Variable Length Subnet Masking
Subnet Calculator — VLSM
Allocate variable-size subnets from a parent network. List your host requirements in any order — the calculator packs them largest-first for optimal use of address space.
Enter the parent network you want to subdivide.
Format:
Name: 50 or just 50. Lines starting with # are comments.Enter a parent network and at least one requirement above to see your VLSM allocation.
One row per allocated subnet, in physical address order. Each name auto-fills Network Name, with a blank row between rows.
Hosts → CIDR Reference
For a given host requirement, the smallest CIDR that fits with two reserved (network + broadcast).
| Hosts needed (≤) | Smallest CIDR | Subnet size | Usable hosts |
|---|
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