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I can't cope with this MS 70-291 Training Kit Task:

What is the configuration error in the diagram below and WHY?

(btw: I have removed original, wrong mask which was editors error and placed big red /17 according to corrections given by editor for this task)

http://img841.imageshack.us/img841/732/subnetting.gif

edit: Excuse my gigantic mistake. I rather meant this one: http://img267.imageshack.us/img267/7823/subnettingproper.gif

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Client D's IP address isn't in the network? –  Daniel Beck Jan 17 '12 at 18:48

1 Answer 1

In the second figure networks on both side of router use the same subnet.

This will mess up the routing table.

Each subnet is mapped to an egress interface. So in your case, packets coming into router will not reach one of the networks , because threre are 2 interfaces with same subnet.

Answer to your question:

The simplest change to make this configuration work is to use "/28" as subnet mask everywhere instead of "/27"

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Definitely I am tired today. I have posted wrong task image. Of course you are right as it comes to the one above. But the one I have problem with is this: img267.imageshack.us/img267/7823/subnettingproper.gif So again, what's wrong with THIS network? –  Kangaroo Jan 17 '12 at 18:54
    
you can update the question with this . –  daya Jan 17 '12 at 18:56
    
@daya: "both side of router use the same subnet." I can agree and that was what I thought at first look, but that's not the proper answer if we consider what Daniel Beck has pointed out - that these adresses are impossible. If I understand correctly, they are impossible in this subnet (/27). Now I am trying to figure it out how to define in which subnet they can be proper. (BTW I know the answer from the key, but can't get to it (calculate) from this diagram yet). –  Kangaroo Jan 17 '12 at 19:22
    
i have updated the answer..use /28 in place of /27 everywhere –  daya Jan 17 '12 at 19:32
    
@daya: Yes, the change from /27 to /28 is given as a correct answer but I think I need additional tips to understand why is that. –  Kangaroo Jan 17 '12 at 19:32

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