It was discover during the developing of the scenario-A data-plane-adoption that OVN has an iptables filter rule that only accepts connections coming from the same network. 

Due to scenario-A testing the adoption where tripleo and next gen has different networks a new step on the adoption process was added, that being adding a new iptables to accept traffic from the new next gen network. Currently this next gen network is hardcoded. It could be nice to have it parameterize so it can be customized. 

The file where the iptables is added is data-plane-adoption:tests/roles/ovn_adoption/tasks/main.yaml [0]

 [0] https://github.com/openstack-k8s-operators/data-plane-adoption/pull/664/files#diff-99bc82f32e98ef131cd9bdf8c3840aca9a0cf58ef6620bac4abd594395991160R157