WLC 9800 Wireless Clients roam back and force

[marvin9876]

Hello Wireless community

WLC and AP Configuration:

• WLC: CL-9800 running version 17.12.3 with ASPS and SMUs applied.
• APs: Cisco 9105 in FlexConnect mode.
• SSID: Single SSID configured with WPA3 FT + 802.1X.
• Data Rates: Low data rates are disabled for both 2.4 GHz and 5 GHz. Clients use 802.11ax.

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Topology:

• Floor Layout:
  • AP A: Centrally located.
  • APs B and C: To the left and right of AP A.
  • APs D and E: At the far edges of the floor.
  • Layout: D - B - A - C - E.

• Site Tag Design:
  • All APs are within the same Site-Tag and also got same Policy and RF Tag applied

• Clients:
  • All Windows 11 Notebooks with Intel(R) Wi-Fi 6 AX201 160MHz adapter 

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Issue:

1. Client Roaming Behavior:

   • Clients positioned near AP A frequently roam between AP A (2.4 GHz) and AP B (5 GHz) every 5–10 minutes.
   • When roaming to AP B (5 GHz) which is further away:
     • SNR, RSSI, and data rates degrade.
     • Clients experience packet loss and connection drops.

2. AP A 5 GHz Slot Not Used:

   • Despite being the optimal choice, clients do not connect to AP A (5 GHz).

3. Neighbor List Anomaly:

   • 2.4 GHz Neighbor List: APs B, A, and C see each other.
   • 5 GHz Neighbor List:
     • APs B and C see each other.
     • AP A is missing from all 5 GHz neighbor lists (isolated).
     • AP D sees AP C, and AP E sees AP B.

4. Channel Utilization:

   • Always below 50% on both 2.4 GHz and 5 GHz.
   • No channel changes observed on the APs.

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Troubleshooting Steps Taken:

1. WLC Debug Analyzer:

   • Shows normal roaming events, no anomalies detected.

2. Power Adjustments:

   • Reduced Min Power Level Assignment for 2.4 GHz to -10 dBm.
   • Adjusted Power Control Threshold from -65 dBm to -70 dBm.

3. Band Select:

   • Activated to encourage clients to prefer 5 GHz.

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Questions:

1. Why are clients roaming to AP B (5 GHz) instead of staying connected to AP A (5 GHz), which has better signal quality?
2. Why is AP A (5 GHz) missing from the 5 GHz Neighbor List for other APs?
3. Are there any additional steps or configurations we should apply to resolve this roaming issue?

Attached are my WLAN advanced configuration for .11v and .11k

Spoiler

[Leo Laohoo]

Let's start with the basic: 

1.  Reboot the APs.  

2.  Disable 802.11k, v, r.

3.  Go back to WPA2. 

4.  Finally, disable 802.11ax. 

What is the wireless NIC of this client and the wireless NIC driver?

[marvin9876]

Will test that.

NIC is Intel(R) Wi-Fi 6 AX201 160MHz adapter with latest driver 

[Karsten Iwen]

The latest driver from Windows or the latest driver from the Intel website? This can make a huge difference.

[Leo Laohoo]

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@marvin9876 wrote:
NIC is Intel(R) Wi-Fi 6 AX201 160MHz adapter with latest driver 

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What is the wireless NIC driver? 

If these are Intel-based NICs, there is an option to disable 802.11ax in the NICs themselves and only allow 802.11ac (and below).  Choose 802.11ac.

[MHM Cisco World]

what is mode of FT you use?

MHM

[marvin9876]

802.11r over the air

[MHM Cisco World]

Try use adaptive mode instead 

MHM

[MHM Cisco World]

Did you use adaptive mode ?

Can I see 

Show wireless client mac <> mobility history <<- share this 

MHM

[Karsten Iwen]

One more question needs to be answered: Is AP A broadcasting on 5GHz at all? Are other clients connecting to AP A on 5 GHz?

[marvin9876]

All WLC metrics indicate that AP A is broadcasting on the 5 GHz channel 112, but clients only connect to it on 2.4 GHz. It had 5 clients on 5 GHz until 12/16/24 at 14:39, and then, without any apparent reason, they roamed away from it. Client debug traces and the wireless analyzer show normal roaming at that time, with no channel changes or other events whatsoever.

[zhenningx]

Try not using channel 112 and other DFS channels. Try to use following channels:

• UNII-1/Lower Band (5.150 to 5.250 GHz) Non-overlapping channels 36, 40, 44, 48
• UNII-2/Middle Band (5.250 to 5.350 GHz) Non-overlapping channels 52, 56, 60, 64
• UNII-3/Upper Band (5.725 to 5.825 GHz) on-overlapping channels 149, 153, 157, 161, 165

[Flavio Miranda]

@marvin9876 

• Power Adjustments:

  • Reduced Min Power Level Assignment for 2.4 GHz to -10 dBm.
  • Adjusted Power Control Threshold from -65 dBm to -70 dBm.

• Band Select:

  • Activated to encourage clients to prefer 5 GHz

 Take care with this feature. Check the other parameters also(link below). -65 to -70 means strong signal and depending on your coverare, you can create a problem.

With Band Select you are refusing clients to connect in 2.4 (how many connect attempt are you refusing). If client can not connect in 2.4Ghz and they dont meet the requirement of -65 dBm to connect in 5.Ghz, what they will do?  They will look around until the can connect to some AP.

 To play with feature like Band Select, Optimized Roaming, etc, you need to make sure your coverage is perfect.

https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/config-guide/b_wl_16_10_cg/802-11-parameters-and-band-selection.html

[marvin9876]

In the building there where three APs where clients connected to them showed this behaviour. All of them where isolated in 5GHz according to neighbour list. After delecting all config from the APs and rebooting they now participate in NDP an are seen in neighbour lists. Clients now connect to them on 5GHz and dont roam away (since yesterday). I still dont understand what triggered this behaviour can someone help me out?

[Leo Laohoo]

After rebooting the APs, everything is normal? 

Good.  Because that is going to be the new future to keep the wireless network "stable":  Daily reboot of the APs.