title: Redirect User if Internal IP Address
body: <p>I am not familiar with PHP but I need to create a simple page to temporarily redirect internal users until a production problem is fixed.</p>
  
  <p>If the user's IP address starts with <code>"10."</code>, <code>"192."</code>, or <code>"172."</code> then I need to redirect them to another server. If the user's IP address does not meet this criteria then I need to display a message telling the user the site is down for maintenance.</p>
  
  <p>Can someone help me with this?</p>