i2050 soft phone from laptop over vpn

[JonathanInOttawa]

When I use my laptop from home and connected via vpn I am having trouble hearing and talking on calls, I can ring a phone but can't hear anything when it picks up.
At home I have a dlink di-604 router, I have added the laptop to the dmz.
At work, my firewall and vpn client is a netscreen ns5xt appliance, when connected via the vpn I believe I am not blocking any ports.

 

[JonathanInOttawa]

I have done a little more testing, I have plugged my laptop directly to my cable modem by-passing the dlink router, I still have the same problem. Looking at the similar post, I have added the IP address of the firewall as the next hop in routing of the BCM.(default gateway)
The BCM is connected to our local LAN via a sigle connection, it is a BCM 300 purchased May 2003.
The laptop i2050 client worked fine when connected directly on the lan at work.