Gamma SIP Trunk

[CBailey]

I am new to the forum so hopefully you can forgive any mistakes

I have 3CX setup in the UK on version 16.09 Debian running windows 2012R2 VM

We have been running for months with a SIP trunk from Talk Talk Business with no problems, we have recently moved to Gamma to provide the SIP trunk

Since then ever 24hrs or so the system seems to develop an issue that we only get 1 way audio, the caller can't hear the person on the 3CX system. They can call internally OK and the only way to clear the issue is a system reboot.

I have spoken with Gamma and they confirmed they can see Audio leaving their system so they are blaming 3CX, can anyone help work out what's causing the problem

Colin

 

[Saqqara]

Are you using the 3CX gamma sip template

What is your license sim calls , how much memory have you assigned to the debian server

 

[CBailey]

I have used the Gamma Sip Template

Pro License, 8 Sims Calls, 8192MB and VCPUs

 

[ChrisC_3CX]

Can you clarify on the following:

You say that "the caller can't hear the person on the 3CX system. " suggesting there is no outgoing audio (leaving 3CX) but then you said that "Gamma confirmed they can see Audio leaving their system" which suggests there is no incoming audio (towards 3CX). In which direction is the audio issue?

Also, do confirm that all required ports have been forwarded and that the firewall checker passes. (Do bear in mind that the firewall checker does not check all ports listed)

It would be helpful if you could also provide the info mentioned here: https://www.3cx.com/community/threads/information-to-provide-when-requesting-help.67558/

 

[CBailey]

The caller can hear the office, its the office that cant hear the caller it seems to be the inbound Audio

I am also Confused by Gama's response they have ran a number of test and confirmed they can see audio in both directions, suggesting the audio gets lost when it hits 3CX

• 3CX Version, 16.0.8.9
• Server OS, e.g. Debian 9 VM / Windows Server 2012 R2
• Is the 3CX Server Hosted and where? Local
• IP Phone Make/Model/Firmware - Yealink SIP-T40G
• Provisioning Method: Auto Provision
• Trunk Provider or Gateway Make/Model : Gama UK
• Has the Firewall Checker passed: YES
• Are custom Phone Templates being used: YES

Just a note, I have another customer running a similar setup and they are having the same issue. They are much smaller site and as a result its taking a week or two before problem appears.

 

[ChrisC_3CX]

I have to say, it does sound awfully like a firewall configuration issue.

I'd suggest waiting for the issue to resurface, and then, before rebooting the server or taking any action to resolve it, make a call to replicate the issue again using the 3CX Webclient while running a packet capture on the server. Then check the packet capture for incoming RTP traffic to see if audio is reaching 3CX or not. If not, I'd then check the firewall again, if it is determined that the RTP is not even reaching the firewall, you might want to talk with Gamma gain.

 

[CBailey]

When you suggest a packet capture is this a 3rd party tool such as wire shark or can this be done via 3CX

Just a question on the firewall, I would have thought it would block audio on all calls and not take unknown period of time to fail.

Also would you expect Gamma to use a different port range than Talk Talk as it worked without problem with TT

 

[Stevetritton]

These are the ports Gamma normally require:

Signalling UDP port 5060 egress/ingress	Gamma IP 1
Media UDP ports 6000 - 40000 egress/ingress	Gamma IP 2

The information is contained in the email from Gamma when you setup the trunk.

 

[ChrisC_3CX]

You can indeed run a packet capture from within the Management Console >> Dashboard >> Activity log section. For a Linux Host you will not need to install anything so you should be able to start a packet capture on demand. You will of course need a tool to inspect the packet capture file once generated and for this I'd recommend wireshark.

I'd highly recommend having a look at our training material on basic troubleshooting which should have all the information you need to run this test: https://www.3cx.com/3cxacademy/videos/advanced/basic-troubleshooting/

Also, since you are having issues with Inbound audio it should have nothing to do with Gamma's source ports, but rather, the ports the 3CX PBX is using. The fact that the issue does not occur from the beginning may mean that you have some ports forwarded but not all. As time goes by, and more and more audio ports are incrementally being used for different calls, you probably reach a port that is not forwarded so audio traffic destined for it never reaches the 3CX PBX. That would explain why the reboot temporarily fixes the issue as the port usage would start from the beginning again. This is of course a mere assumption based on the available information so do investigate further to check if this is the case or not.

 

[CBailey]

Going to runs some tests today when it fails, thanks for your help