Re: [PLUG] home dns notes

[Bill Jonas <bill@billjonas.com>]

On Sun, Aug 05, 2001 at 05:31:48PM -0400, Jeff Abrahamson wrote:
> The problem is that if I claim authority over purple.com, I can't see
> the outside purple things (www, list). If I claim authority over a
> subdomain, I don't get there, since the lookups are com -->
> purple.com, which doesn't know about home.purple.com subdomain.

Is there something I'm missing here?  I can declare myself
authoritative, for example, over doubleclick.net, or ads.doubleclick.net
(to block ads and cookies by making them all resolve to 127.0.0.1 or
something), or, for that matter, .co.uk, or .co.jp, or whatever I want
to, and have the changes take effect.

All you need to do is point your internal machines at the DNS server
*you're* running, and vu-vlsi.ee.vill.edu, ns1.misty.com, and
ftp.ee.vill.edu (your nameservers) will never even see your request for
home.purple.com addresses.  If you leave the clients set to point to
your ISP's nameservers then you'd run into the situation you described.

Now, you may be thinking, wouldn't this slow you down, since you'd be
querying hostnames from the root servers for each new request instead of
taking advantage of the fact that your ISP's nameservers might already
have the lookup cached?  Well, I'm glad you asked.  ;-)  In your
named.conf, assuming you're running BIND v8 (the BIND v9 syntax probably
wouldn't be (much) different), you'd put something like the following in
your "options" section (this is mostly from memory, check the docs for
an authoritative (pun intended) answer):

  forwarders {
    A.B.C.D;
    W.X.Y.Z;
  };

  forward-first;

...where A.B.C.D and W.X.Y.Z are you're ISP's nameserver IP addresses.
This will cause BIND to query them first for any host which it doesn't
already know about.  And since you're querying your nameserver first, it
"intercepts" the requests for home.purple.com and answers them, and
those queries never go out on the 'Net.

-- 
Bill Jonas    *    bill@billjonas.com    *    http://www.billjonas.com/
"As we enjoy great advantages from the inventions of others,  we should
be glad of an opportunity to serve others by any invention of ours; and
this we should do freely and generously."          -- Benjamin Franklin


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