How many radios does the 2600 AP have?

[neil_titchener]

Hi All,

My question relates to how many clients can be connected to a 2600 series AP.  The documentation states 200 clients per radio and the AP has three radios.  However when my AP gets to 200 it rejects further clients with the following log:

Thu May 9 15:40:22 2013 AP with MAC: 08:cc:68:0a:39:e0(AP-BrisHen-405081) radio 0: Associated Clients falls below max limit number:200. Failure Cause:Clear Maximum Client Limit Reached in this AP WLAN..

    Line 72: 71 Thu May 9 15:40:10 2013 AP with MAC: 08:cc:68:0a:39:e0(AP-BrisHen-405081) radio 0: Associated Clients exceeds max limit number:1. Failure Cause:Maximum Client Limit Reached in this AP WLAN..

I see this exact message many times and each time the radio mac address is the same and the number of clients connected is 199.   The same mac address is used for both 2.4ghz and 5ghz so does this AP have a single logical radio covering both 2.4 and 5ghz frequency ranges and is the limit for all connected clients 200?

When viewing the AP details under the Wireless tab it only lists one mac address for each AP for both 2.4ghz and 5ghz frequencies.

Please only reply if you know the answer

Thanks in advance

[Scott Fella]

The rule of thumb is 25 devices per AP.  The 200 client count is a max number, but you have to consider the throuput for each device.  Now you have have 30-40 if its just email and web traffic, but video you might be able to only get 3-5 clients.

Wireless is half duplex, so if you have a connection at 54mbps, that really means half of that (27mbps) is your max for one user.  Every user is then cut in half per say.  So when you design your wireless, you need to take into account density and not really coverage anymore.  Coverage is important, but with all these devices using the wireless, you most likely will have a dense deployment and will have more than enough coverage.

The error can be form the number of session for a login which you might of set to 1.

In the GUI: Security>AAA>User Login Policy

Thanks,

Scott

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[neil_titchener]

Hi Scott,

Thanks for your reply.  The rule of 25 per AP has been around for a long time.  Does this still work for the latest generation of APs?  My question is about the number of radios per AP in relation to the documentation.  From the Gui I can see one Mac address used for two (not three as previously stated) radios (one 2.4ghz and one 5ghz), and there are multiple streams (MIMO 3/4 for the 2600).  So is the limit of 200 per radio mac address, per radio (2.4.or.5ghz) or per AP. 

There is also a limit of 200 in the RF prifile configuration tab; is this limit per profile or per radio.  BT support stated it was per radio but that doesn't seem to correspond to test results.

Anyone with knowledge on this is welcome to join the conversation.

Cheers

[Scott Fella]

It is per radio... max is 200.  It doesn't matter where you set it at, the AP Group wil override the WLAN value.  25 is still best practice no matter what, I use that even with 3602 deployments... you are still limited to the ethernet port on the AP along with client connection speed.

Thanks,

Scott

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[lcd_shouldit]

Hi Scott，Is there some principles that what type ap we would better use ?

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[Leo Laohoo]

Is there some principles that what type ap we would better use ?

Depends on your application and budget.

Personally, from a technical point-of-view, I'd go for 2602 as a "budget" and 3602 if I have black-mail materials.

[lcd_shouldit]

Hi LEO, thanks a lot.
I have read about the compare product between 1600,2600,3600.

So what mainly and exactly different between them?
1600 do not support clean air ?
And 3600 support 802.11AC ?

Other characters are almost the same.

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[Leo Laohoo]

1600 do not support clean air ?

1600 supports CleanAir-EXPRESS and has a 3 x 3 MIMO.

2600 supports full CleanAir and has 3 x 4 MIMO.

3600 supports full CleanAir, has 4 x 4 MIMO, can support (currently) two forms of optional module:  the 802.11ac and 3G "pico" cell for mobile/cellular phones.

[Leo Laohoo]

Does this still work for the latest generation of APs?

The answer will depend entirely with WHO you are directing this question to.

Marketing/Sales people will say 200 clients per radio.  Technical people will say 25.

The main issue with this figure is, as what Scott has stated, is your ethernet connection (from the AP to the switch) and, quite possibly, your uplink from the switch to the core and to the WLC. 

Another issue is the inherit design of wireless as a medium which behaves exactly like a hub:  When one talks, everyone else stops, listens, and waits for their turn.  So if you have, say 200 people sardined into a small room and an AP, tell them all to hit the "Send" button and you'll see how really slow it'll get. 

[neil_titchener]

Thanks for all your responses. 

Scott, you noted a max client limit of 1 which I'm guessing you've got from the log entry

Line 72: 71 Thu May 9 15:40:10 2013 AP with MAC:  08:cc:68:0a:39:e0(AP-BrisHen-405081) radio 0: Associated Clients exceeds  max limit number:1. Failure Cause:Maximum Client Limit Reached in this  AP WLAN..

The limit 1 refers to how many clients over the max limit failed.  As a log is created for each failure every entry will be 1.

Our problem is we have 200 client devices in a charging rack near a single AP.  Whilst they are charging and turned on they consume very little bandwidth.  These devices are not PCs or laptops and consume very little bandwidth when they're in use and this is confirmed by the switch interface reporting throughputs of about 5Mbps for all devices on the wifi network which consists of 11 APs and a single WLC.

I will try and limit the number of clients per AP down to 100 for the AP at the charging rack and 60 for all other APs and see how we go.

[Scott Fella]

Neil,

Thanks for the clarification. It would seem that the devices would have to be smart enough to try to associate to another AP after the 200 max client has been reached. This is what you need look for. If you lower the limit to 100 and these devices don't like that the AP is disassociating them and still try to connect to that AP, that device will fail. If this is the case, you might try to add an additional AP in that room so that the devices hear another AP with good signal and that is typically good enough for a client device to move or choose another AP. it doesn't matter if you don't use any bandwidth as the limit per radio is 200.

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[neil_titchener]

We will be tetsing this setup next monday nigth so I'll post the results.  A few further changes from default we'll make are:

remove rates of 1, 2 & 5.5Mbps from Mandatory to Supported.  These use FHSS and DSSS modulation which we don't need to support

Disable client MFP as our devices run CCXv4 which doesn't support this function

Load balance clients

Use client band-select

Create multiple groups and RF profiles to ensure RF profile limits are not exceeded

We have an ongoing problem across the whole estate which I've seen in many forums.  Clients deauthenticate and fail to reassociate for seconds or even minutes.  We will enable session timeout and see if the reauthentication request from the WLC overcomes these random deauthentications.