i eth1 10.0.0.11; sleep 1; done
post-up ip route add 0.0.0.0/0 nexthop via 10.0.0.11 dev eth1 onlink nexthop via 10.0.0.12 dev eth2 onlink || true
auto eth2
iface eth2
address 10.1.0.101/32
post-up for i in {1..3}; do arping -q -c 1 -w 0 -i eth2 10.0.0.12; sleep 1; done
post-up ip route add 0.0.0.0/0 nexthop via 10.0.0.11 dev eth1 onlink nexthop via 10.0.0.12 dev eth2 onlink || true
...
```
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.
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
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:
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.
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.
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 virtualrouting 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:
The VRF is presented as a layer 3 master network device with its own associated routing table.
You can associate any layer 3 interface with a VRF, such as an SVI, swp port or bond, or a VLAN subinterface of a swp port or bond.
The layer 3 interfaces (VLAN interfaces, bonds, switch virtual interfaces/SVIs) associated with the VRF are enslaved to that VRF; IP rules direct FIB (forwarding information base) lookups to the routing table for the VRF device.
The VRF device can have its own IP address, known as a VRF-local loopback.
Applications can use existing interfaces to operate in a VRF context by binding sockets to the VRF device or passing the ifindex using cmsg. By default, applications on the switch run against the default VRF. Services started by systemd run in the default VRF unless the VRF instance is used. When management VRF is enabled, logins to the switch default to the management VRF. This is a convenience so that you do not have to specify management VRF for each command. Management VRF is enabled by default in Cumulus Linux.
Listen sockets used by services are VRF-global by default unless the application is configured to use a more limited scope (see services in the management VRF). Connected sockets (like TCP) are then bound to the VRF domain in which the connection originates. 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. This sysctl is enabled for Cumulus Linux.
Connected and local routes are placed in appropriate VRF tables.
Neighbor entries continue to be per-interface, and you can view all entries associated with the VRF device.
A VRF does not map to its own network namespace; however, you can nest VRFs in a network namespace.
You can use existing Linux tools, such as tcpdump, to interact with a VRF.
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:
A VRF table can have an IP address, which is a loopback interface for the VRF.
Associated rules are added automatically.
You can also add a default route to avoid skipping across tables when the kernel forwards the packet.
Names for VRF tables can be a maximum of 15 characters. You cannot use the name mgmt; Cumulus Linux uses this name for the management VRF. Also, you cannot use these reserved names: default, unspec, main, or local.
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:
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:
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:
chef-client
collectd
dhcpd
dhcrelay
hsflowd
netq-agent
ntp (can only run in the default or management VRF)
puppet
snmptrapd
ssh
zabbix-agent
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.
An interface is always assigned to only one VRF; any packets received on that interface are routed using the associated VRF routing table.
Route leaking is not allowed for overlapping addresses.
Route leaking is supported for both IPv4 and IPv6 routes.
Route leaking is supported with EVPN in a symmetric routing configuration only.
VRF route leaking is not supported between the tenant VRF and the default VRF with onlink next hops (bgp unnumbered).
The NCLU command to configure route leaking fails if the VRF is named red (lowercase letters only). This is not a problem if the VRF is named RED (uppercase letters) or has a name other than red. To work around this issue, rename the VRF or run the vtysh command instead. This is a known limitation in network-docopt.
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:
You cannot reach the loopback address of a VRF (the address assigned to the VRF device) from another VRF.
When using route leaking, you must use the redistribute command in BGP to leak non-BGP routes (connected or static routes); you cannot use the network command.
Routes in the management VRF with the next-hop as eth0 or the management interface are not leaked.
Routes learned with iBGP or multi-hop eBGP in a VRF can be leaked even if their next hops become unreachable. Therefore, route leaking for BGP-learned routes is recommended only when they are learned through single-hop eBGP.
You cannot configure VRF instances of BGP in multiple autonomous systems (AS) or an AS that is not the same as the global AS.
Do not use the default VRF as a shared service VRF. Create another VRF for shared services.
An EVPN symmetric routing configuration on a Mellanox switch with a Spectrum ASIC or a Broadcom switch has certain limitations when leaking routes between the default VRF and non-default VRFs. The default VRF has underlay routes (routes to VTEP addresses) that cannot be leaked to any tenant VRFs. If you need to leak routes between the default VRF and a non-default VRF, you must filter out routes to the VTEP addresses to prevent leaking these routes. Use caution with such a configuration. Run common services in a separate VRF (service VRF) instead of the default VRF to simplify configuration and avoid using route-maps for filtering.
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
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
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
To view the BGP routing table, run the NCLU net show bgp vrf <vrf-name> ipv4|ipv6 unicast command or the vtysh show ip bgp vrf <vrf-name> ipv4|ipv6 unicast command.
To view the FRR IP routing table, use the NCLU net show route vrf <vrf-name> command or the vtysh show ip route vrf <vrf-name> command. These commands show all routes, including routes leaked from other VRFs.
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
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.
You pre-provision a VRF in FRRouting by running the command vrf vrf-name.
You can pre-provision a BGP instance corresponding to a VRF with the NCLU net add bgp vrf <vrf-name> autonomous-system <value> command. Under this context, all existing BGP parameters can be configured: neighbors, peer-groups, address-family configuration, redistribution, and so on.
An OSPFv2 instance can be configured using the NCLU net add ospf vrf <vrf-name> command; as with BGP, you can configure all OSPFv2 parameters.
You can provision static routes (IPv4 and IPv6) in a VRF by specifying the VRF along with the static route configuration. For example, ip route prefix dev vrf <vrf-name>. The VRF has to exist for this configuration to be accepted - either already defined through /etc/network/interfaces or pre-provisioned in FRRouting.
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
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
...
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:
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:
isc-dhcp-server-<vrf-name>
isc-dhcp-server6-<vrf-name>
isc-dhcp-relay-<vrf-name>
isc-dhcp-relay6-<vrf-name>
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:
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"
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"
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=""
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"
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
Switches using the Hurricane2 ASIC (such as the Penguin Computing Arctica 4804IP) do not support VRFs.
Table selection is based on the incoming interface only; currently, packet attributes or output-interface-based selection are not available.
Setting the router ID outside of BGP using the router-id option causes all BGP instances to get the same router ID. If you want each BGP instance to have its own router ID, specify the router-id under the BGP instance using bgp router-id. If both are specified, the one under the BGP instance overrides the one provided outside BGP.
When you take down a VRF using ifdown, Cumulus Linux removes all routes associated with that VRF from FRR but it does not remove the routes from the kernel.
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:
Run the ifup --with-depends mgmt command
Run ifreload -a command
The following command example brings down the management VRF, then brings it back up with the ifup --with-depends mgmt command:
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:
chef-client
collectd
hsflowd
netq-agent
netq-notifier
netqd
puppet
snmpd
snmptrapd
ssh
zabbix-agent
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).
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.
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.
Run the following command to create a custom service file in the /etc/systemd/system direcotry.
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
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:
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:
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:
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.
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
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.
Edit the /etc/frr/daemons file and add pimd=yes to the end of the file:
Restarting FRR restarts all the routing protocol daemons that are enabled and running.
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.
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.
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:
Any-source Mulitcast (ASM) is the traditional, and most commonly deployed PIM implementation. ASM relies on rendezvous points to connect multicast senders and receivers that then dynamically determine the shortest path through the network between source and receiver, to efficiently send multicast traffic.
Bidirectional PIM (BiDir) forwards all traffic through the multicast rendezvous point (RP) instead of tracking multicast source IPs, allowing for greater scale while resulting in inefficient forwarding of network traffic.
Source Specific Multicast (SSM) requires multicast receivers to know exactly from which source they want to receive multicast traffic instead of relying on multicast rendezvous points. SSM requires the use of IGMPv3 on the multicast clients.
Cumulus Linux only supports ASM and SSM. PIM BiDir is not currently supported.
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:
An RP is not configured or used. SSM does not require an RP since receivers always know the addresses of the senders.
There is no *,G PIM Join message. The multicast sender is always known so the PIM Join messages used in SSM are always S,G Join messages.
There is no Shared Tree or *,G tree. The PIM join message is always sent towards the source, building the SPT along the way. There is no shared tree or *,G state.
IGMPv3 is required. ASM allows for receivers to specify only the group they want to join without knowledge of the sender. This can be done in both IGMPv2 and IGMPv3. Only IGMPv3 supports requesting a specific source for a multicast group (the sending an S,G IGMP join)
No PIM Register process or SPT Switchover. Without a shared tree or RP, there is no need for the PIM register process. S,G joins are sent directly towards the FHR.
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:
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.
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
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.
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: server02 sends traffic to leaf02. leaf02 forwards traffic to leaf01 because the peerlink is a multicast router port. leaf01 also receives a PIM register from leaf02. leaf02 syncs the *,G table from leaf01 as an MLAG active-active peer.
Step 2: leaf02 has the *,G route indicating that traffic is to be forwarded toward spine01. Either leaf02 or leaf01 sends this traffic directly based on which MLAG switch receives it from the attached source. In this case, leaf02 receives the traffic on the MLAG bond and forwards it directly upstream.
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.
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
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.
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.
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
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:
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
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
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
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
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
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
...
Run the ifreload -a command to load the new configuration:
cumulus@switch:~$ ifreload -a
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
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
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
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:
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
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:
Validate that the FHR can reach the RP. If the RP and FHR can not communicate, the registration process fails:
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
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
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:
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
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
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
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
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
Cumulus Linux only supports PIM sparse mode (PIM-SM), any-source multicast (PIM-SM ASM), and source-specific multicast (SSM). Dense mode and bidirectional multicast are not supported.
Non-native forwarding (register decapsulation) is not supported. Initial packet loss is expected while the PIM *,G tree is built from the rendezvous point to the FHR to trigger native forwarding.
Cumulus Linux does not currently build an S,G mroute when forwarding over an *,G tree.
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:
300
600
1200
2400
4800
9600
19200
38400
115200
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:
300
600
1200
2400
4800
9600
19200
38400
115200
To change the serial console baud rate:
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:
After you save your changes to the grub configuration, type the following at the command prompt:
cumulus@switch:~$ update-grub
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.
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.
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:
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.
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:
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.
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:
Use single user mode to assist in troubleshooting system boot issues or for password recovery.
To enter single user mode:
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 |
| |
+----------------------------------------------------------------------------+
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) |
| |
+----------------------------------------------------------------------------+
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
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)
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
Related Commands
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:
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:
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
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:
Number of LEDs per port - Ports that cannot be split; for example, 1G ports must have 1 LED per port. Ports that can be split should have 1 LED per split port. So a 40G port that can be split into 4 10G ports has 4 LEDs, one per split port.
Location - A port LED should be placed right above the port. This prevents the LEDs from being hidden by drooping cables. If the port can be split, the LED for each split port should also be placed above the port. The LEDs should be evenly spaced and be inside the edges of the ports to prevent confusion.
Port Number Label - The port number must be printed in white on the switch front panel directly under the corresponding LED.
Colors - As network port technology improves with smaller ports and higher speeds, having different colors for different types of ports or speeds is confusing. The focus should be on giving a network operator a simple set of indications that provide the operator with basic information about the port. Hence, green and amber colors must be used on the LED to differentiate between good and bad states. These colors are commonly found on network port LEDs and should be easy to implement on future switches.
Signaling - The table below indicates the information that can be conveyed via port LEDs and how it should be done.
Max Speed indicates the maximum speed at which the port can be run. For a 10G port, if the port speed is 10G, then it is running at its maximum speed. If the 10G port is running at 1G speed then its running at a lower speed.
Physical Link Up/Down displays layer 2 link status.
Beaconing provides a way for a network operator to identify a particular link. The administrator can beacon that port from a remote location so the network operator has visual indication for that port.
Fault can also be considered a form of beaconing or vice versa. Both try to draw attention of the network operator towards the port, thus they are signaled the same way.
Blinking amber implies a blink rate of 33ms. Slow blinking amber indicates a blink rate of 500ms, with a 50% on/off duty cycle. In other words, a slow blinking amber LED is amber for 500 ms and then off for 500ms.
Activity
Max Speed indication
Lower Speed Indication
Physical Link Down
Off
Off
Physical Link UP
Solid Green
Solid Amber
Link Tx/Rx Activity
Blinking Green
Blinking Amber
Beaconing
Slow Blinking Amber
Slow Blinking Amber
Fault
Slow Blinking Amber
Slow Blinking Amber
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.
Number of LEDs per unit - Each unit should have only 1 LED.
Location - All units should have their LEDs on the right-hand side of the switch after the physical ports.
Unit label - The label should be printed on the front panel directly above the LED.
Colors - The focus should be on giving a network operator a simple set of indications that provide basic information about the unit. The following section has more information about the indications, but colors are standardized on green and amber. These colors are universally found on all status LEDs and should be easy to implement on future switches.
Defined LED - Every network switch must have LEDs for the following:
- PSU
- Fans
- System LED
- Locator LED
PSU LEDs - Each PSU must have its own LED. PSU faults are difficult to debug. If a network operator knows which PSU is faulty, he or she can quickly check if it is powered up correctly and, if that fault persists, replace the PSU.
Unit Activity
Indication
Installed and power OK
Solid Green
Installed, but no power
Slow Blinking Amber
Installed, powered, but has faults.
Slow Blinking Amber
Fan LED - A network switch may have multiple fan trays (3 - 6). It is difficult to put an LED for each fan tray on the front panel, given the limited real estate. Hence, the recommendation is one LED for all fans.
Unit Activity
Indication
All fans running OK
Solid Green
Fault on any one of the fans.
Slow Blinking Amber
System LED - A network switch must have a system LED that indicates the general state of a switch. This state could be of hardware, software, or both. It is up to the individual switch NOS to decide what this LED indicates. But the LED can have only the following indications:
Unit Activity
Indication
All OK
Solid Green
Not OK
Slow Blinking Amber
Locator LED - The locator LED helps locate a particular switch in a data center full of switches. Thus, it should have a different color and predefined location. It must be located at the top right corner on the front panel of the switch and its color must be blue.
Unit Activity
Indication
Locate enabled
Blinking Blue
Locate disabled
Off
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:
Dell Z9100-ON
Edgecore AS7712-32X
Penguin Arctica 3200c
Quanta QuantaMesh BMS T4048-IX2
Supermicro SSE-C3632S
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.
EdgeCore Minipack-AS8000 Port LED Blink State
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:
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:
Aggregate statistics are available per VNI; this includes access and network statistics.
Network statistics are available for each VNI and displayed against the VXLAN device. This is independent of the VTEP used, so this is a summary of the VNI statistics across all tunnels.
Access statistics are available per VLAN subinterface.
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:
stats.vlan.aggregate, which controls the statistics available for each VLAN. Its value defaults to BRIEF.
stats.vxlan.aggregate, which controls the statistics available for each VNI (access and network). Its value defaults to DETAIL.
stats.vxlan.member, which controls the statistics available for each local/access port in a VXLAN bridge. Its value defaults to BRIEF.
The values for each parameter can be one of the following:
NONE: This disables the counter.
BRIEF: This provides tx/rx packet/byte counters for the associated parameter.
DETAIL: This provides additional feature-specific counters. In the case of stats.vxlan.aggregate, DETAIL provides access vs. network statistics. For the other types, DETAIL has the same effect as BRIEF.
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.
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:
Currently the CPU port is internally added as a member of all VLANs.Therefore, packets sent to the CPU are counted against the corresponding VLAN’s tx packets/bytes. There is no workaround.
When checking the virtual counters for the bridge, the TX count is the number of packets destined to the CPU before any hardware policers take effect. For example, if 500 broadcast packets are sent into the bridge, the CPU is also sent 500 packets. These 500 packets are policed by the default ACLs in Cumulus Linux, so the CPU might receive fewer than the 500 packets if the incoming packet rate is too high. The TX counter for the bridge should be equal to 500*(number of ports in the bridge - incoming port + CPU port) or just 500 * number of ports in the bridge.
You cannot use ethtool -S for virtual devices. This is because the counters available via netdev are sufficient to display the VLAN/VXLAN counters currently supported in the hardware (only rx/tx packets/bytes are supported currently).
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:
Microbursts that result in longer packet latency
Packet buffer congestion that might lead to packet drops
Network problems with a particular switch, port, or traffic class
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:
A fine-grained history of queue lengths using histograms maintained by the ASIC
Packet counts per port, priority and size
Dropped packet, pause frame, and ECN-marked packet counts
Buffer congestion occupancy per port, priority and buffer pool, and at input and output ports
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:
Min = 960
Histogram size = 12288
Max = 13248
Range size = 1536
Bin 0: 0:959
Bin 1: 960:2495
Bin 2: 2496:4031
Bin 3: 4032:5567
Bin 4: 5568:7103
Bin 5: 7104:8639
Bin 6: 8640:10175
Bin 7: 10176:11711
Bin 8: 11712:13247
Bin 9: 13248:*
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:
Open the /etc/cumulus/datapath/monitor.conffile in a text editor.
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]
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
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
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
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
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]
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).
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
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
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.
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:
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:
Queue length histograms are collected every second for swp1 through swp50.
The results are written to the /var/lib/cumulus/histogram_stats snapshot file.
The size of the histogram is set to 12288 bytes, the minimum boundary to 960 bytes, and the sampling time to 1024 nanoseconds.
A threshold is set so that when the size of the queue reaches 500 bytes, the system sends a message to the /var/log/syslog file.
Packet drops on swp1 through swp50 are collected every two seconds.
If the number of packet drops is greater than 100, the results are written to the /var/lib/cumulus/discard_stats snapshot file and the system sends a message to the /var/log/syslog file.
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:
Queue length histograms are collected for swp1 through swp50 every second.
The results are written to the /var/lib/cumulus/histogram_stats snapshot file.
When the queue length reaches 500 bytes, the system sends a message to the /var/log/syslog file and collects additional data; buffer occupancy and all packets per port.
Buffer occupancy data is written to the /var/lib/cumulus/buffer_stats snapshot file and all packets per port data is written to the /var/lib/cumulus/all_packet_stats snapshot file.
In addition, packet drops on swp1 through swp50 are collected every two seconds. If the number of packet drops is greater than 100, the results are written to the /var/lib/cumulus/discard_stats snapshot file and a message is sent to the /var/log/syslog file.
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.
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.
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.
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:
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.
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:
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).
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).
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.
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.
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:
When there is a core file dump of any application (not specific to Cumulus Linux, but something all Linux distributions support), located in /var/support/core.
After the first failure of one of several monitored services since the switch was rebooted or power cycled.
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 the etc Directory. The /etc directory contains the largest number of files; however, log files might be significantly larger in file size.
Troubleshooting Log Files. This guide highlights the most important log files to inspect. Keep in mind, cl-support includes all of the log files.
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.
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:
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.
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.
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)
“RTNETLINK answers: Invalid argument” Error when Adding a Port to a Bridge
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.
MLAG Peerlink Interface Drops Many Packets
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.
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:
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.
Print Route Trace Using traceroute
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>
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:
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
For Broadcom switches, Cumulus Linux supports a maximum of two SPAN destinations.
Because SPAN and ERSPAN is done in hardware, eth0 is not supported as a destination.
For Mellanox Spectrum switches with the Spectrum-2 ASIC or later, Cumulus Linux supports four SPAN destinations in atomic mode or eight SPAN destinations in non-atomic mode. On a switch with the Spectrum 1 ASIC, Cumulus Linux supports only a single SPAN destination in atomic mode or three SPAN destinations in non-atomic mode.
Multiple rules (SPAN sources) can point to the same SPAN destination, but a given SPAN source cannot specify two SPAN destinations.
To configure SPAN or ERSPAN on a Tomahawk or Trident3 switch, you must enable non-atomic update mode.
Mellanox Spectrum switches reject SPAN ACL rules for an output interface that is a subinterface.
Mirrored traffic is not guaranteed. If the MTP is congested, mirrored packets might be discarded.
Cut-through mode is not supported for ERSPAN in Cumulus Linux on switches using Broadcom Tomahawk, Trident II+ and Trident II ASICs.
On Broadcom switches, SPAN does not capture egress traffic.
Cumulus Linux does not support IPv6 ERSPAN destinations.
ERSPAN does not cause the kernel to send ARP requests to resolve the next hop for the ERSPAN destination. If an ARP entry for the destination/next hop does not already exist in the kernel, you need to manually resolve this before mirrored traffic is sent (using ping or arping).
Mirroring to the same interface that is being monitored will cause a recursive flood of traffic and may impact traffic on other interfaces.
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/:
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 -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 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
When using Wireshark to review the ERSPAN output, Wireshark may report the message “Unknown version, please report or test to use fake ERSPAN preference”, and the trace is unreadable. To resolve this, go into the General preferences for Wireshark, then go to Protocols > ERSPAN and check the Force to decode fake ERSPAN frame option.
To set up a capture filter on the destination switch that filters for a specific IP protocol, use ip.proto == 47 to filter for GRE-encapsulated (IP protocol 47) traffic.
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:
IPv4 SIP/DIP
IP protocol
L4 (TCP/UDP) src/dst port
TCP flags
An ingress port/wildcard (swp+) can be specified in addition
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:
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).
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:
Use DNS service discovery (DNS-SD)
Manually configure the /etc/hsflowd.conf file
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:
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
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
Mellanox switches do not support sFlow egress sampling.
The EdgeCore AS4610 switch occasionally sends malformed packets and does not send any flow samples; it sends only counters. This is a known limitation on this Helix4 platform.
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
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
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.
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-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.
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.
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:
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:
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
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.
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.
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.
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:
The default /etc/snmp/snmpd.conf configuration already enables AgentX and sets the correct permissions
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:
Configure AgentX access in FRRouting:
cumulus@switch:~$ net add routing agentx
cumulus@switch:~$ net pending
cumulus@switch:~$ net commit
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:
Make sure that the /var/agentx directory is world-readable andworld-searchable (octal mode 755).
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:
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:
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:
Install the net-snmp-config script that is in libsnmp-dev package:
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:
Link up/down.
Exceeding the temperature sensor threshold, CPU load, or memory threshold.
Other SNMP MIBs.
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:
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.
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:
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:
Using the entPhySensorOperStatus integer:
# without installing extra MIBS we can check the check Fan1 status
# if the Fan1 index is 100011001, monitor this specific OID (-I) every 10 seconds (-r), and defines additional information to be included in the trap (-o).
monitor -I -r 10 -o 1.3.6.1.2.1.47.1.1.1.1.7.100011001 "Fan1 Not OK" 1.3.6.1.2.1.99.1.1.1.5.100011001 > 1
# Any Entity Status non OK (greater than 1)
monitor -r 10 -o 1.3.6.1.2.1.47.1.1.1.1.7 "Sensor Status Failure" 1.3.6.1.2.1.99.1.1.1.5 > 1
Using the OID name:
# for a specific fan called Fan1 with an index 100011001
monitor -I -r 10 -o entPhysicalName.100011001 "Fan1 Not OK" entPhySensorOperStatus.100011001 > 1
# for any Entity Status not OK ( greater than 1)
monitor -r 10 -o entPhysicalName "Sensor Status Failure" entPhySensorOperStatus > 1
You can use the OID name if the snmp-mibs-downloader package is installed.
The entPhySensorOperStatus integer can be found by walking the entPhysicalName table.
To get all sensor information, run snmpwalk on the entPhysicalName table. For example:
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.
Open /etc/apt/sources.list in a text editor.
Add the non-free repository, then save the file:
cumulus@switch:~$ sudo deb http://ftp.us.debian.org/debian/ buster main non-free
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 :
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=
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
Configure Link Up/Down Notifications
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:
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.
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:
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:
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:
log logs the details of the notification in a specified file to standard output (or stderr), or through syslog (or similar).
execute passes the details of the trap to a specified handler program, including embedded Perl.
net forwards the trap to another notification receiver.
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.
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.
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
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
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.
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.
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
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:
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).
cl_poe_pp.py, which is disabled by default as only certain platforms that Cumulus Linux supports are capable of doing Power over Ethernet.
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
SSH to the Cumulus Linux switch that needs to be configured, replacing [switch] below as appropriate:
cumulus@switch:~$ ssh cumulus@[switch]
Open the /etc/snmp/snmpd.conf file in an editor.
Uncomment the following 3 lines in the /etc/snmp/snmpd.conf file, then save the file:
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.
Save the configuration. The switch will now be present in the Network Switch Configuration menu now.
Close the pop up window to return to the dashboard.
Open the Hardware option from the Home dropdown menu:
Click the Table button.
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
Physical Interface (e.g. swp1, swp2). This will only display swp interfaces connected to Nutanix hosts by default.
Switch ID - Unique identifier that Nutanix keeps track of each port ID (see below)
Index - interface index, in the above demonstration swp49 maps to Index 52 because there is a loopback and two ethernet interface before the swp starts.
MTU of interface
MAC Address of Interface
Unicast RX Packets (Received)
Unicast TX Packets (Transmitted)
Error RX Packets (Received)
Error TX Packets (Transmitted)
Discard RX Packets (Received)
Discard TX Packets (Transmitted)
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)
Follow the directions on one of the following websites to enable CDP:
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
Find the MAC address information in the Prism GUI, located in: Hardware > Table > Host > Host NICs
Select a MAC address to troubleshoot (e.g. 0c:c4:7a:09:a2:43 represents vmnic0 which is tied to NX-1050-A).
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
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:
Metrics that you can poll from Cumulus Linux and use in trend analysis
Critical log messages that you can monitor for triggered alerts
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%
2017-03-08T06:26:43.569681+00:00 is the timestamp.
leaf01 is the hostname.
sysmonitor is the process that is the source of the message.
Critically high CPU use: 99% is the message.
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.
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.
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.
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”
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.
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
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)
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
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
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)
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)
# 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.
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.
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.
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:
Whether the application relies on TCP for proper sequencing of data.
Whether the application relies on more than one session as part of the application.
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 sessions are short lived.
The impact of a failed session or TCP reset does not impact the application. For example, a web page refresh is acceptable.
There is application-level session management that is completely independent of the TCP session.
A redirection middleware layer handles incorrectly hashed flows.
TCP applications that have longer-lived flows should not be used as anycast services. For example:
FTP or other large file transfers.
Transactions that must be completed and journaled. For example, financial transactions.
Streaming media without application-level automated recovery.
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:
RoCEv1, which runs at the link layer and cannot be run over a routed network. Therefore, it requires the link layer priority flow control (PFC) to be enabled.
RoCEv2, which runs over layer 3. Use explicit congestion notification (ECN) with RoCEv2 as ECN bits are communicated end-to-end across a routed network.
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.
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:
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.
