We have a customer that has one IP phone at a remote location (only one for now, more to be installed) that after about 12 hours it stops working, says something like server not found. When the routers are power cycled, the IP phone starts working again. Repeat problem. There is a VPN in place, separate from the customer's network. The routers are Cisco routers, about a month old. The customer's IT person says all ports are open and nothing is blocking the IP phone, no firewalls etc. When we bring the IP phone to the main site and connect it to the customer's LAN, no problems.

Has anyone come across this before? Solutions? Ideas? Any help is greatly appreciated. Thanks.

Is the IP phone using NAT traversal thru public internet or riding on customer private VPN tunnels ? If VPN tunnels, they could be hosed up ( router restart the tunneling service again as you described ) .

We are using the customer's private VPN tunnel. Today we sent a tech to remove the Cisco routers and install two NEC Edgemarc routers to see if that resolves the problem. Will update this post.

As madwok indicated, there could be a problem w/ the VPN. If there is some sort of timeout feature turned on in the Cisco, that could cause it.