Re: Split horizon in OSPF???

Well, yes and no. The multi-ABR world has rules to follow when
distributing summaries back to Area 0. Some people describe this as
LIKE split-horizon. I always just thought of it as the rules that OSPF
follows, but I suppose whatever works.

As Darby had pointed out, RFC 3509 is a good description of this
behavior and solutions. And I think that the term "split horizon" is
actually used in there to help people understand!

But in general, yes, you are correct.

The concepts of link-state though as described in the main RFC for OSPF
actually relate to intra-area behavior.

HTH,

*Scott Morris*, CCIE/x4/ (R&S/ISP-Dial/Security/Service Provider) #4713,

JNCIE-M #153, JNCIS-ER, CISSP, et al.

CCSI #21903, JNCI-M, JNCI-ER

swm_at_emanon.com

Knowledge is power.

Power corrupts.

Study hard and be Eeeeviiiil......

Malla, Girish wrote:
> I believe answer to this question is "NO"
> Split horizon is loop avoidance feature in Distance vector protocol. Where the routing information received on an interface will not go out on same interface. Since OSPF is a link state protocol and it doesn't send routing table to neighbor, so the answer is "NO"
>
> Regards,
> Girish Malla
>
>
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of Mark Matters
> Sent: Friday, July 10, 2009 8:49 AM
> To: Darby Weaver
> Cc: Manu Ohri (mohri); Naufal Jamal; ccielab_at_groupstudy.com
> Subject: Re: Split horizon in OSPF???
>
> Ok the RFC does go into how OSPF uses split-horizon. "
> RFC3509 - Alternative Implementations of OSPF Area Border Route
>
> OSPF prevents
> inter-area routing loops by implementing a split-horizon mechanism,
> allowing ABRs to inject into the backbone only Summary-LSAs derived
> from the intra-area routes, and limiting ABRs' SPF calculation to consider
> only Summary-LSAs in the backbone area's link-state database."
>
>
> But where on the doc cd does it state that OSPF uses split-horizon? It
> doesn't. If this was a OEQ, then it's a trick question in my opinion.
>
>
>
> On Thu, Jul 9, 2009 at 10:51 PM, Darby Weaver <ccie.weaver_at_gmail.com> wrote:
>
>
>> RFC3509
>>
>>
>>
>>
>> On Thu, Jul 9, 2009 at 6:10 PM, Manu Ohri (mohri) <mohri_at_cisco.com> wrote:
>>
>>
>>> No Split Horizon in OSPF or any link state protocols. It is on in
>>> distance vector to protect against loops.
>>>
>>> Regards
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
>>> Naufal Jamal
>>> Sent: Thursday, July 09, 2009 11:33 AM
>>> To: ccielab_at_groupstudy.com
>>> Subject: Split horizon in OSPF???
>>>
>>> Hi all,
>>>
>>> someone recently asked me a question that is there any way to disable
>>> split horizon in OSPF as in case of eigrp or NBMA n/w?got pretty
>>> confused.can any one help or send me a link to understand it better.
>>>
>>> Naufal Jamal
>>>
>>>
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Received on Fri Jul 10 2009 - 16:09:51 ART