One way audio

Hi all,

Yes, one way audio again :smile:. I am new on this VOIP matters and I have read a lot about it but I am not able to understand why is happening to me. I know that one way audio issue is related to NAT and yes, I am behind a NAT:

VoIP handset (10.0.0.X) --> TrixBox ( --> GW ( --> internet


  • Softphones work (qutecom)
  • Yealink handsets only work in first call but with a ~8 secs silence at the beginning but not delay in the conversation
  • Yealink handsets one way audio on second and following calls. Caller can hear. Again starts with ~8 secs silence after picking up the phone
  • If the Yealink handset is powered off and on again, first call does work, following doesn’t
  • I tried with 3 yealink VoIP phones, always the same issue

I think that if there were a NAT problem the VoIP, handset and softphones, won’t work ever but I am not sure. SIP and RTP ports are opened in the GW.


Thanks guys

Try doing a packet capture on the Asterisk server with tcpdump and analyze the call with Wireshark. You will quickly see when/if audio reaches the Asterisk sever.

Are you using Asterisk with no GUI or are you using a GUI distribution?

Yes, I did it but forgot to mention. I am able to listen conversation in both ways. That is one of the reasons why I think the problem is with the handsets. The other reason is that softphones work.

It is a trixbox with GUI

If Asterisk receives and sends RTP packets correctly (you confirmed this by capturing the packets on the Asterisk box), the problem is definitly in the handset, the network path between the Asterisk and the handset or in Asterisk server firewall.

Thanks mate. I will continue researching.