Incoming audio drops call stays open

[MarkLB]

We have had several occurrences of all calls dropping on our enterprise version of 3cx, the calls stay open until the agents close the calls but there is no audio coming from the customer.

We are using a cloud hosted Enterprise Annual version of 3cx v 15.5.0

Can anyone advise if this is most likely an issue with the provided VOIP lines, our internet connection or something else.

 

[HRMNY]

Are the phones using DirectSIP/STUN or SBC?

 

[Christopher Reagoso]

Is the system on premise or hosted cloud?

Have you run the firewall checker and got All-Green/Passed on it?

If your 3CX is cloud based, are you running 3CX SBC on prem to connect to the cloud (tip- always do this, unless you have something more enterprise eg, gateway vpn, but sometimes you still want SBC outside of the tunnel since you generally can't prioritize traffic in a tunnel).

 

[MarkLB]

@HRMY & @Christopher

Thanks for your replys
We are using an SBC and the firewall checker in the 3cx dashboard shows as all green.

 

[Christopher Reagoso]

Ok ... so , this one will be fun to fix.

Do a pcap at your onprem site at the phone at the same time the PBX is running a pcap and capture an audio loss event.

If you hear the loss at the phone pcap, but not at the 3cx pcap, it's something between you and your instance.

If you hear the loss at both the phone and 3cx pcap, then it's something with the carrier's audio not making it to/from the hosted instance.

ASLO - try enabling "PBX Delivers audio" for the extension and see if that helps.

On Another topic - The latest rage seems to be cloud hosting the instance.

Don't do this unless you have to. There are so many more benefits to having it onprem. - for example the carrier can release the audio to you - otherwise you're proxying it thru the system in the cloud back to you. You're much better off if your ITSP can release the carriers' audio RTP directly to your instance - and that instance is at your office (or your HQ)

 

[cobaltit]

So is it a problem of calls dropping or is it the calls disconnection (dropping or far end hanging up) but the call persists on your end until you hang up? You can try calling one of your numbers from your cell phone that rings through to an extension on your 3CX system. Don't answer it but hang up and see if your 3CX extension keeps ringing. If it does, then you have an issue with your provider. Otherwise follow the steps outlined by @Christopher Reagoso to find out where your network might be falling down.

 

[MarkLB]

@Christopher & @cobaltit
Thanks for your further replies, we had 2 more instances of this happening today it is a sporadic issue and is not regularly occurring.
The inbound audio from the customers dropped but the calls stayed open until our agents ended the calls.
This is evident in the recordings which are done on the same cloud hosted server, if the agents audio is present on the recording on the same cloud hosted server would this not indicate the issue is more with our voip line provider rather than something on our network between the agents phones and the cloud hosted server?
90% of our agents are using Deskphones in CTI mode, can we run pcap on the workstation connected to the phone to capture the audio? I would thing if the 3cx app on the workstation is in CTI mode then no audio would be going to the 3cx application on the PC.

-Mark