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 and automation.
- 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
net, in addition to running show and clear commands related
ifupdown2 and FRRouting.
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
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
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
Use the following workflow to stage and commit changes to Cumulus Linux with NCLU:
- Use the
net delcommands to stage and remove configuration changes.
- Use the
net pendingcommand to review staged changes.
net abortto commit and delete staged changes.
net commit applies the changes to the relevant configuration files,
/etc/network/interfaces, then runs necessary follow on
commands to enable the configuration, such as
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 showis a series of commands for viewing various parts of the network configuration. For example, use
net show configurationto view the complete network configuration,
net show commit historyto view a history of commits using NCLU, and
net show bgpto view BGP status.
net clearprovides a way to clear
net showcounters, BGP and OSPF neighbor content, and more.
net rollbackprovides a mechanism to revert back to an earlier configuration.
net commit confirmrequires you to press Enter to commit changes using NCLU. If you run
net commit confirmbut 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 permanentretains 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 deletedeletes one or more snapshots created when committing changes with NCLU.
net del alldeletes all configurations.
net del allcommand 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 188.8.131.52/32 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 184.108.40.206 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
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
# 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.
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 220.127.116.11/24 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 18.104.22.168/24 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 22.214.171.124/24 - 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
netshowgroup. A user in the
netshowgroup can run NCLU
net showcommands, such as
net show interfaceor
net show config, and certain general Linux commands, such as
man, but cannot run
- You create user accounts with edit permissions for NCLU by
adding them to the
neteditgroup. A user in the
neteditgroup can run NCLU configuration commands, such
net commitin addition to NCLU
The examples below demonstrate how to add a new user account or modify an existing user account called myuser.
To add a new user account with NCLU show permissions:
cumulus@switch:~$ sudo adduser --ingroup netshow myuser Adding user `myuser' ... Adding new user `myuser' (1001) with group `netshow' ...
To add NCLU show permissions to a user account that already exists:
cumulus@switch:~$ sudo addgroup myuser netshow Adding user `myuser' to group `netshow' ... Adding user myuser to group netshow Done
To add a new user account with NCLU edit permissions:
cumulus@switch:~$ sudo adduser --ingroup netedit myuser Adding user `myuser' ... Adding new user `myuser' (1001) with group `netedit' ...
To add NCLU edit permissions to a user account that already exists:
cumulus@switch:~$ sudo addgroup myuser netedit Adding user `myuser' to group `netedit' ... Adding user myuser to group netedit Done
You can use the
adduser command for local user accounts only. You can
addgroup command for both local and remote user accounts. For
a remote user account, you must use the mapping username, such as
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.
/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_show lines in the
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_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
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
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
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
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.|
|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 |
|groups_with_show||root, cumulus||Controls which groups are allowed to run |
|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
variable to true. The value is not case sensitive.
Caveats and Errata
Unsupported Interface Names
NCLU does not support interfaces named
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.