Re: [PLUG] home dns notes

[Bill Jonas <bill@billjonas.com>]

On Sat, Aug 11, 2001 at 05:10:45AM -0400, Jeff Abrahamson wrote:
> That was my first try, until I realized that foo.home.purple.com first
> queries ., then .com., then .purple.com. to find .home.purple.com.

That's correct, with a caveat.  The application that's looking up an IP
(via gethostbyname(3) or whatever) passes the hostname to the system
resolver, which then (depending on how you have it set up) attempts to
look up the name in /etc/hosts.  If not found, it passes the request
along to a nameserver listed in /etc/resolv.conf.

If the nameserver knows the name already (*because it's authoritative
for the domain* or because it's recently looked up the name), it gives
back that answer.  Otherwise, it performs a recursive query, starting at
the root.

The problem is if you're using your ISP's nameservers.  They won't know
anything about foo.home.purple.com, so they go to the root, which refers
them to com., then to purple.com., which won't know anything about
home.purple.com (unless you have them set up to give a 192.168.x.y
answer).  OTOH, if you point your /etc/resolv.conf to 192.168.x.y, it'll
say, "Hey, I know the answer," and return the proper IP address to you.
If you request bar.purple.com, though, your nameserver will say, "I
don't know anything about .purple.com.," and do a recursive query from
the root.

Of course, this is kind of a moot point since you found a solution that
works for you and that you're happy with.

One note: If the entity hosting your public DNS supports this, you could
have them set up a "hidden master"; that is, they are publicly listed as
authoritative for your domain, but they're actually configured as slaves
to your own nameserver.  This would save you having to make changes
twice.  This is also contingent on your nameserver being accessible from
the outside world (either by having a public IP or via port forwarding).
I know of at least one list member who does his DNS this way.

Just a few thoughts.

-- 
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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