Netplan lacks an option to add multicast routes

[Saverio]

Netplan lacks an option to add multicast routes.

Example:

I have a VM with 2 Ethernet nics, one for management and one for multicast streaming:

   ens3 ens7
   mgmt --[ HOST 1 ]--> mcast out

To route multicast out of the ens7 interface, you would add a route to 224.0.0.0/4 tied to the Ethernet device you want to use.

Using the cli, you would to this:

    ip route add 224.0.0.0/4 dev ens7

This is not possible with netplan; it is just missing the option to add multicast routes, i.e. with a device instead of a gateway.

Notes:

After checking the discussion on Bug #1767607, tried this config:

  network:
    version: 2
    renderer: networkd
    ethernets:
      ens3:
        addresses:
            - 10.0.5.40/24
      ens7:
        addresses:
            - 192.168.200.2/30
            - "2001::172.20.1.2/120"
        routes:
            - to: "224.0.0.0" <--- this
              via: "0.0.0.0"
              on-link: True

Other than being rather counter-intuitive, it passes validation but it does not work:

    root@jsec-server2:/home/lab# netplan try
    Warning: Stopping systemd-networkd.service, but it can still be activated by:
    systemd-networkd.socket
    Do you want to keep these settings?

    Press ENTER before the timeout to accept the new configuration

    Changes will revert in 120 seconds
    Configuration accepted.

    root@jsec-server2:/home/lab# ip route show
    10.0.5.0/24 dev ens3 proto kernel scope link src 10.0.5.40
    192.168.200.0/30 dev ens7 proto kernel scope link src 192.168.200.2
    root@jsec-server2:/home/lab#

The multicast route is missing.

[Franco Albarracin (francofda87)]

Estimated,
You have been able to solve this problem, I am having the same problem and I cannot find that netplan lift with the route.

I await your comments.
Cheers

[Jimi Lindberg (originalzector)]

I attempted to do this today and seem to have been successful using netplan.io version 0.105-0ubuntu2~22.04.1.
Running the following configuration, outgoing multicast traffic is being sent from ens256 as intended.

network:
  version: 2
  ethernets:
    ens192:
      addresses:
      - 192.168.212.111/23
      routes:
      - to: default
        via: 192.168.213.254
      nameservers:
        addresses:
        - 192.168.130.40
        - 192.168.130.2
        search: []
    ens224:
      addresses:
      - 192.168.216.111/23
      nameservers:
        addresses: []
        search: []
    ens256:
      addresses:
      - 192.168.218.111/23
      routes:
      - to: 224.0.0.0/4
      nameservers:
        addresses: []
        search: []

I hope this helps.

[Lukas Märdian (slyon)]

This should be fixed as of netplan v0.104 (https://github.com/canonical/netplan/pull/248)

Using something like this (see comment #2):
```
      routes:
      - to: 224.0.0.0/4
```

What version of Netplan are you using? (dpkg -l | grep netplan)

I'm closing this, please re-open if you're still affected.