Since ovn is the default in OSP15 - makes sense to include the external network under compute in /usr/share/openstack-tripleo-heat-templates/roles_data.yaml Environment: openstack-tripleo-heat-templates-10.5.1-0.20190520170359.0c31f04.el8ost.noarch Compute includes only these networks: networks: InternalApi: subnet: internal_api_subnet Tenant: subnet: tenant_subnet Storage: subnet: storage_subnet Not having External means the user has to always override when deploying the default network backend.
I don't think computes need to be connected to the External network. They only need the br-ex bridge. Connecting the computes to the External network means they would get an IP address on this network which I don't think it's necessary.
As we have a bug for adding br-ex for computes - https://bugzilla.redhat.com/show_bug.cgi?id=1694213, marking this a duplicate. *** This bug has been marked as a duplicate of bug 1694213 ***