Dynamic Frequency Selection

Information About Dynamic Frequency Selection

Dynamic Frequency Selection (DFS) is the process of detecting radar signals and automatically setting the frequency on a DFS-enabled 5.0-GHz (802.11a/h) radio to avoid interference with the radar signals. Radios configured for use in a regulatory domain must not interfere with radar systems.

In normal DFS, when a radar signal is detected on any of the channels in the 40-MHz or 80-MHz bandwidth, the whole channel is blocked. With Flex DFS, if the radar signals are not detected on the secondary channel, the AP is moved to a secondary channel with a reduction in the bandwidth, usually, by half.

Configuring Dynamic Frequency Selection (GUI)

Procedure

Step 1

Choose Configuration > Wireless > Mesh > Profiles

Step 2

Choose a profile.

Step 3

In General tab, check the Full sector DFS status check box.

Step 4

Click Update & Apply to Device.

Configuring Dynamic Frequency Selection

Follow the procedure given below to configure DFS:

Before you begin

  • The corresponding AP must be on one of the DFS channels.

  • Shut down the radio before applying the configuration changes.

Procedure

  Command or Action Purpose

Step 1

configure terminal

Example:

Device# configure terminal

Enters global configuration mode.

Step 2

no ap dot11 5ghz dtpc

Example:

Device(config)# no ap dot11 5ghz dtpc

Disables the 802.11a Dynamic Transmit Power Control (DTPC) setting.

Step 3

ap dot11 5ghz channelswitch mode mode-num

Example:

Device(config)# ap dot11 5ghz channelswitch mode 1

Configures the 802.11h channel switch mode.

Step 4

ap dot11 5ghz power-constraint value

Example:

Device(config)# ap dot11 5ghz power-constraint 12

Configures the 802.11h power-constraint value.

Step 5

ap dot11 5ghz smart-dfs

Example:

Device(config)# ap dot11 5ghz smart-dfs

Configures nonoccupancy time for the radar interference channel.

Verifying DFS

Use the following commands to verify the DFS configuration:

To display the 802.11h configuration, use the following command:

Device# show wireless dot11h

To display the auto-rF information for 802.11h configuration, use the following command:

Device# show ap auto-rf dot11 5ghz

To display the auto-rF information for a Cisco AP, use the following command:

Device# show ap name ap1 auto-rf dot11 5gh