IPv6 ULA Generator
Generate your own local, non-routable IP addresses for your network according to RFC 4193.
This tool uses the first method suggested by IETF using the current timestamp plus the MAC address, SHA-1 hashed, and the lower 40 bits to generate your random ULA.
What are IPv6 ULA Addresses?
Unique Local Addresses (ULA) are IPv6 addresses for private use, similar to 192.168.x.x in IPv4. They always start with fd or fc and are not routable on the public internet. Ideal for local networks.
RFC 4193 – The Technical Foundation
RFC 4193 defines the fd00::/8 address space for locally generated ULAs. The 40-bit prefix is generated via SHA-1 hash from MAC address and NTP timestamp, which minimizes collisions when merging networks.
ULA vs. Link-Local vs. Global Unicast
Link-local addresses (fe80::/10) are only valid in the local segment. ULAs (fc00::/7) are routable within the entire private network. Global unicast addresses (2000::/3) are publicly reachable on the internet.
Frequently Asked Questions
Answers to common questions about the IPv6 ULA Generator
An IPv6 ULA is a private IPv6 address for use in local networks, analogous to private IPv4 ranges (10.x.x.x, 192.168.x.x). ULAs start with the prefix fd00::/8 and are not routable on the public internet.
Link-local addresses (fe80::/10) are only valid in the directly connected network segment. ULAs, on the other hand, can be routed across routers within the private network – ideal for home networks and corporate networks with multiple segments.
The tool combines an NTP timestamp with the EUI-64 address derived from the MAC address into a 16-byte value. This is SHA-1 hashed, and the lower 40 bits of the hash form the global ID part of the /48 prefix.
No – each generation uses the current timestamp, so clicking "Regenerate" will always produce a new ULA. Save your chosen ULA, as it should be used permanently for your network.
RFC 4193 recommends using the MAC address of your router or a network device as the basis. The MAC address does not need to be kept secret – it only serves as an entropy source for the SHA-1 hash.