[131135] in North American Network Operators' Group
=?windows-1252?Q?Re=3A_IPv6_fc00=3A=3A=2F7_=97_Unique_local_addresses?=
daemon@ATHENA.MIT.EDU (Jen Linkova)
Wed Oct 20 20:10:38 2010
In-Reply-To: <4CBF63BF.2000101@mompl.net>
Date: Thu, 21 Oct 2010 11:10:30 +1100
From: Jen Linkova <furry13@gmail.com>
To: Jeroen van Aart <jeroen@mompl.net>
Cc: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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 =97 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 rout=
ing
> prefix intended to minimize the risk of conflicts if sites merge or packe=
ts
> 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..
--=20
SY, Jen Linkova aka Furry
