Comment 3 for bug 1767607

Won't this work?

network:
  version: 2
  renderer: networkd
  ethernets:
    ens3:
      addresses:
        - 10.20.30.40/32
      routes:
        - to: 0.0.0.0/0
          via: 10.10.10.1
          on-link: true

Clearly we need to do better for how to easily define a peer-to-peer interface, since this isn't so easily discoverable.