NVUE Snippets

NVUE supports both snippets and flexible snippets:

Use snippets to add configuration to either the /etc/frr/frr.conf or /etc/network/interfaces file.
Use flexible snippets to manage any other text file on the system.

A snippet configures a single parameter associated with a specific configuration file.
You can only set or unset a snippet; you cannot modify, partially update, or change a snippet.
Setting the snippet value replaces any existing snippet value.
Cumulus Linux supports only one snippet for a configuration file.
Only certain configuration files support a snippet.
NVUE does not parse or validate the snippet content and does not validate the resulting file after you apply the snippet.
PATCH is only the method of applying snippets and does not refer to any snippet capabilities.
As NVUE supports more features and introduces new syntax, snippets and flexible snippets become invalid. Before you upgrade Cumulus Linux to a new release, review the What's New for new NVUE syntax and remove the snippet if NVUE introduces new syntax for the feature that the snippet configures.

Snippets

Use snippets if you configure Cumulus Linux with NVUE commands, then want to configure a feature that does not yet support the NVUE Object Model. You create a snippet in yaml format and add the configuration to either the /etc/frr/frr.conf or /etc/network/interfaces file.

/etc/frr/frr.conf Snippets

Example 1: Top Level Configuration

NVUE does not support configuring BGP to peer across the default route. The following example configures BGP to peer across the default route from the default VRF:

Create a .yaml file with the following snippet:

cumulus@switch:~$ sudo nano ./bgp_snippet.yaml
- set:
    system:
      config:
        snippet:
          frr.conf: |
            ip nht resolve-via-default

Run the following command to patch the configuration:

cumulus@switch:~$ nv config patch ./bgp_snippet.yaml

Run the nv config apply command to apply the configuration:
```
cumulus@switch:~$ nv config apply
```

Verify that the configuration exists at the end of the /etc/frr/frr.conf file:

cumulus@switch:~$ sudo cat /etc/frr/frr.conf
...
! end of router ospf block
!---- CUE snippets ----
ip nht resolve-via-default

Example 2: Nested Configuration

NVUE does not support configuring EVPN route targets using auto derived values from RFC 8365. The following example configures BGP to enable RFC 8365 derived router targets:

Create a .yaml file with the following snippet:

cumulus@switch:~$ sudo nano ./bgp_snippet.yaml
- set:
    system:
      config:
        snippet:
          frr.conf: |
            router bgp 65517 vrf default
              address-family l2vpn evpn
                autort rfc8365-compatible

Make sure to use spaces not tabs; the parser expects spaces in yaml format.

Run the following command to patch the configuration:

cumulus@switch:~$ nv config patch ./bgp_snippet.yaml

Run the nv config apply command to apply the configuration:
```
cumulus@switch:~$ nv config apply
```

Verify that the configuration exists at the end of the /etc/frr/frr.conf file:

cumulus@switch:~$ sudo cat /etc/frr/frr.conf
...
! end of router bgp 65517 vrf default
!---- CUE snippets ----
router bgp 65517 vrf default
address-family l2vpn evpn
autort rfc8365-compatible

The snippets for FRR writes content to the /etc/frr/frr.conf file. When the configuration and snippet is applied via nv config apply, the FRR service goes through and reads in the /etc/frr/frr.conf file.

Example 3: EVPN Multihoming FRR Debugging

NVUE does not support configuring FRR debugging for EVPN multihoming. The following example configures FRR debugging:

Create a .yaml file and add the following traditional snippet:

cumulus@switch:~$ sudo nano mh_debug_snippet.yaml
- set:
    system:
      config:
        snippet:
          frr.conf: |
            debug bgp evpn mh es
            debug bgp evpn mh route
            debug bgp zebra
            debug zebra evpn mh es
            debug zebra evpn mh mac
            debug zebra evpn mh neigh
            debug zebra evpn mh nh
            debug zebra vxlan

Run the following command to patch the configuration:

cumulus@switch:~$ nv config patch mh_debug_snippet.yaml

Run the nv config apply command to apply the configuration:
```
cumulus@switch:~$ nv config apply
```

Verify that the configuration exists in the /etc/frr/frr.conf file:

cumulus@switch:~$ sudo cat /etc/frr/frr.conf
...
!---- NVUE snippets ----
debug bgp evpn mh es
debug bgp evpn mh route
debug bgp zebra
debug zebra evpn mh es
debug zebra evpn mh mac
debug zebra evpn mh neigh
debug zebra evpn mh nh
debug zebra vxlan

The traditional snippets for FRR write content to the /etc/frr/frr.conf file. When you apply the configuration and snippet with the nv config apply command, the FRR service goes through and reads in the /etc/frr/frr.conf file.

/etc/network/interfaces Snippets

MLAG Timers Example

NVUE supports configuring only one of the MLAG service timeouts (initDelay). The following example configures the MLAG peer timeout to 400 seconds:

Create a .yaml file and add the following snippet:

cumulus@switch:~$ sudo nano ./mlag_snippet.yaml
- set:
    system:
      config:
        snippet:
          ifupdown2_eni:
            peerlink.4094: |
              clagd-args --peerTimeout 400

Run the following command to patch the configuration:

cumulus@switch:~$ nv config patch ./mlag_snippet.yaml

Run the nv config apply command to apply the configuration:
```
cumulus@switch:~$ nv config apply
```

Verify that the configuration exists in the peerlink.4094 stanza of the /etc/network/interfaces file:

cumulus@switch:~$ sudo cat /etc/network/interfaces
...
auto peerlink.4094
iface peerlink.4094
 clagd-args --peerTimeout 400
 clagd-peer-ip linklocal
 clagd-backup-ip 10.10.10.2
 clagd-sys-mac 44:38:39:BE:EF:AA
 clagd-args --initDelay 180
...

Traditional Bridge Example

NVUE does not support configuring traditional bridges. The following example configures a traditional bridge called br0 with the IP address 11.0.0.10/24. swp1, swp2 are members of the bridge.

Create a .yaml file and add the following snippet:

cumulus@switch:~$ sudo nano ./bridge_snippet.yaml
- set:
    system:
     config:
       snippet:
         ifupdown2_eni:
           eni_stanzas: |
             auto br0
             iface br0
               address 11.0.0.10/24
               bridge-ports swp1 swp2
               bridge-vlan-aware no

Run the following command to patch the configuration:

cumulus@switch:~$ nv config patch ./bridge_snippet.yaml

Run the nv config apply command to apply the configuration:
```
cumulus@switch:~$ nv config apply
```

Verify that the configuration exists at the end of the /etc/network/interfaces file:

cumulus@switch:~$ sudo cat /etc/network/interfaces
...
auto br0
iface br0
  address 11.0.0.10/24
  bridge-ports swp1 swp2
  bridge-vlan-aware no

Flexible Snippets

Flexible snippets are an extension of regular snippets that let you manage any text file on the system. You can add content to an existing text file or create a new text file and add content.

Flexible snippets do not support:

Binary files.
Symbolic links.
More than 1MB of content.
More than one flexible snippet in the same destination file.

Cumulus Linux runs flexible snippets as root. Exercise caution when creating and editing flexible snippets.

To create flexible snippets:

Create a file in yaml format and add each flexible snippet you want to apply in the format shown below.
```
cumulus@leaf01:mgmt:~$ sudo nano ./<filename>.yaml>
- set:
    system:
     config:
       snippet:
         <snippet-name>:
           file: "<filename>"
           permissions: "<umask-permissions>"
           content: |
             # This is my content
           services:
              <name>:
                service: <service-name>
                action: <action>
```
NVUE appends the flexible snippet at the end of an existing file. If the file does not exist, NVUE creates the file and adds the content.
- You can only set the umast permissions to a new file that you create. Adding the permissions: line is optional. The default umask persmissions are 644.
- You can add a service with an action, such as start, restart, or stop. Adding the services: lines is optional. The SNMP example below restarts the snmpd service.

TACACS+ Client Example

The following example creates a snippet called tacacs-config in a file called ./tacacs.yaml. The snippet adds the server 192.168.0.30 and the shared secret tacacskey to the /etc/tacplus_servers file.

Create the tacacs.yaml snippet:

cumulus@leaf01:mgmt:~$ sudo nano ./tacacs.yaml
- set:
    system:
     config:
       snippet:
         tacacs-config:
           file: "/etc/tacplus_servers"
           content: |
             secret=tacacskey
             server=192.168.0.30

Run the following command to patch the configuration:
```
cumulus@switch:~$ nv config patch ./snmp.yaml
```
Run the nv config apply command to apply the configuration:
```
cumulus@switch:~$ nv config apply
```

NVUE appends the snippet at the end of the /etc/tacplus_servers file.

SNMP Example

The following example creates a snippet called snmp-config in a file called ./snmp.yaml. The snippet adds content to the /etc/snmp/snmpd.conf file to:

Configure the switch to listen on any interface on the management VRF.
Create a read-only community.
Restart the snmpd service.

Create the snmp.yaml snippet:

cumulus@leaf01:mgmt:~$ sudo nano ./snmp.yaml
- set:
    system:
      config:
        snippet:
          snmp-config:
            file: /etc/snmp/snmpd.conf
            content: |
              # Listen on any interface on MGMT VRF
              agentaddress udp:@mgmt:161
              # Create a Read-Only Community
              rocommunity cumuluspassword default
            services:
              snmp:
                service: snmpd
                action: restart

Run the following command to patch the configuration:
```
cumulus@switch:~$ nv config patch ./snmp.yaml
```
Run the nv config apply command to apply the configuration:
```
cumulus@switch:~$ nv config apply
```

NVUE appends the snippet at the end of the /etc/snmp/snmpd.conf file.

Remove a Snippet

To remove a traditional or flexible snippet, edit the snippet’s .yaml file to change set to unset, then patch and apply the configuration. Alternatively, you can use the REST API DELETE and PATCH methods.

The following example removes the MLAG timer traditional snippet created above to configure the MLAG peer timeout:

Edit the mlag_snippet.yaml file to change set to unset:

cumulus@switch:~$ sudo nano mlag_snippet.yaml
- unset:
    system:
      config:
        snippet:
          ifupdown2_eni:

Run the following command to patch the configuration:

cumulus@switch:~$ nv config patch mlag_snippet.yaml

Run the nv config apply command to apply the configuration:
```
cumulus@switch:~$ nv config apply
```

Verify that the peer timeout parameter no longer exists in the peerlink.4094 stanza of the /etc/network/interfaces file:

cumulus@switch:~$ sudo cat /etc/network/interfaces
...
auto peerlink.4094
iface peerlink.4094
 clagd-peer-ip linklocal
 clagd-backup-ip 10.10.10.2
 clagd-sys-mac 44:38:39:BE:EF:AA
 clagd-args --initDelay 180
...

NVUE Snippets

Snippets

/etc/frr/frr.conf Snippets

Example 1: Top Level Configuration

Example 2: Nested Configuration

Example 3: EVPN Multihoming FRR Debugging

/etc/network/interfaces Snippets

MLAG Timers Example

Traditional Bridge Example

Flexible Snippets

TACACS+ Client Example

SNMP Example

Remove a Snippet

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