You have to open ports used by the BCM software for
1. UNISTIM (signaling)
2. RTP (media)
The UNISTIM signaling port number is 7000.
To find out what the configured RTP port range(s) are, connect to the BCM using Element Manager and go to Resources - Port Ranges. In the RTP over UDP section, you'll see the ranges that you must open. By default, I think there is one range 28000-28249.