From: tom cheung (tkc9789@xxxxxxxxxxx)
Date: Thu Apr 12 2001 - 15:08:52 GMT-3
ISIS uses CLNS to form adjancies. IP has nothing to do with it. It'll form
adjancies, if I'm not mistaken, even when router A and B are on different
subnets.
>From: "McCallum, Robert" <Robert.McCallum@let-it-be-thus.com>
>Reply-To: "McCallum, Robert" <Robert.McCallum@let-it-be-thus.com>
>To: "'Ccielab' (E-mail)" <ccielab@groupstudy.com>,
>"Cisco@Groupstudy. Com (E-mail)" <cisco@groupstudy.com>
>Subject: Unusual Aspect of a duplicate IP Address
>Date: Thu, 12 Apr 2001 16:59:32 +0100
>
>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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