What Is an IPv6 ULA Generator?
An IPv6 ULA generator creates a private prefix in the fd00::/8 Unique Local Address space described by RFC 4193. This implementation accepts a desired prefix length from /48 through /64, generates a random 40-bit global ID with the browser crypto API, and shows both the resulting prefix and the first /64 subnet. It is useful for private addressing plans, but it does not coordinate uniqueness with other organizations, generate full routing policies, or allocate every subnet for you.
How to Use the IPv6 ULA Generator
- 1Type the prefix length you want into the Input box, usually 48, 56, 60, or 64.
- 2Read the Output box for the generated fd-based prefix and the first /64 subnet derived from that prefix.
- 3Copy the result into your network plan or lab documentation, and regenerate if you want a different random private prefix for another environment.
Common IPv6 ULA Generation Use Cases
Planning internal IPv6 labs
Generate a private prefix for a home lab, classroom network, or isolated test environment that should not be globally routable on the public internet.
Documenting subnet examples
Create realistic sample prefixes and a first subnet for runbooks, training decks, or change plans without exposing production addressing.
Bootstrapping router configuration drafts
Start an internal IPv6 design with a random ULA prefix before you divide it further into VLANs, site blocks, or service segments.
Frequently asked questions
Does this guarantee that my ULA prefix is globally unique?
No. RFC 4193 uses a random global ID to reduce collision risk, but this tool does not register or coordinate your prefix with any outside authority.
Can it generate every subnet for the whole prefix?
No. The current output shows the generated prefix and the first /64 subnet as a starting point. Further subnet planning still needs to be done separately.