Problem with PoE AP152 and 3750E

Unanswered Question
Mar 27th, 2008
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We are trying to power an AP1252 with a WS-C3750E-48PD-SF switch. We apply the following commands to the switch :


interface GigabitEthernet1/0/31

description Access Point WiFi

power inline port maximum 18400

power inline static

power inline police action log


The power the switch sends seems correct,


3750E_PISC#sh power inline

Module Available Used Remaining

(Watts) (Watts) (Watts)

------ --------- -------- ---------

1 850.0 18.4 831.6

Interface Admin Oper Power Device Class Max


--------- ------ ---------- ------- ------------------- ----- ---- ....

Gi1/0/31 static off 18.4 n/a n/a 18.4



But the facts are that we don't send enough power to the AP, as it disables both interface radio.

The AP and the switch should negotiate power via CDP, but the AP is not seeing any neighbor.

The switch receives CDP anouncments from the AP, but it seems as if the AP doesn't understand the CDP messages send by the switch.

Both AP and switch uses CDP v2 announcements.


3750E_PISC#sh cdp nei gigabitEthernet 1/0/31 detail Device ID: ap Entry address(es):

IP address: ..........

Platform: cisco AIR-AP1252AG-E-K9 , Capabilities: Trans-Bridge IGMP

Interface: GigabitEthernet1/0/31, Port ID (outgoing port): GigabitEthernet0 Holdtime : 147 sec

Version :

Cisco IOS Software, C1250 Software (C1250-K9W7-M), Version 12.4(10b)JA1, RELEASE SOFTWARE (fc2) Technical Support: Copyright (c) 1986-2008 by Cisco Systems, Inc.

Compiled Wed 30-Jan-08 12:04 by prod_rel_team

advertisement version: 2

Duplex: full

Power drawn: 13.000 Watts

Power request id: 6481, Power management id: 0 Power request levels are:18500 13000 0 0 0 Management address(es):


But the AP is not seeing any cdp neighbor.

the message seen on the AP's logs when powered on is :


*Mar 1 00:01:15.171: %CDP_PD-2-POWER_LOW: All radios disabled - NON_CISCO-NO_CDP_RECEIVED (0000.0000.0000)


Versions on 3750E : 12.2(44)SE

Version on AP1252 : 12.4(10b)JA1



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irisrios Wed, 04/02/2008 - 07:06
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This message is received when there is no proper power supply to the Access Point. AP requires 12.95W of power for operation. Some inline power sources are not able to provide 12.95W of power on their ports. Try using Pwer Module and cisco aironet power injectors.

ecorominas Wed, 04/02/2008 - 08:54
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This AP requires 18,5 W and the switch should be able to provide it (is a 3750 "E", a recent model that the data sheet claims to be able to supply until 20 W). But it doesn't work !!

Use of power injectors will be fine, of course, but I have just one option, I need to use the switch.



dfutros Thu, 04/03/2008 - 07:10
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What version of code are you running on the 3750e switch ? You need to minimally running

12.2.44SE code to support the 1252 access point using poe.


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