[90346] in North American Network Operators' Group
Re: How to tell if something is anycasted?
daemon@ATHENA.MIT.EDU (Peter Boothe)
Wed May 17 03:00:43 2006
Date: Tue, 16 May 2006 23:59:54 -0700 (PDT)
From: Peter Boothe <peter@cs.uoregon.edu>
To: David Hubbard <dhubbard@dino.hostasaurus.com>
Cc: nanog@merit.edu
In-Reply-To: <FCD26398C5EDE746BFC47F43EA52A173018A31CD@dino.ad.hostasaurus.com>
Errors-To: owner-nanog@merit.edu
On Tue, 16 May 2006, David Hubbard wrote:
> So I'm looking at a company who offers anycasted DNS;
> how do I tell if it's really anycasted? Just hop on
> different route servers to see if I can find different
> AS paths and then do traceroutes to see if they suggest
> the packets are not ending in the same location?
> >From my routers' perspective I don't see a difference,
> but then I don't think I should, correct?
If they conform to the convention that the DNS root servers practice, then
a dig query from several locations should suffice. Choosing an anycasted
DNS root at random, you can do
dig @f.root-servers.net hostname.bind chaos txt
And the response should include a line like
hostname.bind. 0 CH TXT "pao1b.f.root-servers.org"
From other locations, it might be "sfo2c.f.root-servers.net" or somesuch.
If they don't do that, then you are stuck with more ad-hoc methods like
traceroutes from many different locations, or checking out AS-PATHS in
Routeviews and using your intuition.
-Peter
--
Peter Boothe
PhD Student "Young man, you think you're very
Computer Science smart, but it's turtles all the way
University of Oregon down!"
http://www.cs.uoregon.edu/~peter
