Re:[isp-bgp] BCP for multi-homing to the same provider entail using a private ASN

[Jeffrey Belles <jaffa@...>]

Hi Bob,

Bob Tinkelman schreef:
> A few days ago, Jeffrey Belles <jaffa@...> posted this
> extract from the Sprint web site:
>
> >  From http://www.sprint.net/faq/as1790.html
> > "
> > The Autonomous System 1790 is reserved for use exclusively by those
> > customers that do not currently have another Internet Service Provider,
> > and currently have, or are in the process of implementing, multiple
> > connections utilizing the same IP space (multi-homed neworks) into the
> > Sprintlink backbone, via a dedicated IP Private Line. To utilize AS
> > 1790, please contact your account team for ordering information.
> > "
>
> I remember from when I worked for Verio that they did the same
> thing (but with a different ASN, of course).
>
> Is there any standard terminology for ASNs used in this way?
> I've seen "private ASN" used as a synonym for "reserved ASN",
> that is, referring to the high-numberd ASNs (64512-65535).
> In any case, it appears that both Sprint and Verio and possibly
> other large ISPs have decided that there are advantages to using
> a non-reserved ASN for this purpose, as opposed to using one of
> the reserved ASNs.
>
> Is the reason for this obvious?  Is it just that you don't need
> to worry about making a mistake resulting in a bgp-route with an
> ASN-path containing a reserved ASN leaking to the world?
UUNET/MCI does the same thing (AS7046 in US and AS2830 in EMEA).

The advantages is that this way the AS_PATH is still visible in the 
'outside world' and that customers who are granted the use of these ASs 
can try and tweak their advertisements beyond the scope of the upstream AS.

Furthermore, if a customer using this special AS has ip-space that they 
obtained independently of their upstream, and they would peer using a 
private-AS, it would be stripped on the boundaries and show up as 
internal to their upstream. Not nice.

 -Jeffrey


> In any case, I submitted an application to ARIN for a 2nd ASN to
> be allocated to my network.  I completed the application honestly,
> indicating that the ASN would be assigned to a collection of nets
> at different customer sites, but all the peering would be between
> the new net and my existing net.  I refered to Sprint's 1790 as an
> example.  ARIN rejected the application because the new ASN would
> peer with only a single upstream.
>
> Are Sprint and Verio actually doing something different with their
> ASNs that makes them ARIN-legal?  Or is this simply a case of
> their having acquired the ASNs in a different way, and then using
> them however they want, without ARIN having the energy to track
> things like that?
>
> --
> Bob Tinkelman <bob@...>
> ISPnet, Inc.    718.464.4747




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