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WindowedOffice

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Hello everyone,

We've been trying to resolve an issue with calling out externally. When a user answers a call made from our network there isn't any sound from the callers phone or the callees phone. The calls get connected but no audio can be heard either end.

This appears to only happen after our users have been using our 3CX system for around 4 hours. After the 4 hour mark we can't make any external calls without getting above issue. After this when we restart our 3CX server, it continues to work as normal. It worth to note that we usually get 5 "A trunk failover occurs or max amount of calls available through trunk has been exceeded" emails at once from our 3CX system when the issue slowly starts to occur again. The issue starts again by appearing occasionally at first then happening site wide.

We're curious as to whether this may be an issue with our installation of 3CX as restarting the server appears to temporarily alleviate the issue? Has anyone else had a similar issue?

If we could get any pointers at all, we'd really appreciate it!

WindowedOffice
 
Run the 3CX Firewall Checker to be certain that all required audio ports are forwarded properly.

https://www.3cx.com/docs/ports/

If that passes, you may want to check Codec compatibility with your provider. Check the 3CX Activity log as well for any error messages, on calls, when this happens.
 
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Piggy-backing on leejor's post, look specifically at RTP. The range is now 9000-10999.
 
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So 3CX use to start at the bottom of the range and use ports based on concurrency. It sounds like that has changed (intentionally or not, no knows). So more than likely around the 4 hour mark you are getting pass the original range in your firewall and that is causing the problem.
 
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Thank you for your suggestions!

We'll try run the tests on the server and check the ports. I'll get back to you if we have any joy.
 
We recently had the exact same issue following the installation of the latest patch. We didn't have all the new ports open and this is exactly what happens, the system starts at the low end of the port range working its way up until it reaches 10999 then starts over. The silent external calls are due to the system using a port which has not been opened on your NAT gateway.
 
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We recently had the exact same issue following the installation of the latest patch. We didn't have all the new ports open and this is exactly what happens, the system starts at the low end of the port range working its way up until it reaches 10999 then starts over. The silent external calls are due to the system using a port which has not been opened on your NAT gateway.

We can confirm this now! We spoke to our ISP and their firewall ports had not been updated. They enabled unrestricted outbound UDP traffic which resolved the issue.

Thank you very much everyone for all your suggestions!

Kind regards,
WindowedOffice
 
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