iface eth0 inet static
  address   1.2.3.4
  netmask   255.255.255.0
  gateway   1.2.3.1
  up route add -net 1.2.3.4 netmask 255.255.255.0 gw 1.2.3.1 eth0
  up ip addr add 4.3.2.1/32 dev eth0
  down ip addr add 4.3.2.1/32 dev eth0