North American Network Operators Group

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Re: /24 multihoming issue

  • From: John Payne
  • Date: Thu Oct 20 21:58:05 2005

On Oct 20, 2005, at 2:07 PM, Randy Bush wrote:

Is 7018 preferring 19094 over 701 regardless of
AS-PATH length?

the convention is that, if 19094 is a customer of
7018, then it will always prefer it.

and it was confirmed that this is the case for the
prefix in question

And this is a good reason not to cross "tiers" of your
transit providers.  Either have both "transit free" or
both should have transit.

why?  when it get up to tier-1s it will be the same, the
one(s) who heard it from customers will prefer the

and tier-Ns should be preferring customer routes as well;
see discussion here between vaf, asp, and me in about '96.
slipping back into the tier terminology which i was trying to avoid...

it's only a problem if you want to do inbound traffic engineering. If the tier 2 is well connected to tier 1s (for example Internap), it's typically going to get more inbound traffic than the tier 1 connection because the tier 2 is preferred as a customer in a bunch of tier 1s.