Solved Difficulty provisioning Yealink T21P phones

[Lee Cramman]

We've recently successfully finished prototyping a 3CX server in the cloud and decided it's the way to go for us so we've bought a license and are looking at a production system now. We're set up with a cloud server hosted by Google and decided that an SBC is the way to go, both for ease and because we want hot desking.

We have a mixture of Yealink T21P E2 and T21P phones (T21P E2 being supported and T21P being end of life). I'm aware that the T21P needs the "Only accept trusted certificates" setting to be disabled in order to provision correctly.

We had no difficulty provisioning our phones using the prototype system and the production setup is (supposed to be) configured exactly the same but is giving us issues...

So, the problem - any factory reset phone appears in the list of phones ready to be configured without issue but this is when we become unstuck. If it's a T21P E2 we assign / add an extension, the phone reboots and everything works. However, for the T21P nothing happens. No reboot, no message, no acknowledgement...

I'm obviously doing something dumb because this used to work... and I can't see what is different.

I'm struggling to troubleshoot this because it's not completely broken so there's nothing obviously wrong.

Can anyone give me some suggestions as to where I might try to start and troubleshoot this?

 

[AramS_3CX]

We've recently successfully finished prototyping a 3CX server in the cloud and decided it's the way to go for us so we've bought a license and are looking at a production system now. We're set up with a cloud server hosted by Google and decided that an SBC is the way to go, both for ease and because we want hot desking.

We have a mixture of Yealink T21P E2 and T21P phones (T21P E2 being supported and T21P being end of life). I'm aware that the T21P needs the "Only accept trusted certificates" setting to be disabled in order to provision correctly.

We had no difficulty provisioning our phones using the prototype system and the production setup is (supposed to be) configured exactly the same but is giving us issues...

So, the problem - any factory reset phone appears in the list of phones ready to be configured without issue but this is when we become unstuck. If it's a T21P E2 we assign / add an extension, the phone reboots and everything works. However, for the T21P nothing happens. No reboot, no message, no acknowledgement...

I'm obviously doing something dumb because this used to work... and I can't see what is different.

I'm struggling to troubleshoot this because it's not completely broken so there's nothing obviously wrong.

Can anyone give me some suggestions as to where I might try to start and troubleshoot this?

Hi Lee Cramman,
Please follow the following guide:
https://www.3cx.com/sip-phones/yealink-t20p-t22p-t26p-t28p/
Pay special attention to the point #2 of the "Known Limitations" section.
Also, due that it's a cloud installation and the phones are provisioned remotely, check the "SSL Transport and Ciphers" feature (Settings->Security page) - it must be disabled when the End of Life (T21P) phones are used remotely.

 

[Lee Cramman]

Thank you.

As I said in my post re point 2 of known limitations, I'm aware that the T21P needs the "Only accept trusted certificates" setting to be disabled in order to provision correctly.

However, your other suggestion about changing the SSL Transport and Ciphers setting in 3CX solved it (although I can't for the life of me remember having to disable that setting in the prototype system).

Many thanks for you help

 

[YiannisH_3CX]

Glad to see the issue has been resolved and thank you for updating the thread with your solution.