For what it's worth,
I recently discovered that when you have multiple controllers and want to implement Mobility Groups, more is needed than simply entering the same Default Mobility Group Name for each controller within the mobility group. The following is required:
a) The IP address of the "Virtual" interface on each controller must be identical on each controller within the mobility group.
b) The Default Mobility Group Name must be identical on each controller within the mobility group (case sensitive).
c) The mobility table must be populated with an entry for each controller within the mobility group.
Otherwise, you will see some inexplicable behavior such as:
* LWAP access points refusing to change to a different controller, even if their primary controller is explicitly set and the LWAP is rebooted.
* LWAP access points unable to find any other wireless controller other than the one pointed to by the "CISCO-LWAPP-CONTROLLER" DNS entry (presumably, this would also be the case if DHCP Option 43 is used to point the LWAP to a controller). Once the first controller reaches its max. capacity of LWAPs, no more LWAPs can join.
* Even MASTER CONTROLLER MODE has no effect.
Cisco TAC was able to explain the great mystery of the Mobilty Group Table to me. However, unless you know your problem is related to mobility groups issues, you might not know to start there (I know I didn't).
The least difficult method I have found for populating the mobility group table is as follows:
Build a text file with one entry for each controller in the mobility group as follows:
Log into the GUI for each controller and selecting: Controller -> Mobility Management -> Mobility Groups, click the "EDIT ALL" button and copy the MAC and IP address from the text box into a text file using NOTEPAD. Repeat this for each controller, creating a new line for each:
The format for the entries is as follows:
Once the text file is completed (one entry for each controller in the mobilit group), click the EDITALL button and copy the entire contents of the text file and paste it into the text box on the controller GUI, click the APPLY button and click Save Changes. Repeat for each controller.
Again, make sure that the following settings are IDENTICAL in each of the controllers in the Mobility Group:
* The IP address of the "virtual" interface ( Controller -> interfaces ) must be the same on all controllers.
* The "Default Mobility Domain Name" ( Controller -> General ) must be identical on each controller in the mobility group (note: the Mobility Domain Name is case sensitive).
After making changes directly to the controllers, a "refresh from controller" in the WCS might be needed to get the WCS to attempt to synchronize itself with the controllers.
Here is a link to the 4.2 Wireless Controller Configuration Guide which discusses this in greater detail.
It is unfortunate that there are currently no mechanisms in the WCS 4.2 to make these changes in bulk (i.e.: The WCS has no Controller Template to do this).
Also, if you ever need to replace a controller, you will need to update the Mobility Group Table in each controller in the Mobility Group (since the tables will have the MAC address of the old controller which will now be different in the new replacement controller).
Despite having used the "unified" product for some time now, there are still surprises from time to time. I just thought that I would share my experience for those who may want avoid it and/or who may be encountering any of odd the behavior described above.