Configuring Drupal with a dynamic IP address
There's no need to use external DNS when working locally on a development box.

You can add the required mapping to your /etc/hosts file

e.g:

127.0.0.1 drupalsite1 drupalsite2 drupalsite3


Then you can access the site by visting, e.g http://drupalsite1 in your browser

You could even use something like

127.0.0.1 drupalsite1.no-ip.org drupalsite2.no-ip.org 


If you'd prefer.

The /etc/hosts file is checked prior to external DNS lookup and will override / take precedence over the latter. There's a similar file in Windows as well.

More info: http://en.wikipedia.org/wiki/Hosts_(file)