From: M_A_Jones@DellTeam.com
Date: Thu Jul 03 2008 - 17:18:05 ART
Naribik! seriously dude..Are you human? we have a running tally here of people whom are starting to suspect you're not !
Michael Jones
Network Engineer
Global Network Operations
Dell Inc. | J&M Consultants
W. 512.723.3268 | C. 512.966.6908
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Narbik Kocharians
Sent: Thursday, July 03, 2008 3:10 PM
To: Ashwani ranpise
Cc: Cisco certification
Subject: Re: EIGRP QUERY & Reply process
Before we go into the explanation remember that the queries by default are set to 3 minutes and can be modified by "timers active-time" this can be increased or decreased or totally disabled.
Now back to what you were asking, Let's say:
RA is connected to RB and RB is connected to RC, RA is advertising network 1.0.0.0 /8.
"SIA-Queries" and "SIA-Replies" are two new features that Cisco recently added as an extra TLV in Eigrp packets and the beauty is that you don't need to configure anything for this feature to be available and it's on by default starting IOS 12.1 something.
In IOSes prior to 12.1, if RA lost network 1.0.0.0/8 and it had no feasible successor, RA would send a query for network 1.0.0.0 /8 to RB. RB has no entry for this network, so it would send a query to RC.
If there was a problem on the link connecting RB to RC, the reply packet from RC will never get to RB, and as a result of that RA assumes that because RB did not response in a timely manner (3 minutes by default, and can be changed using the "timers active-time" command in the sub-router configuration mode) it must be down. Therefore, RA will tear down the adjacency to RB.
Now, with this new feature, RA sends a query down to RB (A SIA-Query) at the midway point of the active timer which is 1.5 minutes (If default values are used), and RB responds with a SIA-Reply, and once RA receives the SIA-Reply, RA will know that RB is up and therefore, it does not tear down the neighbor ship.
What happens down stream between RB and RC is as follows:
RB will send up to three SIA-Query to RC, if it does not receive a response back from RC, it will tear down their adjacency and it will immediately notify RA that it has no clue about network 1.0.0.0 /8.
Note, the adjacency between RA and RB is still up.
I hope this helped.
On Thu, Jul 3, 2008 at 10:08 AM, Ashwani ranpise <ashwani.ranpise@gmail.com>
wrote:
> Hello ,
>
> Can someone explain EIGRP query & reply process?
>
> 192.168.1.0/24 & 192.168.2.0/24----R1---R2---R3----R4----R5
>
> 1) What if link between R3 & R2 failed ? How many query & reply R4 &
> R5 will get & for which routes (assuming no summary on R3)
> 2) What if R3 is summarizing those routes & sending it to R4 & link
> failed between R3 & R2?
>
> I was going through this document but couldn't understand.
>
> http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a00
> 80094cb7.shtml
> Any help will be useful for me.
>
> Thanks,
> Ashwani
>
>
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-- Narbik Kocharians CCSI#30832, CCIE# 12410 (R&S, SP, Security) www.Net-Workbooks.com Sr. Technical Instructor
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