ULA vs public IPv6 — what is the difference?

Public addresses are globally routable and assigned by your provider. ULAs work only inside your network, never leave your router, and survive provider changes — good for infrastructure that should not be exposed.

Why generate the prefix randomly instead of picking fd00::1?

RFC 4193 mandates a random global ID precisely so two sites that later merge their networks will not clash. Hand-picked prefixes like fd00::/64 are a common source of hard-to-debug conflicts.

Can a ULA reach the internet?

No. Routers must not forward fd00::/8 to the public internet. Use it for internal services; hosts still get global addresses from your provider for outbound traffic.

IPv6 ULA generator — Guide

Generate your own local, non-routable IP addresses for your network according to RFC4193.

What it is and when to use it

A ULA (Unique Local Address) is the IPv6 counterpart of the private IPv4 ranges: addresses under fd00::/8 that are free to use inside your organisation but must not be routed on the public internet. RFC 4193 asks for a randomly chosen 40-bit global ID so independently generated prefixes almost never collide, and that is exactly what this tool generates.

Generates an IPv6 Unique Local Address (ULA) prefix per RFC 4193 for local networks — handy for addressing internal devices.

How to use it

Click generate to get a prefix
Combine it with a subnet and interface ID as needed
Copy and use it

A worked example

Paste a sample MAC address

00:11:22:33:44:55

Copy this into the tool, or open IPv6 ULA generator

Things that trip people up

A ULA is the IPv6 counterpart of a private IPv4 range and must not be routed on the public internet

Questions people ask

ULA vs public IPv6 — what is the difference?: Public addresses are globally routable and assigned by your provider. ULAs work only inside your network, never leave your router, and survive provider changes — good for infrastructure that should not be exposed.
Why generate the prefix randomly instead of picking fd00::1?: RFC 4193 mandates a random global ID precisely so two sites that later merge their networks will not clash. Hand-picked prefixes like fd00::/64 are a common source of hard-to-debug conflicts.
Can a ULA reach the internet?: No. Routers must not forward fd00::/8 to the public internet. Use it for internal services; hosts still get global addresses from your provider for outbound traffic.

Next steps

Open the IPv6 ULA generator tool

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