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Cisco 521 Wireless AP and POE

Posted on 2009-02-20
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Hello all,

I'm installing a Cisco 521 wireless access point (actually 5) with a Cisco 526 Wireless Express Mobility Controller.  I have a POE switch with 8 ports that is capable of 120 watts.  When I plug the access points into the POE switch, they light up, but do not function properly.  There is no wireless network and I get a "Radio Down" status.  When I use the supplied power supply, they work fine.  This seems like a silly question, but do I have to use some kind of splitter on the access point end that splits the POE ethernet signal to an ethernet cable and the power to a power connector?  This can't be the case, can it?

Any input would be greatly appreciated.

Thank you.
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Question by:erik_r
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by:wantabe2
ID: 23696354
The power brick actually has three connections. One to the AP, one to the switch, and a power cable going to an outlet. One thing to check is, make sure CDP is turned off at the switch port level. Once you get into the switch via telnet or hyperterminal, the command is:

no cdp enable


One other thing is, make sure they sent your an AP with LWAPP & not an automonous AP.
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by:erik_r
ID: 23696766
Hi wantabe2,

The power supply for the access point only has a cable to the access point (power connector) and a power plug (wall outlet).  I am not using a Cisco switch.  It is a TrendNet 8-port POE switch.
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by:wantabe2
ID: 23697200
One question, is this wireless controller the one Cisco has that can't be managed via a web browser? You said you can give the AP power via the AC adapter (not the POE) & it works? It just isn't working if you use the PoE switch?
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by:erik_r
ID: 23697857
Yes, it is managed via the Cisco Configuration Assistant.  I can view the status of the APs with a web browser, but there is minimal configuration.  When I use the CCA software, everything works, but it shows the radios (APs) with a status of DOWN.  If I plug the AP into a non-POE switch or disable POE on the POE switch, it will work as long as I also have the power supply plugged into the AP.  I'm positive that it's supposed to work with only the network cable connected as long as it's connected to a POE port.  The TrendNet switch has plenty of power.  It has 8 ports and is rated for a maximum of 120 watts.  The Cisco 521 AP specs. out at a max. of 9 watts or so.  This is so perplexing to me.
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by:wantabe2
ID: 23700154
Ok, I bought 21 access point a month ago & all of the radios were turned off by default. I think if you look on the CIsco box the APs came in, there will be a sticker either on the box or maybe on the AP that says the radios are turned off by default. Look at that & let me know.
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by:erik_r
ID: 23700740
Hi wantabe2,

Each Cisco box does have that sticker, but it mentions something about IOS.  The radios do work when they are plugged into the power supply without me having to do anything.  The Cisco Mobility Express Controller also mentions that no Cisco IOS commands will work in this setup other than debugging.  I'm beginning to think that my TrendNet POE switch is just not applying the proper POE class to the Cisco APs.  The switch is only showing 3.03 watts to the AP and the max. draw on the AP is 9 watts or so.  I would figure that they should be drawing at least 5 watts or more from the POE switch.
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by:wantabe2
ID: 23700760
Yes, it sounds like it is a power issue. Does that model of wireless controller have any build in PoE switch ports in the back?

Is the model number on the AP  AIR-LAP521G-A-K9 or  AIR-AP521G-A-K9?
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by:erik_r
ID: 23700808
The AP is the controllerd based model (AIR-LAP521G-A-K9) and the Mobility Express Controller does not have any POE ports.
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wantabe2 earned 2000 total points
ID: 23700870
I've only used Cisco PoE switches when deploying WLANs. When a Cisco PoE switch was not available I use a Cisco power injector. It sounds like your switch is not supplying enough power to enable the radios on the APs. To save you some $$$ I'd buy these http://www.superwarehouse.com/Cisco_Aironet_Power_Injector/AIR-PWRINJ3=/ps/346459

These supply 15 watts of power to the APs.
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Author Closing Comment

by:erik_r
ID: 31549433
Yes, I think that is my only solution.  Thank you, wantabe2.
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by:wantabe2
ID: 23700966
You're very welcome! Good Luck!
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