Why subnet semantics matter
Subnet arithmetic is simple until edge cases become operationally important. A traditional /30 has network and broadcast addresses plus two usable hosts. A /31 is different: on a point-to-point link, RFC 3021 treats both addresses as endpoints and removes ordinary directed-broadcast semantics. A /32 represents one address, often used as a host route or loopback.
Worked example
For 192.0.2.17/27, the network is 192.0.2.0/27, the broadcast is 192.0.2.31, and the ordinary usable range is 192.0.2.1–192.0.2.30.
Use the VLSM Planner when you need to allocate several requirements inside one parent block.