auto br0
iface br0 inet static
        address 10.20.30.1
        netmask 255.255.255.0
        network 10.20.30.0
        broadcast 10.20.30.255
        pre-up /usr/sbin/openvpn --mktun --dev tap0
        post-down  /usr/sbin/brctl delbr br0
        bridge_ports tap0 eth1