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Cisco Catalyst CE500 with 4 POE ports

Posted on 2013-05-30
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I have a 4 POE ports Cisco switch and I see that the POE utilization is at 99%. Do I need to worry about it? Thanks
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Question by:leblanc
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TomRScott earned 334 total points
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How many of the ports are in use?

I would reference Cisco On-line Manual.

If all ports are in use, you MAY be OK at 99%. However, that depends on if the attached PoE devices have a VERY stable draw.  Obviously, if ANY of the PoE devices have a variable power draw, said device and possibly others will experience brownouts (worst case scenario) or blackouts.  Brownouts are the worst because corruption may be introduced with wild results.

If some ports are NOT in use, then I would certainly not add any devices, PoE or otherwise, to the switch.  Not adding non-PoE devices may be over cautious on my part but I detest intermittent failures.

I would add that even though you may be OK today, I would be uncomfortable with any power device running at 99% for any length of time as power supplies sometimes trail off over their life and may not be able to supply enough power in the near or distant future.

Switches are cheaper than down-time and labor, especially for intermittent failures that you may be faced with in the future.

 - Tom
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by:leblanc
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This switch has 24 ports but only 4 ports are POE.  The POE ports are all occupied. 5 other ports are occupied by PCs.So total 9 ports are being used. So if I understand correctly, I should be worry and don' add any more devices. Correct?
But I have 24 ports and I can only use 9 ports because the power is 99%. Is there a way to lower that percentage and use all 24 ports? Thx
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by:TomRScott
TomRScott earned 334 total points
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Diagnostic Steps & Possible Fix:
1 - If one or more of the devices on the PoE ports is a non-PoE device, I would move them to the non-PoE ports one at a time and check utilization after each is moved. It is possible that a non-PoE device may be drawing power due to a manufacture defect. If this is the case, checking the utilization should make it evident.

If Step 1 resolves the issue, go no further but consider repairing/replacing the non-PoE device that appears to be at fault.

2 - If all PoE ports have PoE devices, then I would try removing them one at a time to see if one of them is the majority of the utilization.

This step is just a diagnostic, not a fix.  If one of the devices seems to have an inordinate utilization, you may wish to check the manufacturer to see what that device should draw and compare to the supply of the switch.

3 - If all PoE ports have PoE devices and no one PoE device appears to be an issue, then I would move one of them to another PoE switch and review the utilization.
With a 24/4 port switch, I'm not too worried about the non-PoE devices that are not on PoE ports as long as the utilization on the PoE ports provides a little "headroom".


 - Tom
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by:leblanc
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There are 24 ports but only 4 ports are POEs. The other ports are non-POEs. It is a ws-ce500-24LC.
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by:Craig Beck
Craig Beck earned 166 total points
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The CE500-24LC only supplies PoE to 4 specific ports.  Therefore you can only use 4 PoE devices on that switch.  That means you don't have to worry about adding more devices as no other PoE devices will draw power from any other ports.  You can use the rest of the ports for PCs, etc, without having to worry about the power.

The fact that the PoE budget is at 99% just tells me that your devices are all working at the full 15.4W.
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