Is there any way in Hell this could happen?

System Asterisk 13.

Customer using SIP trunks. Occasionally they get a call that appears to be merged, at least one side of the audio. This has happened in about a half dozen times in the last 6 months. I think that it is on the other end of the call before it gets to the SIP trunk provider. I have never been able to capture this or re-create this.

You say “merged” but talk about a whole bunch of single things. I’d quote “The Princess Bride” here, but that’s just mean.

Of course, it’s possible. In the olden days, it was called “getting your wires crossed.” It can happen with POTS phones at almost any point in the circuit, so wouldn’t it be impossible here. We go out of our way to simulate all sorts of stupid stuff like that all the time.

Sorry I guess I didn’t explain the issue so well. They hear one side of another conversation. I might think that they somehow enabled Channel Spy. I have seen this in pots lines, but all this is now digital. OK so it probably is way out of our control and due to some instance of a crossed pots line somewhere.

Are the random calls that they are hearing, are they of other people in the organization, or random calls belonging to totally unrelated people? This would be one way of starting to trace the problem. If its pure sip calls, possible its a provider issue on their PRI’s or PBX system.

If your using a sip trunk make sure any sip alg and upnp is disabled on your router then port forward the sip port 5060 and the correct rtp ranges

Dickson – They did not recognize the person on the call, so we thing it is outside the organization. Their calls are all SIP and the Clec is using a Metaswitch. I do not know what their trunk situation is.

Jas_williams – They have been using SIP through the same Sonicwall for several years.

yep seen it with chan spy as well.

what versions of asterisk are you using ?

We have also had it where someone enables chanspy in whisper mode and left headset on desk so skipped about as calls stared and ended.

might be worth recording calls for a short while and listen to them , Thats how we tracked it down

Thanks Ian

I will just remove the Chanspy code, they are a health org so listening in on a conversation is a big No No.


Just on a whim, double check your UDP range for RTP ports. If you are using a “trimmed down” range, you might be double allocating an RTP port in the firewall?

Good idea Dave. As far as I know the firewall is open to udp 10000-20000 as well as the phone system.