Thanks for the detailed info! This makes giving advice so much easier.
All you need is port 1556 (PBX) and 13724 (vnetd).
Master <- 1556 -> media server (bi-directional)
Master <- 13724 -> media server (bi-directional)
Because media server is robot control host, you also need:
media 1 <- 1556 -> media 2 (bi-directional)
Port Usage Guide for Windows and UNIX Platforms (
http://seer.entsupport.symantec.com/docs/281623.htm )