[Nods thoughtfully] Ah, that sounds like a job for Dynamic Frequency Selection, or DFS. Let me explain what it is and how it can help.

DFS stands for Dynamic Frequency Selection. It’s a feature that enables wireless networks to avoid interfering with radar systems that operate in the 5 GHz frequency band. This is crucial because radar systems are critical for things like weather monitoring and national defense.

Precisely. Regulatory agencies like the FCC in the United States and ETSI in Europe require DFS compliance. They have set aside parts of the 5 GHz band for Wi-Fi but still allow radar systems to use it. DFS helps Wi-Fi networks identify channels where radar is operating and switch to other channels to avoid interference.

Great question. In the U.S. and Europe, channels fall within these bands:

• U.S.:

  • U-NII-1: Channels 36, 40, 44, and 48 (No DFS)
  • U-NII-2A (Lower DFS): Channels 52-64 (DFS-enabled)
  • U-NII-2C (Extended DFS): Channels 100-144 (DFS-enabled)
  • U-NII-3: Channels 149-165 (No DFS)

• Europe:

  • U-NII-1: Channels 36, 40, 44, and 48 (No DFS)
  • U-NII-2A (Lower DFS): Channels 52-64 (DFS-enabled)
  • U-NII-2C (Extended DFS): Channels 100-140 (DFS-enabled)

Great question. It works in several steps:

1. Radar Detection: An access point (AP) detects radar signals in the channel it’s using. It analyzes the incoming patterns to determine if they match known radar signatures. If a match is found, the AP stops using that channel.

2. Channel Switch Announcement: Before switching, the AP notifies all connected clients that it’s changing channels. It does this via a Channel Switch Announcement.

3. Channel Selection: The AP then scans other channels to find one that is clear of radar activity.

4. Quiet Period: The AP and its connected clients stop transmitting for a while, usually around 60 seconds, to ensure the new channel is truly free of radar signals.

5. Channel Transition: Once the new channel is confirmed clear, the AP and clients transition to it, and normal communication resumes.

Here’s what we’ll do:

1. Ensure Radar Detection is Enabled: Make sure the APs have DFS detection enabled so they can recognize radar signals and move to safer channels.
2. Channel Reconfiguration: Reconfigure the APs to use non-DFS channels like those in U-NII-1 or U-NII-3, which don’t require DFS and are less likely to be impacted by radar.
3. Monitor and Test: After reconfiguration, monitor the network for stability by checking signal quality and channel performance.

Exactly. This quiet period ensures that Wi-Fi devices aren’t disrupting radar operations.

A few key things:

• Channel Availability Check: Before switching, APs should ensure the new channel is free of radar activity.
• Client Compatibility: Not all devices fully support DFS. If your network includes these devices, they may lose connectivity when switching channels.
• Certification Compliance: APs must comply with regional regulations to avoid fines or penalties.

Exactly. Implementing DFS ensures a peaceful coexistence between Wi-Fi and radar, providing reliable, interference-free connectivity.

Let’s dive into the steps for each system.

Cisco AireOS Configuration

Professor Network: We’ll start with Cisco AireOS, a widely used wireless controller OS, but Keep in mind that slight variations may occur based on the OS version. Also, Cisco already announce that AireOS controllers will be End of Life and End of Support in a few years. You can check Cisco EOL/EOS announcement on their webpage for exact dates.

1. GUI Method:

• Log In: Access the Web GUI with your admin credentials.
• Access RF Profiles: Go to Wireless > RF Profiles.
• Select the RF Profile: Choose the RF profile associated with your APs using the 5 GHz band.
• Disable DFS Channels:
  • Click Edit to modify the profile. Select the RRM tab.
  • Scroll down to DCA Channel List and uncheck the DFS channels (52-64, 100-144).
  • Only keep non-DFS channels like 36, 40, 44, 48, 149, 153, 157, 161, and 165, but the availability of the channels depends on the region.
• Apply Settings: Click Save Configuration to update the APs.

2. CLI Method:

• Access CLI: Use SSH or a console connection to access the controller.
• Remove DFS Channels from RF Profile: Use config rf-profile channel delete #channel-number <profile_name> to modify your RF profile.
• Example:
  • config rf-profile channel delete 52 RF-PROFILE-TEST
• Save Configuration: Apply the changes by typing save config.

3. Verify AP Groups:

Keep in mind that RF-Profile need to be applied to the AP Group, were the targeted APs are added in order for this to take effect.

• GUI – Access AP Groups: Go to WLANs > Advanced > AP Groups.. Select the <ap_group_name> and click on RF-Profile Tab. Check that the previously modified RF Profile is assigned to 802.11a for 5Ghz.
• CLI – Check AP Groups:show wlan apgroups and check the RF Profile section of the output to see that the previously modified RF Profile is assigned to 802.11a for 5Ghz.

Cisco IOS XE Configuration

Professor Network: Now, let’s look at Cisco IOS XE. Here’s how to manage it through both GUI and CLI. We will start with the GUI method, and configure the settings via the RF Profiles, but we can also do it via Global settings, and like in AireOS, RF Profiles are overwriting the global settings.

1. GUI Method:

• Log In: Access the Web GUI using your credentials.
• Navigate to RF Profiles: Go to Configuration > Tags & Profiles > RRM. Select a profile RF_Profile_name and click on the RRM tab.
• Disable DFS Channels:
  • In the RRM tab, go to DCA section.
  • Uncheck DFS channels (52-64, 100-144) and leave only non-DFS channels checked.
• Save Configuration: Click Save configuration icon on the top right of the screen and click OK to confirm.

2. CLI Method:

• Access CLI: Connect via SSH or console.
• Enter Global Configuration Mode: Type configure terminal.
• Select the RF Profile:
  • Configure specific RF Profile: ap dot11 5ghz rf-profile <RF_Profile_name>
• Disable DFS Channels:
  • Type channel remove <channel_number> to disable DFS channels.
  • To add a DFS channel back to the profile channel add <channel_number>, command can be used.
• Save Configuration: Type end and write memory to save the changes.
• Don’t forget to have the RF Profile assigned to the correct RF Tag and that the RF Tag si applied to the AP for which you are trying to change the DFS channel list.

[Smiles] Exactly, Sophie. With these steps, you’ll be able to handle channel assignments for any deployment type effectively. Let’s get the configurations applied and test the network’s stability.