Does Containerlab support the creation of topologies with multiple subnets?

[stephane-klein]

I tried using Containerlab to improve my understanding and practical mastery of IPv6.

I wanted to create two IPv6 networks connected by a router.

I tried this topology:

(My source code playground: https://github.com/stephane-klein/containerlab-playground/tree/main )

name: network-a-b

mgmt:
  network: net-custom
  ipv6-subnet: 2001:db8:a::0/48

topology:
  nodes:
    vm-a1:
      kind: linux
      # image: alpine-ssh
      # https://hub.docker.com/r/mitchv85/ohv-host
      image: mitchv85/ohv-host
      mgmt-ipv6: 2001:db8:a:1::1
      # Here I don't know how to specify: 2001:db8:a:1::1/64

    vm-a2:
      kind: linux
      image: mitchv85/ohv-host
      mgmt-ipv6: 2001:db8:a:1::2
      # Here I don't know how to specify: 2001:db8:a:1::2/64

    vm-a3:
      kind: linux
      image: mitchv85/ohv-host
      mgmt-ipv6: 2001:db8:a:1::3
      # Here I don't know how to specify: 2001:db8:a:1::3/64

    vm-b1:
      kind: linux
      image: mitchv85/ohv-host
      mgmt-ipv6: 2001:db8:a:2::5
      # Here I don't know how to specify: 2001:db8:a:2::5/64

  kinds:
    linux:
      binds:
        - ./authorized_keys:/home/admin/.ssh/authorized_keys
      sysctls:
        net.ipv6.conf.all.disable_ipv6: 0
        net.ipv6.conf.default.disable_ipv6: 0

Problem: At the moment, I don't understand how to create two separate networks with Containerlab.

I don't know how to define the ipv6 prefix length of the eth0 interfaces of the different nodes.
For the moment, all the nodes belong to the same subnet 2001:db8:a::0/48, whereas I'd like to separate them into two networks:

• 2001:db8:a:1
• 2001:db8:a:2

Containerlab may not be suitable for this need.

It might be wise to explore the other alternatives mentioned in https://brianlinkletter.com/2024/02/open-source-network-simulation-roundup-2024/

Alternatively, this issue could potentially address my objective in the future: #2513

Question: Does Containerlab support the creation of topologies with multiple subnets?

See also: #2475

[hellt]

You will need to use bridges as a layer 2 network to which you connect Linux nodes with their non Management interfaces https://containerlab.dev/manual/kinds/bridge/

[steiler]

You should overall be looking at the links section of the topology definition. Thats how you define traffic carrying interfaces other then the once connected to the docker mgmt network.
https://containerlab.dev/manual/topo-def-file/#links

[stephane-klein]

Problem: At the moment, I don't understand how to create two separate networks with Containerlab.

I don't know how to define the ipv6 prefix length of the eth0 interfaces of the different nodes.
For the moment, all the nodes belong to the same subnet 2001:db8:a::0/48, whereas I'd like to separate them into two networks:

• 2001:db8:a:1
• 2001:db8:a:2

I managed to fix my problem and achieved my goal of creating two networks. See the result in this playground: https://github.com/stephane-klein/containerlab-playground