After having a fun twitter exchange with Andrew Yourtchenko on some post Cisco Live! IPv6 presentations that Andrew gave on MAP we ended up chatting about IPv6 only networks and some of the challenges we will face in the next phase of the IPv6 transition. While many of those in IT haven't even gotten their arms around deploying IPv6 there are folks looking ahead to address what to do when you run an IPv6 only network.
It turns out that many client OS behavior is NOT what you want. Particularly in the mobile device space which is ironic since mobile is driving many of the needs for IPv6. There are dependencies on IPv4 or some deployments simply lack functional support to operate when in an IPv6 only network. Android will wait on RFC 6106 for RDNSS support but most networks do not provide that however it does NOT support DHCPv6 via wifi soooo, the device will get an IPv6 address but then do nothing because it has no DNS information at all.
Andrew gave a nice presentation at RIPE earlier this year that is worth watching to understand what the core problem currently is with running an IPv6 only network. His presentation is at https://ripe66.ripe.net/archives/video/1196/
Just for fun, set up an IPv6 only network and see if you can get your environment working. You should be able to hit an IPv6 dual stacked site to determine what is and is not working. If you need some IPv6 sites to try here is a short list to get you started: