title: How do I validate the format of a MAC address?
body: <p>What's the best way to validate that an MAC address entered by the user?</p>
  
  <p>The format is <code>HH:HH:HH:HH:HH:HH</code>, where each <code>H</code> is a hexadecimal character.</p>
  
  <p>For instance, <code>00:29:15:80:4E:4A</code> is valid while <code>00:29:804E4A</code> is invalid.</p>