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

  • From: Hank Nussbacher
  • Date: Sat Apr 08 14:16:39 2000

At 21:04 07/04/00 -0400, Dmitri Krioukov wrote:

The route object described in
states that origin AS is a single occurence.  RIPE-189 should then be
updated to allow multiple occurences of the origin tag.


>it does generate inconsistent origin as'es and it does break
>path filters, but not only. it breaks all the tools/methods
>based on the uniqueness of the route->origin-as mapping. i'm
>looking for a more or less complete list of these tools/methods.
>it seems, though, that the inconsistent-as list is growing and
>this doesn't produce too much panic.
>and if you examine this list more closely, you'll notice that it
>looks like the major part of it is generated by the isps doing
>the aforementioned trick.
>> -----Original Message-----
>> From: Greene, Dylan [mailto:[email protected]]
>> Sent: Friday, April 07, 2000 6:06 PM
>> To: 'Dmitri Krioukov'; Jesper Skriver
>> Cc: [email protected]
>> Subject: RE: Policies: Routing a subset of another ISP's address block
>> 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.
>> ..Dylan
>> > -----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?
>> --
>> dima.