I'm sharing my IPv6 experiences to this forum, in case others may benefit from my testing.
I've spent many hours testing as much as I could with management functions over IPv6 on the mobility controllers and APs, to try to learn what worked, and what did not. I have learned a lot, so wanted to share my results. All my recent testing was with 6.1.3.5. My controller doesn't do any routing, as I have a neighboring router that provides all the layer 3 functions. Some of this information is also covered in Chapter 36 "IPv6 Support" in the 6.1 Users Guide (although I discovered much of this the hard way, before I found that chapter in the manual). Also, this is only discussing the management functions of the system, not the client IPv6 functionality, which has been working fine for us for years.
First, there are many things in the controller that do NOT work over IPv6. These include:
SNMP
RADIUS
NTP
SMTP
DNS
TFTP
There is no sign of a DHCPv6 client in either controller or AP.
Things that do work just fine over IPv6, for management access to the controller, are HTTP, HTTPS, and ssh. SYSLOG also works over IPv6.
There are a number of cosmetic bugs, like IPv6 addresses that show up in logs are truncated or mangled. Also, if you use a ULA address, those will not display in the GUI for some reason, although they do work fine.
You are able to give all controller interfaces an IPv6 address. APs will use SLAAC to get an IPv6 address if they hear RAs from a router. An easy way to verify that this all works is to ping6 any of the controller interfaces or the AP's SLAAC addresses.
For debugging from the controller, you can "ping ipv6", but you can't "traceroute ipv6". The documentation says you can "tracepath ipv6", but that is wrong. You can tracepath to an IPv6 address and it works, but you must leave out the phrase "ipv6", and there is no way to tracepath to an IPv4 address. Very inconsistent and confusing.
IPSEC over IPv6 is not implemented, so you cannot get a master controller talking to local controllers over IPv6 in a multi-controller environment. This also means that you can't reach remote APs over IPv6.
If you want to get your APs to communicate via IPv6 to your master or local controllers, it is a bit tricky. There are a number of caveats that you need to be aware of. The obvious way to configure which LMS the AP should use would be to configure your "ap system-profile" to specify an lms-ipv6 address and NOT give it an lms-ip address. You would think that would force it to use the IPv6 address for the LMS. However, that has no effect whatsoever. The only thing that works is to provision the AP to have a "Master Controller IP address" setting that is the IPv6 address of the LMS that you want to use. You cannot set the Host controller to an IPv6 address, because it cannot do the TFTP boot via IPv6.
The other major caveat is that you must have a path MTU of 1500 all the way from controller to AP, when operating over IPv6. When using IPv6, the controller does not do anything to try to learn the path MTU to the AP, so assumes that the path can handle full ethernet frames. There are some large packets that get sent from the controller, that get IPv6 fragmented down to something that will just fit into 1500 byte frames, that will then get dropped by any tunnels you have along the path. In my case, I had an IPSEC tunnel in the path, with an MTU of 1422. Talking to APs over IPv4 works just fine over this path, but the large IPv6 packets will fail, and the AP will never come all the way up. However, if on the controller you run a "tracepath" to the IPv6 address of the AP, the controller will learn the path MTU, and remember it, and will resend the packets using smaller fragments, and the AP will immediately come up. Unfortunately it doesn't remember path MTU forever, and you'll eventually have to do another manual tracepath to get it to come back up again.
Do a "show datapath tunnel ipv6", and watch the "MTU" column to see what's going on here.
So, I have given up doing IPv6 to any APs that are at locations where I don't have a full 1500 byte path MTU. But, I can run them locally over IPv6 from any routed subnet just fine. Unfortunately I have to now manually configure the master controller address in every AP where I want this to work. So, a little more provisioning hassle if you want your APs operating over IPv6. And obviously any hope of running IPv6-only is gone for now.