IPv6 ULA prefix and subnet planner

  1. Options
  2. Result

Prefix source

The fd prefix contains a 40-bit random Global ID and a 16-bit subnet identifier. A new prefix uses the browser’s cryptographic random generator; existing-prefix mode does not change your allocation.

ULA prefixes are not intended for public Internet routing. Random generation makes collisions unlikely, not impossible. These are planning examples, not automatic router configuration.

Quick start

Generate a random local /48 or reuse your existing prefix. Plan up to 256 consecutive /64 subnets with example router addresses and export the address plan.

  1. Enter your data and check the settings.
  2. Run the tool using the action button and review the result below.
  3. Save the last result; run the tool again after changing the settings.

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