Caller cannot hear the 3CX user.

[Earthbound]

Version" 18.0 update 9 build 20
Windows Server 2022 (hyper-v guest)
Hosted: On-Premise
Provisioning: Local
Trunk provider: Callcentric (green light)
Firewall Checker: Passes
Custom templates: no

Incoming and outgoing calls; the 3cx user cannot be heard. Dialing out to the works but the receiver of the 3CX call cannot hear us. No changes have been made to the router or to our 3CX system in a very long time. I the admin that inherited this VOIP 3CX system and I am stumped. Everything was working fine Monday, Tuesday it started to get worse. Did a recovery of Sunday nights backup just to ensure nothing changed. Any suggestions as what I should look at would be very much appreciated. Thank you in advance!

More pertinent info, two Patton Gateways, SN4141 connected to Xfinity. Everything in the Pattons checks as "ok".

 

[SweetAction]

Normally I would say this is a firewall issue with the RTP ports between the SIP Provider and 3CX. But if you are getting a PRI from Xfinity and terminating into a patton, then the patton to 3CX, I'm going to assume that the patton and 3CX are in the same LAN and no firewall is between them.

In which case you want a packet capture from 3CX to see if the media stream makes it from the patton over and if not, a packet capture on the patton to see if it gets the media from Xfinity.

 

[Earthbound]

Correct on the assumption. I will double check the RTP ports as a potential issue before moving onto the wiresharking. Thank you for the feedback will post my results.

 

[SweetAction]

RTP ports

9000-10999 UDP If I remember correctly. From Patton to 3CX.

 

[OlegR_3CX]

Range 9000-10999 will be for all the external ports (Trunks, WebRTC, STUN etc).
Internal ports (when communication directly between the local IP of the Phonesystem to the phone, and gateway) are 7000-8499

 

[Earthbound]

In conclusion... it ended up being the Xfinity telephony modem. We finally put a handset directly to each of the 4 lines and the primary line and one other where the issue. After pulling the power and the battery out of the unit and forcing a reboot, it became fully operational again. We are having it replaced.

Thank you very much for your time and help!