Do all media servers need to communicate with each other in SSO at 7.6 or greater?

[TomAbrams]

We have a complicated multi-tenant (different customers) with media servers on separate networks separated by multiple firewalls. Does port 1556 have to be opened in all of the firewalls between all of the media servers for SSO, or does the master control all this coordination now? Make sense to me the master would do this now with all of the enhancements made to simplify firewall configs in netbackup over the years, nothing can run if the master is not running, so seems logical place to control all the communication / coordination. Does anyone know if all of the media serverrs need to talkj to each other still? Thanks, Tom.  

[TomAbrams]

Additional Info: This is for sharing a SAN attached tape lib and tape drives only, no shared disk, no need for the media servers to need to communicate with each other for any other reason. Thanks, Tom

[Marianne · Accepted solution]

If memory serves me right, only connectivity to the Master (EMM server) is needed as well as with Robot Control Host (if not the master). 
Only port 1556 (bidirectional) is needed.