North American Network Operators Group

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Re: AS announcement question (easy)

  • From: Mikael Abrahamsson
  • Date: Mon Aug 04 14:37:50 2003

On Mon, 4 Aug 2003, Mike Donahue wrote:

> My company owns a class C, and we're switching ISPs.  The "new" provider is
> telling us that they can start announcing, without us having to tell the old
> provider to stop announcing.  I.e., a 2-3 day period where both are
> announcing our class C.
> 
> This conflicts with my extremely (admittedly)limited knowledge.  Can someone
> let me know if this is OK/not OK?

Originating the same prefix from two different ASes violates the RFC (or
whatever bible you might pray to), but works most of the time. 

See "show ip bgp inconsistant-as" on cisco. YMMV.

-- 
Mikael Abrahamsson    email: [email protected]