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HP Procurve 3500 PoE Drops

Posted on 2013-01-07
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Last Modified: 2013-01-31
We have a 4 month old HP Procurve 3500yl 48port PoE switch. For the past week, every morning around 9am the devices connected using PoE (our phones, WAPs, and cameras) will lose their power and then reboot normally. Sometimes they will do it once, others they will do it 2 or 3 times in a row and then they are fine the rest of the day.

I have updated the firmware to the latest release for the switch and this has not solved the problem. I also removed the WAPs from the switch because they were drawing the most power. The total power being used is about one third of what is available for the switch.

The logs on the switch show no errors or PoE alarms. The only thing that does come up is the "loss of Link" message for the devices that lose power and in turn, network access.

Does anyone have any idea what may be a cause of this issue?
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Question by:shanehooton
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by:convergint
convergint earned 500 total points
ID: 38752668
A high percentage of network issues are caused by bad network cabling.  Have you tried plugging in a device directly into the switch with a certified CAT6 cable to see if that device also reboots at 9am?

Typically with POE devices they negotiate with the switch on power up on how much power they require and the Procurve allocates that power.  However you can force the allocation of the power using a different method.  In the configuration try allocating one of the devices by usage, another by class and the third by value.  Then see if all three still reboot randomly.

The syntax is: interface {port number} poe-allocate-by {usage\class\value}.
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by:shanehooton
ID: 38759596
This is occurring in a newly remodeled building with all new CAT6 cabling. We had no problems with this for the first 3 months in service.

All of the PoE was set with usage. I moved several to class to see if that alleviates the problem. I notice when I put them in class it shows the voltage as 7.74. That is what is allocated correct?

I have found online where issues can be caused when phones come out of power save mode first thing in the morning and the power allocation goes crazy causing reboots. I'm thinking that if I put the mode to Class that should permanently have the power allocated correct?
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convergint earned 500 total points
ID: 38776435
Putting the mode to Class allocates the power to a range of the class.  For example, class 3 should give it a range of 6.49 to 12.95 watts, the voltage for POE is always around 48V regardless of class.  7.74 watts sounds about right

With a new building and CAT6 it shouldn't be cabling issues.  However, we did install all brand new CAT6 patch cables to connect the patch panel to the switch and we experienced a few bad cables that caused exactly the issue you had.  However, I doubt that would be the issue since it is happening to almost all your devices.

It is very odd that everything worked fine for the first 3 months and that leads me to believe that something has changed to cause this issue.  Was the switch always on a UPS?  Would there be anything plugged into the network that you were not aware of?
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