IPv6 ULA Generator

Generate a Unique Local IPv6 Address (ULA) /48 prefix. ULAs (FD00::/8) are for local communications and are not globally routable.

Generated ULA Prefix

About IPv6 Unique Local Addresses (ULA)

Unique Local Addresses (ULAs), defined in RFC 4193, are IPv6 addresses intended for local communications within a site or set of sites. They are analogous to private IPv4 addresses (e.g., 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16).

Key Characteristics:

  • ULA prefixes are in the FD00::/8 range.
  • The 'L' bit (8th bit) is set to 1, indicating "locally assigned". The range FC00::/8 (L-bit = 0) was reserved for central assignment but is not currently used.
  • The following 40 bits form a "Global ID" which should be generated pseudo-randomly to ensure a high probability of uniqueness if sites later merge or interconnect.
  • The subsequent 16 bits are the "Subnet ID", allowing for up to 65,536 subnets within the /48 ULA prefix assigned to a site.
  • ULAs are not intended to be routed on the public internet.

This tool generates a pseudo-random /48 ULA prefix that you can use for your internal IPv6 network planning.