# interface "eth0"
  auto eth0
  iface eth0 inet static
      address 0.1.2.3
      netmask 255.255.255.255
      dns-nameservers ns1.invalid ns2.invalid
      post-up ip route replace 0.1.2.1 dev eth0
      post-up ip route replace default via 0.1.2.1
      post-down ip route del default via 0.1.2.1 || true
      post-down ip route del 0.1.2.1 dev eth0 || true