This plugin allows users of a WordPress MU site or WordPress 3.0 network to map
their blog/site to another domain.

Super administrators must configure the plugin in Super Admin->Domain Mapping.
You must enter the IP or IP addresses (comma deliminated) of your server on
this page. The addresses are purely for documentation purposes so the user
knows what they are (so users can set up their DNS correctly). They do nothing
special in the plugin, they're only printed for the user to see.

You may also define a CNAME on this page. It will most likely be the domain
name of your network. See below for some restrictions and warnings.

Your users should go to Tools->Domain Mapping where they can add or delete
domains. One domain must be set as the primary domain for the blog. When
mapping a domain, (like 'example.com') your users must create an A record in
their DNS pointing at that IP address. They should use multiple A records if
your server uses more than one IP address. If your user is mapping a hostname
of a domain (sometimes called a "subdomain") like http://www.example.com or
blog.example.com it's sufficient to create a CNAME record pointing at their
blog url (NOT IP address).

The login page will almost always redirect back to the blog's original domain
for login to ensure the user is logged in on the original network as well as
the domain mapped one. For security reasons remote login is disabled if you
allow users to use their Dashboard on the mapped domain.

Super admins can now choose to either allow users to setup DNS ANAME records by
supplying an IP (or list of IP addresses) or set a CNAME but not both (entering
a CNAME for the end user voids the use of IP's)

There is a lot of debate on the handling of DNS using CNAME and ANAME so both
methods are available depending on your preference and setup.