[Major cross post, set reply-to to NANOG, please honor it... ]
[Note: I am not talking about ULA Central here, though it could apply]
To stop the pesky emails about ULA, I hereby present a (partial)
solution to this problem.
We have ULA as per RFC4193. With a little math one can generate a ULA
prefix sized /48 which is most likely globally unique. According to
the RFC with 10.000 connections the collision probability is still a
Some people have expressed a problem with this, especially when they
want to use the generated ULA prefix for their large organization.
The simple, cheap and quick solution: a ULA registry.
This comes close to ULA-Central, but what we do is simply make a list
of the "in use" ULA's, without any allocation policies whatsoever
except: first come first serve and no cash to pay.
The tool is here: http://www.sixxs.net/tools/grh/ula/
The page allows one to generate a ULA based on a given MAC address
(multicast + locally defined + unregistered are not accepted) and then
register it. The Name + Email are mandatory to restrict abuse a little
bit. Email is not shown, except in whois and can be used to possible
contact people who are leaking ULA prefixes.
Note, it is indeed a _partial_ solution. When somebody still generates
the same ULA prefix and does not check the list you can still collide.
As this is primarily a problem for big organizations, they should be
checking this list for collisions and registering their prefix when
they see that they have a need for that.
The list is available from the website, but also per whois.sixxs.net
which is now serving up fd00::/8. It does not cover ULA-C (fc00::/8).
As SixXS is a private hobbyproject kind of thing, we of course are not
liable for anything that this might cause to you, your family, company
etc. But enjoy it nevertheless. Full copies of the list in inet6num
format are available from the site.
PS: GRH still classifies ULA's as "BAD" of course
PPS: Thanks to Peter van Dijk for the multicast/locally defined MACs
PPPS: Folks registering prefixes like crazy will nicely get locked out
automatically, so don't even try...
PPPPS: Thanks to SUZUKI Shinsuke and Holger Zuleger for the generator.