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Cumulus Linux

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This documentation is for the extended support release (ESR) version of Cumulus Linux. We will continue to keep this content up to date until 21 February, 2023, when ESR support ends. For more information about ESR, please read this knowledge base article.

If you are using the current version of Cumulus Linux, the content on this page may not be up to date. The current version of the documentation is available here. If you are redirected to the main page of the user guide, then this page may have been renamed; please search for it there.

Network Command Line Utility - NCLU

The Network Command Line Utility (NCLU) is a command line interface 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, rolling back and deleting snapshots, 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.

Install NCLU

If you upgraded Cumulus Linux from a version earlier than 3.2 instead of performing a full disk image install, you need to install the nclu package on your switch:

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

The nclu package installs a new bash completion script and displays the following message:

Setting up nclu (1.0-cl3u3) ...
To enable the newly installed bash completion for nclu in this shell, execute...
 source /etc/bash_completion

NCLU Basics

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

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

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

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

If you provision a new switch without setting the system clock (manually or with NTP or PTP), the NCLU net commit command fails when the system clock is earlier than the modification date of configuration files. Make sure to set the system clock on the switch.

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 snapshot taken when committing the change. Otherwise, the snapshots created from NCLU commands are cleaned up periodically with a snapper cron job.

  • net commit delete deletes one or more snapshots created when committing changes with NCLU.

  • 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 correct syntax is used. 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] [description <wildcard>]
    net commit delete (<number>|<number-range>)
    net help [verbose]
    net pending
    net rollback (<number>|last)
    net show commit (history|<number>|<number-range>|last)
    net show rollback (<number>|last)
    net show configuration [commands|files|acl|bgp|ospf|ospf6|interface <interface>]
 
 
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 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 bgp debug bestpath <ip/prefixlen>
    net del bgp debug bestpath [<ip/prefixlen>]
    net show bgp (<ipv4>|<ipv4/prefixlen>) [bestpath|multipath] [json]
    net show bgp (<ipv6>|<ipv6/prefixlen>) [bestpath|multipath] [json]
    net show bgp vrf <text> (<ipv4>|<ipv4/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@leaf01:~$ 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) ability will work on all subsequent sessions on the switch.

cumulus@leaf01:~$ 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 users 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
dot1x            :  Configure, Enable, Delete or Show IEEE 802.1X EAPOL
link-settings    :  Physical link parameters
lnv              :  Lightweight Network Virtualization
management-vrf   :  Management VRF
mlag             :  Multi-Chassis Link Aggregation
ospf             :  Open Shortest Path First (OSPFv2)
vlan-interfaces  :  IP interfaces for VLANs

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
# Review and commit changes
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, don’t give edit permissions to the tacacs group.

Restart the netd Service

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

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

Back Up the Configuration to a Single File

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

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

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

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

cumulus@leaf01:~$ source leaf01.txt

Advanced Configuration

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

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

cumulus@switch:~$ sudo nano /etc/netd.conf
cumulus@switch:~$ sudo systemctl restart netd.service
Configuration Variable Default Setting Description
show_linux_command False When true, displays the Linux command running in the background.
enable_ifupdown2 True Enables net wrapping of ifupdown2 commands.
enable_frr True Enables net wrapping of FRRouting commands.
users_with_edit root, cumulus Sets the Linux users with root edit privileges.
groups_with_edit root, cumulus Sets the Linux groups with root edit privileges.
users_with_show root, cumulus Controls which users are allowed to run show commands.
groups_with_show root, cumulus Controls which groups are allowed to run show commands.
ifupdown_blacklist address-purge, bond-ad-actor-sys-prio, bond-ad-actor-system, bond-mode, bond-num-grat-arp, bond-num-unsol-na, bond-use-carrier, bond-xmit-hash-policy, bridge-bridgeprio, bridge-fd, bridge-hashel, bridge-hashmax, bridge-hello, bridge-maxage, bridge-maxwait, bridge-mclmc, bridge-mclmi, bridge-mcmi, bridge-mcqi, bridge-mcqpi, bridge-mcqri, bridge-mcrouter, bridge-mcsqc, bridge-mcsqi, bridge-pathcosts, bridge-port-pvids, bridge-port-vids, bridge-portprios, bridge-stp, bridge-waitport, broadcast, hwaddress, link-type, mstpctl-ageing, mstpctl-fdelay, mstpctl-forcevers, mstpctl-hello, mstpctl-maxage, mstpctl-maxhops, mstpctl-portp2p, mstpctl-portpathcost, mstpctl-portrestrrole, mstpctl-portrestrtcn, mstpctl-treeportcost, mstpctl-treeportprio, mstpctl-txholdcount, netmask, preferred-lifetime, scope, vxlan-ageing, vxlan-learning, up, down, bridge-ageing, bridge-gcint, bridge-mcqifaddr, bridge-mcqv4src Hides corner case command options from tab complete, to simplify and streamline output.

Net Tab Complete 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.

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