Stage 1 → IP planning

VLSM Calculator for ISP and MikroTik Address Plans

Plan non-overlapping variable-length subnets instead of guessing pool sizes in a live MikroTik network.

Free to use · Runs locally in your browser · Last reviewed 2026-09-26
Review before deployment: VLSM allocations are largest-first so the requested blocks do not consume space needed by larger networks. The result is a plan, not an automatic route advertisement.

Inputs

Use a network boundary such as 10.50.0.0/24.

One item per line: name=hosts. Two extra addresses are reserved for network and broadcast.

vlsm-plan.txt
Change an input to recalculate.
How to use this result
Each requested size is rounded to the next power-of-two subnet that can contain the hosts plus network and broadcast. Allocate the largest request first, then verify that every result remains inside the base network and that no two blocks overlap.
For PPPoE pools, remember that a pool plan and a routed subscriber design are related but not identical. Document how the client address is routed back to the gateway.
Related tools
IP Pool PlannerTurn an address block into a pool with reserve capacity.


Sources and safe-use notes
This page follows the RouterOS documentation and the networking standards linked below. RouterOS syntax, hardware limits, and packet direction depend on your exact release and topology. Export a backup, test one controlled case, and keep a rollback path before applying generated output.
MikroTik documentation · RouterOS manual · RFC 4632 — CIDR · RFC 6598 — shared address space · RFC 8200 — IPv6 · RFC 4632 — CIDR · MikroTik IP addressing