So I've set up a he.net IPv6 tunnel on my DSL router (an AVM Fritz!Box), works like a charm. The router is giving out the IPv6 addresses to all my devices. My main computers are all running OS X Lion.
There I've noticed that sometimes the priority for outgoing connections is given to IPv6, and sometimes to IPv4. For example, when going to pages like www.ipv6-test.com, it will say "When both protocols are available, your browser uses IPv6", and a couple of refreshes later it will say "When both protocols are available, your browser uses IPv4", without changing anything. I have set 2001:470:20::2 as my DNS. It happens with all browsers I've tried (Safari, Firefox, Chrome).
By the way, the exact same thing happens on my iDevices (iPhone, iPad).
It's as if the OS is "load balancing" or doing round robin between IPv4 and IPv6.
Is there a way to force OS X Lion to always use IPv6 if it's available?
This is what you're running into
http://en.wikipedia.org/wiki/Happy_Eyeballs
And no, as far as I know, you can't turn it off
This explanation makes perfectly sense. Thank you!
Too bad we'll have to live with it, at least until Apple updates the OS to make this an option.