Re: POE switches and lightning

[Larry Sheldon <LarrySheldon () cox net>]

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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