IPv6 ULA – what and how?

ULA (Unique Local Addresses, or Unique Local IPv6 Unicast Addresses to give them their full name) are IPv6’s equivalent of IPv4’s “private” addresses.

The idea is to append a random 40 bits to the reserved ULA prefix fd00::/8, thus building a /48 that you can call your own. You can use this /48 wherever and however you like, with the sole proviso that it must not be routed on the public Internet. The ULA space is defined in RFC4192 (http://tools.ietf.org/html/rfc4193).

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