[150974] in North American Network Operators' Group
Re: Questions about anycasting setup
daemon@ATHENA.MIT.EDU (Elmar K. Bins)
Fri Mar 9 03:12:33 2012
Date: Fri, 9 Mar 2012 09:11:31 +0100
From: "Elmar K. Bins" <elmi@4ever.de>
To: Bill Woodcock <woody@pch.net>
Mail-Followup-To: "Elmar K. Bins" <elmi@4ever.de>,
Bill Woodcock <woody@pch.net>, Anurag Bhatia <me@anuragbhatia.com>,
NANOG Mailing List <nanog@nanog.org>
In-Reply-To: <F8CEE717-99DE-44AA-8C43-9E035A5B3E4A@pch.net>
Cc: NANOG Mailing List <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Bill,
woody@pch.net (Bill Woodcock) wrote:
> > 2. We plan to use this anycasting based setup for DNS during initial few
> > months. Assuming low traffic for DNS say ~10Mbps on average (on 100Mbps
> > port) and transit from just single network (datacenter itself) - is this
> > setup OK for simple software based BGP like Quagga or Bird?
>
> Yes, and in fact, that's how nearly all large production anycast networks are built??? Each anycast instance contains its own BGP speaker, which announces its service prefix to adjacent BGP-speaking routers, whether those be your own, or your transit-provider's. Doing exactly as you describe is, in fact, best-practice.
Well, let's say, using Quagga/BIRD might not really be best practice for
everybody... (e.g., *we* are using Cisco equipment for this)
Using anycasting for DNS is, to my knowledge, best practice nowadays.
> > 3. IPv6! - Is /32 is standard? We have only one /32
> > allocation from ARIN and thus if using /32 seems like hard deal - we have
> > to likely get another /32 just for anycasting? or we can use /48 without
> > issues? Also, is /48 a good number for breaking /32 so that we can do /48
> > announcements from different datacenters in simple uni casting setup?
>
> A /48 is quite reasonable. Announcing a whole /32 just for your anycast service would be wasteful.
Why? It's simply another prefix, no matter how big. It might look
wasteful, but if *that* is the allocation you *have*, it's the
one you ought to use.
One should be careful - people do filter on allocation lengths, so
breaking out a /48 out of a /32 allocation and advertising it on its
own can lead to it being filtered.
Elmar.
