Problem with LAP and PowerInjector

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Aug 11th, 2008
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Hi!

I have little problem. When i connect LAP to switch, use PowerInjector, i got message on WLC - *AP's interface:1(802.11b) Operation Status Down:Base Radio MAC:xxxxx Cause=Low in-line power*


But if I use switch with PoE - all ok.

Somebody know what to do?

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dennischolmes Tue, 08/12/2008 - 04:38
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Which LAP and which injector? The 1252 does not support 802.3af. Some older injectors for old autonomous deployments did not provide sufficient power. It depends on the AP model number and PoE Injector model number.

kudachkin Wed, 08/13/2008 - 23:19
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LAP 1131 and AIR-PWRINJ3.

Я use it in our test network - all ok.

dennischolmes Thu, 08/14/2008 - 04:19
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That is the correct PoE injector. I suspect you have a bad injector. Did you try another? Also, make sure the port you're plugged into on the switch is not PoE. The two PoE devices could conflict.

Rob Huffman Thu, 08/14/2008 - 04:46
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Hi Yurij,


Just to add a note to the good info from my friend Dennis.


This has happened to us a few times.


Power Issue with the AP


When an AP uses a power injector as the power source, in some cases, the AP displays this error message:


CDP_PD-2-POWER_LOW: All radios disabled - LOW_POWER_CLASSIC inline


This message indicates that the AP is in low-power mode with all radios disabled and detects a Cisco switch that is unable to supply sufficient power to the AP. Even though the power injector, which can provide sufficient power, is connected with the AP, the AP still displays a LOW POWER error message and disables the radios. Therefore, the AP remains in low-power mode.


One possible reason for this issue might be that the AP supports the Intelligent Power Management feature. The Intelligent Power Management feature uses Cisco Discovery Protocol (CDP) to allow powered devices, such as an AP, to negotiate with a Cisco switch for sufficient power. The AP supports the Intelligent Power Management feature. As a result of the power negotiations, the AP either enters full-power mode or remains in low-power mode with the radios disabled.


In this case, the AP might be connected to a switch which cannot provide the necessary power to the AP. Therefore, even though the power injector is connected to the AP that uses this Intelligent Power management feature, it gives priority to the CDP information to identify whether or not the switch can provide the power. Once the AP knows, via CDP message, that the switch does not provide sufficient power, it disables the radios and remains in low-power mode.


The workaround to this issue is to tell the AP to ignore the CDP information for power. You can perform this by telnetting into the APs. Issue these commands to enable the APs to use the power injector:


power inline negotiation prestandard source


power inline negotiation injector H.H.H


The power inline negotiation command configures the Cisco Aironet 1130AG or 1240AG Series AP to operate with a later version of switch software that does not support Cisco Intelligent Power Management power negotiations.


The prestandard source portion of the command specifies that the Cisco switch runs a later version of software that does not support Intelligent Power Management negotiations, but is able to supply sufficient power to the AP.


The injector H.H.H portion of the command specifies that a power injector supplies power to the AP, and that the AP connects to a new switch port with the indicated MAC address (H.H.H). Enter the MAC address (in xxxx.xxxx.xxxx hexadecimal format) of the new switch port where the power injector is connected.


Note: This command should only be used when you move an AP and power injector to a different switch port.


From this good doc;



http://www.cisco.com/en/US/products/hw/wireless/ps441/products_tech_note09186a00800a86d7.shtml#new3



Here is the method used via WLC GUI;


http://www.cisco.com/en/US/docs/wireless/controller/4.0/configuration/guide/c40lwap.html#wp1134787



Hope this helps!

Rob


dennischolmes Thu, 08/14/2008 - 04:50
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Hey Rob,


That's exactly where I was going with the switchport statement I made above. He could also disable CDP on the switchport and it should work as well I think.

Rob Huffman Thu, 08/14/2008 - 05:26
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Hey Dennis,


You always seem to "hit the nail on the head" my friend! +5 points for your great work here. You have really been a wonderful addition to these Forums.


Take care,

Rob

kudachkin Thu, 08/14/2008 - 23:22
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Hi Rob,


Thanks for your answer.


1) Yes, i know about this

power inline negotiation prestandard source

power inline negotiation injector H.H.H

but it use in Automous AP, but i have LAP

2) My catalist don't use PoE

3) And I test another PowerInjector and LAP

and it's not work to.


kudachkin Fri, 08/15/2008 - 06:07
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Very usefull link!!!

But when i try reproduce this error in test lab, i can't do this.

A try to check in mondey.

Rob Huffman Mon, 09/01/2008 - 06:30
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Hi Yurij,


You are most welcome my friend :) Glad to hear that you got this working. Nice job!


Take care,

Rob

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