dns

[Robert Buecker]

Hey everyone,

  Here's a little story about DNS, about a rather evil problem that occurs
sometimes. Why? Because eventually you will run into it.  And the reason why
named "isnt working right" isn't readily apparent to most.  We have this
situation now (with linuxhi.com), and I thought I should point it out. It's
not very long, or confusing, it's just "one of those things."

First of all, I'm not sure how Deven updated linuxhi.com, however one thing
is certain. If a nameserver is actually called www.linuxhi.com with an
address of 216.136.57.83, then no matter if dns/bind is running on
216.136.57.83 that points to linuxhi.org/net ip address, all nameservers
will obtain the ip address of the nameserver www.linuxhi.com.

Why? Well in the root nameservers, domains are NS'd to a hostname, which is
an A rec. In our case for www.linuxhi.com:

linuxhi.com.            2D IN NS        NS1.GRANITECANYON.COM.
linuxhi.com.            2D IN NS        WWW.linuxhi.com.
linuxhi.com.            2D IN NS        NS1.GRANITECANYON.COM.
linuxhi.com.            2D IN NS        WWW.linuxhi.com.
NS1.GRANITECANYON.COM.  2D IN A         205.166.226.38
WWW.linuxhi.com.        2D IN A         216.136.57.83

Which means when you point your browser to http://www.linuxhi.com, your
ISP's nameservers (or your own) will return the A rec from the root
nameservers.  DNS has found the A record for www.linuxhi.com, so it's done
searching.

So hey Deven, change nameservers/deletes the nameserver www.linuxhi.com , or
of course it will never resolve correctly. Sure, http://linuxhi.com will,
but that's not the point of this little email.

I've seen this a couple times.  It's evil.  Oh well :-p  I'm sure I've
confused a bunch since I suck ass at explaining things, so just roll out the
questions and the smart people will answer them.

Good night,
Robert