WIFITECHBLOG

Settings that must be configured identically to allow wireless mobility between controllers:

LWAPP Transport Mode (layer 2 or layer 3)
config switchconfig mode {L2|L3}

Virtual IP
config interface address virtual 1.1.1.1

Mobility Tunneling Mode (symmetric or asymmetric)
config mobility symmetric-tunneling {enable|disable}

Mobility Security Mode
config mobility secure-mode {enable|disable}

DHCP Proxy
config dhcp proxy {enable|disable}

WLAN
All parameters for the WLAN should be identical (other than security settings), including the WLAN numbering on the WLCs in the mobility group.

Best Practices for Mobility:

1.  Use the same, non-routable virtual IP.  To verify the virtual address, use the show interface summary command.  Also, ping the virtual address to make sure it's not routable.

2.  All controllers must be configured for the same LWAPP transport mode.  Use the show switchconfig command to verify LWAPP transport mode, and the config switchconfig mode to change any of the parameters.

3.  IP connectivity between all WLCs is required (checked by creating the tunnel)

4.  WLCs must have the same mobility group (except for guest tunneling)

5.  WLCs must be running the same version of code.

6.  MACs and IPs are required to build the tunnel.

7.  Do not create overly large mobility groups.

Source
http://www.cisco.com/en/US/customer/tech/tk722/tk809/technologies_tech_note09186a0080810880.shtml