POE switches and lightning

Larry Sheldon LarrySheldon at cox.net
Thu May 13 11:19:11 CDT 2010


On 5/13/2010 10:36, Caleb Tennis wrote:
> We had a lightning strike nearby yesterday that looks to have come inside our facility via a feeder circuit that goes outdoors underground to our facility's gate.  
> 
> What's interesting is that various POE switches throughout the entire building seemed to be affected in that some of their ports they just shut down/off.  Rebooting these switches brought everything back to life.  It didn't impact anything non-POE, and even then, only impacted some devices.  But it was spread across the whole building, across multiple switches.
> 
> I was just curious if anyone had seen anything similar to this before?  Our incoming electrical power has surge suppression, and the power to the switches is all through double conversion UPS, so I'm not quite sure why any of them would have been impacted at all.  I'm guessing that the strike had some impact on the electrical ground, but I don't know what we can do to prevent future strikes from causing the same issues.  Thoughts?


I don't know how to account for this in a PoE world, but when I last
managed a campus network, we had major issues (particularly in an
active-thunder-storm environment) of severe difference in
ground-potential between buildings.

The only way we could survive was to connect buildings (including
free-standing kiosks) with their own "grounds" using glass.

Does anybody make a CAT 5 1-to-1 isolation transformer?

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