topic Re: Cisco 9800 5GHz disabled low data rates with Clients in Wireless

Cisco 9800 5GHz disabled low data rates with Clients

Gehrig_W — Wed, 14 May 2025 09:14:25 GMT

Hello Cisco WLAN experts,

I have followed Best Practices on 9800-WLC and disabled 5 GHz Low Data Rates 6 and 9 Mbps.

Configuration > Radio Configurations > Network > 5 Ghz Band

To my surprise I can still see WLAN Clients that operate at these speeds and are pingable.

Client MAC Address : 000e.8e5e.cde3
Client MAC Type : Universally Administered Address

AP Name: KFR-AP75
AP slot : 1
Client State : Associated
Policy Profile : WLANUKW
Flex Profile : N/A
Wireless LAN Id: 7
WLAN Profile Name: WLANUKW
Wireless LAN Network Name (SSID): WLANUKW
BSSID : 8c1e.80a0.beec
Connected For : 5669 seconds
Protocol : 802.11ac
Channel : 108
Client IIF-ID : 0xa0001223
Association Id : 3
Authentication Algorithm : Open System
Idle state timeout : N/A
Re-Authentication Timeout : 86400 sec (Remaining time: 79055 sec)
Session Warning Time : Timer not running
Input Policy Name : None
Input Policy State : None
Input Policy Source : None
Output Policy Name : None
Output Policy State : None
Output Policy Source : None
WMM Support : Enabled
U-APSD Support : Disabled
Fastlane Support : Disabled
Client Active State : Active
Power Save : OFF
Current Rate : 6.0
Supported Rates : 12.0,18.0,24.0,36.0,48.0,54.0

Client Statistics:
Number of Bytes Received from Client : 191195
Number of Bytes Sent to Client : 166452
Number of Packets Received from Client : 2376
Number of Packets Sent to Client : 673
Number of Policy Errors : 0
Radio Signal Strength Indicator : -65 dBm
Signal to Noise Ratio : 34 dB

Is it possible that disabled data rates within 802.11a do not have an effect on WLAN client operating with 802.11ac instead ?

Do You have an explanation for this ?

Please check and come back with information to improve my knowledge.

Thank You in advance

Greetings from Frankonia

Wini

Re: Cisco 9800 5GHz disabled low data rates with Clients

Scott Fella — Wed, 14 May 2025 14:12:37 GMT

That setting is your global setting, this can be overridden if you define an "RF Profile" and have assigned that profile in to an "RF Tag Name". So take a look at what you have set. You can either set it as global which you have configured, or you can use on of the rf/radio profiles that are there. You can add your own and change the data rates on them also. Gives you an opportunity to have different sites to use different profiles if you need.

Re: Cisco 9800 5GHz disabled low data rates with Clients

Gehrig_W — Fri, 16 May 2025 06:37:43 GMT

Hello Scott,

thank You very much for Your explanation of differences between global and individual settings uisng RF-Profiles.

I use RF-Profiles already in this huge university hospital to differentiate between buildings with an elder WLAN setup where APs were placed only in floors and refreshed buildings, where we put additional APs also in patient rooms.

In this case the following RF-Profile comes into play, where also the lower data rates are disabled in 5-GHz:

I'm still not quite sure, whether this "Best practice"-advice is really a good idea to use in our hospital.

We often receive complaints about poor WLAN-availability in patient rooms for our mobile devices that are used to document patient data and control vital parameters like blood pressure an so on. Would it not be better to allow the lower speeds to guarantee even a bad connection over 5-GHz through a wall or several people standing around the mobile device like doctors ands nurses, when they enter the patient rooms with a mobile wheel-chair-PC ?

Also because I can see mobile devices operating at speeds of 6 Mbps in 802.11ac that are disabled officially ?!?

It this a bug or a feauture of 802.11ac ?

Kind regards

Wini

Re: Cisco 9800 5GHz disabled low data rates with Clients

Scott Fella — Fri, 16 May 2025 14:49:26 GMT

Okay... since you also work in healthcare, listen to the complaints. "poor WLAN-availability in patient rooms". How dense are your wireless? When you go on-site to troubleshoot these issue, are you getting information from the staff on where wireless is not good vs good? That can tell you if maybe your ap locations are not ideal. Meaning, areas that have poor wireless, do not have access point and or ap's in the adjacent room do not provide adequate signal due to attenuation/interference. Don't chase the data rate until you figure out if the areas of complaint is just due to poor ap locations or sticky clients. You need to go onsite to be honest and work with those that have issue so you have a better understanding of the complaint.

Re: Cisco 9800 5GHz disabled low data rates with Clients

Scott Fella — Fri, 16 May 2025 14:57:00 GMT

Keep in mind that there is a radio section for the other protocols. I would not make changes unless you know that you have enough coverage in all area that users have complaints.

Re: Cisco 9800 5GHz disabled low data rates with Clients

Saikat Nandy — Sat, 17 May 2025 01:50:11 GMT

Please note that 'Connection Speed' and 'data rate' are 2 independent factors although 'Connection Speed' is largely dependent on 'data rate'.
The data rate configured Globally or inside the RF Profile defines which data rate AP should use to transmit and receive all the wireless frame. However the 'connection speed' gets derived from multiple inputs, largely from date rate used for communication, RSSI/SNR, MCS rate used for communication.
If you really want to ensure that there is no communication happening on 6 & 9 Mbps, you need to take OTA capture and validate the data rate. Also to note that you might end up seeing some 'funky' devices are sending traffic using the disabled data rates because that's the data rate those devices are using/initiating for the talk. From the AP perspective it's kind of thing - conservative in what you transmit but be liberal in what you receive.
Coming back to your question if enabling lower data rate will give you a better coverage even in bad shape - I really don't think it's a good idea in anyway, especially in an healthcare environment. You are not helping an endpoint connecting over 5Ghz using -70dBm RSSI. It just means that the devices is 'just' connected but won't be of that use. We always suggest healthcare should not be a sub-optimal network, rather always need an optimal network. There are hospital which has disabled all the lower data rates till 18, made 24 as Mandatory and rest above as supported. But to achieve something like this, you need enough APs.
My suggestion would be to get in touch with a site survey team first - they know how a hospital wifi should be. First they will feed in all the required input and tell you if the total AP count is enough or you need more. Accordingly, you might need to add more APs and then work on the config. But to re-iterate again, enabling lower data rates just for the sake of wifi, in a healthcare deployment is absolute no-go.

Re: Cisco 9800 5GHz disabled low data rates with Clients

Gehrig_W — Mon, 19 May 2025 05:58:41 GMT

Hello Scott and Saicat,

thank You very much for Your explanations.

I was not aware of the radio section for other protocols that can be found under

Configuration -> Radio Configurtions -> High Throughput

I only looked at

Configuration -> Radio Configuration -> Network

But still I haven'T found an explanation for Clients running at a disabled speed:

Current Rate : 6.0
Supported Rates : 12.0,18.0,24.0,36.0,48.0,54.0

Is this really possible ?

Kind regards

Wini

Re: Cisco 9800 5GHz disabled low data rates with Clients

Leo Laohoo — Mon, 19 May 2025 07:25:29 GMT

What firmware is the WLC on?

I think this is a bug with the WLC's GUI.