External Calls Not Connecting to PBX Every time

[James Price]

Hi,
I have 3CX up and running on the latest version (16.0.5.622) and since the system updated automatically to this version I am now experiencing issues with external calls. If someone tries to call any of the 3 numbers attached to the PBX 9/10 times the caller hears nothing, complete silence and then eventually the call is dropped. Calling outbound from the system works fine without any issues. The one time the call does connect everything works as expected with no issues with audio etc. All 3 Trunks are from the same provider, I have also checked with them if they were having any network issues but they had none to report.

I have today run a full firewall check though the console and no issues found there. I have also checked the rules on the server incase anything had changed, however it would be me that would make any changes on the network (or would have prior knowledge of any changes). There has been no issue with inbound or outbound calls up until this point. As mentioned this issue has only been appearing since the update to the version mentioned above which was applied within the last week.

3CX is installed on Windows Server 2016 machines, i have checked today and there is a servicing stack update which I will apply this evening to see if this helps / resolves the issue on the off chance. It is sat behind Sonicwall but there have been no configuration changes to the firewall appliance either.

If anyone has any thoughts or suggestions as to what may be causing this, as you can imagine, it is a little inconvenient! Assistance would be greatly appreciated.

 

[leejor]

So...to be clear..in every case, the calls are all ringing though to a destination (set actually rings and is answered), it is just that there is no audio at times? Are you talking about 3 separate trunks, or 3 DIDs on the same trunk?

 

[James Price]

So...to be clear..in every case, the calls are all ringing though to a destination (set actually rings and is answered), it is just that there is no audio at times? Are you talking about 3 separate trunks, or 3 DIDs on the same trunk?

hi leejor,

Sorry, no 99% of calls don't appear to be reaching a destination, none of the sets are ringing (Physical, App or Windows App). There is no entry into any 3CX log showing anything related to the silent calls, successful calls are however logged correctly. There are 3 Separate trunks with one number on each, all 3 trunks are provided by the same supplier.

 

[leejor]

If there is nothing in the 3CX Activity Log for any of the calls that fail, then I have to assume that your provider is not sending them, or is unable to, because the trunk is not seen as registered, or registered incorrectly. I would check with them, to see what issues they see, when attempting to send the calls.

 

[James Price]

If there is nothing in the 3CX Activity Log for any of the calls that fail, then I have to assume that your provider is not sending them, or is unable to, because the trunk is not seen as registered, or registered incorrectly. I would check with them, to see what issues they see, when attempting to send the calls.

Thanks for the advice, i'll check with them and see if they can have a closer inspection. 3CX is showing them as registered and connected and I can successfully make calls out. Once i've had a response from them i'll feedback either way.

 

[JohnS_3CX]

Hi James,

With such a high degree of failure, it should be fairly straightforward to run a capture on your PBX and investigate what happens during the failed calls.

Depending on what you find in the captures, you may then have to run Sonicwall captures alongside with the PBX captures simultaneously.

This should tell us whether the provider is sending something wrong, or whether the firewall is stopping some traffic against your knowledge.

In case it is the provider, the captures will also serve to help make your case when you contact them.

Do not ignore the possibility that it is a firewall issue, even if you changed nothing on your network, this happens more often that one might imagine. If you need help with the troubleshooting let us know and we can advise you accordingly


https://www.3cx.com/docs/capture-network-traffic/

 

[James Price]

Hi John,

I've spoken with the SIP Trunk provider today and they have sent over a copy of their call log (where I have been testing) They have said the calls are being cancelled or given a Channel Unavailable message.

I won't rule out any cause yet, however from the providers side all the calls are being sent to our 3CX server. I have also ensured that particular server is fully up to date with any outstanding Windows Server Updates as of yesterday evening. I have also re-created the Sonicwall Access Rules today however this has not had any success in resolving the issue.

 

[Saqqara]

Are you restricting the number of calls per trunk, could it be you have no free channel to take the call.

'Number of Sim Calls' field under Trunk Details.

What is your 3CX license - in terms of Sim Calls.

 

[James Price]

Are you restricting the number of calls per trunk, could it be you have no free channel to take the call.

'Number of Sim Calls' field under Trunk Details.

What is your 3CX license - in terms of Sim Calls.

I haven't got any restictions on the calls per trunk, the number of sim calls is set to 8 currently (matching the 3CX free annual licence). This configuration has been working untouched for approx. 3 years with no issues.

The installation was migrated from a Win 2012 server to Win 2016 at the beginning of the year and had continued to work without any issues.

 

[JohnS_3CX]

Ok give us all the relevant details so we have a good view of what the setup is (see below)
https://www.3cx.com/community/threads/information-to-provide-when-requesting-help.67558/


Then I would definitely recommend that you run a capture as per my previous message, so we can have a clean view of what the SIP exchange is between the PBX and the provider.