auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
auto usb0
iface usb0 inet static
        address 192.168.2.15
        netmask 255.255.255.0
        gateway 192.168.2.14

auto br0
iface br0 inet dhcp
    bridge_ports gprs0
    bridge_fd 5
    bridge_stp no