ccnp bsci eigrp question

Unanswered Question
Sep 18th, 2007

Here is a question I got on a sample test and I can't determine how to answer it:

Given the topology table for EIGRP on a router, select which two networks have feasible successors.

I looked at the table thinking that's easy you find the networks with multiple entries where only 1 is listed as the successor.

The problem is, 3 networks in the table fit that category and all three were in the list of choices, but only two choices were allowed.

So, how do you narrow down? What else do you examine for clues?

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Overall Rating: 4 (1 ratings)
cyphur353 Wed, 09/19/2007 - 05:03

Anthony, thanks for the link. Very clear and concise explanations. Good stuff!

suelange Wed, 09/19/2007 - 11:32

Thank you for this link. It is very good but confirms what I thought: if a route doesn't match the feasibility condition it won't even be in the topology table.

That being the case if you are looking at a topology table and you see a network with 1 successor but multiple paths, you must conclude that particular network has a feasible successor.

Or am I still missing something?

compsolv Wed, 09/19/2007 - 13:40

Hmmm - I sure would love to see the output...yes, as you have learned, if show ip eigrp topology is used without any options, only routes that are feasible successors are displayed.

Perhaps one of the route destinations has been marked Active in your output? This would indicate that the router is currently trying to converge for that destination and is not entirely sure about the successor/feasible successor information.

suelange Thu, 09/20/2007 - 08:20

Yeah cut and paste would be nice, no?

Anyway the routes are all marked "P". The option on the command appears to have been "all-links".

The information in parenthesis on a given route is (FD/AD) I think. In every case AD is less than the successor's FD, which is listed in the first line for each network. They should all be valid. I dunno. Bad test question I'm guessing.

suelange Thu, 09/20/2007 - 09:10

Thank you and, I've studied the output again more closely...I could have just located the detail I was missing...

a route is feasible if the AD is LESS THAN the FD...not LESS THAN OR EXACTLY EQUAL TO?

In one case the AD of a potential route is equal to the FD of the that grounds to toss it out? If so, I've narrowed it down to the two choices left and that would fit the question requirements.

I am going out to look at link right now.

Thanks for additional clarification.

compsolv Thu, 09/20/2007 - 10:00

Looks like someone might have written an excellent exam question!


You are right - the rule is LESS THAN!

Great job tearing things apart to this level - it is a key to your success in this profession!

Anthony J. Sequeira



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