'Create a vlan and bridge unless they already exist.'

@staticmethod
def ensure_vlan_bridge(vlan_num, bridge, bridge_interface, net_attrs=None, mac_address=None, mtu=None):

    interface = LinuxBridgeInterfaceDriver.ensure_vlan(vlan_num, bridge_interface, mac_address, mtu)
    LinuxBridgeInterfaceDriver.ensure_bridge(bridge, interface, net_attrs)
    return interface
