The best approach to make it work is the following:
Imagine you have networks A and B.
When networks A and B have connectivity between them, use the OpenVidu server of network A as the only OpenVidu server and just forget the OpenVidu Server of network B. Only when there is no connectivity between networks, the users of network B will use the server in network B.
You don’t have to connect OpenVidu servers in any way. Just use the same OpenVidu server for all users when networks are connected.
Regards