network:
  version: 2
  ethernets:
    eth0:
      addresses:
        - 1.1.1.1/24
        - "2001:cafe:face::1/64"
      routes:
        - to: default
          via: 1.1.1.254
  tunnels:
    he-ipv6:
      mode: sit
      remote: 2.2.2.2
      local: 1.1.1.1
      addresses:
        - "2001:dead:beef::2/64"
      routes:
        - to: default
          via: "2001:dead:beef::1"