How does a CIDR Calculator work?
Classless Inter-Domain Routing (CIDR) replaced the old classful network architecture (Class A, B, and C). It allows for variable-length subnet masking (VLSM), meaning network administrators can allocate IP addresses precisely according to their needs without wasting address blocks.
Using this calculator, you can quickly convert a CIDR notation (like /24 or /27) into its corresponding decimal subnet mask. It instantly figures out the Network IP (the very first address identifying the segment) and the Broadcast IP (the very last address used to communicate with all hosts simultaneously).