>Hi All,
>
>I've added a Cisco 803 router to a small LAN but cannot persuade it to drop the ISDN connection when idle. I've set the idle-timeout to 300 but even if I physically isolate the router from the LAN the connection stays up. There seems to be a regular blip of data being transmitted/received every ten seconds although I don't know whether this is responsible.

I don't know DDR well (this appears in a later semester), but I remember reading something about the router being able to distinguish important and not-so-important data. In your case, the router seems to consider it necessary to transfer the data. Or perhaps there are configuration commands with which you can influence the DDR.

I think your first step will have to be, find out what this traffic is. You can use a packet sniffer to check individual packets. Or how about a firewall like ZoneAlarm: here, you can specify which programs may contect the Internet (or even the LAN), and which programs may not. If you delete its program database, it will ask for permission for each individual program that wants to access the net. I have it on an individual computer; I am not sure how you would do it on a network: perhaps, connect one computer at a time.