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VLSM subnet planner
Allocate unequal subnets from one IPv4 base — largest-first, every sizing decision shown as a step, failures named per subnet.
workerless environment — same engine, this tab · up to 64 subnets
Set the base and rows, then press Plan.
- Deterministic largest-first (classic VLSM): same inputs, same plan, every time — equal sizes keep entry order. It is a teaching/planning layout, not a claim of optimality.
- "Usable hosts" is the IPv4 convention (network + broadcast reserved; RFC 3021 /31 and /32 exact) — the same rule the subnet calculator prints.
- A request the base cannot satisfy is a named failure on its row — the plan never silently drops or shrinks it.
- Caps: 64 subnet rows per plan. Bulk tables run in the network family worker so planning never blocks the page.
Nothing in yet
Paste, drop, or type to begin. Everything stays on this device.
nothing plans until you press Plan