Power problems with 1252's

Unanswered Question
Feb 20th, 2009


I've been reading through the forum and thought we have done everything we need to do to get our twenty 1252's at full PoE levels. I know this is beating a dead horse but I'd love to get this fixed.

We have three stacks of WS-C3750E-48PD's running IOS version 12.2(44)SE1. All the switches have the C3K-PWR-1150WAC power supply in them to reach full PoE levels for our 1252's connected to the switches. Each stack has either three or four switches in the stack, five AP's on stack one, ten on stack two and five on stack three....the AP's are spread between the switches in the stack. All the AP ports have been configured like....

interface GigabitEthernet1/0/16

description WAP - Front Desk

power inline port maximum 20000

switchport trunk encapsulation dot1q

switchport trunk native vlan 900

switchport trunk allowed vlan 140,144,145,900

switchport mode trunk



Interface Admin Oper Power Device Class Max


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

Gi1/0/16 auto on 0.0 AIR-LAP1252AG-A-K9 3 20.0

Interface AdminPowerMax AdminConsumption

(Watts) (Watts)

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

Gi1/0/16 20.0 20.0

I noticed on my 4404 controller that the AP's are at "Medium 15.4W" and when I brought up WCS yesterday I got twenty critical alerts reporting the power issue. We do have Cisco IP phones running here as well but there pulling between 6W and 15W depending on the phone....most are 7941's pulling 6.3W per port. Am I missing something here??

I have this problem too.
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Scott Fella Fri, 02/20/2009 - 12:10

I have seen that when running Version 12.2(44)SE2. I can't remember or find the bug id for that, but it was fixed on a later version of code.

Scott Fella Fri, 02/20/2009 - 14:09

It is not a "FEATURE" in any code available as of yet. So upgrade might not help you. You can alway open a TAC case to see if they have fixed it, but I would think it would show on the bug info.

mike-greene Fri, 02/20/2009 - 18:44

TAC said the switch is giving the AP the power thats needed. He said he contacted the wireless group about the WCS alerts and asked me to open a case with the wireless group.

Has anyone seen a 3750-E with the 1500W power supplies, correct IOS and the correct config supply more then 15.4W to a 1252 AP? Should I be using power injectors?


Scott Fella Sat, 02/21/2009 - 16:22

I have seen that.... most of the 1252's showed 20W, but there where a few in certain stacks that showed only 15.4W. When that bug was open, we haven't heard of a fix yet. We did end up moving those ap's that didn't fully power up to power injectors. The issue is the switch shows 15.4W and the ap sows 15.4W... so why is TAC telling you to go to the wireless group about WCS? WCS just reports what the AP is showing. Did you give them the bug id?

Leo Laohoo Fri, 02/20/2009 - 20:06

Cisco has developed new codes for the WCS/WiSM AND the AP1250 after receiving tremendous amount of complaints. The new codes will allow the 1250 to operate both radios at standard PoE rates BUT the transmission power has been scaled back.

By the way, your switch has the correct IOS version to ramp up the power inline switchport up to 20W.

Scott Fella Fri, 02/20/2009 - 20:40

From what I know, the new 1140's can use the 802.af standard, but not the 1250. The problem is the code is correct to supply 20mw, but in some cases you see the AP showing degraded power akin with the switch port.


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