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Re: Bootcamp Lab 8 Demand Circuit question posted 05/16/2001
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I just did Lab 8 again yesterday and came up with a similar, yet different

First, to respond to Justin with what I think is happening. It sounds to me
that you're ISDN line is coming up whenever there's a topology change. Now,
based on your description, it comes up every time the ISDN line drops. So,
the ISDN line dropping is causing a topology change. Although OSPF knows
about it, what if OSPF redistributed the information about the ISDN line
drop into other protocols? How would the other protocols handle this event?
I don't want to give away what is going on here, but those are some clues to
get you going.

My question is slightly different. The requirement of the ISDN is that it
"only comes up when the ethernet goes down". It also says you have to use
Demand Circuit. Now, my line doesn't flap due to the ISDN topology change,
but it does come up when there is a topology change elsewhere in the
network. I regard this as normal behaviour for Demand Circuit. Now, like
Justin said, I could block, but I believe that will hinder the
resiliency of the line.

Looking at Marc's solutions, he has basically the same configs as myself. I
suspect it is normal behaviour for the line to come up when the network

Regarding the actual lab, if presented with a situation like this, I presume
the best thing to do is "ask the proctor"?

----- Original Message -----
From: "Dean, Justin" <Justin.Dean@xxxxxxxxxx>
To: <ccielab@xxxxxxxxxxxxxx>
Sent: Wednesday, May 16, 2001 11:26 AM
Subject: Bootcamp Lab 8 Demand Circuit question

> I am doing lab 8 again and I am running into the problem where I cant keep
> the demand circuit from coming up without using a "deny ospf any any" on a
> dialer list. I know that this is not allowed. When I debug dialer packets
> just shows me "caused by R6 to" but I can't figure out what is
> causing it to trigger the ospf traffic. One thing that is strange is that
> when it connects it will not send any interesting traffic until the moment
> it disconnects then it generates a "" packet and brings up the
> line. Does anyone have an idea what is going on. I already made sure that
> is showing up as a demand circuit and I also shut the serial on R4 just to
> make sure it wasnt something with the igrp/ospf redistribution. thanks,
> justin
> **Please read:
**Please read:
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