POE switches and lightning

Matlock, Kenneth L MatlockK at exempla.org
Thu May 13 15:50:54 UTC 2010

My first guess would be the lightning was close enough/powerful enough,
to send out an EM Pulse which got picked up by the copper going to the
devices. This EM Pulse may have been interpreted at the switchport as
the device relinquishing power?

Had you tried just unplugging one of the devices from Ethernet, and
plugging it back in to reset the PoE exchange?

Ken Matlock
Network Analyst
Exempla Healthcare
(303) 467-4671
matlockk at exempla.org

-----Original Message-----
From: Caleb Tennis [mailto:caleb.tennis at gmail.com] 
Sent: Thursday, May 13, 2010 9:37 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.

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