Solved SIP Trunk no longer connects

[Chris927]

Our trunk suddenly disconnected from our ISP after 12 months and has refused to register for more than a week. ISP reports nothing abnormal, but no sign of registrations. Wireshark shows attempts to send packets to the trunk provider but we get the error that seems common to some others here "Registration at Generic SIP Trunk has failed. Destination (sip:X.X.X.X:5060;lr) is not reachable, DNS error resolving FQDN, or service is not available." Firewall check is OK; 3CX v 16.0.8.9; Win10 on premise; local provisioning of Polycom phones; SIP trunk provider is generic (but is a certified 3CX partner). The only circumstance that has changed is that our first year free Standard subscription renewed automatically to a second year (did we forget to do something?) and there may have been a recent update. We can ping and traceroute satisfactorily to the SIP supplier's IP address and FQDN. We are using a 3CX supplied FQDN. and 3CX is installed on a NUC i3 with plenty of memory. The event log shows attempts to register timing out. I have an identical setup at a second location using the same supplier and it works perfectly.

I'm a newbie to this and have tried most of the suggested debugging tests - can you assist please?

 

[YiannisH_3CX]

Hi @Chris927

You mentioned that you are seeing registration attempts going to your provider. Do you see a response from the provider in Wireshark? What happens to those registration messages? Also run a packet capture on your firewall and confirm that the registration messages are leaving your network and look for a reply. Since that PBX is trying to register then you should see a reply from the provider.

Also check that the registration is sent to the correct IP address.

 

[cdeacon]

G'day YiannisH The IP address is correct and has not been changed. Wireshark SIP flow shows SIP registration request from port 5060 on PBX to port 5060 at provider then timeout. No response from the provider! I guess I will have to check again with the provider...but it is curious that my other site is OK...

 

[YiannisH_3CX]

You should have them check again. In my experience some times your IP might get blacklisted by accident and they won't know until they check their firewall.

 

[cdeacon]

You were correct! Although our provider advised that they had NOT blacklisted our IP address, when they whitelisted it, the service was restored! Problem solved after many hours of anguish.

 

[YiannisH_3CX]

Glad to see the issue has been resolved.