WHy can't I access my web application on IIS 6.0 using a host name

Hi all,

I'd like to know why I cannot access my web application running on IIS6.0 using a host name, I seem forced to use an IP instead.

e.g.

I want to use something like http://myserver.net.au/myApplication/

But am forced to use something like http://111.1.1.111/myApplication

Thanks for any help.