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In a production environment with 10 mac, in 2 of them, the network card stopped to work. After repairing on of them, again the network card stopped to work, for hardware failure. So, my quetion is: can a switch burn electrically a network card ?

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Yes, in fact it's quite possible. How sure are you that this facility is electrically-grounded correctly? – Mike Pennington Jun 26 '12 at 9:39
Make sure your switches are properly plugged into surge protectors and/or UPSes. – Bigbio2002 Jun 26 '12 at 19:14
up vote 3 down vote accepted

I have seen it happen twice.
About 10 years ago with a Cisco 1900 series switch that was located in a badly grounded patch-cabinet. It fried 3 NIC's (all 3Com 3c900 cards if memory serves). Several other computers (on-board Intel NIC's) malfunctioned but after taking them of the power-grid overnight they were OK the next morning. (I'm guessing that gave the circuitry a chance to gradually discharge.)

Just last week I had a HP ProCurve 2610-48 Power of Ethernet switch with bad circuitry on ports 1-24. Ethernet kept working (even on bad ports) but the PoE failed completely. Fried 2 ip-phones (using PoE), other 10 phones on those ports survived. Computers were also fine.

In the old days (coax networks) it was very common as the coax lines would build up a capacitive charge that could go upwards of 100V. You could even feel it if you touched the metal of the T-connectors or vampire-taps.
In those days NIC's often had a small neon light-bulb on the card which acted as a fuse. If it blew it was very easy to solder a new one on and the (expensive) NIC survived.

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Yes. It's possible (although somewhat unlikely) that your switch has malfunctioned in such a way as to become an etherkiller.

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Potentially yes, I've never personally heard of that happening but certainly it could happen yes. Of course it's much more likely to be poor quality network adapters but it could be the switch I guess.

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