For example, in the URL http://www.iinet.net.au, the DNS zone is iinet.net.au and the hostname is www. This is fine, because iinet.net.au is a valid third-level DNS zone, and the owner has every ability to create a host record for www. But what about http://afl.com.au? Does that mean that the owner of the com.au zone has created a host record called afl? Well, no. They aren’t allowed to do that. See com.au is a second-level DNS zone, which means it isn’t owned by a specific company, so you can’t just go adding host records as you please.
So how do they get http://afl.com.au to resolve? Well, I’m glad you asked.
ANSWER: It’s all got to do with the default settings in DNS. When you open up the DNS console on a Windows 2000/2003 PC, you will see the (same as parent folder) entries. Basically, these are the ones that control the default behaviour of that DNS zone. So, in the example given below, http://bug-wars.com would be interpreted as http://203.59.242.131 because the (same as parent folder) host (A) record for the bug-wars.com zone has been set to 203.59.242.131. Incidentally, if there was no MX record defined for the bug-wars.com domain it would also mean that email sent to paul@bug-wars.com would be attempted to be delivered to 203.59.242.131 because SMTP defaults to delivering to an A record in the absence of an MX record.
And if you are using a UNIX DNS system, then you can edit the DNS file directly with a text editor. The (same as parent) entries are the ones listed in the zone records area.
So what all that means is that the owners of the afl.com.au domain must have pointed their (same as parent) A record at the IP address of their primary web server. Problem solved!
Regards
Paul Eddington