nanog mailing list archives
Re: IPv6 fc00::/7 — Unique local addresses
From: Jen Linkova <furry13 () gmail com>
Date: Thu, 21 Oct 2010 11:10:30 +1100
Hi Jeroen, On Thu, Oct 21, 2010 at 8:48 AM, Jeroen van Aart <jeroen () 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
Current thread:
- Re: IPv6 fc00::/7 — Unique local addresses, (continued)
- Re: IPv6 fc00::/7 — Unique local addresses Mark Smith (Oct 20)
- RE: IPv6 fc00::/7 — Unique local addresses George Bonser (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Matthew Kaufman (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Mark Andrews (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Matthew Kaufman (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Mark Andrews (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Mark Smith (Oct 20)
- Re: IPv6 fc00::/7 — Unique local addresses Owen DeLong (Oct 21)
- Re: IPv6 fc00::/7 — Unique local addresses Matthew Kaufman (Oct 21)
- Re: IPv6 fc00::/7 ??? Unique local addresses Steve Meuse (Oct 21)
- Why ULA: low collision chance (Was: IPv6 fc00::/7 — Unique local addresses) Jeroen Massar (Oct 21)
- Re: Why ULA: low collision chance (Was: IPv6 fc00::/7 — Unique local addresses) Ray Soucy (Oct 21)
- Re: Why ULA: low collision chance (Was: IPv6 fc00::/7 — Unique local addresses) William Herrin (Oct 21)
- Re: Why ULA: low collision chance (Was: IPv6 fc00::/7 — Unique local addresses) Joel Jaeggli (Oct 21)
- Re: Why ULA: low collision chance (Was: IPv6 fc00::/7 — Unique local addresses) Jack Bates (Oct 21)
- Re: Why ULA: low collision chance (Was: IPv6 fc00::/7 — Unique local addresses) Joe Hamelin (Oct 21)
- Re: Why ULA: low collision chance (Was: IPv6 fc00::/7 — Unique local addresses) Owen DeLong (Oct 21)
- Re: Why ULA: low collision chance (Was: IPv6 fc00::/7 — Unique local addresses) Owen DeLong (Oct 21)