[120341] in North American Network Operators' Group
Re: DNS question, null MX records
daemon@ATHENA.MIT.EDU (Joe Abley)
Wed Dec 16 19:09:34 2009
From: Joe Abley <jabley@hopcount.ca>
In-Reply-To: <4B297530.8030302@mail-abuse.org>
Date: Thu, 17 Dec 2009 00:08:56 +0000
To: Douglas Otis <dotis@mail-abuse.org>
X-SA-Exim-Mail-From: jabley@hopcount.ca
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 2009-12-17, at 00:02, Douglas Otis wrote:
> To avoid server access and hitting roots:
>=20
> host-1.example.com. IN A 192.0.2.0
> ...
> host-10.example.com. IN A 192.0.2.9
>=20
> example.com. IN MX 0 host-1.example.com.
> ...
> example.com. IN MX 90 host-10.example.com.
This will still cause DNS requests to be sent towards 192.0.2.0 and =
192.0.2.9, and they may not be dropped at the first router depending on =
local conditions. There are implications of state in the local resolver.
Choosing MX RDATA with a name that is known not to exist ideally will =
only exercise the local cache for the non-existent name, since it will =
perhaps not be the first such query and the non-existence will already =
be cached.
SINK.ARPA doesn't exist today. The document I referred to only exists to =
enforce that non-existence in the future; operationally you could =
install MX records towards SINK.ARPA today and get the desired effect, =
regardless of the state of the document.
Joe=
