Cisco Catalyst 9800 Series Wireless Controller Software Configuration Guide, Cisco IOS XE 26.1.x

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Cisco Catalyst 9800 Series Wireless Controller Software Configuration Guide, Cisco IOS XE 26.1.x

Zero wait dynamic frequency selection

Updated: April 10, 2026

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Describes a wireless feature that eliminates service outages when access points move to DFS channels by pre-monitoring potential channels.

Zero wait dynamic frequency selection is a wireless feature that

  • eliminates the 60-second to 10-minute service outage when access points move to Dynamic Frequency Selection (DFS) channels

  • enables access points to pre-monitor and perform Channel Availability Check (CAC) on potential DFS channels before switching, and

  • is supported only in U.S. and Europe regulatory domains.

Channel availability check process

APs monitor and perform Channel Availability Check (CAC) on a potential channel for 60 seconds when AP moves to Dynamic Frequency Selection (DFS) channels. Further, the AP ensures that there is no radar operating in the same frequency range before advertising beacons and serving clients. When the AP moves to a DFS, there is a service outage for a minute. This outage can be higher and extend up to 10 minutes.

Configure zero wait dynamic frequency selection globally

Zero Wait DFS allows access points to change to Dynamic Frequency Selection channels without experiencing service interruption. This configuration applies globally to all access points in your network.

Follow these steps to configure Zero Wait Dynamic Frequency Selection globally:

Procedure

1.

Choose Configuration > Radio Configurations > RRM.
2.

In the RRM page, click the 5 GHz Band tab.
3.

Click the DCA tab.
4.

Select the Zero Wait DFS check box to allow the AP to change to DFS without a service outage.
5.

Click Apply.

Zero Wait Dynamic Frequency Selection is now enabled globally for all access points in your network.

Configure zero wait dynamic frequency selection globally (CLI)

Enable Zero Wait Dynamic Frequency Selection to improve channel availability and reduce channel change delays on 5-GHz radios.
Zero Wait Dynamic Frequency Selection optimizes radar detection and channel switching processes by allowing access points to pre-scan DFS channels. This reduces service interruption when radar is detected on the current operating channel.

Procedure

1.

Enter global configuration mode.

Example:

Device# configure terminal
2.

Enable the Zero Wait Dynamic Frequency Selection feature.

Example:

Device(config)# ap dot11 5ghz rrm channel zero-wait-dfs

By default, the feature is disabled.

Use the no form of this command to disable the feature.

Note
The Zero Wait Dynamic Frequency Selection feature is only available on a 5-GHz radio.
Zero Wait Dynamic Frequency Selection is now enabled globally, allowing 5-GHz radios to perform background DFS scanning for improved channel switching performance.

Enable zero wait dynamic frequency selection on a RF profile (GUI)

Enable Zero Wait Dynamic Frequency Selection to allow the AP to change to DFS without a service outage.

Before you begin

Follow these steps to enable Zero Wait Dynamic Frequency Selection on a RF Profile:

Procedure

1.

Choose Configuration > Tags & Profiles > RF/Radio.
2.

In the RF tab, click Add.

The Add RF Profile page is displayed.
3.

Enter the name for the RF profile.
4.

From the Radio Band drop-down, choose the 5 GHz band.
5.

Click the RRM tab.
6.

Click the DCA tab.
7.

Select the Zero Wait DFS check box to allow the AP to change to DFS without a service outage.
8.

Click Apply to Device.

Enable zero wait dynamic frequency selection on a RF profile (CLI)

Enable the Zero Wait Dynamic Frequency Selection feature to reduce DFS channel availability delays on 5 GHz RF profiles.
Zero Wait DFS allows access points to immediately use DFS channels by pre-scanning them, eliminating the typical 60-second wait time required for DFS channel availability checks. This configuration is applied at the RF profile level to improve wireless performance and channel utilization.

Procedure

1.

Enter global configuration mode.

Example:

Device# configure terminal
2.

Configure a radio frequency (RF) profile and enter RF profile configuration mode.

Example:

Device(config)# ap dot11 5ghz rf-profile profile-name

Example:

Device(config)# ap dot11 5ghz rf-profile test-dfs
3.

Enable the Zero Wait Dynamic Frequency Selection feature for the RF profile.

Example:

Device(config-rf-profile)# channel zero-wait-dfs

Use the no form of this command to disable the feature.
Zero Wait DFS is now enabled on the RF profile, allowing access points using this profile to immediately utilize DFS channels without the standard waiting period.

Zero wait dynamic frequency selection configuration verification

Use the following commands to verify the DFS configuration.

To display the Zero Wait DFS configuration on an AP, use the following command:

Device# show ap name ap1 config slot 1 | inc Zero

  Zero Wait DFS Parameters
    Zero Wait DFS Capable                       : Yes
    CAC Domain                                  : None

To display the global configuration related to the Zero Wait Dynamic Frequency Selection feature, use the following command:

Device# show ap dot11 5ghz channel | inc Zero

  Zero Wait DFS Parameters
    Zero Wait DFS Capable                       : Yes
    CAC Domain                                  : None

To display the RF profile configuration related to the Zero Wait Dynamic Frequency Selection feature, use the following command:

Device# show ap rf-profile name test detail | sec Zero

Description                       : 
RF Profile Name                   : test
Band                              : 5 GHz
Transmit Power Threshold v1       : -70 dBm
Min Transmit Power                : -10 dBm
Max Transmit Power                : 30 dBm
.
.
.
Guard Interval                    : default
Zero Wait DFS                     : Enabled