Causes of sip phone de-registration

[Hoygen83]

Hello,
Some customers with a multi site environment, have decided not to use sbc and not to use stun on theyr request.
They bough a 3cx pbx in our cloud and then asked me to route traffic throug specific vpn from the sites to the pbx in cloud.
Everything worked fine for several months, but suddently ip phones started unprovisioning.
If I go to the ip phone, all parameters are fine but on the pbx i see the phone is not present in the phones list.
If I reset the phone and provision it again everything works fine but I am sure that eventually the problem will reoccur.
Is there a variable in 3cx that I should set somewhere to have the phone always provisioned?
I am aware that I should just deploy SBC (other customers have it) but right now that is not the customer will.
If it is a phone problem, I can tell that the models involved are: Yealink SIP-23G, Yealink SIP-27G, Grandstream GXP1610 and will then ask the supplier.
Kindest Regards.

 

[JohnS_3CX]

Hi @Hoygen83

If the phones keep their settings, then they are not unprovisioned.
I think what you meant to say is that they become unregistered from the PBX.

There is no such variable which you describe, registration just requires a solid connection between the phones and the PBX. I think you will have to look into why the phones stop registering after a while.

Since you have a site-to-site VPN, this is the first thing I would suspect, because if it stops working the phones will then behave like you described. We do not support running a VPN directly on the PBX machine, so I cannot tell how the system will behave in such conditions (even if it worked before). Usually in cases like yours, the problem is often down to something on the network interrupting the connection between phones and PBX. Some helpful suggestions to get you started are the below:

Basic tests:

- Next time a phone becomes unregistered, see if the others are still fine during that moment, or if they all unregister within that same 2-3 minutes time window
- Restart the phone and see if it will register, do not reprovision it
- Ensure there are no blacklisted IPs in the management console


Advanced Tests

- Check your VPN logs for disconnections
- Check your VPN configuration on both sides
- Check whether your firewall had recent firmware updates or settings changes
- Do some network troubleshooting, see if you can capture traffic on the PBX and at the same time capture traffic on your network switch/firewall to see if the phone IP sends any SIP traffic to the PBX IP. If you see the phone sending and the PBX not receiving, you will have your answer as to why the phones became unregistered.