This is a question about a Netbackup 6.5 deployment.  We are currently using separate master servers for our internal clients and our external clients in both of our primary datacenters.  This equates to four separate backup environments to manage.  We would like to have one master for all of our environments.  We are thinking about one master server in our primary location, a media server in the secondary location and media servers for the two external environments.  We would open ports to allow the external media servers to communicate through the firewall to our internal master server, giving us a single view for all backups. 

  However, when reading the documentation, Symantec recommends having a separate master per firewall domain and using NOM to manage all of them.  We do not want to pay for three additional master server licenses and a NOM license.  Is anyone already doing this, or have any opinions as to why I would not do it?

Thanks.