Wireless Lan Controller users randomly get disconnected

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Mar 21st, 2010
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Hi to all,

We have issues where clients randomly get disconnected from the wireless network, i have a 4400 WLC with the version and suddenly users are getting disconnected, what i've noticed is that the users are attached to one access point at 100% signal straight and at 54Mbps but suddenly the signal and the speed goes down and the client roams to another access point that is far away from the users location (the user never moves and is next to the access point that they should connect to).

It seems that the Auto RF algoritm is not working correctly, I upgrade to the release but the problem still remains.

Any ideas of what else should i try??

Thanks in advance

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dhirajgrover Thu, 04/01/2010 - 12:24
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We are facing similar issues in our environment and zeroed in on issues on 802.11n network only. So when we disabled the 802.11n on the clients, these clients work fine without any issues (on 802.11g). I am, however, looking for a complete resolution myself.


Hey Guys,

I believe this is issue with the WLC vesion as i face the same with WISM controller same image version.

But when i configured alerts in WCS i come to know that association of LWAP with WLC is not stable and they are

Frequently re associating.

Hence would request you to check in the WLC about the particular AP association time with WLC.



alfonso.cornejo Tue, 04/13/2010 - 08:16
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Hi Karim,

I was in the version when this problem started, thinking that this might be a software issue we upgrade it up to the but the problem still remains.

What troubleshooting steps have you done???


dhirajgrover Tue, 04/13/2010 - 08:37
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Further on this investigation is that we are using Intel based Wireless adapters in our laptops across the company. All adapters that support 802.11n specifications had issues, except one particular model X200 running Windows XP SP3. Intel has also come up with a fix for the 802.11n clients dropping their connectivity and it is available here:


The specific section on this page is as below:

Version 13.01.1000 (6MWC18WW)
(New) Added support for Intel WiFi Link 5150.
(Fix) Fixed an issue where wireless connection might be dropped in 802.11n mode.

Would be curious to know what type of Wireless NICs is everyone else using. What is the driver version? Driver date?


alfonso.cornejo Tue, 04/13/2010 - 09:35
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I have alot of network adapters in my users, but the most common are the intel that i attach here and the 4.5 of the cisco wireless adapter.


patoberli Wed, 04/14/2010 - 03:43
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Hi Alfredo

We also have several problems with our 802.11n clients, but nearly all are caused because of old wifi drivers.

Intel offers it's drivers here (preselected the 5100/5300 adapter): http://downloadcenter.intel.com/SearchResult.aspx?lang=eng&ProductFamily=Wireless+Networking&ProductLine=Intel%c2%ae+WiFi+Products&ProductProduct=Intel%c2%ae+WiFi+Link+5300+and+Intel%c2%ae+WiFi+Link+5100+products

The latest to todays date 14. april 2010 is driver release



glen.grant Mon, 04/26/2010 - 10:49
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   Interesting , this sounds like what we are seeing after converting  1130 and 1230 AP's to LWAPP

mode which connect to local wirless controllers or  for larger sites WISM cards .  Whats the general consensus of what might be causing this ?  Not good if the answer is to upgrade wireless drivers across 1000's of clients .  We are running across the board in the wlc's .

patoberli Mon, 04/26/2010 - 23:39
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Here the problem was coupled with deploying new 1142 Accesspoints, with 2,4 and 5 GHz modules. We didn't use 5 GHz before, nor 802.11n. The new drivers are needed mostly because of 802.11n on the accesspoints.

dhirajgrover Mon, 04/26/2010 - 12:02
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Another observation: This issue is apparent when there is a high utilization on the link between the sites where APs are the site where the WLC is. At least I have observed this in my case. What about others? Has anyone taken a note of this as well?

Kayle Miller Mon, 04/26/2010 - 12:20
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Are the AP's in Local Mode or H-REAP Mode?

If they are in Local Mode and they are losing the heartbeat to the controller due to the high utilization on the link between them and the controller then that can cause the AP's to go off-line which would cause the clients to drop. Once the connection is restored then the AP get's it's configuration back and becomes operational again and will serve clients again. You can check this to a point by looking at the logs for the AP join messages or when they report an outage look under

Wireless> Access Points> All Access Points - Select any AP and then look at the Uptime of the AP as well as the Time Connected to Controller value.

see example below.

alfonso.cornejo Mon, 04/26/2010 - 12:21
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Im my case is a lan enviroment, there is no high utilization between the controller and the APs.

glen.grant Mon, 04/26/2010 - 12:36
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   I have not seen this in our case either .  We have high speed gig links in the lan which aren't even breaking a  sweat  and no observed interface errors on the links..  All are in local mode, not using hreap .


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