Networking / FREE BROWSER TOOL
VLSM Subnet Planner
Design variable-length subnet allocations for office, guest, voice, and server networks with automatic largest-first assignment.
✓ Free to use✓ Runs locally✓ No account needed
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Enter the values below to calculate or convert.
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Using the vlsm subnet planner
Enter a parent CIDR and one network per line using the format Name,HostCount. The planner sorts the requests by capacity and allocates the smallest fitting traditional subnet for each.
Real-world example
Example: allocate 120 workstations, 60 phones, and 28 guest devices inside 10.20.0.0/22.
Good to know
VLSM reduces unused address space, but the design must still account for gateways, statically assigned devices, and future expansion.
This tool is a planning aid, not a substitute for verifying values in vendor documentation or production configurations.