Subnet Planner
Plan IPv4 VLSM subnets by host count and IPv6 networks by prefix. Export subnet tables locally.
How to use Subnet Planner
Enter a parent network. For IPv4, list host requirements such as 100, 50, 20. For IPv6, list desired subnet prefixes such as 64, 64 within a /48 parent.
Understanding the results
Allocates largest-first, without overlapping networks. Rejects plans exceeding the parent network. IPv4 reserves network and broadcast addresses; IPv6 has no broadcast. Export the allocation table as CSV or JSON.
How does VLSM planning differ from a subnet calculator?
A calculator describes one network. The planner divides a parent network into several allocations based on IPv4 host requirements or IPv6 prefixes, and provides an exportable table.