Dynamic Frequency Selection channels

In many countries, regulatory requirements may limit the number of 5 GHz channels available or restrict their usage because the spectrum is shared with other technologies and services. For example, in the US, sixteen of the twenty-five 5 GHz channels are used by military, weather radar, and satellite communications. Wi-Fi networks operating in those bands are required to employ a radar detection and avoidance capability known as Dynamic Frequency Selection (DFS).

Using DFS, supported FortiExtenders automatically scan for and adjust the frequency of a radio if a radar event is detected. This greatly expands the number of channels available for use, improving performance.

DFS channels are enabled on FEV21xF and FBS10F models, but access is dependent on regional regulations. For example, in the CE region, regulations forbid FEV models from using DFS models when operating in AP mode. They can only use DFS 100-140 channels when operating in client mode.

Note the following behavior when selecting channels:

• You cannot select a fixed DFS channel and must select at least one non-DFS channel. This is to prevent FortiExtender from spending 60-600 seconds running a Channel Availability Check (CAC) to check for signals on that channel.
• To ensure that Wi-Fi on FEV21xF devices is available as quickly as possible, DFS channels are skipped during the automatic initial channel selection on the 5GHz Wi-Fi radio.

The following table summarizes the conditions under which DFS channel selections are available for each FortiExtender model:

Scenario	DFS channel selection permission
	FEV21xF	FBS10F
Fixed channel	Deny	Deny
Initial channel selection once the radio is up	Deny	Allow
Running time channel selection	Allow	Allow

In FEV-21xF models: Channels 132/136 can only work in 20/40MHz. Channels 140/165 can only work in 20MHz. Channel 144 is not available. In FEV-21xF-AM: Channels 132/136/140/144 can work in 20/40/80Mhz. Channel 165 can only work in 20MHz.

To configure DFS channels on a standalone FortiExtender - GUI:

1. From the FortiExtender GUI, go to WiFi > Radio Profiles and create a new or edit an existing profile.

   

2. Make your channel selections.

3. When you are finished, click Save.

To configure DFS channels on a standalone FortiExtender - CLI:

config wifi
  config radio-profole
    edit <profile>
    set channel <choose from DFS channel list>
  next
end