From: Justin Menga (Justin.Menga@xxxxxxxxxxxxxxxxxx)
Date: Fri Feb 02 2001 - 09:48:13 GMT-3
Rob,
You are correct about split-horizon disabled on a frame physical interface
by default - HOWEVER, this only applies to RIP and IGRP. To configure
split-horizon for EIGRP you need to use 'ip split-horizon eigrp xx' and by
default on ANY interface, split horizon for EIGRP is enabled.
Regards,
Justin Menga CCIE #6640 MCSE+I CCSE
WAN Specialist
Computerland New Zealand
PO Box 3631, Auckland
DDI: (+64) 9 360 4864 Mobile: (+64) 25 349 599
mailto: justin.menga@computerland.co.nz
-----Original Message-----
From: Rob Webber [mailto:rwebber@callisma.com]
Sent: Friday, 2 February 2001 6:57 a.m.
To: 'Johnny Dedon'; 'Groupstudy'
Subject: RE: CCIEbootcamp lab 2
Router 2 is configured for EIGRP and is using Frame Relay without
subinterfaces. Thus ip split-horizon is disabled by default. Thus everything
r2 learns from R1 via EIGRP, it will turn right around and advertise back to
R1. On a "hub" router you often need split-horizon disabled, but on a
"spoke" router (like r2) you almost always want it enabled.
In this case it could be very dangerous. If r1 redistributes OSPF into
EIGRP, then advertises all of those EIGRP updates to r2, r2 will advertise
them all back to r1. Since EIGRP has a lower distance than OSPF, r1 will
prefer the EIGRP routes coming from r2 - even for networks connected to r5 -
routing loop!
Hope this helps, Rob.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Johnny Dedon
Sent: Wednesday, January 31, 2001 8:02 PM
To: Groupstudy
Subject: CCIEbootcamp lab 2
Can anyone help with an explanation as to why split horizon is an issue on
router2? Its late and I'm sure I'm missing something...be gentle :)
Johnny Dedon
Senior Staff Consultant
Exodus Professional Services
johnny.dedon@exodus.net
www.exodus.net
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