Hi Stuart:
Usually, you need to add a bridge to all network nodes, you can use "ovs-vsctl add-br {br-name}" to add a ovs bridge, then you need to add a physical port to that bridge by executing "ovs-vsctl add-port {bridge} {port}".
another alternatives, you can append the physical port to neutron_external_interface variable in globals.yml. in this case, kolla will create the ovs bridge automatically.
both of them, you need set octavia_network_interface and configure external switch properly.
if you really don't know how this works, I propose you use "octavia_network_type: tenant" ref: [0] , in this case, kolla-ansible will setup the octavia management network for you, you don't need to do anything.
thanks.