Hi, as Karanbir announced on the centos-announce mailing list about a week ago ( http://lists.centos.org/pipermail/centos-announce/2012-June/018677.html ), mirrorlist.centos.org is now available over IPv6.
The new IPv6-enabled mirrorlist servers will only hand out mirror URLs that can be accessed over IPv6. Previously IPv6-only CentOS servers had to have their yum configuration changed to point to some IPv6-enabled mirror to receive updates, but now those IPv6-only CentOS servers can get their updates with the default configuration.
A side effect of this change is that dual-stacked boxes will also retrieve the list of mirrors over IPv6, and consequentially, they will no longer try to download the updates from IPv4-only mirrors, as the mirrorlist served to them does not contain any IPv4-only mirrors.
This means that the IPv6-enabled mirrors will now receive slightly more traffic than the IPv4-only mirrors. If you're running an IPv6-enabled mirror, now would be a good time to check the stats of your mirror to see if there's any increase in traffic. If you notice anything particularly interesting in your traffic stats, feel free to share your observations.
Just like the IPv4 mirrorlist, the IPv6 mirrorlist also uses GeoIP information to give a list of nearby mirrors. The coverage will improve as we get more IPv6-enabled mirrors. Additional IPv6-enabled CentOS mirrors are always welcome. The mirror monitoring scripts will pick up any added IPv6 addresses automatically, so you don't need to notify us if you add an IPv6 address for your mirror.
I'm running the scripts which check that the IPv6-enabled mirrors are up to date. While running the tests I noticed that there are still quite a few mirrors that have a published IPv6 address but are nevertheless unreachable by IPv6. http://tursas.miuku.net/tmp/centos_ipv6_mirrors.txt lists the current status of the mirrors that have an IPv6 address. Please check the status of your mirror from that list. Especially if you think "our organization can't possibly be affected", please check the list. There are some distinguished organizations on the list with a nice fat FAIL label next to them.
Please note that due to the way the list is compiled, the rsync mirror URLs (which are actually not used for the mirrorlist) are at the bottom of the list. The HTTP and FTP URLs are checked hourly, while the rsync URLs are checked only daily.
The next services to be enabled for IPv6 are most probably mirror.centos.org and msync.centos.org. The former would be needed for the CR repo, and the latter can be accomplished quite easily once the mirror.c.o IPv6 servers are in place.
If you run into problems with the new IPv6 mirrorlist, we'd be happy to hear about the problems. We're also available for questions on #centos-devel at irc.freenode.net.
Thanks for your attention :)