CIDR

• CIDR generalizes classes A, B, and C

• • The boundary between the network and host parts on an IP address can be anywhere
  • /8, /16, /24 becomes /x where x is between 8 and 31

• Assignees can be allocated close to the number of addresses they need

• • The next greatest power of 2

• Address registrars and ISPs allocate addresses on a regional or topological basis

• • Routes can be aggregated, reducing table size

• Netmasks now have to be explicit

• Very useful tool to check your work with:

• • http://www.subnetmask.info/
  • http://www.wildpackets.com/products/ipsubnetcalculator