Re: Split Horizon

Being a little picky I believe that the concept found in most discussions
is that a routing update received in an interface is not advertised back
out that same interface.

The implementation as far as I understand does not keep track of what
interface an update comes in. Rather the next-hop is used - the update is
not sent out an interface used to reach the next hop. Try redistributing
a static route with a next hop out a rip enabled interface into rip- the
redistributed static route won't be advertised out the interface used to
reach the next hop even though technically the route was not received in
that interface.

Ivan

> R.B,
>
> I would just clean that up a little and replace "packet" with
> "destination" or something along that line.
>
> People sometimes (recently) use this in iBGP discussions, which I
> believe to be a slightly improper application of the term. The full
> mesh/synchronization requirement has as much if not more to do with
> serving as an anti-blackholing mechanism vs. preventing loops from
> forming. And even to the extent that it does prevent loops, it does
> so slightly differently as contrasted to, say, RIP split-horizon, so
> this is not a term that I personally use in the context of BGP.
> Others do, though, and so this is probably one context worth making
> note of.
>
> The term has also been borrowed for split-horizon DNS and so forth.
> But it generally infers a behavior where otherwise flooded information
> is not reflected back towards its point of origin relative to any
> given point in a topology.
>
> What was the catalyst for your question?
>
> Regards,
>
> Scott
>
>
>
> On Apr 23, 2009, at 7:03 , Robin Betterley wrote:
>
>> Hi GS,
>>
>> The basic principle is simple: Information about the routing for a
>> particular packet is never sent back in the direction from which it
>> was received.
>>
>> Is there any other known principle of split horizon?
>>
>> Cheers,
>> R.B
>>
>>
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Received on Fri Apr 24 2009 - 11:23:48 ART