Some calls end up being silent

[thebitguru]

Hi,

I am running FusionPBX version 4.4.3. I have Yealink phones in a Simultaneous ring group attached to an inbound DID. Almost all calls terminate correctly, but sometimes the phones ring and end up with no sound when you pick it up. There are 24 NAT'd phones and one DID in this installation. Outbound calls always work, and so do the internal extension-to-extension calls. It's only some inbound calls from DID that have this issue. I am unable to reproduce it.

Any ideas on what might be going on?

Thanks!

 

[hfoster]

NAT shenanigans no doubt. Have you tried using the Enterprise strategy? The separate threads sometimes help with edge cases like this.

 

[thebitguru]

Thanks for the info! Yes, unfortunately, Enterprise strategy had the same issues.

I have a very similar (Unifi Dream Machine Pro, NAT'd, etc.) setup at another site to the same FusionPBX server. What type of NAT issues have you seen in the past?

 

[hfoster]

SIP ALG, hyperactive firewalls, etc. It's highly dependant on make and model. UDP timeouts for firewall rules help to be the same as the register timer.

Make sure you have the firmware on the latest, in 2020/21 they had a firmware out that was busted, people would pick up calls and it would be dead. 66.85.0.5 I think it was.

 

[thebitguru]

I upgraded the firmware on the Yealink T46s and that didn't address the issue. The phones are using TCP connections, and I confirmed that the SIP module is disabled on the Unifi Dream Machine Pro.

Any other suggestions for troubleshooting this further?

 

[thebitguru]

Quick update, I noticed that the CPU usage in the logs was pretty high when this happened. You can see more specifics in this thread.

I upgraded the cloud server with more CPU cores and RAM, and this resolved the issue for me.