[192778] in North American Network Operators' Group
Re: nested prefixes in Internet
daemon@ATHENA.MIT.EDU (Victor Sudakov)
Mon Nov 21 09:08:14 2016
X-Original-To: nanog@nanog.org
Date: Mon, 21 Nov 2016 21:08:07 +0700
From: Victor Sudakov <vas@mpeks.tomsk.su>
To: nanog@nanog.org
In-Reply-To: <20161121120133.GI45065@excession.tpb.net>
Errors-To: nanog-bounces@nanog.org
Niels Bakker wrote:
> >I have reports that in case (2), some operators (e.g. Rostelecom)
> >don't accept the /24 or even /23 prefix on the grounds that it is
> >part of a larger /19 route already present in the routing table.
> >
> >Could they have a reason not to accept these more specific prefixes
> >other than a whim?
>
> If you announce a prefix you must deliver traffic sent to addresses
> covered by it. You don't go announcing 0.0.0.0/0 to your peers either.
>
> If a customer takes a /24 and announces it elsewhere, a transit
> provider runs the risk of accepting inbound traffic without having
> the possibility to bill their customer for it if it accepts more
> specifics from e.g. a peer.
That's all correct from the point of view of the provider annoncing
the /19 route, and should be their risk.
My question was however from a different perspective. If AS333
receives a /19 from AS111 and a /24 from AS222 (where AS222's /24 is
nested within AS111's /19), what reason might AS333 have to ignore the /24?
AS333 is not concerned with possible monetary relations between AS111
and AS222.
--
Victor Sudakov, VAS4-RIPE, VAS47-RIPN
sip:sudakov@sibptus.tomsk.ru
