From: Narbik Kocharians (narbikk@gmail.com)
Date: Sun Jun 15 2008 - 17:29:35 ART
OK here it goes; 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.
On Sun, Jun 15, 2008 at 12:55 PM, Narbik Kocharians <narbikk@gmail.com>
wrote:
> Don't forget the "SIA quries and SIA replies"
>
> On Sun, Jun 15, 2008 at 8:22 AM, shahid Ansari <shahid1357@gmail.com>
> wrote:
>
>> Normally In Eigrp,
>> If No Feasible successor available ,the route lost and goes into active
>> state .
>> If neighboring Router hve info abt lost route they reply to quering router
>> .
>> If neighbor doesnt have routes info ,query send to its next neighbor
>> the process go till the end of the network .
>> query diameter increases as query send till end of the network and
>> decreases when reply received .
>> 2 methods to limit query scope
>> 1.stub routers - doest send query only send update to stub routers
>> 2.Route summarization
>>
>> You must Read Jeff Doyle to understand the concept
>> Thanks
>>
>> Shahid Ansari
>>
>>
>>
>>
>> On 6/15/08, Joseph Brunner <joe@affirmedsystems.com> wrote:
>> > You want to be a Jedi like us, huh?
>> >
>> > what does
>> >
>> > debug eigrp packets query
>> >
>> > tell you?
>> >
>> > -----Original Message-----
>> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>> > Gyori Gabor
>> > Sent: Sunday, June 15, 2008 4:37 AM
>> > To: ccielab@groupstudy.com
>> > Subject: EIGRP query question
>> >
>> > Hello group!
>> >
>> > Scenario: I a have a star topology network, and one of the spokes
>> advertise
>> > a
>> > route (f.e 192.168.1.0/24) to the hub.
>> > The link fails in between the hub and the advertising spoke, this way
>> there
>> > is
>> > no feasible sucuccessor for 192.168.1.0/24.
>> > The others spokes hasve never advertised 192.168.1.0/24.
>> > In this case, does the hub query the others spokes for 192.168.1.0/24,
>> or
>> > simpli removes it from routing table?
>> >
>> > Thanks,
>> > Gabor
>> >
>> >
>> > _______________________________________________________________________
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>> >
>> > _______________________________________________________________________
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>>
>> _______________________________________________________________________
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>>
>>
>>
>>
>
>
> --
> Narbik Kocharians
> CCSI#30832, CCIE# 12410 (R&S, SP, Security)
> www.Net-Workbooks.com <http://www.net-workbooks.com/>
> Sr. Technical Instructor
-- Narbik Kocharians CCSI#30832, CCIE# 12410 (R&S, SP, Security) www.Net-Workbooks.com Sr. Technical Instructor
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