Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface dot11radio {0 | 1 slot / port }
Enter interface configuration mode for the radio interface.
The 2.4-GHz radio and the 802.11n 2.4-GHz is radio 0.
The 5-GHz radio and the 802.11n 5-GHz is radio 1.
Step 3
channel
{frequency | least-congested | width [20 | 40-above | 40-below] | dfs}
Set the default channel for the wireless device radio. To search for the least-congested channel on startup, enter least-congested.
Use the width option to specify a bandwidth to use. This option is available on all 802.11n APs, but only for the d1 (5 GHz) radio. It has three settings: 20, 40-above, and 40-below. Choosing 20 sets the channel width to 20 MHz. Choosing 40-above sets the channel width to 40 Mhz with the extension channel above the control channel. Choosing 40-below sets the channel width to 40 MHz with the extension channel below the control channel.
Note The channel command is disabled for 5-GHz radios that comply with European Union regulations on dynamic frequency selection (DFS). See the “Setting the 802.11n Guard Interval” section for more information.
Step 4
end
Return to privileged EXEC mode.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
https://www.cisco.com/c/en/us/td/docs/wireless/access_point/15-3-3/configuration/guide/cg15-3-3/cg15-3-3-chap6-radio.html#15202