Plan IPv4 allocations with split and join

How to use the workspace

1. Enter a base CIDR and create the plan. The engine normalizes or rejects the network according to the allocation rules.
2. Select one allocation in the proportional map or keyboard table. Split creates two equal child networks. Add a note and color to explain its purpose.
3. Select two sibling leaves to join them. Review the annotation first: the displayed note and color become the joined block annotation.
4. Prepare a JSON export for a round trip, or CSV for a spreadsheet. Download is a separate explicit action.

A concrete starting point

Base: 10.42.8.0/24
Split into: 10.42.8.0/25 + 10.42.8.128/25
Split the first child again for two /26 allocations.

This private-address example illustrates subdivision; it does not recommend an address plan for your environment.

Read the result carefully

The diagram uses total address counts, not usable-host counts. A /31 point-to-point block has two usable addresses; a /32 represents one host. /0 spans the entire IPv4 address space. The table shows network, usable ranges and the appropriate broadcast semantics.

Common mistakes to avoid

• Equal prefix length does not make two blocks siblings. An invalid join is rejected.
• Annotations do not reserve addresses in DHCP, cloud networks or IPAM. This is an offline plan.
• An imported plan must exactly partition its base with canonical, disjoint leaves. The last valid plan remains visible after a rejected import.

Limits & privacy

Up to 4,096 leaves. JSON imports are bounded to 2 MiB. JSON is the supported import format; CSV is export-only in this release. No automatic saving.