Solved Phones unregister and register

[netcomm1]

Have Yealink T48S that have been working over a VPN to the PBX. A couple days ago all the phones started un-registering and registering. Nothing on the PBX side has changed. WE have multiple other 3cx PBX's not having problems. This PBS is hosted on a hyper V vm.

If someone does make a call the call is clear and will not drop. There have been phone calls that lasted hours with no issue. However, the phones are not in use will randomly start un-registering normally 3-4 at a time. Then a minute or two later they will register again. This can be happening while someone is having a perfectly normal call on another extension.

Firewall checker passes. We do have custom templates to change backlight settings however even when we use the standard 3cx template the issue still remains. Checked time Sync settings on the VM. Adjusted SIP registration times as I saw as suggested by other threads. Has anyone seen something similar?

 

[Brian Oli]

I am having an issue with a phone unregistering and registering in the middle of a call. It drops the call immediately. Our system is however on premise. Where is the checked time sync settings? I have seen this on another thread and that is something I have not done. We are using Yealink t48 g's

 

[netcomm1]

What server os are you using?

 

[eddv123]

This behaviour is expected from mobile app devices but not static endpoints.

If it happens regularly enough to capture with wireshark I would give that a go and see if you can understand why the phones de-registration is occurring.

 

[netcomm1]

Here is the pcap from the pbx when it occurs. We also have one from the other side of the VPN listed below.

(Edited by Admin)

 

[eddv123]

Thanks for uploading the PCAP traces. After having a look through most responses/errors are call related. I cannot see any errors in regards to registration requests. That could mean that there are none - or that they aren't making their way back up the tunnel.

I can see your using a SonicaWall here, can you confirm if the traffic is NAT-ted between the PBX site and remote (phone) site -- this should be avoided in router configuration if possible.

I am going to have another check through but currently cannot see what 3CX is saying in response to the Yealink - this would be most useful.

 

[ccomley]

Might not be relevant but one issue you get with Sonicwall is it doesn't keep the link up as long as other devices might think! That's to stop it running out of database entries for live links. But you can increase it. It's part of the firewall rule taht permits the traffic in question, so you can increase it ONLY for the phones, if you set the phones up with their own rule, even if the rule is otherwise identical to the default.

Edit rule
Go to "advanced" tab
Increase TCP timeout. I have mine set to 12 minutes!
Possibly increase UDP timeout as well. UDP timeout wont' be a problem for RPT packets, they're dead as soon as they're sent, but it might matter for UDP connections on other ports.

 

[netcomm1]

Thanks for taking the time to look through everything! I will try ccomley's suggestion as well as confirm that the traffic is not NAT-ed

 

[netcomm1]

Found the problem on sunday. The issue was the ports on the DELL switch set for VOIP. For whatever reason when we removed this setting all the phones have stayed registered.

 

[YiannisH_3CX]

Glad to see the issue has been resolved and thank you for updating the thread with your solution. Please be careful what you share in public forums as wireshark capture contain sensitive information. If someone is willing to look at them please share them in personal messages and not publicly.