Ask the Expert: Cisco Wireless LAN Controllers (WLCs)

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Jun 27th, 2011
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Read the biowith Cisco Expert Nicolas Darchis

Welcome to the Cisco Support Community Ask the Expert conversation. This is an opportunity to learn about the most recent generation of access points from Cisco and the integration of the CleanAir technology to locate and mitigate interferences with Cisco subject matter expert Nicolas Darchis.

Nicolas Darchis is a wireless and authentication, authorization, and accounting expert for the Technical Assistance Center at Cisco Europe. He has been troubleshooting wireless networks, wireless management tools, and security products, including Cisco Secure Access Control Server since 2007. He also focuses on filing technical and documentation bugs. Nicolas Darchis holds a bachelor's degree in computer networking from the Haute Ecole Rennequin Sualem and a master's degree in computer science from the University of Liege. He also holds CCIE Wireless certification number 25344.

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Overall Rating: 0 (4 ratings)
zhenningx Wed, 06/29/2011 - 13:13
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Hi Nicolas,

I heard the Persistent interference avoidance and Spontaneous interference avoidance (ED RRM) are only available

with full CleanAir enabled installation –not overlay. Can you confirm and commend on that? Thanks.

Nicolas Darchis Thu, 06/30/2011 - 00:23
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it's correct.

Only CleanAir APs can take RRM decisions based on CleanAir information. That means for example, that your 1130 AP cannot use the AirQuality information of a 3500 located close for interference avoidance. The 1130 will still avoid interference but without the enhanced algorithm that CleanAir allows, so it will still act like it was behaved.

It is not possible because the CleanAir APs know how the interferers are affecting themselves. they can't know how interferers are affecting non-CleanAir APs.

And if your overlay deployment is dense enough to allow for Location of the interferers (so 3 cleanair APs observing the interferer), then you have enough CleanAir APs to do your whole deployment with Cleanair and not an overlay anymore :-)

Overlay network typically allows to buy less CleanAir APs, to have those APs working in monitor mode (scanning all channels, improving location and monitoring of the network). If you're buying plenty of CleanAir APs, just use a 100% cleanair deployment then.

kevin75_zhou Mon, 07/04/2011 - 00:19
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Hi Nicolas,

I want to know the coverage of Cisco Airnet 1140 Wireless AP. Could you please do me a favour? Thank you!

Nicolas Darchis Mon, 07/04/2011 - 00:34
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Based on google search, some websites says 50 meters :

Why is Cisco not giving numbers ?

Well that's because it's an indoor AP and there are not 2 indoor deployments that are the same. The range could vary from 10 meters in a bank with super thick walls to 50 meters in an office space, maybe more if you put the AP outdoor (which you're not supposed to). So what's the point of giving a number that will not be right for you in the end ?

It reminds me of bluetooth devices sold with a sticker "up to 100 meters". Right, right ... if I move into the next room, it stops working.

I guess you're asking this question because you are planning for a deployment. How to know then ? :

-Use WCS planning tool

-Get 2-3 1140s and go on site and do a site survey to verify the actual coverage in that precise environment.

If you're asking to compare with competitors then you're chosing the wrong number to compare. You should rather look into transmit power and antenna gain. But since this is a regulation maximum, there should not be differences between brands (except if one brand goes beyond the regulatory maximum).


Leo Laohoo Mon, 07/04/2011 - 15:28
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Nice one.  +5

sidy soumare Tue, 07/05/2011 - 02:58
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Hello Dear,

What's CleanAir technology? Thanks for your time, I appreciate.


Nicolas Darchis Tue, 07/05/2011 - 03:00
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Please watch the videos that are in the first post of this page, it explains it all.

Hriday Goswami Tue, 07/05/2011 - 03:43
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spamApTask0: Jul 05 07:22:13.660: %LWAPP-3-DISC_MAX_DOWNLOAD: spam_lrad.c:1381 Ignoring discovery request from AP 00:3a:99:33:14:30 - maximum number of downloads (0) exceeded This is the  error I am getting when I am trying to replace one old 5500 WLC with the new one, I have already uploaded the same configuration from the OLD one to the new one & I have checked the software version but this was not same in the new one so, I have downloded the same version of software which was in the old one & uploaded in the new one still I am getting same problem, please help..

Nicolas Darchis Wed, 07/06/2011 - 07:26
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This is a cleanair specific "ask the expert". Your question is best suited in the wireless community forum here.

However, for the record, the resolution of your issue was the fact that you need to rehost the license on the new WLC.

JASON CHOQUETTE Wed, 07/06/2011 - 07:21
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Is it recommended to enable all access points in a specific area for CleanAir, or just a few?  Could there be performance degridation on APs that are CleanAir enabled and servicing clients?  For example, if you have a floor with 30 access points how many should be enabled for CleanAir?


Nicolas Darchis Wed, 07/06/2011 - 07:30
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I can't imagine any reason why you would want CleanAir on all APs.

As explained in the video, there is no performance degradation at all :

-Spectrum sampling is done by the SaGe chipset (same as in the Spectrum Expert) that is inside the CleanAir AP, so wifi chipset is not involved.

-Calculations and device identification is done by this dedicated chipset, still no overhead on the AP CPU.

-Only Air Quality reports and Interference Device Reports are sent by the AP to the WLC. So the AP doesn't spam a lot of traffic on the network. Merely a small "Air quality is 70% in the last minutes and I detected a microwave oven and a bluetooth device with these caracteristics". So totally negligible.

The more CleanAir AP you have, the more interferer you can detect/identify and locate.

christopher.jubilo Fri, 07/08/2011 - 07:23
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Hi Nicolas,

Good Day, I just want to ask if it is possible to make a Cisco Linksys E4200 works as an Access point? we have a cisco 3560 switch and cisco 2811 router and we would like to use our Linksys E4200 as an access point.

Kindly advise.




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