Re: EIGRP - Split Horizon

Hey Dave,

There's a nuance in the description of EIGRP split horizon in the
command ref:

http://www.cisco.com/en/US/docs/ios/iproute_eigrp/command/reference/ire_s1.html#wp1058799

"The split-horizon rule prohibits a router from advertising a route
through an interface that the router itself uses to reach the
destination."

I'm guessing neither R3 nor R4 use the other to reach R1's Lo0, correct?

Cheers,

Scott

On Jan 8, 2011, at 10:54 , Dave Serra wrote:

> Hi Guys,
>
> I thought I understood the split horizon rule until I built the
> following topology in GNS:
>
> R3---------R4
> | ----R2----|
> |
> R1
>
> What I'm trying to depict in the above diagram is a triangle
> topology between
> R2, R3, and R4. R1 hanging off of R2 outside the triangle.
> All routers are running EIGRP on all interfaces. I create a
> loopback of
> 1.1.1.1/32 on R1. I then see the route travel from R1 to R2, from
> R2 to R3
> and
> R4 and finally (and most confusingly) from R3 to R4 and from R4 to R3.
> It is this last part that I am having trouble with. When R3 learns
> the
> route of
> 1.1.1.1/32 from R2 and sends it to R4, shouldn't R4 NOT send that
> same route
> back to R3 due to split horizon???
>
> I show in the 'show ip eigrp
> top all' on both R3 and R4 that this route is
> learned from each other.
>
> Can
> someone help me to better understand this?
>
> Thanks in advance :)
>
> Dave
> Make a small loan, Make a big difference - Kiva.org
> ________________________________
> From: Juan <fferrer10_at_gmail.com>
> To: Cisco
> certification <ccielab_at_groupstudy.com>
> Sent: Fri, January 7, 2011 1:35:34 AM
> Subject: Test, Please ignore
>
> Test
>
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Received on Sat Jan 08 2011 - 11:05:08 ART