auto eth0 iface eth0 inet static address 192.168.200.101 netmask 255.255.255.0 gateway 192.168.200.1
if [ $IFACE = "eth0" ] ; then ip addr add 192.168.200.102/24 dev eth0 fi
if [ $IFACE = "eth0" ] ; then ip addr del 192.168.200.102/24 dev eth0 fi