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Yealink T21P E2 and 3CX V16.2 not playing nicely

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Sergio Fernandez

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Hi all

I have done a system upgrade from V15.5.6 to V16.2 which seems OK in itself. I have noticed that there are some peculiarities that are now occurring. We are using Yealink T21P E2 with firmware 52.84.0.35. This firmware is what 3CX and Yealink recommend for 3CX V16.2.

Some of the desk phones disconnect/un-register after a certain period of time
When there are several phones in a Call Queue and one of the phones tries to pick up several things happen
Call connects occasionally
Call does not connect
Call does connect but other phones in call Queue keep ringing
Call shows as ringing in the system but no desktop phones are ring.

Firewall tests show all is good. Wireshark traces show that the 3CX system is not getting the exspected response from the phones.ie
180 ringing
200 OK.

The resolve to this issue for me was to put the Yealink T21P E2 phone back to a known good firmware of 52.83.0.55

I suspect the issue is that the Yealink firmware has changed the way the it responsed back to the 3CX system, possibly on a different port or with a different code. This would be something for 3CX and Yealink to work on together

Regards
Sergio Fernandez
 
Hi Sergio,

After upgrading the PBX and the firmware of the phone, I would recommend to reset one of the phones at least and reprovision it again using the default updated 3CX templates.

By the way how are the phones connected to the PBX (STUN/Local/SBC/VPN) ?
 
STUN
 
Hi Sergio

I have tried to replicate the issue as per your description but my T21P E2 on FW 52.84.0.35 appears to work correctly under V16SP2 for the past couple of days.

It might be worth upgrading a phone again in this case, and running a capture on the phone itself to see if and where your phone is sending it and possibly the message is lost somewhere in transit for whatever reason.

Just to be sure, have you done port forwards on your firewall per each phone at the site? You might have the alternative of using the new SBC as well if you have several phones to help make NAT traversal easier.
 
Hi

I have factory reset the phone (Yealink T21P E2) and upgraded it from 52.83.0.55 to 52.84.0.35 and it is definitely doing something funky.
Phone is provisioned using Direct SIP (STUN - remote) using auto provisioning on the phone.


  • Calling the phone from another extention gives a ring tone but the phone does not ring.
  • Calls comeing into the queue ring on all phones in the queue but NOT this one,.
  • Webclient running in Chrome Version 75.0.3770.142 (Official Build) (64-bit) shows phone connected (see attched screen shot Screenshot 2019-07-17 at 09.31.57.png)11412


I suspect the phone system thinks the phone has gone to sleep as a restart of the phone allows direct calls.

This was not happening in Firmware 52.83.0.55

Regards
 
Below is an an extract from the event log to show what is happening



 
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