POE switches and lightning

Marshall Eubanks tme at americafree.tv
Fri May 14 22:52:37 UTC 2010

On May 13, 2010, at 2:26 PM, Mark Mayfield wrote:

> About a month ago, we had a lightning strike near our main campus.   
> We lost one POE Cisco 3560 completely (apparently blown power  
> supply), and in a separate but nearby building, another 3560 lost  
> the ability to deliver POE, but continued to operate as a switch.   
> Both had to be replaced. Both were on wiring closet type UPS'es with  
> surge suppression, and those were unaffected.
> Mark
> -----Original Message-----
> From: Caleb Tennis [mailto:caleb.tennis at gmail.com]
> Sent: Thursday, May 13, 2010 10:37 AM
> To: North American Network Operators Group
> Subject: POE switches and lightning
> 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?

It is not clear to me from the above if there are copper circuits  
coming into the building, but lightning can certainly zap those as  
well. In very high impact areas (such as mountaintops or Miami) it is  
a good idea to mandate that all incoming / outgoing circuits are on  
fiber, without exception.


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