So, according to the new features list and multiple beta screenshots I saw, iOS 4 should have IPv6 support. My local home network is dual stacked, running both a DHCP (v4) server and an IPv6 Router Advertisement Daemon. Everything on my network (that is IPv6 aware) autoconfigures just fine, but my iPhone 4 doesn't seem to configure itself against the RA daemon. According to screenshots I've seen, there should be an IPv6 section in my access point's config section under iOS settings, but it's just not there for me. And it's not doing it silently behind the scenes, because when I go to http://ipv6.he.net, it shows my IPv4 address. Edit: Huh, http://ipv6.google.com works. And it connects to my web site (http://www.finnie.org, which has both IPv6 and IPv4 addresses in DNS) via IPv6, so it's not a matter of iOS preferring IPv4 over IPv6. Weird, I don't know why it preferred IPv4 over IPv6 for just http://ipv6.he.net.