Facebook started its transition to make everything* internally IPv6 slightly before then. It was indeed a lot of work. But worth it. * When I was there we sti

Facebook started its transition to make everything* internally IPv6 slightly before then. It was indeed a lot of work. But worth it. * When I was there we still had a handful of weird things that couldn't be made IPv6. If you needed to access such things you could get a dual-stack dev server.