[192763] in North American Network Operators' Group
Re: nested prefixes in Internet
daemon@ATHENA.MIT.EDU (Victor Sudakov)
Sat Nov 19 21:07:10 2016
X-Original-To: nanog@nanog.org
Date: Sat, 19 Nov 2016 20:10:05 +0700
From: Victor Sudakov <vas@mpeks.tomsk.su>
To: nanog@nanog.org
In-Reply-To: <CAJx5YvE=t2e_tdhDanutJV=y2H=rpSUkKhA6L78Prz5toi1+oA@mail.gmail.com>
Errors-To: nanog-bounces@nanog.org
Martin T wrote:
>
> let's assume that there is an ISP "A" operating in Europe region who
> has /19 IPv4 allocation from RIPE. From this /19 they have leased /24
> to ISP "B" who is multi-homed. This means that ISP "B" would like to
> announce this /24 prefix to ISP "A" and also to ISP "C". AFAIK this
> gives two possibilities:
>
> 1) Deaggregate /19 in ISP "A" network and create "inetnum" and "route"
> objects for all those networks to RIPE database. This means that ISP
> "A" announces around dozen IPv4 prefixes to Internet except this /24
> and ISP "B" announces this specific /24 to Internet.
>
> 2) ISP "A" continues to announce this /19 to Internet and at the same
> time ISP "B" starts to announce /24 to Internet. As this /24 is
> more-specific than /19, then traffic to hosts in this /24 will end up
> in ISP "B" network.
Excuse me for intruding on American Operators from Siberia, but I find
this topic very interesting.
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?
--
Victor Sudakov, VAS4-RIPE, VAS47-RIPN
sip:sudakov@sibptus.tomsk.ru
