I wasn't aware that there was "less" IPv6 functionality in Snow
Leopard than previous releases. Someone mentioned that 10.6
"defaults" to IPv4, I'm not sure what this means. I'm hoping that
there is a way in 10.6 to influence how name lookups are performed,
as well as a way to influence IPv6 Source Address Selection.
Proper operation of a dual stack system is to always prefer IPv6
over IPv4 when you get both AAAA and A records from a DNS query.
So, if (from a dual stack machine) you use a browser to connect to a
dual-stack web site, you should always connect using IPv6, unless it
fails for some reason and then you will fall back to IPv4. This is
the way it works in every other OS. Then, with Snow Leopard (10.6)
it did the opposite and now prefers IPv4 over IPv6, at least as
observed with Safari and Firefox. Since our enterprise network is
highly IPv6-enabled, we had to recommend to people that they NOT
upgrade to 10.6, since those users now see large timeouts when first
trying to connect to dual stack web sites that cannot be reached
over the IPv4 path. Note that this was based on observations on the
first few machines that we upgraded to 10.6, and I'm not aware if
later patch releases fixed the problem or not.
I wouldn't be surprised if this was done to avoid the next worse
option: people deactivating IPv6, which is something I have read
happening in a number of forums. In reality the reversal of priority
won't effect most people at this point, but I would be curious if
there is a configurable option to allow this to be modified?
