title: Apache2 warning about NameVirtualHost directive
body: <p>Can someone help me to understand why I receive the following errors when restarting my apache2 webserver:</p>
  
  <pre><code>[Fri Nov 09 09:46:43 2012] [warn] VirtualHost 172.30.30.12:443 overlaps with VirtualHost 172.30.30.12:443, the first has precedence, perhaps you need a NameVirtualHost directive
  [Fri Nov 09 09:46:43 2012] [warn] VirtualHost 172.30.30.12:443 overlaps with VirtualHost 172.30.30.12:443, the first has precedence, perhaps you need a NameVirtualHost directive
  </code></pre>
  
  <p>The error always appears twice.  What is a NameVirtualHost directive?</p>
  
  <p>Thanks.</p>