Solved Outgoing calls randomly start failing

[richieb]

I’ve just got our server and sip trunk (gamma) ‘working’, but I have a really weird issue with outgoing calls.

We’re in the testing phase (before numbers get ported) but I’ve successfully made and received calls. The problem is, sometimes outgoing calls just stop working and repeated attempts at making calls all end with a timeout after the initial ‘invite’ gets sent - 30 seconds later or whatever.

Wireshark shows the attempts to contact the sip endpoint being made, but no response.

What makes it really weird is that if we receive an incoming call, we can then make outgoing calls again.

The server is the latest on-premises Linux distro. It’s a school and our internet provider controls the firewalls etc. All required ports have been forwarded / allowed, but sip and media are locked down to just the gamma IPs - so the firewall test can’t really be used.

Has anyone ever experienced anything like this before or can anyone suggest anything for me try? Many thanks!

 

[YiannisH_3CX]

Hi @richieb

The first thing I would suspect is a firewall/network issue especially since things start working after you receive an inbound call. I am guessing you are running wireshark on the 3CX machine showing that the Invites are leaving the system so you also need to run a capture on the firewall to see if the messages are forwarded correctly. You may need to ask the provider to run a capture for you to confirm.
You could also contact Gamma and ask them if the Invites are reaching them or not.

 

[richieb]

Thank you, yes, I suspect the same thing.
Yes, I ran the trace on the 3CX machine - handy feature to include in the frontend like that.
I contacted our ISP and Gamma just before creating this thread, but it was at close of play on Friday and so I'm waiting to hear back.

 

[YiannisH_3CX]

Great. Let us know of the results. Generally we have a lot of customers using Gamma without issues that's why my first hunch is that its a firewall issue.

 

[richieb]

Yes, it was firewalls and routing of traffic. Seems that when it wasn't working, it was because the traffic had gone out from the school's public NAT IP and not the dedicated PBX one - thereby being ignored/blocked on Gamma's end.
When I called the school, it created a connection that could then be reused for an outgoing call, taking it out via the proper IP where Gamma would then talk to us.

 

[YiannisH_3CX]

Glad to see you were able to figure out what the issue was and thank you sharing your solution.