I have the same problem with an Win2k Advanced Server configured as an PDC an dial-on-demand-router. The connection to the internet is declared as permanent, there is ***igned a permanent ip address and everything works fine.
But every 1 1/2 week the server (or something else) cuts the connection, redials after that, says that the connection has been established but I'm not able to ping anything on the internet. The intranet works fine, but even without connectivity to the internet. Win2k ignores all settings made in the routing and ras console including the ip address. The provider says that there is no connection active on the line reserved for my server, but the server says he is connected and has the ***igned ip address (but is not reachable from outside). Where and what in the hell is that thing dialing?
Perhaps someone has an idea was went wrong or what is misconfigured.
 
Thanks...
 
[This message has been edited by Imi (edited 11 December 2000).]

It sounds like you need to go into your router configuration and check the box that says renew lease continually. If you don't have that box checked your willperiodically lose your ip address from your isp which will cause the symptoms you describe....