Two extensions cannot hear each other, no other extensions affected

[JimNX]

I set up a new 3CX system yesterday for a client and pretty much everything is working as planned -- they have approximately 40 extensions, 5 of which are physical desk phones. All phones (desk and mobile app) can call out and receive calls. Extensions can dial each other and communicate without issues, except...

We discovered that two specific extensions cannot hear each other when they dial each other, however they both can hear any other extension. We discovered this when one of the extensions parked a call and then tried to dial the other extension to notify them of the call.

The problem extensions are 200 and 236, both Yealink T46S desk phones.

Ext 200
- SIP 5065
- RTP Start 14000
- RTP End 14019

Ext 236
- SIP 5068
- RTP Start 14060
- RTP End 14079

We're running a professional license on version 18.0 (Build 1379), hosted by 3CX.


Is there an options or something small that I'm missing?

 

[Kevin@voxtelesys]

Do you have PBX delivers Audio enabled on both extensions? What codecs are you using?

 

[JimNX]

I do not have "PBX Delivers Audio" enabled on any of the extensions. Just to be sure, I went and checked other instances of 3CX and they are all set up the same way -- that is not enabled. (the other instances work fine and all other extensions work fine too)

The codecs listed for both problem extensions (and all others are):

PCMU
PCMA
G722
G729

 

[JohnS_3CX]

Hi Jim,

It sounds like you have deployed STUN phones.

Please go ahead and read the following article, ensure that all requirements are met.
Don't be fooled by the fact that the rest happen to work - it's simply a matter of luck.
They will also develop issues later on unless all the requirements are all met


Alternatively if you have a bunch of phones at the same site, consider deploying an SBC there - it will make your life much easier and trouble-free.

Let us know how it goes!