One Way Audio

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Asterisk Users 7 Comments

I am having trouble with no return audio on inbound calls. I have been
working on this for 18 hours and even built a fresh server and moved
everything over and I am getting the same results. I need someone that can
help get this resolved tonight. I can provide access to all machines

Please email me at if you can help.

7 thoughts on - One Way Audio

  • One way audio is almost always a NAT issue. Have you setup your RTP
    ports properly on your firewall?

  • Can you do a tcpdump to look at the rtp streams on your box and check they are both generating and aiming at the right places

    IAX will have no issue with NAT/firewall but SIP / RTP can.

    tcpdump -nn udp and portrange 10000-20000
    (pick your portrange if its operating on something else)

    Should show you mad lines of rtp going backwards and forwards (like below) when there is a conversation in place. If you can see it being sent from the asterisk box but not heard by the client then either try a different client, or something is blocking the return leg to your client

    13:00:21.309139 IP > UDP, length 172
    13:00:21.328703 IP > UDP, length 172
    13:00:21.348572 IP > UDP, length 172
    13:00:21.369096 IP > UDP, length 172
    13:00:21.388572 IP > UDP, length 172

    Cheers Duncan

  • So that suggests audio is flowing as follows in a unidirectional manner

    Somewhere near the end this pops up which is slightly different, I am guessing is your asterisk box

    I am not sure why this is happening or if its still part of the same conversation

    Overall it looks a bit like the asterisk box thinks it needs to send rtp to a different location than perhaps its meant to i.e. its asymmetric – you can check the sdp in the sip invite to see where media is expected to be sent to

    There is no rtp coming back from so possibly this is device that isn’t meant to be part of the conversation and either doesn’t exist or is not expecting anything and thus not responding

    What are the addresses of the devices in this conversation? so that you can match the traffic to device

    Cheers Duncan

  • I’ve been having a similar (well exactly the same) problem this last
    week and have been bashing my head trying to fix it.

    Just one question, are you using RealTime?


  • Still not working now that audio is restored jitter makes it inaudible? I
    am ready to move this to commercial if someone can tell me how I need to pay
    for support,