We recently picked up a client who is using a Samsung OfficeServ 7200 for their phone system and they want us to set it up so that users outside the internal network can connect back to it across the web. This system was in place before we came on board with them. Currently what will happen is if you place a call out from the phone that is outside the network it won't get any kind of ring trills but it will ring the phone you are calling, when you pick up the phone audio cannot be heard on either end. If you call into the direct dial number for the phone it will ring typically once and then the phone you calling it from will start emitting a loud screeching sound, and everyonce in a while you will get a busy signal. In addition to forwarding the below ports I have also tried setting up a VPN, configuring the phone to point to the Office Serv's local IP and it would just sit there and try to reconnect over again. I have forwarded the following ports to the phone system:
UDP: 30000-30031 (RTP)
TCP and UDP: 9000 and 9001 (SIP I think)
TCP and UDP: 6000 (this was in their old firewall config so I added it to the list)
Firewall on Both Sides: Cisco ASA 5505 (ASA 5505 at client site where the Office Serv is located replaced a firebox
So from what i can tell and from looking at the firewall logs 9000 and 9001 are getting through just fine, and the phone does register with the phone system, and I can see different lamps on the phone lighting up, which indicates that the phone can communicate with the system but for whatever reason the actual voice traffic doesn't seem to be going through in either direction.