Classless Inter-Domain Routing (CIDR) Calculator - includes full support for CIDR. Use of CIDR addresses reduce the size of routing tables and make more IP addresses available within organizations. This CIDR classless subnetting feature is particularly useful for ISPs, colleges, or large corporations with many Class C addresses. Again, we give you the ability to export this data so you can work with the data to meet your requirements. Subnet Addresses - You can generate a list of addresses for any subnet, which then becomes the working document from which to assign current and future IP addresses.