No Audio to certain extension from certain extensions, without any obvious common propertis or logic

[teichhei]

Hi,
I thought I share this due to its weirdness, maybe somebody has an explanation.
I'm running on V14 SP 3, with local and remote extensions. One day, without changing anything, certain local extensions and also certain remote extensions were not transmitting audio in any direction anymore to a door station, a local extension. They worked between each other and on trunks, as well as some could still talk to the door. In wireshark the call setup was fine and RTP packets went both ways, same CODEC on both legs, but they only contained low volume noise. The door station could still go out on any trunk OK.
After a long night and a lot of investigation I couldn't see the logic in it. So I registered the phoned that did not work with credentials of phones that did work. And all of a sudden the door started working again.
Then I recreated the faulty extensions and they came good.
So for myself I ruled out firewall issued, phone/door firmware, any STUN or proxy settings, transcoding issues. I think it is a 3CX service itself playing up.
Settings were the same as before in the 3cx GUI, but something must be different.
Does anybody have any idea how this can happen or had a similar case? Or a better fix than deleting and recreating extensions?

Kind Regards

Heinz

 

[leejor]

Could it be a device (switch?) on your network? I've seen other, inexplicable issues caused by "something" that "shouldn't do that".

 

[teichhei]

I thought that too since it is a layer 3 switch.
But the disturbing thing is that after deleting and recreating the extension it was fine. Same switch, same MAC addresses. Didn't even reboot the switch.
As if something in the extension configuration told that one endpoint during the call setup to send an empty audio stream when connecting to those other affected phones.
Like a Codec mismatch, but wireshark said the Codec was PCMU on both legs.