ULA (Unique Local Address)
A Unique Local Address (ULA, RFC 4193) is an IPv6 address range reserved for private, local-network use, playing a role similar to RFC 1918 private ranges (like 192.168.0.0/16) in IPv4. ULAs fall within fc00::/7, with fd00::/8 the portion in practical use, and each site generates its own /48 prefix from a pseudo-random algorithm so two independently configured networks are very unlikely to collide if they're later merged or interconnected. Unlike a public IPv6 address, a ULA is not supposed to be routed on the open internet, making it useful for internal services, inter-device communication, or dual-stack networks that want stable local addressing independent of whatever public IPv6 prefix an ISP assigns, which can change over time.
By AdminKit team, Netbase JSC · Updated