IPv6 ULA Generator
Generate IPv6 Unique Local Addresses (ULA) per RFC 4193 from a MAC address or randomly. Runs entirely in your browser.
Local processingWhat is IPv6 ULA Generator?
An IPv6 Unique Local Address (ULA) is a site-local address prefix in the fc00::/7 range, defined by RFC 4193. It provides globally unique but non-routable addressing for private networks, analogous to RFC 1918 private addresses in IPv4.
How It Works
Per RFC 4193, the generator creates a 40-bit Global ID by combining the EUI-64 identifier (derived from the MAC address with the U/L bit flipped) with the current NTP timestamp, computing SHA-1, and taking the lower 40 bits. The prefix is then fd00::/8 + Global ID + subnet ID.
Common Use Cases
- Assigning private IPv6 ranges to home or enterprise networks
- Lab and testing environments
- Internal services not requiring global routing
Technical Details
Standard: RFC 4193. Range: fc00::/7 (fd00::/8 used for locally assigned). Global ID: 40 bits from SHA-1(EUI-64 + NTP time). Prefix length: /48.
How to Use
- Optionally enter a MAC address (or leave blank for random)
- Click Generate
- Copy the ULA prefix
Privacy
All processing happens in your browser. Your data is never uploaded to any server.
FAQ
What is a ULA?
A Unique Local Address (RFC 4193) is an IPv6 prefix for local communications within a site, not routable on the global internet, in the fc00::/7 range.
How is the ULA generated?
Per RFC 4193: a 40-bit global ID is derived from the EUI-64 of a MAC address (with the universal/local bit flipped) combined with the current time in NTP format, then SHA-1 hashed.