IPv6 ULA Generator
Generate a random IPv6 Unique Local Address prefix (fd00::/8) with a pseudo-random 40-bit global ID, per RFC 4193, for private networks.
Last reviewed by the Radiatus Cloud team
Generate a random IPv6 Unique Local Address (ULA) /48 prefix for private networks.
Need this monitored 24/7?
Radiatus delivers managed cloud & network operations.
Generate a Unique Local Address prefix
IPv6 Unique Local Addresses, defined in RFC 4193, are the IPv6 equivalent of private IPv4 ranges: they are used inside a network and are not routed on the public internet. A ULA prefix begins with fd, followed by a pseudo-random forty-bit global identifier, which gives each site its own /48 prefix with a very high probability of being unique. This generator creates a random global identifier and assembles a complete ULA /48 prefix, along with an example /64 subnet and address.
Generating the global identifier randomly, rather than choosing a memorable value, is important because it makes accidental collisions between networks extremely unlikely if they are ever interconnected.
Why use Unique Local Addresses
ULAs give an internal IPv6 network stable, private addressing that does not depend on an internet provider and will not change if the provider does. They are ideal for internal services, lab environments and networks that must work without internet connectivity. Because they are globally unique with high probability, two organisations can merge their networks without renumbering, unlike with the old deprecated site-local addresses.
The fd00::/8 portion of the fc00::/7 range is the part reserved for locally assigned prefixes, which is what this tool generates. Each click produces a fresh random prefix. All generation happens locally in your browser.
Related tools
- Port Scanner — Check which common ports respond on a host and understand what each exposed service means. Scan only systems you are authorised to test.
- DNS Misconfiguration — Analyze DNS records (TXT, SPF) for security gaps.
- TLS Compat Tester — Check client-server compatibility for TLS versions.
- Firewall Rule Risk — Evaluate firewall rules for over-permissive exposure.
Frequently Asked Questions
What is an IPv6 ULA?
A Unique Local Address is private IPv6 addressing in the fd00::/8 range, used inside a network and never routed on the public internet.
Why is the global ID random?
A random forty-bit global identifier makes each site prefix almost certainly unique, so networks can interconnect later without address clashes.
How is a ULA different from a private IPv4 range?
It serves the same purpose but is globally unique with high probability, so two ULA networks can be merged without renumbering, unlike overlapping IPv4 private ranges.
What size prefix does this generate?
It generates a /48 prefix, the standard ULA site allocation, which you can divide into many /64 subnets for your internal networks.
Should I pick a memorable global ID instead?
No. The standard recommends a random global ID precisely to avoid collisions, so a memorable value increases the risk of clashing with another network.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Click to generate a random ULA /48 prefix and an example subnet.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
Related Tools
Port Scanner
NetworkCheck which common ports respond on a host and understand what each exposed service means. Scan only systems you are authorised to test.
DNS Misconfiguration
NetworkAnalyze DNS records (TXT, SPF) for security gaps.
TLS Compat Tester
NetworkCheck client-server compatibility for TLS versions.