Previously, in Red Hat Enterprise Linux OpenStack Platform 7, the networks that could be used on each role was fixed. Consequently, it was not possible to have a custom network topology with any network, on any role.
With this update, in Red Hat OpenStack Platform 8 and higher, any network may be assigned to any role.
As a result, custom network topologies are now possible, but the ports for each role will have to be customized. Review the `environments/network-isolation.yaml` file in `openstack-tripleo-heat-templates` to see how to enable ports for each role in a custom environment file or in `network-environment.yaml`.