The new Cisco AIR-CT3504 wireless controller support High Availability with SSO (Stateful SwitchOver). In this setup one WLC acts as primary unit, the other as secondary unit (so-called Active/Hot Standby). The wireless controllers have a dedicated redundancy port which must be connected with a standard Cat.6 patch cord.
First the primary unit must configured with a management, redundancy-management and its peer-redundancy-management (i.e. the second WLC) IP address.
Then the primary unit must be configured as primary and the redundancy mode must be set to sso. Note: This will reboot the wireless controller.
The next step is to setup the secondary wireless controller with a management, redundancy-management and its peer-redundancy-management (this time the primary WLC) IP address.
Similar to the primary unit the secondary unit must be configured as secondary and the redundancy mode must be set to sso. Note: This will reboot the wireless controller.
After a restart the wireless controllers will look for each others peer and sync the configuration, Access Point license count, etc. The status of can be verified with:
On the second wireless controller the status should be verified as well:
The configuration should be verified by powering the primary unit off. The secondary unit should recognize that the primary unit failed and should do a so-called WLC switch over as shown below:
Note: the CLI prompt changed from (Cisco Controller-Standby) into (Cisco Controller) after a successful switch over.