[c-nsp] BGP blackholling with communites

[Gert Doering]

Hi,

On Mon, Mar 21, 2005 at 11:17:13AM +0000, David Freedman wrote:
> I had assumed that it would bypass the "next-hop-self" action which may
> be applied to the peering router's iBGP peers (countering the ability to
> propogate the new next-hop around the network), there are some mixed
> opinions about whether this should or should not work to do this,
> (whether it actually works and is implemented is another matter!)

"Origin" has no influence on "next-hop-self" - it's only an attribute that
will be used as a tie-breaker somewhere low in the BGP decision hierarchy.

So if you use next-hop-self, you'll need to do it via route-map and exclude
prefixes carrying the blackhole community.

Oli - this is an important point indeed.  How do other networks handle this?

> however its nice to have a determined "origin" attribute anyway :)

As the route is coming in from a customer, overriding the "origin" attribute
that they send to you might not be what they want...

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
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