Please Heeeeelp me!

Unanswered Question
Jul 13th, 2009
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Hi,

I will be crazy, I read in (CCNP BSCI Official Exam Certification Guide, Fourth Edition)


Page#64 the author said,

"If the querier does not receive a reply from each of its neighbors, it repeats the

query as a unicast to each unresponsive neighbor until it either gets a reply or gives up after

sixteen tries."


And in Page#70the author said,

"When queries are produced, the router changes to an active state and sets a timer (typically three minutes). If the timer expires before an answer comes back then the router is considered stuck in active."


My question is it is tries 16 attempts to get replay or waiting 3 minute to consider is SIA or both is different.



BR,

Auos

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Rick Morris Mon, 07/13/2009 - 07:05
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Two different processes.


One is a hold timer and the other is number of tries.


For instance.

I will try to call my wife 10 times to get a hold of her. If she does not answer I will wait a little bit until I try again, or just not call her back at all after my timer has expired.

Istvan_Rabai Mon, 07/13/2009 - 08:24
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Hi Auos,


The standard wording for EIGRP packet types is the following:


HELLO

ACKNOWLEDGMENT

UPDATE


QUERY

REPLY


SIA-QUERY

SIA-REPLY


I don't have the book at hands, but based on the post I can tell you the following:


On page #64 it talks about EIGRP reliably sending a QUERY to multicast address 224.0.0.10.

The router sending the QUERY waits for an ACKNOWLEDGMENT from each of its neighbors.


So it's only an ACKNOWLEDGMENT of receiving the QUERY, and not a REPLY to a QUERY.


The difference between an ACKNOWLEDGMENT and a REPLY:


ACKNOWLEDGMENT:

The router says: I have received your QUERY.


REPLY:

The router says: Here you are the information you requested in your QUERY.



On page #70 it talks about not receiving a REPLY to a QUERY. After 3 minutes the ROUTE requested goes into stuck-in-active in the topology table.

Be aware that it is NOT the router that goes into stuck-in-active, but a ROUTE in the topology table goes into stuck-in-active.


You can check the topology table with the "show ip eigrp topology" command.


So your confusion may come from the author not using a consistent wording.


Cheers:

Istvan


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