title: get subnet mask and gateway from IP address
body: <p>How can i calculate <code>subnet mask</code> and <code>gateway</code> from an <code>IP address</code>?</p>
  
  <p>Suppose my IP address is <code>180.12.24.68</code></p>
  
  <p>Then how can i calculate this IP's subnet mask and gateway?</p>