North American Network Operators Group

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RE: Policies: Routing a subset of another ISP's address block

  • From: Greene, Dylan
  • Date: Fri Apr 07 18:12:32 2000

Hey there..

I'd imagine this works fine, but doesn't it leave you w/ inconsistent-as,
where you've got a prefix being advertised from the private ASN, stripped &
replaced w/ each upstream ASN?

I mean, it should work, but is it a very good idea? The inconsistent-as list
isn't _too_ big right now, which is good, as each one effectively breaks a
number of common path filters. But if that starts to becomes common
practice, the list gets bigger and bigger & more filters get broken.

> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On Behalf Of
> Jesper Skriver
> Sent: Friday, April 07, 2000 2:21 PM
> To: Daniel L. Golding
> Cc: David Harrison; [email protected]
> Subject: Re: Policies: Routing a subset of another ISP's address block
> Actually I've helped quite a few such customers, my recommendation
> usually is to get PI space from RIPE, and get both providers to announce
> it from their ASN, this works quite well, and also save a ASN - if the
> customer really want to run BGP, we have arrangements with other ISP's
> here, that we find a private ASN (that none of us use currently), and
> assign this ASN to the customer, and we then strip the private ASN on
> the edges of our network.

this is interesting (since it overwrites the rule that multihoming to two
isps requires a public asn assignment) and i've tested exactly this scenario
(again, a customer uses some private asn and is peering with two isps;
both of them strip this asn at their boundaries (remove-private-as))
in my lab before and it worked fine. it results in propagating routes to
the same networks with two distinct as path attributes, though. i've been
looking for any operational experience with this setup. so, do you claim
that you couldn't detect *any* problems with this setup?