Call forward media problems


We use an UCM6301 as our PBX. We have multiple GXP2135 and some GXP2170 behind the pbx. When doing an initial setup we also checked if the Callforwarding was working and I guess we concluded that it is working once hearing that the forwarded destination rang. Guess noone checked if there was media.

Now we noticed that the signaling part of the Forwarded call does work, the media however does not.

We have the following users:

userA external user
userB GXP phone behind the PBX
userC mobile phone of the userB

On the PBX we turned on userB call forward if no answer towards userC. Once the call is made from userA towards userB the call rings and after the set period jumps over to userC. If userC answers the call he does not hear userA.

Just to make something clear. If userA calls userC (both being external) they hear each other. If userB calls userC they can also talk. The only problem is that the media fails if the call from A to C goes through the PBX (following the CFWD logic).

Is there something I can check quickly or does the problem require a trace?


increase RTP timeout to 10 or 15
PBX setting=> SIp settings=> tos

also ensure all network are entered into sip nat settings if still fails do network capture , also confirm SIp alg is turned off at all sites


In the end I looked at some other PBX systems I configured in the past. Similar problems were solved by forcing the PBX to not route the media. I did some searching and in the end found the “IPVT mode” setting under the SIP trunk. Once this setting was enabled the call forwarding media problems were solved.


I am not sure that is the solution you seek; although if it works, its hard to argue with.

IPVT mode is for connection using a peer trunk to IP Video Talk or an IPVT server. I had to find the 6202 manual as GS apparently has changed the product pages around making it problematic to find things. The manual does not go into detail as to what the setting does other than to indicate its usage with the IPVT service and that if not enabled, it could cause problems.

I have never set IPVT and have not had an issue in forwarding externally.


I get this description under the UCM6301:

“Similar to Enable Direct Media . The PBX will attempt to redirect the RTP media streams to bypass the PBX and to go directly between caller and callee. Primarily for use with trunks to IPVT.”


Then that same setting is in the extension settings under media and is what I will use when needed.