Troubleshooting No Audio on Specific External Calls

[dsmithspcc]

Dear All

We have had 3CX in place for a number of years now and it has been working very reliably. However, very occasionally we come across the odd external number which connects but there is no audio. We make a large volume of external calls every day so the number of external numbers this happens with is tiny.

There are two specific external numbers that this is happening with currently. They are both Colleges in Brighton so perhaps are using the same telephone system as each other.

Please could you help me with any troubleshooting steps I should be following in this specific scenario as I am unsure where to begin? I have re-run the firewall checker to make sure this looks ok and everything returns as good.

Many thanks

Dan

 

[TheodorosG_3CX]

There are many facts and various ways to troubleshoot.
You need first to eliminate. you mentioned that this is specific to 2 external numbers. In your PBX you are using a Supported Provider? Have you checked first?
Also are you using ip phones or 3CX Clients?

 

[dsmithspcc]

There are many facts and various ways to troubleshoot.
You need first to eliminate. you mentioned that this is specific to 2 external numbers. In your PBX you are using a Supported Provider? Have you checked first?
Also are you using ip phones or 3CX Clients?

No, we do not have a support provider in our PBX. We are using a mix of IP phones and 3CX clients. The same issue occurs on both.

The issue is that when we call these two specific external numbers from either an IP phone or 3CX client, we hear the usual ringing sound, the call connects and the duration starts counting upwards but there is no audio. With at least one of the numbers, we know the same is true in reverse. When they call us, the call connects, but they never hear our audio (Digital Receptionist).

As previously mentioned, all other numbers that we are using regularly work.

 

[TheodorosG_3CX]

This sounds like a provider side issue. I would suggest to check with them first.

 

[dsmithspcc]

We find that when we check with our provider, they say everything looks fine, and it is difficult to get cooperation from the other organisation's provider. It becomes extremely difficult to resolve.

 

[N_G]

Hi - It would be a provider issue. But what you can do is if you are running V20 - switch on the voip quality monitor, make the calls and with the logs that it can generate contact the voip provider. Else try calling those numbers with a different voip provider account

 

[dsmithspcc]

Hi - It would be a provider issue. But what you can do is if you are running V20 - switch on the voip quality monitor, make the calls and with the logs that it can generate contact the voip provider. Else try calling those numbers with a different voip provider account

Thank you, I will try and generate the logs for the provider.

 

[OlegR_3CX]

Feel free to post your findings and feedback for the other community members.

 

[SteveITS]

We find that when we check with our provider, they say everything looks fine, and it is difficult to get cooperation from the other organisation's provider. It becomes extremely difficult to resolve.

Had an issue once where calling from anyone on our SIP provider to a specific number had a ~10 second audio delay in one direction. Luckily we used them also so were able to test ourselves. That let us determine it was not related to the client's 3CX server. Ultimately our SIP provider changed the call routing in their system for that number, to resolve the issue. So, it is possible, and yes, it took a while.

See if you can record a call, to "show" them.

 

[TheodorosG_3CX]

The voip quality monitor will give you also the information needed. If there is no indication there this can also prove that the issue is related from the other provider.

 

[dsmithspcc]

The SIP provider have come back to us after investigating a number of the calls made to the two affected numbers with the following:

"Upon reviewing the media traces I have found that site is not attempting to send RTP(Audio). As a rule, audio must be sent to receive it. Please request the PBX maintainer looks into why RTP is not being sent."

We don't have a PBX maintainer, so will need to try and figure out the issue ourselves. This brings me back to our original question about how we gather this kind of information on our 3CX instance. We aren't on v20 yet, we are planning to do this upgrade in the summer holidays.

Many thanks

 

[OlegR_3CX]

This guide shows you how to collect the networking logs from the OS.
You can also see this video on 3CX troubleshooting

 

[dsmithspcc]

Thank you - collected data and viewing through WireShark. Ran the capture for as short as possible, but it is still a large log file. There are 10-20 errors that stand out more than other lines relating to:

Source IP: IP of 3CX Server
Destination: IP of my handset
Protocol: ICMP
Info: Destination unreachable (port unreachable)

Is it possible this is the issue?

Many thanks

 

[SweetAction]

Protocol: ICMP

This is just a simple ping usually. Not everything supports it though, so it's not a reliable indicator of network blocks.

But make sure that the 3CX server and the IP phone can communicate with each other. No firewalls or other network blocking tools in the way.

 

[dsmithspcc]

Thank you - good to know this is a potential red herring. I have gone back to the provider as we have listened to the calls in WireShark and can hear our audio but nothing from the receiver so we think they might be wrong when they say we are not sending audio. The firewall checker confirms everything is ok our side, I can't think of any other firewall or network blocks on our side.

Thanks

 

[TheodorosG_3CX]

They need to clarify if they do sent the audio or not. Now you know that at least from the PBX side all is good.
Ask them to check again otherwise this can be firewall or even ISP issue.

 

[dsmithspcc]

But we make hundreds of calls every month. It is just two specific numbers that we are having an issue with where they connect but we cannot hear audio. It is hard to believe that we have a firewall issue.

 

[TheodorosG_3CX]

That is true but you need to eliminate it. In any case, my opinion is that this is clearly a provider issue.

 

[OlegR_3CX]

It's one way to find out and you will need to do troubleshooting and examine the logs, and find the cause, alone or with the provider.