Weird Polycom VVX400 Behavior

[MammerJammer]

I have provisioned Zoiper and X-Lite soft phones that are working great inbound and outbound. I have a Yealink T46S that provisions easily and works great inbound and outbound. And then there's the VVX400...

The phone provisions easily. Inbound and outbound calls work great. Then the phone sits idle for just a few minutes and inbound is lost. Internal or external, nothing can ring the extension. However, if you pick up the Polycom and make an outbound call, internal or external, it can receive inbound again for a few minutes. I can reproduce this behavior all day. It seems like it might be a UDP timeout issue, but the session timeout is defaulted at 3600 seconds and this happens in just a few minutes.

Has anyone seen this behavior? Better still, does anyone know how to fix this behavior?

 

[paradym]

Sounds like the firewall is closing the connection. Check to see if the phone is sending a keep-alive signal.

 

[MammerJammer]

Paradym, you got it. I was so stuck on UDP timeout I totally ignored NAT Keep-Alive. Apparently Polycom ignores it too, because for some reason the default setting is disabled. Enabled it, rebooted and inbound is working fine.

I knew it had to be an issue with a session terminating because when you re-initiate the session by making an outbound call it can receive inbound again, and was completely reproducible. Anyway.. thanks for saying "keep alive" and shaking my brain out of UDP timeout mode.

Anyone else using Polycom out there will want to make sure you populate the Settings >> Network >> NAT >> Keep-alive interval. Yealink T46S has it enabled by default at 30s.