Customer AS

Curtis Villamizar curtis at
Sat Aug 17 11:57:02 UTC 1996

In message <m0urb70-00080OC at>, Randy Bush writes:
> > Not sure what you mean here concerning 'unroutable' prefixes, but the
> > issue with obtaining an allocation for one of the upstream provider's
> > CIDR block when multihomed *does* have its drawbacks, at least from
> > the end-user perspective. If said prefix (let's say a /24) is announced
> > in the 'allocating' provider's aggregate, and the more specific is
> > announced via the 'other' provider, the more specific will always be
> > preferred.
> This is brain damaged.  Given
>             AS1 ----- Sprint
>              |
>              |
>              |
>              |
>             AS2 ----- anything else not Sprint
> You can not announce a bit of Sprint space AS1->AS2->MCI as a fallback (note
> the 'extra' AS hop) because Sprint aggregates your announcement and the
> longer prefix is announced to the world via <anything else>.
> Use Sprint space, bye bye fallback.
> To the best of my knowledge (which ain't that hot), all other providers have
> discovered suppress-map.
> randy


What are you saying is brain damaged?  The idea of announcing a dual
homed route as part of an aggregate?  Or Sprint?

You clearly want to avoid using space in any provider that is not
willing to suppress your more specific when generating their
aggregate, particularly since they can no longer pass the aggregate to
you (with your AS in the as-set).  We've seen this effect.

Using your own aggregate and allowing a customer to dual home, leaving
the alternate provider's contribution out of the aggregate is a
certainly not brain damaged.


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