Are we talking about opening ports between ePO servers? If so you'll need to register each server, which means they'll need to communicate on 8443 (by default.) For rollup reporting the "parent" server will also need to query the SQL server for each registered ePO server - you configure this as part of the server registration - so the SQL port (1433 by default) will also need to be open.
Yeah, I understand the need to register the servers. Thanks for the assistance.