Trouble With RTP

[Vaxley]

Hello,

I am tying to figure out an issue that I am having with an SMBC and some SIP trunks.
I have an SMBC on a customers LAN, without an MBG. It communicates out through a firewall to register with the SIP provider.

I am troubleshooting an issue where inbound calls need to get transferred back out to an external number, and when this transfer is made all audio gets lost. I have gone through the PCAPs I could pull out of the SMBC, and the PCAPS from the SIP provider side. So far, all I have been able to determine is that RTP packets are not flowing once the transfer operation completes.

Does anyone have any input on how to troubleshoot this, or forms and fields to check?
Any help would be greatly appreciated!

[ralph]

Not gonna happen without an MBG as an anchor point.
After the call is set up then the audio sent directly from endpoint to end point.
Without an MBG to act as an endpoint, the audio won't know how to get to the external number.

Ralph

[Tech Electronics]

Vaxley,

Ralph is correct, but here is a more "technical' explanation if you need one.
 
You have to be aware that the MCD is not NAT aware and has nowhere to put a public IP Address for transfers out of its own network.

Although the call will go out it will not know how to route the packets properly after that.

Look at the SDP portion and see where it is showing the RTP packets are to be routed, and it will make more sense to you then.

Thanks,

TE