About Wireless Controller Redundancy
In a redundancy architecture, one wireless controller is in the Active state and a second controller is in the Standby state. The Standby controller continuously monitors the health of the Active controller via a redundant port. Both controllers share the same configurations, including the IP address of the management interface.
The Standby or Active state of a controller is based on the redundancy Stock Keeping Unit (SKU), which is a manufacturing ordered unique device identification (UDI). A controller with redundancy SKU UDI is in the Standby state for the first time when it boots and pairs with a controller that runs a permanent count license. For controllers that have permanent count licenses, you can manually configure whether the controller is in the Active state or the Standby state.
In this release, a stateful switchover of access points (AP SSO) is supported. An AP SSO ensures that the AP sessions are intact even after a switchover.
Stateful switchover of clients is not supported. This means that nearly all clients are deauthenticated and forced to re-associate with the new controller in the Active state. The only exceptions to this rule are clients on locally switched WLANs on access points in FlexConnect mode.