infr/topology.py: add external port to ovs managed by mininet
infr/topology.py: add external port to ovs managed by mininet

hsnlab/escape,5GExchange/escape,5GExchange/escape,hsnlab/escape,hsnlab/escape,5GExchange/escape,5GExchange/escape,5GExchange/escape,hsnlab/escape,5GExchange/escape,hsnlab/escape,hsnlab/escape