Re: EIGRP Neighbors Flapping b/c of mismatch MTU ?

From: Narbik Kocharians (narbikk@gmail.com)
Date: Sun Feb 15 2009 - 16:33:22 ARST

What is the topology?

On Sun, Feb 15, 2009 at 10:23 AM, Salahaddin Elshekeil <
salah.elshekeil@gmail.com> wrote:

> EIGRP Neighbor Problem Cause: Mismatched K Values
> For EIGRP to establish its neighbors, the K constant value to manipulate
> the
> EIGRP metric must be the same. In EIGRP's metric calculation, the default
> for the K value is set so that only the bandwidth and the delay of the
> interface are used to calculate the EIGRP metric. Many times, the network
> administrator might want other interface factors, such as load and
> reliability, to determine the EIGRP metric. Therefore, the K values are
> changed. Because only bandwidth and delay are used in calculations, the
> remaining K values are set to a value of 0 by default. However, the K
> values
> must be the same for all the routers, or EIGRP won't establish a neighbor
> relationship.
>
> example: K1 is bandwidth and K3 is delay. when you change the K values
> of Router B to all 1s from K1 to K4, while Router A retains the default
> value of K1 and K3 to be 1. In this example, Router A and Router B will not
> form EIGRP neighbor relationship because the K values don't match
>
> Router A------------------ Router B
>
> to change the K values
>
> use this command under the eigrp process "*metric weights* *tos k1 k2 k3 k4
> k5 * "
>
> Default values:
>
> *tos**: *0
>
> *k1**:** *1
>
> *k2**:* 0
>
> *k3**:* 1
>
> *k4**:* 0
>
> *k5**:* 0
>
> the metrics between the two routers should be matched so they can form
> neighbor relationship
>
>
> On Sun, Feb 15, 2009 at 8:52 PM, Hussam EL Kebbi
> <hussamkibbi@hotmail.com>wrote:
>
> > Actually I was working on real network environment that I don't have
> access
> > now anymore.
> >
> >
> >
> > I am only surprised that nothing worked when neighbors were flapping
> unless
> > when I put MTU equal to each others!!!
> >
> >
> >
> > Does it have to do with LMI can't be fragmented or something? any idea?
> >
> >
> >
> > The output error was (K-values mismtach).
> >
> >
> >
> > > Date: Sun, 15 Feb 2009 10:44:12 -0500
> > > Subject: Re: EIGRP Neighbors Flapping b/c of mismatch MTU ?
> > > From: all.from.nj@gmail.com
> > > To: hussamkibbi@hotmail.com
> > > CC: ccielab@groupstudy.com
> > >
> > > A quick lab test:
> > >
> > > %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 1.1.1.1 (Serial0/0.1) is
> > down:
> > > Insufficient MTU
> > >
> > > R3(config-if)#do sho debug
> > > IP routing:
> > > IP-EIGRP Neighbor Target Events debugging is on
> > > IP-EIGRP Route Events debugging is on
> > >
> > > I get this message when I tune the MTU to a very low value, but I was
> not
> > > able to get it when the MTU were only slightly different.
> > >
> > > Have you progressed through the lab to a point where other configs have
> > > caused problems? For EIGRP, slightly different MTU sizes should not
> > matter
> > > much in the lab type environment.
> > >
> > > Any additional insight to what your configs look like might help / be
> fun
> > > for those of us wanting to lab test this along with you. I will be out
> > for
> > > most of the day ... going snowboarding! ;-)
> > >
> > > andrew>
> > > andrew>en
> > > andrew#
> > > andrew# config brain
> > > andrew(wacky brain)# go snowboarding today
> > >
> > > Andrew Lee Lissitz
> > >
> > >
> > >
> > > On Sun, Feb 15, 2009 at 5:17 AM, Hussam EL Kebbi
> > <hussamkibbi@hotmail.com>wrote:
> > >
> > > > Hi Experts,
> > > >
> > > >
> > > >
> > > > I was working on a lab (EIGRP over Frame Relay) and I noticed that
> when
> > MTU
> > > > is
> > > > different between neighbors
> > > >
> > > > it starts flapping, but when I changed MTU to same on both neighbor
> > > > interfaces, it works just fine.
> > > >
> > > >
> > > >
> > > > Any idea why?
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > Thank You,
> > > >
> > > > Hussam
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > _________________________________________________________________
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> > > >
> > >
> > >
> > > --
> > > Andrew Lee Lissitz
> > > all.from.nj@gmail.com
> > >
> > >
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-- 
Narbik Kocharians
CCSI#30832, CCIE# 12410 (R&S, SP, Security)
www.MicronicsTraining.com
www.Net-Workbooks.com
Sr. Technical Instructor

Blogs and organic groups at http://www.ccie.net

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