Avaya Phone will ring but cant answer it

[NGHAGHJI]

We have Avaya Phones model 9608's at our office connected through a VPN to the call server across town. Everything works great except at least once every day; at no particular time, the phone will ring with an incoming call, and when you pick up the handset, it still just rings, and you cant answer the call. This last for about 3 mins and some phones will reboot, and some will say "Retrieval Successful" or "discovered 192.168.42.100" and start working. Does anyone know why this is happening?

 

[derfloh]

Sounds very much like a firewall issue

IP Office remote service
IP Office certificate check
CLI based call blocking
SCN fallback over PSTN

 

[nnaarrnn]

UDP Timeout needs adjusted on your firewalls.

 

[NGHAGHJI]

Thanks, guys
I'll check the UDP timeout on the Firewall to see how it goes..

 

[NGHAGHJI]

Unfortunately, there is no way to change the UDP timeout on Meraki MX64.(the defult timeout value is 300 seconds)
Is there a way to adjust the timer on the Avaya gear to be longer, though, to resolve this?

 

[NGHAGHJI]

Anything