Using _default_ in VirtualHost in Apache

Using default vhost to serve unspecified IP & port

i.e. Catching every request to any unspecified IP address and port, i.e., an address/port combination that is not used for any other virtual host

    <VirtualHost _default_:*>
      DocumentRoot /www/default
    </VirtualHost>

A default vhost never serves a request that was sent to an address/port that is used for name-based vhosts.

    <VirtualHost _default_:80>
    DocumentRoot /www/default80
    # ...
    </VirtualHost>

    <VirtualHost _default_:*>
    DocumentRoot /www/default
    # ...
    </VirtualHost>

This is the same as the 1st one, but serve port 80 pointing to /www/default80