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IP Allocation Planner

The IP allocation planner helps you carve up a supernet into named CIDR blocks and see the whole plan at a glance. Enter a parent network such as 10.0.0.0/22, then list each allocation on its own line with an optional label: "prod 10.0.0.0/24", "mgmt 10.0.1.0/25", "guest 10.0.1.128/26".

The planner returns a table of every allocation with its address range and size, flags allocations that overlap, and shows the remaining free blocks in the supernet with a running utilization percentage - the two numbers that matter when someone asks for space and you need to know, in one glance, what is actually left to give them.

IP Allocation Planner

Plan IP allocations inside a supernet: assign CIDR blocks per site or VLAN and see used, free, and overlapping space instantly.

Enter values above to see results.

Frequently Asked Questions

How do I plan IP allocations inside a subnet?
Enter the parent supernet in CIDR form (e.g. 10.0.0.0/22), then list each allocation on its own line with an optional label followed by a CIDR block, such as "prod 10.0.0.0/24". The planner shows every allocation, flags overlaps, and lists the free blocks that remain.
How is utilization percentage calculated?
The planner sums the size of every allocated block and divides by the total number of addresses in the supernet. Free blocks are computed by walking the range and collecting the gaps between allocations, so the percentage reflects what is actually assigned rather than what was claimed.
What happens if two allocations overlap?
Overlapping allocations are kept in the table but flagged in the summary line. Because the same address space cannot be assigned twice, resolve the overlap before deploying - the planner makes the conflict visible instead of letting it surface as a duplicate IP later.

Read More

Guides that go deeper on the same topic.

IP Planning: The Complete Guide, Tools, and Best Practices
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Stop reaching for a spreadsheet

Obelinf keeps every subnet, device, circuit, and rack in one live source of truth, with audit logs and a topology view. Free for personal use.

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