Blended/mixed audio on phone calls

[mcreedjr]

This is going to sound bizarre, so please be gentle.

I've got a customer with a self-hosted v20 PBX and ~20 Yealink T43U phones that is experiencing an intermittent problem where they claim audio from inbound PSTN calls is 'mixed' or 'blended' together which results in the two external participants able to hear portions of one another's calls.

Unfortunately, I'm using an unsupported SIP trunk provider, so I believe my official support options are limited. The SIP trunk is presented to the 3CX VM using a second NIC. Inbound and outbound calls work fine over this trunk save for this very intermittent issue.

The PBX and the phones are all in the same VLAN with no firewall between the PBX and the phones.

Anyone have thoughts on how best to start troubleshooting this problem? I plan to run a tcpdump process capturing SIP traffic on a rotating buffer in hopes I can retroactively go back and look at SIP messages when a reported incident occurs. Any thing else I may be overlooking?

 

[Alphabetic]

How are the phone provisioned? Default templates? Firewall check passing?

 

[Lee Cramman]

I would be taking a long hard look at the SIP trunk provider.

I would start by adding a supported provider for testing - if the problem is not present for calls through the second provider, you know where to look for the issue.