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Local IPv6 Address Generator: Create a ULA Prefix

This free local IPv6 address generator creates a random unique local address (ULA) prefix for your private network. You get a /48 prefix, a list of /64 subnets and sample host addresses, all made in your browser.

By Debmedia Technologies LLP · Kolkata, India · Updated

What Is a Local IPv6 Address?

A local IPv6 address, formally a unique local address (ULA), is a private IPv6 address for use inside your own network. It is the IPv6 counterpart of private IPv4 ranges such as 10.0.0.0/8 and 192.168.0.0/16. ULAs start with fd, belong to the range fc00::/7 and are never routed on the public internet.

They are ideal for lab networks, internal services, VPN links between sites and any device that should talk privately even if the provider changes your public prefix.

How to Use This Local IPv6 Address Generator

  1. A new prefix is generated as soon as the page opens.
  2. Choose how many /64 subnets you want to see, up to 16.
  3. Optionally enter a MAC address to see how its interface ID and link-local address are built.
  4. Press Generate new prefix for another random prefix, and copy the one you want to keep.

Structure of a ULA

PartSizeMeaning
fd8 bitsThe ULA prefix with the local flag set
Global ID40 bitsA random value that makes your prefix unique
Subnet ID16 bitsLets you create 65,536 separate /64 networks
Interface ID64 bitsIdentifies a single device

The format and the advice to choose the global ID at random come from RFC 4193, unique local IPv6 unicast addresses.

Tips for Using Your Prefix

  • Pick it once and keep it. Write it in your network documentation so nobody generates a second prefix by mistake.
  • Use one /64 per segment. IPv6 features such as SLAAC need a /64.
  • Do not use fd00:: by itself. A prefix such as fd00::/8 with an easy ID is likely to clash with other networks.
  • Keep ULAs private. Never advertise them to the internet or publish them in public DNS.

Privacy and Randomness

The prefix is created in your browser with a secure random number generator, so we never see or store it. If you enter a MAC address for the optional example, it is also processed only on your device.

What to Do Next

Work out the range of any prefix with the IPv6 range calculator, shorten addresses with the IPv6 compression tool or see every group with the IPv6 expansion tool. For IPv4 planning, the IPv4 subnet calculator does the same job.

Why Use a Local IPv6 Address Generator?

A local IPv6 address generator saves you from inventing a prefix by hand and risking a clash. With a random global ID, two companies that later join networks almost never overlap. Use the local IPv6 address generator once per organisation, record the prefix and then carve out /64 subnets for every segment. Keep the prefix in your documentation, because it is hard to change once devices use it.

Frequently Asked Questions

A ULA is the IPv6 counterpart of private IPv4 ranges such as 192.168.0.0/16. It starts with fd, works inside your own network and is not routed on the internet.
A random 40-bit global ID makes it very unlikely that two organisations pick the same prefix, which avoids clashes when networks later connect through a VPN or merger.
It shows how an EUI-64 interface ID and link-local address are built from a MAC address. It is optional and processed only in your browser.
No. It is created in your browser with a secure random number generator, and we never see or save it.

Disclaimer: results come from live requests and can change as records and servers change. We cannot guarantee that every answer matches what every visitor sees.