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Community Member

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz simultaneously?

I have a 5508 WLC and 6 3500 LAP's at the main office, 2 at another office and 2 at yet another office.

I noticed that even when I specify 5.2 GHz on my wireless adapter (Intel Centrino Advanced-N 6230) It says the data rate is 144 Mbps.  I want to try to get 300 Mbps out of it and I believe I have to enable 40 MHz wide channels in the 5.2 GHz range.  Well I don't want to cause any network disruption to currently associated clients.  Is this something I can do?  What if a client adapter does not support 40 MHz wide channels?  Can I keep 2.4 GHz at 20 MHz wide channels and then they would just connect to the 2.4 GHz freqency range?

Where would I go to change the channel width for 5.2 GHz only?  Is it set globally or do I set it for each AP?  I did see a radio button for 20 MHz or 40 MHz in this location: Wireless > 802.11a/n > RRM > DCA  

Is this where I would make the settings change?  If I do this would it bump clients off the network briefly?  Do all 802.11n adapters with 5.2 GHz radios support 40 MHz channels?

Looking at the channel usage with a program called inSSIDer 3, there isn't anything going on in the 5 GHz band except for us.

Thanks for the help.  Just looking to get the best possible network throughput as I've had some SMB based applications respond slowly or poorly when on wireless connections... even when the OS reports 144 Mbps.

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Hall of Fame Super Silver

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Here is a screen shot... mine will look different as I'm using a beta code:

Thanks,

Scott

Help out other by using the rating system and marking answered questions as "Answered"

-Scott
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18 REPLIES
Hall of Fame Super Silver

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Yes you do have to enable 40mhz... but you have to disable the 802.11a band before you can make the change.  So it will interrupt the wireless.

Thanks,

Scott

Help out other by using the rating system and marking answered questions as "Answered"

-Scott
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Hall of Fame Super Silver

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Here is a screen shot... mine will look different as I'm using a beta code:

Thanks,

Scott

Help out other by using the rating system and marking answered questions as "Answered"

-Scott
*** Please rate helpful posts ***
Community Member

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Ok thanks, it looks like I was at the right place.  I'll setup a maint. window Friday morning to make this change.  Looking forward to better throughput.

We have a lot of 802.11n clients, but there are a few 802.11g only clients as well.  I would imagine they would connect to the 2.4 GHz band where 40 MHz channels would not apply.

Nice beta code.  I see you have 80 MHz as an option and also 802.11ac.  That's bleeding edge!

Community Member

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Ok I can do this before work hours on Friday morning.

Where do I make this change?  Was I correct with this path? 

Wireless > 802.11a/n > RRM > DCA

Are there clients that would have a problem with 40 MHz wide channels at 5.2 GHz?  If so, would they still be able to connect to 20 MHz wide channels at 2.4 GHz?

Also what is Client Band Select?  Is there a way to inform the wireless client to connect to 5.2 GHz, 40 MHz wide channels if it supports it?

Hall of Fame Super Silver

Re: Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4

Are there clients that would have a problem with 40 MHz wide channels at 5.2 GHz?  If so, would they still be able to connect to 20 MHz wide channels at 2.4 GHz?

Yes

Also what is Client Band Select?  Is there a way to inform the wireless client to connect to 5.2 GHz, 40 MHz wide channels if it supports it?Thanks,

No... Band select trys to trick the client to connecting to the 5ghz over the 2.4ghz but its the client that needs to negotiate if it can do 20mhz or 40mhz (modulation).  Band select only works if your radio policy is set to all.


Scott

Help out other by using the rating system and marking answered questions as "Answered"

-Scott
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Community Member

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Thanks for the info.  Our radio policy on the SSID I wish to alter is set to all.

Previously to force 802.11a or n at 5.2 GHz, I would have to set "Prefer 5.2 GHz" on the client's machines device driver properties for thier network adapter.  If I can get the clients to auto-negotiate, that would be much better than manually touching every client machine.

I think I will try to enable band select and also set the channel width to 40 MHz.  I'll then grab an older laptop with only a 54g card in it, and then also test with my laptop which as the Centrino N card in it.  I do know we don't have any old 802.11b stuff.  It's g or n  (no 802.11ac here yet either).

Thanks for your help.  Trying to get the most out of our network without any adverse side effects.

Hall of Fame Super Silver

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

You don't want to make a change to the client device or else they will have issue when they go home or use the wireless elsewhere.  The device will make the decision and if it chooses 2.4, then allow it to as some devices will still connect to the 2.4ghz than the 5ghz.

Thanks,

Scott

Help out other by using the rating system and marking answered questions as "Answered"

-Scott
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Community Member

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Ok so the best option would be...

On client:
802.11n channel width for band 2.4 : AUTO

802.11n channel width for band 5.2 : AUTO

802.11n Mode: ENABLED
Fat Channel Intolerant : DISABLED

Preferred Band: 1. NO PREFRENCE

Then on the wireless controler, for the SSID in question, Enable band select.

Then go to

Wireless > 802.11a/n > RRM > DCA and choose 40 MHz, apply.

Wait a brief moment while the network goes down and then comes back up.

Test speeds, and then put a fork in it, your done.

Hall of Fame Super Silver

Re: Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4

All I can say is to leave the client setting default. Only need to change the setting in the WLC which you already have that info.

Sent from Cisco Technical Support iPad App

-Scott
*** Please rate helpful posts ***
Community Member

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Fair enough.

One last question... When I go to Monitor > Clients... I see a bunch of clients with 802.11an as the protocol.  When I change the channel width to 40 MHz, will it show 802.11n instead of 802.11an as the protocol?  Or doesn't it matter that it says 802.11an ?

We don't have any 802.11a (only) cards.  We either have 802.11g, or 802.11n cards.

Hall of Fame Super Silver

Re: Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4

It will show up like that... doesn't matter if they connect with n or not.

Sent from Cisco Technical Support iPad App

-Scott
*** Please rate helpful posts ***
VIP Purple

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Hi Scott,

What will happen to 5 GHz devices that will only support 20MHz bandwidth (like Phones) ? Are they still able to join with this channel bonding setting ?

Rasika

Hall of Fame Super Silver

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Yes, they will still be able to connect.... I would have to know since all my clients would be calling me if their dang phones didn't work:)  Now I did run into issues with the Intel 6200 cards with a v14 firmware.... 40mhz didn't work well until the driver was upgraded.  It almost looked like there was a duplicate ip address on the network as the ping times were slow and then you would loose connectivity for a few seconds.  So the main thing to understand here is that if you have clients that have many consultants and maybe have these cards or important guest users that have these cards, then disable 40mhz.  The issue I see is that you can't support these users and until these cards gets phased out, you might just have to disable 40mhz.  So in my installs now, I make this clear to my clients so they can either enable 40mhz or just use 20mhz.

Thanks,

Scott

Help out other by using the rating system and marking answered questions as "Answered"

-Scott
*** Please rate helpful posts ***
Community Member

Can I choose 40 MHz channels for 5.2 GHz and 20 MHz for 2.4 GHz

Well I made those changes and there doesn't seem to be any issues.  I am seeing 300mbps on my laptop.  Also took out an older model that we have in circulation that supposidly is 802.11n but only has 2.4 GHz radio in it (why IEEE allowed "N" to work on 2.4 GHz is confusing and a rant for another thread).  Those clients work fine as well.

As far as what if a device can't associate to a 40 MHz wide channel?  Well I would have to imagine that it wouldn't 'see' the channel at 5 GHz and it would then scan the 2.4 GHz range and find the regular 20 MHz wide channels.  That's my guess.  I mean if it's tuner only has a reception width of 20 MHz (ie, not wideband) then it wouldn't see the channel so it would continue to scan.  I did read that all modern operating systems automatically scan 5 GHz but then if they don't find anything there they scan 2.4 GHz (unless you override this in the device properties).  This applies to Windows and Mac OS.

My iPhone 5 was able to connect. Had some trouble authenticating, but I did a "forget this network" and re-created it and it got online fine.

I enabled band select, disabled the 802.11a, enabled 40 MHz and the extended UNII-2 channels, 802.11h channel announcement and channel quiet mode, CCX Location Measurement and then re-enabled the 802.11a network.

Not seeing any issues on the Intel or Dell wireless adapters out there so far.

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