Detecting a Controller Failure
When HA is required, make sure that you design your wireless network to support it properly. Fortunately, Cisco APs and controllers are built with HA in mind, so you have several strategies at your disposal. First, it is important to understand how APs detect a controller failure and what action they take to recover from it.
Once an AP joins a controller, it sends keepalive (also called heartbeat) messages to the controller over the wired network at regular intervals. By default, keepalives are sent every 30 seconds. The controller is expected to answer each keepalive as evidence that it is still alive and working. If a keepalive is not answered, an AP running Software Release 7.0 will escalate the test by sending ...
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