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Re: honoring AS-path prepend from a peer or customer?
At 10:33 PM 2/18/99 -0500, Avi Freedman wrote: >FYI, this is dangerous. >For example - > >You have a customer A who has a customer B. >B is multi-homed to A and 701. >B's link to A goes down. > >So, if A's network is broken, they will send you a given prefix >with as-path ^701 B$ or ^1239 701 B$ or ..., depending on how B >sees 701. > >And you will transit it. > >Shouldn't cause any major damage, but something to be aware of. I'm wondering why I shouldn't transit it? In fact, by prepending certain ASNs to each prefix, you can enforce selective route propagation through loop detection from networks two or more hops away. This is something which is very difficult to do otherwise without a *very* nice upstream. Of course, I would never recommend such practices. (It's not like I know anyone who has ever done anything even remotely like that..... ;) >Avi TTFN, patrick I Am Not An Isp www.ianai.net ISPF, The Forum for ISPs by ISPs, <http://www.ispf.com> "Think of it as evolution in action." - Niven & Pournelle