From: MADMAN (dave@interprise.com)
Date: Fri Feb 28 2003 - 18:53:10 GMT-3
And it you just use point-to-point subinterface on your NBMA networks
you need not worry about split horizon!
Dave
Brian Dennis wrote:
> The "ip split-horizon" command relates only to RIP and IGRP. The "ip
> split-horizon eigrp <AS>" command relates only to EIGRP. One doesn't
> have anything to do with the other. Also these commands have nothing to
> do with how "routed" traffic is forwarded. They only determine if a
> "routing" updated received on a particular interface will be sent back
> out that same interface.
>
> Brian Dennis, CCIE #2210 (R&S/ISP Dial/Security)
> brian@labforge.com
> http://www.labforge.com
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Connie Nie
> Sent: Friday, February 28, 2003 7:14 AM
> To: ccielab@groupstudy.com; 'brian@cyscoexpert.com'
> Subject: RE: Split-horizon mystery
>
> Brian,
>
> Can you elaborate a little bit on the effect of IP split-horizon and
> eigrp
> split-horizon if used together? If I have a hub interface with ip
> split-horizon enabled but eigrp split-horizon disabled, then the routed
> traffic will observe split-horizon rule but routing traffic will
> not---do I
> understand it correctly? If that is the case then the spoke will have a
> route for the other spoke, but won't receive any traffic from the other
> spoke. I guess my question is how do these two work together?
>
> Thank you very much.
>
> Connie
>
> -----Original Message-----
> From: Brian McGahan [mailto:brian@cyscoexpert.com]
> Sent: Friday, February 28, 2003 1:11 AM
> To: 'OhioHondo'; 'Brian Dennis'; 'Hunt Lee'; 'Jim Brown'
> Cc: ccielab@groupstudy.com
> Subject: RE: Split-horizon mystery
>
> IP split horizon and EIGRP split horizon are independent of each other.
> EIGRP split horizon is always on unless you disable it. You can disable
> IP split horizon, and leave EIGRP split horizon on, and vice versa.
>
> As Brian mentioned, sub-interfaces count as different logical entities,
> so you could have IP or EIGRP split horizon disabled on one and enabled
> on the other. To check if IP split horizon is on, use the 'show ip
> interface [int]' command.
>
> HTH
>
> Brian McGahan, CCIE #8593
> Director of Design and Implementation
> brian@cyscoexpert.com
>
> CyscoExpert Corporation
> Internetwork Consulting & Training
> Toll Free: 866-CyscoXP
> Outside US: 847.674.3392
> Fax: 847.674.2625
>
>
>
>>-----Original Message-----
>>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
>
> Of
>
>>OhioHondo
>>Sent: Thursday, February 27, 2003 9:40 PM
>>To: Brian Dennis; 'OhioHondo'; 'Hunt Lee'; 'Jim Brown'
>>Cc: ccielab@groupstudy.com
>>Subject: RE: Split-horizon mystery
>>
>>Brian
>>
>>Do you know how to check if EIGRP Split Horizon is set?
>>
>>It is possible to set split horizon and ip eigrp split horizon
>
> separately.
>
>>Setting split horizon seems to manipulate the value shown in "sho ip
>
> int".
>
>>
>>-----Original Message-----
>>From: Brian Dennis [mailto:brian@labforge.com]
>>Sent: Thursday, February 27, 2003 9:25 PM
>>To: 'OhioHondo'; 'Hunt Lee'; 'Jim Brown'
>>Cc: ccielab@groupstudy.com
>>Subject: RE: Split-horizon mystery
>>
>>
>>Normally you aren't processing IP on the major interface if you are
>>using sub-interfaces so anything relating to split-horizon on the
>
> major
>
>>interface has nothing to do with the sub-interface.
>>
>>Rack4R3#sho ip int | include (Serial)|(Split)
>>Serial1/0 is up, line protocol is up
>>Serial1/0.32 is up, line protocol is up
>> Split horizon is enabled
>>Serial1/0.243 is up, line protocol is up
>> Split horizon is enabled
>>Rack4R3#sho ip int s1/0
>>Serial1/0 is up, line protocol is up
>> Internet protocol processing disabled
>>Rack4R3#
>>
>>Brian Dennis, CCIE #2210 (R&S/ISP Dial/Security)
>>brian@labforge.com
>>http://www.labforge.com
>>
>>-----Original Message-----
>>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
>
> Of
>
>>OhioHondo
>>Sent: Thursday, February 27, 2003 5:36 PM
>>To: Hunt Lee; 'Jim Brown'
>>Cc: ccielab@groupstudy.com
>>Subject: RE: Split-horizon mystery
>>
>>Hunt/Jim
>>
>>I believe that split horizon on an interface works for the entire
>
> MAJOR
>
>>interface. If you have applied split horizon applied to an interface
>
> it
>
>>applies to all of the sub-interfaces on that MAJOR interface.
>>
>>I know that you can apply "ip split eirgp xx" directly on a
>>sub-interface,
>>but does it then only apply to that sub-interface?
>>
>>-----Original Message-----
>>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
>>Hunt Lee
>>Sent: Thursday, February 27, 2003 6:10 PM
>>To: 'Jim Brown'
>>Cc: 'ccielab@groupstudy.com'
>>Subject: RE: Split-horizon mystery
>>
>>
>>Hi Jim,
>>
>>That's kinds of fall into what I was thinking... hence the answer to
>
> my
>
>>lab
>>scenario would be wrong?? Since the EIGRP is only running on a
>>point-to-point network here?
>>
>>Or am I completely off?
>>
>>Thanks in advance,
>>
>>Regards,
>>Hunt
>>
>>
>>-----Original Message-----
>>From: Jim Brown [mailto:Jim.Brown@caselogic.com]
>>Sent: Friday, 28 February 2003 1:48 AM
>>To: Hunt Lee; ccielab@groupstudy.com
>>Subject: RE: Split-horizon mystery
>>
>>
>>Think about what split horizon is....
>>
>>Split horizon basically keeps a router from advertising a route out
>
> the
>
>>interface it learned the route from. Most of the time this is the
>>desired behavior, but in the case of a multipoint interface it might
>
> not
>
>>be.
>>
>>If the spokes are advertising routes to the hub and the hub has split
>>horizon enabled, it will not advertise routes from one spoke to
>
> another
>
>>if they are on the same interface.
>>
>>Split horizon only affects DV protocols and to disable it for EIGRP
>
> you
>
>>must use a different command than other DV protocols. The command is
>
> no
>
>>ip split-horizon eigrp <AS> while all other DV protocols us the
>
> command
>
>>no ip split-horizon.
>>
>>You can also use show ip interface to determine the status of split
>>horizon on an interface.
>>
>>-----Original Message-----
>>From: Hunt Lee [mailto:huntl@webcentral.com.au]
>>Sent: Thursday, February 27, 2003 12:20 AM
>>To: 'ccielab@groupstudy.com'
>>Subject: Split-horizon mystery
>>
>>
>>Hi Group,
>>
>>Does anyone know when one should use "ip split-horizon" for EIGRP?
>>
>> RTD
>> /
>>RTA---- RTB
>> \
>> RTC
>>
>>RTA, RTB & RTD are using OSPF, while RTA & RTC are both using EIGRP...
>>
>>RTA & RTC are point-to-point, while..
>>
>>RTA, RTB & RTD are point-to-multipoint
>>
>>On the solutions, I was told that I need to use "ip split-horizon" on
>>RTC
>>outgoing interface (to RTA), why??? I thought we only need to use
>
> this
>
>>command on the hub if it is point-to-multipoint sub-interface...
>>
>>anyway, here's the config:-
>>
>>On RTC:-
>>
>>interface Serial0
>> ip address 137.20.200.18 255.255.255.240
>> ip nat outside
>> encapsulation frame-relay
>> ip split-horizon <------ Do we need this???
>> no ip mroute-cache
>> keepalive 15
>> no fair-queue
>> frame-relay lmi-type ansi
>>
>>
>>router eigrp 10
>> network 137.20.0.0
>> no auto-summary
>>
>>
>>And on RTA:-
>>
>>interface Serial0.1 multipoint
>> ip address 137.20.100.34 255.255.255.224
>> ip ospf network point-to-multipoint
>> frame-relay de-group 1 502
>> frame-relay map ip 137.20.100.33 502 broadcast
>> frame-relay map ip 137.20.100.35 503 broadcast
>>!
>>interface Serial0.2 point-to-point
>> bandwidth 2000
>> ip address 137.20.200.17 255.255.255.240
>> frame-relay interface-dlci 504
>>
>>router eigrp 10
>> redistribute ospf 10 metric 2000 100 255 1 1500
>> passive-interface BRI0
>> passive-interface Ethernet0
>> passive-interface Serial0.1
>> passive-interface Serial1
>> network 137.20.0.0
>> no auto-summary
>> no eigrp log-neighbor-changes
>>
>>
>>Any help / ideas would be greatly appreciated.
>>
>>Regards,
>>Hunt
>
>
>
-- David Madland CCIE# 2016 Sr. Network Engineer Qwest Communications 612-664-3367"You don't make the poor richer by making the rich poorer." --Winston Churchill
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