Solved Yealink T48S Network Unavailable when DND turned ON

[Jim Friesen]

Good morning
I hope I'm posting in the correct place.
We have a client that has an interesting issue that has manifested in the last 30 days

When turning on DND on a Yealink phone, the phone has a popup that says "network unavailable". It also disappears from the phone list in 3CX and we cant access the phone UI thru IP
However the PC connected thru the phone has network connectivity.
If we turn off DND and reboot the phone seems to come back online.
Nothing major has been done to the system and no major changes in settings that we are aware of

We have tried:
DHCP settings as well as Static IP settings on the phone.
Factory resetting the phone, and re provisioning.
Swaping out the phone with a known working phone. The original phone was a Yealink T29G it is now a T48S
Factory resetting the T48S phone, and re provisioning it as well.
Double checking extension settings, all appear to be set correctly and unchanged
Restarting the PBX

Everything we have tried gives the same results

The phones seem to work as expected when provisioned to another extension or on another PBX

As it is the main incoming extension in a large medical clinic we cant just test it and run wire shark during business hours

Has anyone seen something similar? Or give me a hint as to where to start looking?

• 3CX Version, 18.0 (Build 461)
• Server OS, Debian
• Is the 3CX Server Hosted and where? On-premises
• IP Phone Make/Model/Firmware version, Yealink T48S
• Provisioning Method: Local
• Trunk Provider , ThinkTel
• Has the Firewall Checker passed: YES
• Are custom Phone Templates being used: No

 

[CentrexJ]

Good morning
I hope I'm posting in the correct place.
We have a client that has an interesting issue that has manifested in the last 30 days

When turning on DND on a Yealink phone, the phone has a popup that says "network unavailable". It also disappears from the phone list in 3CX and we cant access the phone UI thru IP
However the PC connected thru the phone has network connectivity.
If we turn off DND and reboot the phone seems to come back online.
Nothing major has been done to the system and no major changes in settings that we are aware of

We have tried:
DHCP settings as well as Static IP settings on the phone.
Factory resetting the phone, and re provisioning.
Swaping out the phone with a known working phone. The original phone was a Yealink T29G it is now a T48S
Factory resetting the T48S phone, and re provisioning it as well.
Double checking extension settings, all appear to be set correctly and unchanged
Restarting the PBX

Everything we have tried gives the same results

The phones seem to work as expected when provisioned to another extension or on another PBX

As it is the main incoming extension in a large medical clinic we cant just test it and run wire shark during business hours

Has anyone seen something similar? Or give me a hint as to where to start looking?

• 3CX Version, 18.0 (Build 461)
• Server OS, Debian
• Is the 3CX Server Hosted and where? On-premises
• IP Phone Make/Model/Firmware version, Yealink T48S
• Provisioning Method: Local
• Trunk Provider , ThinkTel
• Has the Firewall Checker passed: YES
• Are custom Phone Templates being used: No

Are you using AC adapter? Make sure the AC adapter is 2A. The T48 might be more sensitive to a lower amperage than a T29 would be. Failing that if you are using correct 3CX template or firmware and another phone works on that network jack its likely a defective phone.

 

[Jim Friesen]

Are you using AC adapter? Make sure the AC adapter is 2A. The T48 might be more sensitive to a lower amperage than a T29 would be. Failing that if you are using correct 3CX template or firmware and another phone works on that network jack its likely a defective phone.

Thanks for the reply
Yes we are using an AC adapter but it is the 2A supplied with the T48S
I also originally thought defective phone but both the phones work properly on DND provisioned on a completely different PBX.

 

[Saqqara]

Make sure you are running the correct firmware - https://www.3cx.com/sip-phones/yealink-t4-series/

If you factory default the phone, and press the DND does the same thing happens ?

 

[Jim Friesen]

Make sure you are running the correct firmware - https://www.3cx.com/sip-phones/yealink-t4-series/

If you factory default the phone, and press the DND does the same thing happens ?

Hi
The firmware is the current one that 3cx supplies, i cant verify the number it as it seems to be off line at the moment.
Your saying If the phone is factory reset and not provisioned then turn on DND? If that is done then nothing happens, network connectivity stays

 

[complex1]

You were saying "Swaping out the phone with a known working phone. The original phone was a Yealink T29G it is now a T48S"

Do this means that both T29G as T48S have the same issue if they located on the same physical position?

 

[Jim Friesen]

You were saying "Swaping out the phone with a known working phone. The original phone was a Yealink T29G it is now a T48S"

Do this means that both T29G as T48S have the same issue if they located on the same physical position?

That is correct

 

[complex1]

If the phones seem to work as expected when provisioned to another extension, then I suggest removing the "original" not working extension and create a new one.

 

[Jim Friesen]

We figured it out.
It looks as though the cleaners unplugged the T29 to move it and plugged in the network cables backwards when they replaced the phone. When the phone was replace with the T48 the person just swapped the cables as they were plugged in so the problem transferred.
The really odd thing was the phone appeared to drop network connection when DND was turned on, which was not the case
Here's what really happened.
With the network cables reversed, the phone and PC had internet connection, as long as the PC was turned on and logged in.
If the PC was turned off, the phone lost the network connection. (Rather odd how that seems to back feed thru the computer)
When the PC was turned off the user pressed the DND button at the same time making it look like the problem was with DND.

Thanks for all the suggestions

 

[complex1]

Thanks for the feedback.