'Create namespace, request port creationg from Plugin,
then configure Floating IP gateway port.'

def _create_gateway_port(self, ex_gw_port, interface_name):

    self.create()
    LOG.debug('DVR:    adding    gateway    interface:    %s', interface_name)
    ns_name = self.get_name()
    self.driver.plug(ex_gw_port['network_id'], ex_gw_port['id'], interface_name, ex_gw_port['mac_address'], bridge=self.agent_conf.external_network_bridge, namespace=ns_name, prefix=FIP_EXT_DEV_PREFIX, mtu=ex_gw_port.get('mtu'))
    ip_wrapper = ip_lib.IPWrapper(namespace=ns_name)
    devices = ip_wrapper.get_devices()
    for device in devices:
        name = device.name
        if (name.startswith(FIP_EXT_DEV_PREFIX) and (name != interface_name)):
            LOG.debug('DVR:    unplug:    %s', name)
            ext_net_bridge = self.agent_conf.external_network_bridge
            self.driver.unplug(name, bridge=ext_net_bridge, namespace=ns_name, prefix=FIP_EXT_DEV_PREFIX)
    ip_cidrs = common_utils.fixed_ip_cidrs(ex_gw_port['fixed_ips'])
    self.driver.init_l3(interface_name, ip_cidrs, namespace=ns_name, clean_connections=True)
    self.agent_gateway_port = ex_gw_port
    cmd = ['sysctl', '-w', ('net.ipv4.conf.%s.proxy_arp=1' % interface_name)]
    ip_wrapper.netns.execute(cmd, check_exit_code=False)
