Currently Kolla operators are restricted to configuring one physical
network (physnet1).

This change along with ml2_conf.ini augmentation can be used to setup
multiple physical networks in openvswitch.

E.g. To configure two physical networks, physnet1 and physnet2, with
ports eth1 and eth2 associated respectively:

In /etc/kolla/globals.yml, set

neutron_bridge_name: "br-ex,br-ex2"
neutron_external_interface: "eth1,eth2"

In /etc/kolla/config/neutron/ml2_conf.ini

[ovs]
bridge_mappings = physnet1:br-ex,physnet2:br-ex2

Co-Authored-By: Mick Thompson <michael.a.thompson@oracle.com>
Closes-Bug: #1625700
DocImpact

Change-Id: I9454ca98d9b058368129123109ccc56f95519874