iface eth1 inet static
iface eth2 inet static

auto br1
iface br0 inet static
    address 192.168.1.230
    netmask 255.255.255.0
    gateway 192.168.1.1
    bridge_maxwait 0
    bridge_ports eth1
    bridge_fd 0

auto br2
iface br0 inet static
    address 172.16.1.254
    netmask 255.255.255.0
    gateway 172.16.1.1
    bridge_maxwait 0
    bridge_ports eth2
    bridge_fd 0