From: McCallum, Robert (Robert.McCallum@xxxxxxxxxxxxxxxxxx)
Date: Thu Apr 12 2001 - 12:59:32 GMT-3
Here is a scenario which caught me out BIG time in a real life situation
using ISIS.
To make it easier
Router A has a serial connection to Router B
Everything is up layer 1 & 2i.e CDP can indeed see Router B if you are on
Router A and vice versa. Router B can't see any routes from Router A or
beyond.
NOW Routers A serial 0's ip address is 172.16.130.5, Routers B serial 0's
ip address is 172.16.130.5.
Spot the deliberate mistake.
Although you say AHA he has the same ip address on the serial connections.
SO, quite rightly ISIS says, go away I will never make an adjacency with
myself !!!! :-(
However, it took me quite a while to discover that these IP addresses were
indeed duplicated.
REASON or should I make it a question? I think question would be better.
Q: What do you think would happen if I was on Router A and telnetted to
172.16.130.5, would I telnet to Router A or B. :->
A: This is why it took me a while to realise this. I started debugging
adjacencies, blaming a new controller card which was the first time I had
used this in ISIS, everything bar the easy problem. Mental Note for me here
is don't dive in head first, always fault find the layers and remember this
fault because it is nasty!!!! :-<
What made it worse was the customer sitting over my shoulder saying WHY
isn't this working, I knew we shouldn't have bought those new fangled router
things!!!!!
Oh the joys of life!!!!
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