What is the use of the Dead VLAN tag 4095 on quantum openvswitch plugin?

Asked by Vangelis Tasoulas

When I run "ovs-vsctl show", sometimes I see some ports with VLAN tag 4095

After doing some search I couldn't find much references on it except the source file "ovs_quantum_agent.py" which looks like this:

# A placeholder for dead vlans.
DEAD_VLAN_TAG = "4095"
def port_dead(self, port):
        '''Once a port has no binding, put it on the "dead vlan".

        :param port: a ovs_lib.VifPort object.'''
        self.int_br.set_db_attribute("Port", port.port_name, "tag",
        self.int_br.add_flow(priority=2, in_port=port.ofport, actions="drop")

The question is why '''Once a port has no binding, put it on the "dead vlan" and not destory it?

Question information

English Edit question
neutron Edit question
No assignee Edit question
Solved by:
Salvatore Orlando
Last query:
Last reply:
Revision history for this message
yong sheng gong (gongysh) said :

I think it is just for the sake of 'safety'. we don't want the quantum components to make mistake. but I am not sure.

Revision history for this message
Best Salvatore Orlando (salvatore-orlando) said :

Every port on the integration bridge which cannot be mapped to a neutron port, and is therefore unknown to neutron, is put on this vlan, thus avoiding this port cannot snoop or generate traffic on tenants' networks.

Revision history for this message
Vangelis Tasoulas (cyberang3l) said :

Thanks Salvatore, it makes sense now.