[Serusers] No audio when terminating on the PSTN

[Andrei Pelinescu-Onciul]

On Jun 20, 2004 at 15:00, John A. Hull <john at tech-terra.com> wrote:
> I'm a SIP/SER newbie, so please forgive me if the answer to this is
> obvious to someone experienced:
> 
> I currently have SER running as a registration and outbound proxy
> server, and I am able to forward calls to a PSTN gateway. Right now
> SIP-to-PSTN calls are establishing sessions, being neither side is able
> to hear the other talking. The softphone user is behind a
> restricted-cone NAT, for which I'm using a STUN server to traverse. I
> have surmised that this is an issue of the RTP packets not being able to
> reach the client through the firewall, but I would expect the PSTN phone
> to be able to hear the audio from the client. Is there a simple cause of
> and solution to this problem that I'm overlooking?

Your nat might be missdetected as restricted cone and might be in
fact symmetric port-preserving.
Try to dump the udp traffic before and after the nat box. This is the
only way you can tell what's happening.


Andrei