I try to ask you for some hints of how I solve this.
I have a fully function Backup Exec 10e installation that backups the server it's installed on, and one another server who are member in the same AD. Now there are a third server, that's a web server. Because it's a webserver it's located on DMZ and the firewall is set to block ALL Traffics between LAN and DMZ. This of course for security. The only traffic that are allowed, is ALL ports for LAN --> DMZ. But only an single SQLSERVER port from DMZ --> LAN.
This will of course cause som problems when I want to attach the third server to the backup routines. I don't know so much about what ports are needed to be open, and what software who needs to be installed (or remote installed?) for making this task. All comments about this might be of help.