NovaException: Unexpected vif_type=binding_failed

nova/virt/libvirt/vif.py:                _("Unexpected vif_type=%s") % vif_type)
NovaException: Unexpected vif_type=binding_failed

:/opt/stack/nova$ git grep binding_failed
nova/tests/unit/compute/test_compute_mgr.py:    def test_init_instance_with_binding_failed_vif_type(self):
nova/tests/unit/compute/test_compute_mgr.py:        # this instance will plug a 'binding_failed' vif
nova/tests/unit/compute/test_compute_mgr.py:                    "Unexpected vif_type=binding_failed")),

创建instance出错时出现以上错误。

在neutron vif binding出错时会返回：

vif_type=binding_failed

-- ::32.775 ERROR neutron.plugins.ml2.managers [req-6541d965-bf7f-44a6-aae7-70773042fc1a neutron c8ce7938e38b4612a8b3daab441b804c] Failed to bind port 78de1224-0c09-40e0--0e009380dacd on host yuntong-ThinkStation
-- ::32.775 ERROR neutron.plugins.ml2.managers [req-6541d965-bf7f-44a6-aae7-70773042fc1a neutron c8ce7938e38b4612a8b3daab441b804c] Failed to bind port 78de1224-0c09-40e0--0e009380dacd on host yuntong-ThinkStation

neutron/extensions/portbindings.py:VIF_TYPE_BINDING_FAILED = 'binding_failed'

-- ::02.122 ^[[;31mERROR neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent [^[[;36mreq-d618ca64-5f42--8f5f-8d7d1e40a4fd ^[[;36mNone None^[[;31m] ^[[;35m^[[;31mBridge br-ex for physical network public does not exist. Agent terminated!

neutron log显示缺少br-ex bridge,查看devstack中如何创建该bridge：
devstack/lib/neutron_plugins/linuxbridge_agent

function neutron_plugin_configure_l3_agent {
    sudo brctl addbr $PUBLIC_BRIDGE
    iniset $Q_L3_CONF_FILE DEFAULT external_network_bridge
    iniset $Q_L3_CONF_FILE DEFAULT l3_agent_manager neutron.agent.l3_agent.L3NATAgentWithStateReport
}

创建br-ex bridge：

sudo ovs-vsctl add-br br-ex