auto lo br0
iface lo inet loopback

if br0 inet static
  address 10.20.30.2
  netmask 255.255.255.0
  gatweay 10.20.30.1
  bridge_ports eth0

iface eth0 inet manual
  up ifconfig $IFACE 0.0.0.0 up
  up ip link set $IFACE promisc on
  down ip link set $IFACE promisc off
  down ifconfig $IFACE down