VLSM Subnet Planner

Give it a base network and a list of host-count requirements (one per line, largest first isn't required — it sorts for you), and it allocates the smallest subnet that fits each one, packed efficiently with no wasted space. The inverse of the CIDR Aggregator.

Provided as-is, with no warranty of any kind. This runs entirely in your browser as a convenience tool, not a certified reference — always double-check results before relying on them for anything important, especially production changes. See the full disclaimer.