I can’t seem to get capsman to accept a 2.4Ghz 40Mhz turbo channel
2412 @ 40 Turbo extensino Ce = ‘no supported channel’
I’ve run up through all the channels and switched Ce to eC. Removed extension channel config. Just can’t figure out when I’m supposed to put in here to get the 40Mhz extension working.
Why would you use 40Mhz Channel on the over crowded 2.4Ghz Band that has only 3 non-overlapping channels? No way… 
Besides that, i do not think that there is ANY client on the 2.4Ghz band that supports a 40Mhz Channel width…
And, if i remember right, it is not even supported…
So, you will set it to 20Mhz…
Well, @zacharias, there are many clients that support 40MHz channels on 2.4GHz. And not everybody lives in city centres where everybody (including their dogs) run at least one AP on 2.4 GHz. There are also suburban/rural users where house to house distance (counting also wall attenuation) actually exceeds typical wifi range. In addition: you’re living in Europe where (unlike in the US) list of allowed channels include channels 12 and 13 … giving 4 almost non-overlapping channels (1, 5, 9, 13 … check charts in wikipedia article … they don’t overlap when using 802.11g/n that use OFDM, they do overlap in 802.11b)… so you can stop spreading that incomplete information about only 3 non-overlaping channels (which is true for US).
To @syadnom’s question: it works if set like this:
/caps-man channel
add band=2ghz-g/n control-channel-width=20mhz extension-channel=XX <the rest of settings>
If you explicitly want to use channel 1 as control channel, then add frequency=2412 to the rest of settings. Setting extension-channel=XX allows ROS to automatically select whether it’ll use Ce or eC arrangement, but of course you can fix that as well - using channel 1 as control channel only allows arrangement Ce though.
To @syadnom’s question: it works if set like this:
Code: Select all
/caps-man channel
add band=2ghz-g/n control-channel-width=20mhz extension-channel=XX
Nothing guarantees that the client will connect using 40Mhz channel width… but nice try @mkx…
It can be either 20Mhz or 2*20Mhz(40Mhz)… At least with the line of code you provided… So i think you should mention that…
Also the OPs question was about 40Mhz Turbo, wihich in terms of configuration is different from the 20/40XX that you proposed…
And Turbo Mode must be hardware supported as well if i remember correct..anyways…
The 2.4 Ghz Band is overcrowded for the whole world… No problem if it is not for you, use it as much as you like 
Numerours Articles around the Internet explaining why we moved on from the 2.4Ghz Band, you might as well take a look…
Excuse me that i said 3 non overlapping channels and not 4, i guess it is a huge difference…
My bad for not noticing the “turbo 40MHz”, I (perhaps wrongly) assumed OP wanted to use 20+20 mode (which is usual these days) and had issues configuring that. And I assumed OP used that particular wording for no special reason.
Re use of 2.4GHz: the problem about many articles (not just about networking) is that they draw conclusions based on some (statustical) pattern. If the pattern was different, conclusions might be entirely different as well. So it’s wrong to blindly follow conclusions without knowing if the underlying pattern applies to one’s use case.
I fully agree that 2.4GHz spectrum is overcrowded for majority of users … because majority of users are concentrated in small geographic areas.[*] Meaning that rule of using one of non-overlaping channels in 20MHz configuration is pretty valid for majority of users. But as I illustrated in my previous post, blindly suggesting channel numbers to be used without considering geographic area is wrong (we’re wasting 1/4 of channels in Europe if we follow recommendations for US). At the same time minority of users can safely use 40MHz channels and telling someone that such use is wrong without considering possibility that 2.4GHz is not overcrowded for that particular user is wrong again.
[*] The largest number of 2.4GHz BSSIDs, present in one spot and with signal levels which would allow decent experience if there weren’t the rest to interfere, was 369. You can imagine the level of performance of any of them 
Surely in that case using 20+20 would gain exactly zero.
@mkx personally i will never use 40Mhz channel width to any CapsMan setup in the 2.4Ghz Band…
20+20 was what I was after. I found that I can just select Ce/eC/XX and a 20Mhz channel and that enables the auto 20/40 mode.
and that enables the auto 20/40 mode.
Correct…
Well, what you personally do is your business and nobody (except regulator’s inspectors) can force you to do otherwise. However, when you try to help other users, you can only nicely suggest they set things differently than they planned (and explain why your suggestion is so much better) … at the same time you should show them how to reach their initial goal. It’s up to them to decide whether they still want to pursuit their original or rather to follow your advice.
But then, why do I even bother explaining that to you … you already prooved that you don’t take counter-suggestions easily.
@mkx on your first post i see no explanation as to why use of 40Mhz Channel width is good or not… You just gave the configuration and thats it…
At least i explained why i do think 40Mhz is not a good Choice for this Band, and ofcorse the OP can follow my suggestion or not…
Also you missed the Turbo mode and more important you didn’t explain that 20/40Ce or eC or XX does not force the use of 40Mhz Channel width…
So where are your suggestions here ?
The fact that a wide channel on 2.4Ghz Band can cause many problems and lead to extremelly poor performance sorry but it is not some kind of personal opinion… And since the OP uses CapsMan it is obvious that there will be a X number of Clients under a Y number of APs which makes more easy the decision to avoid any extention channel on the 2.4Ghz Band…
For the OP, just a quick look here https://www.ekahau.com/blog/2019/04/18/channel-planning-best-practices-for-better-wi-fi/ can help understand some basic principles…
you already prooved that you don’t take counter-suggestions easily.
Ofcorse i do when i see a point behind that…
wtf guys. I asked HOW to do something. Why did this turn into an argument about why something should or shouldn’t be done? Just stop. I have my answer, all is well.
I get better performance using 20/40 than 20.