In a brief summary of DDR, I read the following:
The router dials (or maintains the connection) if it receives "interesting traffic", meaning traffic that has to be routed.
You can control what is "interesting traffic" using ACL (access-control lists).
With ACLs, the router forwards or rejects traffic, depending on certain rules. These rules can include origin address, destination address, and specific protocols. For instance, you can reject FTP traffic, but allow HTTP traffic.
>Hi Hilmar,
>
>>>
>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.
>>
>
>Thanks for the response. At the moment I'm not too concerned with individual machines that generate traffic and thus hold the connection - I can deal with those later. As mentioned, at the moment the router keeps the line up even when it is physically detached from the hub that connects it the local LAN. Also, since the traffic is occurring beween the router and the IDSN connection/ISP I don't know if there is any sniffer I can use to monitor this. Again I don't know if this exchange is initiated by the router here or at the ISP or whether this is, in fact, responsible for the problem. I set up the router using the Cisco 'Fast Step' utility and am looking at the resulting setup from the Monitor utility. Maybe I'm going to have to start digging using the console interface. Any further suggestions would be welcome.
>
>Thanks again,
>Viv
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)
