Hi Jeroen, On Thu, Oct 21, 2010 at 8:48 AM, Jeroen van Aart <jer...@mompl.net> wrote: > According to http://en.wikipedia.org/wiki/IPv6_address#Special_addresses an > fc00::/7 address includes a 40-bit pseudo random number: > > "fc00::/7 — Unique local addresses (ULA's) are intended for local > communication. They are routable only within a set of cooperating sites > (analogous to the private address ranges 10/8, 172.16/12, and 192.168/16 of > IPv4).[12] The addresses include a 40-bit pseudorandom number in the routing > prefix intended to minimize the risk of conflicts if sites merge or packets > are misrouted into the Internet. Despite the restricted, local usage of > these addresses, their address scope is global, i.e. they are expected to be > globally unique." > > I am trying to set up a local IPv6 network and am curious why all the > examples I come accross do not seem to use the 40-bit pseudorandom number? > What should I do? Use something like fd00::1234, or incorporate something > like the interface's MAC address into the address? It'd make the address > quite unreadable though.
RFC4193 specifies a suggested algorithm to do it: http://tools.ietf.org/html/rfc4193#section-3.2.2 The section 3.2.1 also states that "Locally assigned Global IDs MUST be generated with a pseudo-random algorithm consistent with [RANDOM]. Section 3.2.2 describes a suggested algorithm. It is important that all sites generating Global IDs use a functionally similar algorithm to ensure there is a high probability of uniqueness." I'm not sure where did you find the examples you've mentioned. If it's just a documentation example - seems to be fine. If someone is doing it in real networks - that's just not right.. -- SY, Jen Linkova aka Furry