Yealink handsets showing "No Service"

[avalon4]

We are experiencing a strange issue affecting some Yealink handsets at some client sites.

Setup:
- all 3CX instances are 15.5
- all yealink handsets are running latest firmware and connecting using STUN.
- port redirection is in place for all handsets

The problem happens seemingly at random and causes some Yealink handsets to show "No Service". Rebooting the phone sometimes resolves the issue but in some cases we have to factory reset the device. When we check 3CX for the handset it shows registration failed.

This only affects one handset per client at a time, when it happened at a site this morning only one handset out of 30 were affected.

I am struggling to identify what is causing this, so would welcome any suggestions

 

[YiannisH_3CX]

Hello @avalon4

After you make sure that port forwarding is correctly implemented on the firewall and that phones are using the supported firmware and the default templates, the next next step would be to use wireshark to troubleshoot the issue.
Once the issue occurs, log in to the web interface of the affected phone and start a capture. You can do so by navigating to Settings / Configuration / Pcap feature.
You will also need to start a capture on the 3CX server at the same time and track the REGISTER messages. This way you will be able to see if the phone is trying to register to the server, if the messages reach the PBX and what is the reply from the PBX. You can also determine if the messages leave from the correct port.

 

[eddv123]

No Service on Yealink phones is normally always to do with SIP registration for your account settings.

It must be something network related - I would doubt this would be port forwarding related as it would effect all SIP registration attempts all of the time but perhaps look at SIP ALG. Does your firewall check complete without errors ?

I trace would also help as YiannisH_3CX has stated above as well.