two AS announce the same adress space
What will break if two different ASes announce the exact same adress space? It's the old multihoming issue, small company wants to multihome, does not want to get an AS of its own, and wants to use one address space via both providers. This adress space is from PI space so ISP1 already announces the exact net (no aggregation) and would like ISP2 to also announce this, perhaps via a private peering using "private AS" but I would like to avoid that. I know the RFC says this should not be done (or at least I'm told so), but I would like to know if someone does this anyway and if they do, what problems arise? -- Mikael Abrahamsson email: swmike@swm.pp.se
On Tue, 1 Aug 2000, Mikael Abrahamsson wrote:
What will break if two different ASes announce the exact same adress space?
I have gotten approx 10-12 replies to this privately, and would just like to say thanks for all the good input. To summarize: This is not allowed during to RFC. It is "best practice" not to do it. Several people do it and report that it works well. Some warn that some BGP implementations might drop the announcement. end summary: One of the reason to do this is because one would not want to "waste" AS just because one wants to do a single multihoming. What will happen when we run out of ASes? As far as I can see 1/4 of the AS space is now consumed. -- Mikael Abrahamsson email: swmike@swm.pp.se
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Mikael Abrahamsson