This article describes the behavior that radio 2 (5GHz) of an AP has when it is enabled and configured to use a channel from the UNII-2, UNII-3 and UNII-3extended.

When an 11a radio is enabled in a regulatory domain that requires DFS, it does not transmit anything for 60 seconds. This is called the initial channel check.

A. If no radar is detected during the initial channel check, then the radio's transmitter is enabled at the end of 60 seconds.

B. If the radar is detected during the 60 second initial channel check, it does the following:

1. The AP sends a syslog to the wireless controller indicating that radar has been detected.


2. The AP reports a 'radar detected' status to the wireless controller for this AP.


3. The AP sends a notification to clients that it has detected radar on the current channel.


4. The AP ceases/does not start transmitting on the current channel.


5. The AP starts a 30 minute timer, called the quiet period timer.


6. The AP continues monitoring the current channel for radar.