About VLSM Subnet Calculator
Plan multiple conventionally addressed IPv4 networks inside one parent network.
Input is processed locally in your browser and is not sent to Navorika.
How the calculation works
Block sizing
Each request reserves hosts plus network and broadcast addresses, then rounds up to a power of two.
Largest first
The largest requirements are allocated first on valid block boundaries to reduce fragmentation.
How to use this tool
- 1Enter the parent CIDR.
- 2Name each network and enter required usable hosts.
- 3Review warnings or allocations.
- 4Verify capacity and waste.
Understanding the result
Capacity excludes conventional network and broadcast addresses.
Waste is allocated usable capacity minus requested hosts.
Important limitations
- IPv4 only; each allocation uses conventional subnet semantics and does not use /31 or /32 host exceptions.
- The tool plans address space but does not configure routing or VLANs.
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Frequently asked questions
Why allocate largest first?
It reduces the chance that small early allocations fragment space needed by a large subnet.
Can allocations overlap?
No. Successful allocations are aligned sequentially and tested against the parent boundary.
What happens when space runs out?
The tool shows the request that cannot fit and preserves earlier results for diagnosis.
Use with
These tools support a practical next or previous step in the same workflow.
Related tools
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