'Plug in the interface.'

def plug_new(self, network_id, port_id, device_name, mac_address, bridge=None, namespace=None, prefix=None, mtu=None):

    ip = ip_lib.IPWrapper()
    tap_name = self._get_tap_name(device_name, prefix)
    (root_dev, ns_dev) = ip.add_veth(tap_name, device_name)
    root_dev.disable_ipv6()
    self._ivs_add_port(tap_name, port_id, mac_address)
    ns_dev = ip.device(device_name)
    ns_dev.link.set_address(mac_address)
    if mtu:
        ns_dev.link.set_mtu(mtu)
        root_dev.link.set_mtu(mtu)
    else:
        LOG.warning(_LW('No    MTU    configured    for    port    %s'), port_id)
    if namespace:
        namespace_obj = ip.ensure_namespace(namespace)
        namespace_obj.add_device_to_namespace(ns_dev)
    ns_dev.link.set_up()
    root_dev.link.set_up()
