Cisco Cisco 5520 Wireless Controller 기술 참조

The new architecture for HA is for box-to-box redundancy. In other words, 1:1 where one WLC will be 
in an Active state and the second WLC will be in a Hot Standby state continuously monitoring the health 
of the Active WLC via a Redundant Port. Both the WLCs will share the same set of configurations 
including the IP address of the Management interface. The WLC in the Standby state does not need to 
be configured independently as the entire configuration (Bulk Configuration while boot up and 
Incremental Configuration in runtime) will be synced from the Active WLC to the Standby WLC via a 
Redundant Port. The AP's CAPWAP State (only APs which are in a run state) is also synced, and a mirror 
copy of the AP database is maintained on the Standby WLC. The APs do not go into the Discovery state 
when the Active WLC fails and the Standby WLC takes over the network's Active WLC.

There is no preempt functionality. When the previous Active WLC comes back, it will not take the role 
of the Active WLC, but will negotiate its state with the current Active WLC and transition to a Standby 
state. The Active and Standby decision is not an automated election process. The Active/Standby WLC 
is decided based on HA SKU (Manufacturing Ordered UDI) from release 7.3 onwards. A WLC with HA 
SKU UDI will always be the Standby WLC for the first time when it boots and pairs up with a WLC 
running a permanent count license. For existing WLCs having a permanent count license, the 
Active/Standby decision can be made based on manual configuration.

AP SSO is supported on 5500/7500/8500 and WiSM-2 WLCs. Release 7.3 only supports AP SSO that 
will ensure that the AP sessions are intact after switchover. 

Client SSO is supported on 5500/7500/8500 and WiSM2 WLCs from release 7.5 onwards. For more 
information see