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PoE Issue

Unanswered Question
Nov 21st, 2013
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Hi All,


We have recently deployed 72 Cisco Wireless Access Points (AIR-CAP1602I-E-K9), managed by a pair of Cisco 5508 Wireless LAN Controllers (SW Version (7.4.100.60). Everything was working fine until a few days ago when one access point went down and subsequently refused to power up using PoE. Prior to this, it appeared to be working OK.


However, when I use an external power supply for the WAP, it works fine. This isn't really an option for us as our solution called for purely PoE.


I have tested all cable runs between the WAP and network switch (C3560E-UNIVERSALK9-M), Version 12.2(46)SE) and they appear fine.


I also used the 'test cable tdr interface' command and got the following outputs when the external power supply was connected (WAP booted OK):



Interface     Speed     Local pair     Pair length               Remote pair     Pair status

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

Gi0/35     1000M     Pair A             0    +/- 1  meters      Pair A             Normal             

                             Pair B             0    +/- 1  meters      Pair B           Normal             

                             Pair C             0    +/- 1  meters      Pair C           Normal             

                             Pair D             1    +/- 1  meters      Pair D           Normal


I again ran the 'test cable tdr interface' command and got the following output when the NO external power supply was connected (WAP failed to start):


Interface     Speed     Local pair     Pair length                    Remote pair     Pair status

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

Gi0/35     1000M     Pair A             152    +/- 1  meters      N/A                Normal             

                             Pair B             152    +/- 1  meters      N/A                Normal             

                             Pair C             2       +/- 1  meters       N/A               Open             

                             Pair D             1       +/- 1  meters       N/A               Open




Is it possible that there is a fault with the physical ethernet port on the WAP itself? The switch port is working fine as I have plugged in a spare access point and it booted up fine over PoE.


Any help would be much appreciated,


Many thanks,


JP



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Sandeep Choudhary Thu, 11/21/2013 - 07:01
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HI,


AP1600: 12.95 W

When deployed using PoE, the power drawn from the power sourcing equipment will be higher by some amount dependent on the length of the interconnecting cable. This additional power may be as high as 2.45W, bringing the total system power draw (access point + cabling) to 15.4W.


Sh power inline from swicth ???


Regards

isoffice1 Thu, 11/21/2013 - 07:13
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Hi Sandeep,


Thank you very much for your input. Originally the overall cable length from WAP to switch was 32-33 metres. To minimise disruption to our users I replaced the offending WAP as soon as I was aware there was an issue.


The output from the TDR test in my original post was using a 2 metre patch cable which I tested with a Fluke Cable Tester to ensure its reliability.


The company that installed the wireless network will be replacing the WAP shortly as it is still under warranty. I was just hoping to gain a little better understanding to this problem and how to address it should the same situation occur again.


Many thanks,


JP

Leo Laohoo Thu, 11/21/2013 - 13:14
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Gi0/35     1000M     Pair A             152    +/- 1  meters      N/A                Normal

                      Pair B             152    +/- 1  meters      N/A                Normal

                      Pair C             2       +/- 1  meters       N/A               Open

                      Pair D             1       +/- 1  meters       N/A               Open

152 metres?


Can you change the patch cable connected to switch port 35?  If the problem still persists, get the punch block checked out. 


Be aware that the TDR function of 3560-series is not as accurate as the 2960 and 3750.  At 152 metres the speed should've dropped down to 10 Mbps.


What kind of power supply are you talking about?  Is this a power brick or a power injector?

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