I have a DT800 set up to connect over NAT as a test phone. I am having an issue with the remote phone resetting at times, you get Network Busy Error and then reset. The MLC Apps work fine over NAT but the customer wants to go to a more permanent work from home set up with a physical phone for about 50 users. The users are working from individual homes.

VPN Question.
If we used the VPN they do not want to invest in VPN routers for the homes. Has anyone set up the VPN utilizing the built in firmware on the phone? This customer has a Barracuda Firewall. Tried looking on NTAC, but does anyone have a simplified guide to configuring the VPN on the phone itself? Have you had any issues with resets or call quality set up this way?

Resets are caused by a couple of main things. SIP ALG and timeouts because the firewall/router at main site timer is set to low..looking at you Sonicwall..LOL

You need to disable ALL SIP ALG at every site. If you cannot get the firewall at main site to fix their timer (UDP timeout or some nonsense) or are clueless, in the NEC in 15-05-47&48 set these to 90 or 60 and test. The higher the less traffic you put on network.

VPN works but you are using more overhead for this. It can actually make call quality worse.