No Audio on incoming and outgoing external calls to other 3CX systems

[Kerckhaert | Niels]

hi all,

since a couple of weeks we have a strange behavior and i cannot tell if it has something to do with the latest update we did.
When we call to external numbers, some of them have the following behavior:

the call rings, but when picked up, the audio is dead.
After the third different number with this behavior calling the same numbers with my mobile phone (outside of the 3CX environment) i notice all these numbers are behind a 3CX system (one of a customer i checked with and two i recognized the waiting tune
Perhaps someone else has seen this behavior.

We use the 3CX desktop app in default, but also have DECT phones (SNOM) and use the 3CX mobile app on our mobile phones.
This behavior persist on all of the systems above.

We have the following setup:

• 3CX Version, Enterprise Annual 18 update 4 (build 965)
• Server OS, Debian 4.19.208-1
• Is the 3CX Server Hosted and where? Locally
• Has the Firewall Checker passed: YES
• Are custom Phone Templates being used: NO

Hope someone can help me.
Thanks
Niels

 

[noord]

You can do a capture on the 3CX server itself and then make a call. You can then analyze that call with Wireshark and see if your 3CX is sending and/or receiving audio.

Having said that, I have had this problem before myself. The problem ultimately lied with our voip provider. They had some setting incorrect, that cause issues when calling to 3CX. It also meant other users that were using that same voip provider, could also not call customers that had 3CX.

So, to rule that out very quickly: contact your voip provider and ask them to call one of the numbers you cannot call. I assume they use their own lines for calling as well. And perhaps even have them call you. If the issue lies with them, they should get no audio as well.

I also spend a lot of time on this once and it turned out our voip provider had updated something or changed some settings. After I alerted them to the issue, they immediately knew what they had done and changed it back
Hope that's the case for you as well!

 

[Kerckhaert | Niels]

You can do a capture on the 3CX server itself and then make a call. You can then analyze that call with Wireshark and see if your 3CX is sending and/or receiving audio.

Having said that, I have had this problem before myself. The problem ultimately lied with our voip provider. They had some setting incorrect, that cause issues when calling to 3CX. It also meant other users that were using that same voip provider, could also not call customers that had 3CX.

So, to rule that out very quickly: contact your voip provider and ask them to call one of the numbers you cannot call. I assume they use their own lines for calling as well. And perhaps even have them call you. If the issue lies with them, they should get no audio as well.

I also spend a lot of time on this once and it turned out our voip provider had updated something or changed some settings. After I alerted them to the issue, they immediately knew what they had done and changed it back
Hope that's the case for you as well!

hi Noord,

thank you for the tip.
This sounds very plausible.

I will contact the voip provider and will tell them the case.
Like i said, the issue came up suddenly and probably reported weeks later because of the small number impact it has.

best regards

 

[Kerckhaert | Niels]

UPDATE.
All solved here,
It was a firewall issue, which i somehow still cannot explain.
Our 3CX is located in our DMZ with an outbound rule from Phone system ip to WAN for only the service ports 3CX uses.
The inbound rules from WAN to DMZ (also Phone system ip specified) uses the same service ports.
This has been setup since we started using 3CX in 2019.
In the last few weeks i have never seend any block of deny in our firewall logs, so did not focus on this part.
Our Voip provider could call the numbers and had not seen this issue before.
I have change the outbound rule to ALL instead of the specified services.
And all is working again.

the strange thing is, it are just a bunch of phone numbers who behave like this.
The only comparison is that i know some of the companies (all external) also use a 3CX system.

Can it be there has been an addition of ports for 3cx to 3cx communication?

Happy colleagues before the weekend starts

thanks for the support.

 

[leejor]

It is always a good idea to run the 3CX Firewall Checker as a first step, when you have audio issues (in particular no audio incoming) on externals calls

 

[Kerckhaert | Niels]

h

It is always a good idea to run the 3CX Firewall Checker as a first step, when you have audio issues (in particular no audio incoming) on externals calls

Well that is the funny part.The firewall checker show all was ok as described in my first post..