[109994] in North American Network Operators' Group
Re: What is the most standard subnet length on internet
daemon@ATHENA.MIT.EDU (Andy Davidson)
Fri Dec 19 03:45:53 2008
From: Andy Davidson <andy@nosignal.org>
To: lionair@samsung.com
In-Reply-To: <15850784.26571229661837046.JavaMail.weblogic@epml12>
Date: Fri, 19 Dec 2008 08:45:36 +0000
Cc: nanog@nanog.org
Errors-To: nanog-bounces@nanog.org
On 19 Dec 2008, at 04:43, =C1=A4=C4=A1=BF=B5 wrote:
> It seems so simple. Currently annoucement of /24 seems to be okey, =20
> most upstream providers accept this.
> However I wonder if there is any ground rule based on any standard =20
> or official recommandation.
The only rule is "my network, my rules" ;-)
But if general rules did exist, they might say 1) not to announce =20
smaller than a /24 to external parties without agreement, and 2) not =20
to carve up registry assigned address blocks into individual =20
announcements.
1 - You might announce your registry assigned block, AND deaggregated =20=
blocks to upstreams or peers for traffic engineering purposes, but you =20=
need to work closely with them to make sure that they don't filter the =20=
deaggs from your session, and also to make sure they don't onwardly =20
announce the deaggs).
2 - The default free routing table is 270,000 entries large, and this =20=
is too big for lots of kit, so networks ARE FILTERING TODAY on =20
registry boundaries. If you don't understand the implications of this =20=
do not deaggregate the addresses that the registry assign you.
Good luck with your project. Drop me a note offlist if you need =20
specific advice.
Andy
