EIGRP Query control

Unanswered Question
Feb 12th, 2009

Hi Everybody,

I want to know to control or restrict EIGRP Query in my network. I know that this can be achieved by route summarization.

But I am not able to figure out where to configure the command "ip summary-address eigrp 1 x.x.x.x". My intention is

1. No Query propogation should cross beyond the Router B to Router A if the Query originate either from Router D or E.

2. No Query propogation should cross beyond the Router B to Router D and E if the Query originate either from Router A

Kindly help me to solve this


I have this problem too.
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Giuseppe Larosa Thu, 02/12/2009 - 04:58

Hello R.B Kumar,

I suppose routerD and router E are spokes or branch routers and that RA represents Head Quarter.

Under these hypthotesis I would:


int ser0/0

ip summary-addresss eigrp 1



On RD and RE use the EIGRP stub feature

router eigrp 1

eigrp stub connected



Hope to help


hclisschennai Thu, 02/12/2009 - 06:04

Hi Giuseppe,

Thanks for your comment.I have gone thru the document you provided. Thanks again.

But you mentioned "ip summary-address eigrp 1". Won't this advertise default network towards Router B? which cisco says it will create Null Route. (mentioned in the link you provided).

My contention is if network in Router A ( goes down, will it create query message towards Router B and will propogate towards Router D and Router E?

I am not able to understand by which means Router reply the query? For example i assume if a query comes to Router D, it will check in its topology table for details for, if neither Successor / Feasible succesor is avaialble it goes to Active state and query its neighbour. It want to stops this query goes from Router B using summarisation?

Please help me how to get this


hclisschennai Thu, 02/12/2009 - 09:16


Kindly let me know how EIGRP Query process works with summarization when it reaches a router.

1. What decision is made to decide

whether the query has to be send further to its neighbour when summarization is enabled and if not enabled?

2. How Summarization avoids this?

I am not getting clear documents to explain this


Giuseppe Larosa Thu, 02/12/2009 - 11:55

Hello R.B. Kumar,

my understanding is that the router receiving a summary route in this case a default route summary route when receives the Query can answer back with a Reply telling it is not a possible backup path for the route.

This should be the reason why route summarization helps to limit EIGRP query scope.

Something similar happens with the EIGRP stub router feature.

So you need to summarize out the interface of the core router where you want to stop EIGRP queries

Using a default route summary route has the effect to stop every possible Query.

Hope to help


hclisschennai Thu, 02/12/2009 - 23:17

HI Giuseppe,

Thanks for your initiative to educate me on this.

Can you please explain the concept below:

1. When a query reaches a router i know that i will see whether this router is having route for the queried prefix in either as successor or Feasibile Successor. If both are not avaialble it will start querying its neighbour and move to Active state.

But When it is having summarized Route for the queried prefix, whether it will do this same activit or it will simply reply the router telling it is not having the route and donot go to active state?

Can you please explain


Giuseppe Larosa Fri, 02/13/2009 - 07:59

Hello R.B. Kumar,

when a router receives a Query for a route from a neighbor performs a basic check:

it sees if it has a detailed route matching the requested route in the EIGRP topology table.

If it hasn't and the route is contained in a less specific route and that route is learned only from the Query originator the router is allowed to answer with a negative Reply stopping Query propagation.

The idea is that if no detailed information has been learned downstream up to now, and the only possible match is a summary route that has come from the same interface that received the Query there is no chance to get an alternate path by propagating the Query.

So this router RB in your scenario can simply answers back "no alternate path here".

if on interface between RA and RB RB receives only a default router whatever Query RA sends out RB will answer with a negative Reply.

Hope to help



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