Using all of 5.0 ghz channel

Martin Scott · ‎09-26-2012

hello,

I have a 2112 wlc and 6 1142ap's. I noticed that the 2.4ghz channel is filled with lots of networks but the 5.0ghz area is empty. I tried to manually change the channel but it keeps reverting back to 2.4. Any suggesstions?

Yahya Jaber · ‎10-09-2012

what do you mean reverting back to 2.4?

disable b/g/n on the WLC and let it run on a/n

but you have to configure the 802.11n by this document

http://www.cisco.com/en/US/products/ps6366/products_tech_note09186a0080a3443f.shtml

George Stefanick · ‎10-09-2012

Not sure I follow. If 2.4 is full, disable it entirely. Enable 5 ghz only ..

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"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
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Andrew MacTaggart · ‎10-10-2012

My take on this

most places 2.4Ghz will be busy and 5Ghz will not

but depending on your environment and user base and client devices

consider that 2.4 will have a wider coverage

many older i-devices won't connect to a 5Ghz only network

APs can support about 25 device on 5Ghz radio and another 25 on the 2.4Ghz radio

you may have to add more APs to get the same coverage with the dual band

you could have ssid that connects to 5Ghz radio only as well

but what I find, assuming your device wireless radio firmware is upto date is that the device 99% of the time makes the correct choice as far as which band has the biggest bang for your buck.

But I have found that Apple devices seem to store a profile, and won't let go sometimes to the connection settings.

Cheers

Yahya Jaber · ‎10-10-2012

Hi,

just wondering where did you get this info

"APs can support about 25 device on 5Ghz radio and another 25 on the 2.4Ghz radio"

the thing that i know is on 2.4 the number is 24 but on 5GHz i have'nt seen it.

now just to let you know, the connection preference is totally a client issue, nothing can be done on the AP.

and even if you did, you will mess up the way that other clients chose thier prefered AP.

George Stefanick · ‎10-10-2012

Yahya,

Not to comfuse the issue, your comment that 2.4 the number is 24 ? Are you sure about this?

__________________________________________________________________________________________
"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin

"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
___________________________________________________________

Yahya Jaber · ‎10-10-2012

Q. How many clients can associate to the AP?

http://www.cisco.com/en/US/products/hw/wireless/ps430/products_qanda_item09186a008009483e.shtml

the math behind that is

54Mbit / 2 = 27Mbit half Duplex

27 - 3 "overheads" = 24Mbit

24Mbit = 1Mbit for 24 clients "the same calcuation as the Hub"

but if you are having the 300Mbit..i dont know what is the minimum speed to consider the clients on /n, 1Mbit is not reasonable, but i have never read that.

A. The AP has the physical capacity to handle 2048 MAC addresses, but, because the AP is a shared medium and acts as a wireless hub, the performance of each user decreases as the number of users increases on an individual AP. Ideally, not more than 24 clients can associate with the AP because the throughput of the AP is reduced with each client that associates to the AP.

George Stefanick · ‎10-10-2012

I was wondering if your comment was 24 was max and no more than 24 was allowed. Thats were I was going ..

Although 2048 macs are allowed, 802.11-2007 standard says there is a max of 2007 AID. Wonder if cisco plays by that rule or not ..

+5

__________________________________________________________________________________________
"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin

"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
___________________________________________________________

Andrew MacTaggart · ‎10-10-2012

I think somewhere in here

http://www.cwnp.com/certifications/cwdp/

https://supportforums.cisco.com/docs/DOC-20630

but real world

I suppose I assumed a lot. But my understanding is that controllers can manage load between frequency bands and between neighboring Aps

Well we ran online tests for our students and the administration crowded many kids in a small area. The threshold alarm went off in the WCS, and looking at AP statistics 40 + clients were connected. some were on 5Ghz and others on the 2.4 Ghz band. so it looked like load balancing between spectrums, but as we got near 50 performance complaints started to emerge. test issue and so forth. So I might have made the numbers up although I coould have sworn I read it somewhere. specifically because I was worried about the load threshold alarms.

I supose the load threshold doesn't really mean you can't have more then 25 on 5Ghz, but I thought it was a good rule of thumb.

Anyway I thought I was trying to say let the client make the choice and use both bands

George Stefanick · ‎10-10-2012

That threshold is just a number set and can be changed. So take that for what it is ..

A problem I suspect in letting clients pick what band is that not all clients will behave in such a way. Some may get sticky, some may bounce on and off frequency. This is why you can bandselect on the WLC.

CWDP is a good book. Did you read it ? Im actually mentioned in there.. know the authors personally .. Great material.

__________________________________________________________________________________________
"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin

"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
___________________________________________________________

George Stefanick · ‎10-10-2012

Oh and one more item. Load Balance. It uses reason code 17, which again, not all clients will abide by. So load balance really is good in theory but doesnt really work

__________________________________________________________________________________________
"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin

"Satisfaction does not come from knowing the solution, it comes from knowing why." - Rosalind Franklin
___________________________________________________________

Andrew MacTaggart · ‎10-11-2012

I just found your name in the book. That is really cool. Nice to meet you. I am in the process of reading the book. If I have said anything that is wrong, or incorrect, I apologize. I did say it was my take on going to all 5Ghz.

So let me ask you, do you think disabling 2.4Ghz band is a good thing. Does it depend on the enviornment, clients in that environment and the coverage you will have using 5Ghz band.

By sticky, i assume the client continues to connect to same band even if there is a better choice. We experience that with MBPs they seem to store last connection profile at times.

I have not experienced the bouncing on and off frequency as of yet.