Radios Shutdown

Unanswered Question
Jul 17th, 2008
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My setup:

WLC 4402

1131 Access points

Problem: Some AP radios are shutdown

and cant be brought up. out of 17 APs

3 APs are like this.

Trap Logs show this:

AP's Interface:0(802.11b) Operation State Down: Base Radio MAC:00:1f:9e:27:6e:20 Cause=Radio Low Power

What could be causing this?

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Overall Rating: 5 (1 ratings)
pirateoftheairwaves Thu, 07/17/2008 - 04:02
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there is a feature called PoE override in the WLC on each ap page. try to play around with that settings.

Rob Huffman Thu, 07/17/2008 - 04:26
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Hi Raul,

Just to add a note to the godd info from Pirate (+5 points for this ARRGGHH!!) 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;

Here is the method used via WLC GUI;

Hope this helps!


acomiskey Thu, 07/17/2008 - 11:53
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Here's the specific command that did it for me...

>config ap power injector enable all

rocampo Thu, 07/17/2008 - 19:19
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Hello to all,

This resolved my issue.

I reset the APs to factory default then under

Power Injector settings I checked

Power Injector state.

thanks to all,


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