From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Fri Nov 05 2004 - 19:12:38 GMT-3
John,
This is an issue in a partial mesh design, such as Frame Relay
hub-and-spoke.
For example, suppose that R1, R2, and R3 are connected to the
Frame Relay cloud, with circuits provisioned between R1 & R2, and R1 &
R3. For traffic to go between R2 and R3, it must pass through R1. If
this network uses the same IP subnet (i.e. the same interface is used on
R1 to connect to R2 and R3) split-horizon for EIGRP can be an issue.
When R1 receives an EIGRP update from R2, it cannot pass it on to R3 due
to split horizon, and vice versa. To resolve this issue, split horizon
for EIGRP must be disabled on R1's interface attached to the Frame Relay
cloud.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
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> -----Original Message-----
> From: Sheahan, John [mailto:John.Sheahan@priceline.com]
> Sent: Friday, November 05, 2004 4:08 PM
> To: Brian McGahan
> Subject: RE: Split horizon for eigrp ???
>
> Thanks Brian,
>
> Now that I think about it, I was under the impression that I didn't
have
> to worry about split-horizon with EIGRP or OSPF due to the Link State
> qualities of EIGRP. I know that EIGRP is a hybrid and is more like a
> Distance Vector but didn't realize it could be a problem.
> Where would this be likely to cause a problem?
>
> Thanks for the help.
>
> john
>
> -----Original Message-----
> From: Brian McGahan [mailto:bmcgahan@internetworkexpert.com]
> Sent: Friday, November 05, 2004 3:51 PM
> To: Sheahan, John; network.cisco@gmail.com; ccielab@groupstudy.com
> Subject: RE: Split horizon for eigrp ???
>
>
> Keep in mind that "ip split-horizon" applies only to RIP and
> IGRP. "ip split-horizon eigrp" applies to EIGRP. The output from
"show
> ip interface" shows the status of "ip split-horizon". To check the
> status of "ip split-horizon eigrp" simply check the configuration, as
it
> is enabled by default on all interfaces.
>
>
> HTH,
>
> Brian McGahan, CCIE #8593
> bmcgahan@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987 x 705
> Outside US: 775-826-4344 x 705
> 24/7 Support: http://forum.internetworkexpert.com
> Live Chat: http://www.internetworkexpert.com/chat/
>
>
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Sheahan, John
> > Sent: Friday, November 05, 2004 10:20 AM
> > To: network.cisco@gmail.com; ccielab@groupstudy.com
> > Subject: RE: Split horizon for eigrp ???
> >
> > show ip interface <interface #>
> >
> > will specifically show if split horizon is enabled or disabled
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf
Of
> > Georg Pauwen
> > Sent: Friday, November 05, 2004 5:39 AM
> > To: network.cisco@gmail.com; ccielab@groupstudy.com
> > Subject: RE: Split horizon for eigrp ???
> >
> >
> > Hello,
> >
> > since EIGRP Split-Horizon is on by default, you will only see it if
it
> is
> > turned off on an interface with the interface command <no ip
> split-horizon
> > eigrp x> command. If you do a <sh run> and do not see <no ip eirgp
> > split-horizon eigrp x> command on the respective interface, it means
> that
> > split-horizon is turned on.
> >
> > Regards,
> >
> > Georg
> >
> > >From: Cisco Net <network.cisco@gmail.com>
> > >Reply-To: Cisco Net <network.cisco@gmail.com>
> > >To: Group Study <ccielab@groupstudy.com>
> > >Subject: Split horizon for eigrp ???
> > >Date: Thu, 4 Nov 2004 19:08:24 -0800
> > >
> > >Hi
> > >
> > >How to see if i have disabled or enabled the split horizon for
eigrp
> > >on a given interface. I can not see on sh ip protocol.. Any other
way
> > >?
> > >Thx
> > >Cert
> > >
> >
>
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