Re: using ULA for 'hidden' v6 devices?

[Cameron Byrne <cb.list6 () gmail com>]

On Jan 26, 2012 8:44 AM, "Owen DeLong" <owen () delong com> wrote:
> On Jan 26, 2012, at 6:39 AM, Jima wrote:
>
> > On 2012-01-26, Owen DeLong wrote:
> > > If you can't point to some specific advantage of ULA over secondary
> > > non-routed GUA prefixes, then, ULA doesn't have a reason to live.
> >
> > My biggest concern with secondary non-routed GUA would be source address
> > selection.  If you're trying to talk to something in 2000::/3, it's
> > obvious to the OS that it should be using its address in 2000::/3 rather
> > than the one in fc00::/7.  When both the "external" and "internal"
> > addresses live in 2000::/3, more care has to be taken to ensure the
> > system DTRT.
>
> It's very easy to configure SAS to handle this. Frankly, you have the
same challenge with ULA in many scenarios.
> > > I'm not sure where DNS64/NAT64 comes into play here for v6 to v6
> > > communication. For IPv4, I don't see any advantage in ULA+NAT64 vs. the
> > > more reliable and easier RFC-1918 with NAT44 possibilities, even if you
> > > have to run multiple RFC-1918 domains to get enough addresses, that
will
> > > generally be less complicated and break fewer things than a NAT64
> > > implementation.
> >
> > My best guess there is the ability to a) only manage a single-stack
> > network (I really wish more software supported IPv6 so this could be a
> > more feasible reality), and b) use the same NAT64 prefix across various
> > NAT64 instances (64:ff9b::/96 is a blocker if you actually want to allow
> > NAT64 to RFC1918 space).  While I can see the potential appeal of the
> > second point, I'm not sure I'd agree with it myself.
>
> But with NAT64, you're supporting both stacks, you just move the problem
around.
> Having done experiments with both methods, I assure you it is a true
statement based on experience. NAT64 really offers more problems than it
solves, not the least of which is the stateful DNS interaction problem.
>

I have a very different opinion. Nat64/ dns64 fits my needs great

Horses for courses.

Cb
> Owen