Re: EIGRP - Split Horizon

Yes I did read Dave post carefully.
I pointed it out to in a private email that your first post mislead Dave on
the issue he was having:

" According to that definition, depending on the timing of things, R3 would
advertise R1's Lo0 to R4 - or the other way around - and then the learning
router would not advertise R1's Lo0 back to the other neighbor."

What you are missing here is:
1- "Split horizon blocks information about routes from being advertised by a
router out of any interface from which that information originated."
2- "The split-horizon rule prohibits a router from advertising a route
through an interface that the router itself uses to reach the destination."

1 & 2 are what make up Split Horizon. Don't just focus on 2 to explain split
horizon while the real heart lies on 1.

Now I would explain why after changing the cost Dave saw a different result:

R3 is advertising to R2 its path via R3-->R4-->R2-->R2
and
R2 is advertising to R3 it path via R2-->R1

Again same prefix, but different path and more importantly received on
different INTERFACES.

Please read my post careful; the metric I used is just to illustrate the
path and not the cost. Also please read through the end.

HTH

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Received on Mon Jan 10 2011 - 09:58:59 ART