Inbound and outbound calls need to be made twice to hear

[Paulh]

I have a problem where I need to call an outbound number twice to get through. The first time I call, I get silence. If I call again, it works. Same with inbound calls. When the phone rings, I get silence. Then if the other person rings again, I can hear them. The other party hears silence too the first time. I keep getting voicemails with silence, so not sure if anyone's leaving messages or hanging up.

It's extremely frustrating would like to resolve the issue rather than change phone servers.

Phone is Linksys SPA941 or Snom M3 (happens with both - although the M3 doesn't ring half the time, but that's another issue). Using NexVortex as the IP phone provider.

Does anyone know why this may be happening?

Paul

 

[NickD_3CX]

This capture seems to contain only the communication between the 3CX Client and the 3CX Server. Anyway though, as the issue is related to the actual audio not working, the RTP packets would have to be included as well, as a txt file would not be enough.

I read through the whole post and I think I am missing something. It has been repeatedly stated in this thread that the ports that have been opened are 9000-9015 and the Firewall Checker passes. The firs time I though it was a typo, but I have seen it a few times.

Now unless you are using an older version prior to V15, the default external audio ports that need to be opened are 9000-9255 so unless you open the whole range, you will have problems.

If you manage to get a packet capture with a full call (start to end) with no audio from the 3CX Server, that could enlighten us more. Also, from what I can tell under Settings --> Network, you have set the PBX to "Dynamic IP". If you can, set this to Static, fill in the correct Public IP and restart services.

 

[itglaafs]

Hello Nick,

Thank you for your input. We actually opened up ports from 9000-9500 UDP for RTP and audio transmit, this is what manual says for v15.5. So this should be enough I guess.

We have already static ip address setup under 3CX settings, we do not use dynamic or stun servers.

There is newer capture that I did yesterday and it contains one of the calls with one way audio (number <removed by Admin>). I took this capture on 3CX Server NIC. Please find link below:

(removed by Admin)

Best Regards,

Slaven.

 

[AlexDBarrett]

Don't install on SBS20XX.
Dedicate the installation to a Debian, Windows or Windows Server system. Alternatively as stated look at Cloud.
We use Google Cloud Services as this works well and is stable.

 

[NickD_3CX]

Don't install on SBS20XX.

First of all, I agree 100%

There is newer capture that I did yesterday and it contains one of the calls with one way audio (number <removed by Admin>). I took this capture on 3CX Server NIC. Please find link below:

(removed by Admin)

I removed the attachment and number, but I got the information. What is happening is the following:
On the problematic call, the PBX is requesting the audio on port 9108:


This port will be used for both sending and receiving audio for this call. Sending seems to be OK as 3CX is sending from 9108 to 42664 on IP 65.254.44.194 as requested from the Provider, but what is being received is quite interesting.
Traffic is being received on port 9108, but it is not from IP 65.254.44.194, is from another IP:


This is wrong as the RTP exchange is supposed to happen between the same 2 IPs.

The fact that you are not getting any audio is because something else is "spamming" your 9108 port even before the call starts, so when the Media Server tries to use this port, this happens.

Solution is to stop whatever is sending UDP packets to your ports, especially those used by the media server.
You can also from a CMD check if there is anything listening on those UDP ports using: netstat -ano

My initial comment about SBS any version is because generally there are so many services running on it that many many ports are used, so don't be surprised if your UDP ports are being used by something else SBS-related.