Force mode 802.11 for station using wpa_supplicant

Ben Greear greearb
Fri Jul 11 02:29:18 PDT 2014

On 07/11/2014 01:51 AM, Vu Hai NGUYEN wrote:
>>>> Hi all,
>>>> I wonder if we can use wpa_supplicant to force mode 802.11 for a station when it connects to an AP.
>>>> For example my AP using hostapd and was set up in 802.11ac VHT80, channel 36.
>>>> Normally all the device support 802.11n can connect to that AP too.
>>>> But because the wifi module in my station is the same as my AP and they are all support 802.11ac so
>>>> if I set up the channel 36 for my station it connect automatically with my AP in mode 802.11ac VHT80.
>>>> Is there any way that I can force my station to connect to my AP in mode 802.11n HT20 or HT40?
>>>> I don't see any parameter in the configuration file of wpa_supplicant that allow me to do this.
>>> If I set the parameter "disable_vht=1" in the configuration file of wpa_supplicant, my station can connect in
>>> mode 802.11nHT40  with my AP (set up in 802.11ac VHT80).
>>> Then I add "disable_ht40=1", but my Station still connects to my AP in mode 802.11n HT40 (I verify this
>>> by checking bandwidth and rate report from command "iw").
>>> I added "disabled_ht20" but this did not create any effect too. Any one gets the same issue like me?
>>> Here is an example of my configuration file for wpa_supp:
>> Try listing a set of rates that are acceptable, and only put in 802.11b rates?
> Thank you for your response, did you mean this parameter  in the config file of wpa?
> # ht_mcs:  Configure allowed MCS rates.
> #  Parsed as an array of bytes, in base-16 (ascii-hex)
> # ht_mcs=""                                   // Use all available (default)
> # ht_mcs="0xff 00 00 00 00 00 00 00 00 00 "   // Use MCS 0-7 only
> # ht_mcs="0xff ff 00 00 00 00 00 00 00 00 "   // Use MCS 0-15 only
> But both 802.11nHT40 and HT20 can be config from MCS0 to 23 (I have 3 streams)
> so what can it makes the different?
> 802.11b work in 2.4Ghz band while my AP is set up in 802.11ac VHT80 I guess this is
> not compatible, right?

Sorry, I thought you meant you wanted 11b, not 11n.

That disable_ht40=1 should force it back to HT20 /n when combined with
the disable_vht=1.  What driver/NIC are you using?

I have only tested this sort of thing well on ath9k, and that obviously doesn't
do /AC anyway.


Ben Greear <greearb at>
Candela Technologies Inc

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