"Registered ULA" (Was: using ULA for 'hidden' v6 devices?)

Jeroen Massar jeroen at unfix.org
Wed Jan 25 23:55:58 UTC 2012

On 2012-01-25 19:51 , William Herrin wrote:
> On Wed, Jan 25, 2012 at 8:08 AM, Jeroen Massar <jeroen at unfix.org> wrote:
>> On 2012-01-25 18:55 , Justin M. Streiner wrote:
>> [..]
>>>> Locally managed means locally manage, though.  The RFC is more of
>>>> a suggestion than a requirement at that point.
>>> Right, though it's a shame that the registry-assigned ULA concept didn't
>>> take off.
>> What everybody calls "Registered ULA" or ULA-C(entral) is what the RIRs
>> already provide. Also entities that have such a strict requirement are
>> perfectly served with address space the RIRs provide.
> Jeroen,
> Not so. The registries provide GUA, not ULA. Not everybody considers
> the difference significant, but many if not most of the folks who want
> to use ULA for anything at all do.

I think you misunderstood my terminology, which is afaik the one used by
the relevant documents, but lets see where we go astray.

ULA consists out of two portions inside fc00::/7 which are:
  fd00::/8 for ULA-L (local) as the one defined by RFC4193
  fc00::/8 reserved for ULA-C which for instance is mentioned
           in http://tools.ietf.org/html/draft-hain-ipv6-ulac-02

ULA-L is the one everybody uses and what most people just call ULA.

ULA-C is very close to GUA as they are both registered at some entity.
ULA-C does not exist though, the prime reason for that being that nobody
could come up with extensive reasons why it would be any different from
GUA and thus why anyone would bother having a registry for it (well,
apart from earning more money by registering numbers of course, like
what the rest of the industry is doing).

The only other reason would be that one can filter fc00::/7 away
completely and be done with both of them in one go. But, the moment that
one is using ULA space in one's network one is likely not applying that
rule, also, it does not come per default in boxes. And as we all know,
folks don't filter per BCP-38 either, thus it will be very unlikely that
there will be a global fc00::/7 block (and if that was one's line of
defense in their network then good luck with that ;)

>> But if you want to stick to ULA anyway and you want a bit more certainty
>> that your ULA prefix does not clash, you can generate a random one as
>> per the RFC and register it:
>> https://www.sixxs.net/tools/grh/ula/
> My "registration" was erased from that page. Don't know when. Don't
> know why. But it speaks poorly for its function as a registry.

This was likely caused by the little note at the bottom:

"Prefixes which are not generated using the ULA generator will be
silently removed; ULAs are not supposed to look pretty."

Various folks are registering fd00::/48 or 'fun' stuff like
fd00:b00b::/48 or whole series of /48s (fd01::/48, fd02::/48 etc) and
then claim that they generated that prefix. For some obvious reason the
system does not agree with those statements.

Unfortunately there is no drop log, thus in case that the system did
make a wrong decision, there is a contact page where one can notify to
and we'll dig into it.


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