title: Calculate in which subnet is IP address
body: <p>I have an IP address and mask (for example IP is 10.128.20.1, mask is 255.255.248.0). How I can calculate, in which subnet range is IP added? </p>
  
  <p>I try implement founded solution, where I list all subnets by IP and mask and next I do test IP address, whether is in subnet. But I try find easier way.</p>