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# Split and aggregate CIDR blocks

Divide one block into equal children, or paste sibling blocks and merge them into supernets — every merge shown, every precondition refused with its reason.
SplitAggregateRunClear

workerless environment — same engine, this tab · split cap 256 children
must be longer than the parent's prefix — the children carry the host bits

Press Run to compute.

- Split needs a LONGER prefix than the parent — merging is the other mode, and the error says which to use.
- Aggregation is for disjoint sibling blocks. Overlapping inputs are refused outright — hiding an overlap inside a merge would lie about your network.
- Only exact siblings merge: same size, adjacent, and aligned at the parent boundary. Paste 10.0.1.0/24 + 10.0.2.0/24 and the answer is "already maximally aggregated", not a wrong /23.
- IPv4 and IPv6 cannot aggregate together; either family splits fine. Caps: 256 children per split, 256 blocks per aggregate.
Nothing in yet

Paste, drop, or type to begin. Everything stays on this device.

nothing runs until you press Run

## Next door in Network

- [VLSM planner](/network/vlsm)
- [IPv4 subnet calculator](/network/ipv4-subnet)
[All network tools](/network)

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Markdown version: https://nutter.tools/network/subnet-split/index.md
Plain-text version: https://nutter.tools/network/subnet-split/index.txt
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