Adding network to machine deployed by Juju

Question

I have a small OpenStack cluster deployed with Juju/MAAS. How can I add an extra network to one of the already deployed machines? Because the cluster is operational I would like to avoid redeploying the machine.

What I want to achieve is for the machine and all its LXCs to have interfaces on the new network, this in order to be able to use the os-public-network option on the various OpenStack API charms.

I have been unable to find any documentation on how Juju sets up networks, but this is how I imagine it would work. Let us assume the interface of the new network is eth2. Then Juju would:

• Create a bridge interface br2 and connect eth2 to it. Add to /etc/network/interfaces:

  auto eth2
  
  source /etc/network/eth2.config
  

  Add to /etc/network/eth2.config:

  iface eth2 inet manual
  
  auto br2
  iface br2 inet dhcp
    bridge_ports eth0
  

• Update templates from LXC in /var/lib/juju/containers/juju-trusty-lxc-template/lxc.conf and /var/lib/lxc/juju-trusty-lxc-template/config by appending

  lxc.network.type = veth
  lxc.network.link = br2
  lxc.network.flags = up
  

• Do the same thing for existing LXC in /var/lib/juju/containers/juju-machine-*-lxc-*/lxc.conf and /var/lib/lxc/juju-machine-*-lxc-*/config.

Is this a correct interpretation of how Juju would set things up? Are there other considerations?