Customer AS

Randy Bush randy at
Sat Aug 17 20:20:00 UTC 1996

Hi Hank,

>>> 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.
> This is mainly due to the fact that Sprint does not listen to any
> announcements from its peers for anything within its "non-portable"
> blocks.

What?!?  I.e. if a Sprint customer C is multi-homed and their Sprint line
goes down, traffic to C from other Sprint customers will not be able to
reach C?

> BTW, Sprint also does not listen to any of its peers ASes through
> other peers so peering with Sprint and still paying someone for
> transit services do not help you get more redundancy with Sprint's
> network.

And this is considered good networking architecture?  Jeezus!


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