A customer had a problem with a server’s network connection disconnecting and reconnecting often.  When I got onsite, I checked the event log and noted disconnect/reconnect messages occurring quite frequently.  I checked the NIC properties and noted the server was set to 100/full.  I noticed the server, and another server, were both directly connected with new cables, to gigabit ports on a switch.  I also noticed the presence of APC Ethernet surge protectors being used on both server’s network connections.  I removed the surge protector from the server I was working on and ran some ping tests.  The NIC was no longer being disconnected.  I set it to autonegotiate and it went to gigabit speed. [more]

I then checked the NIC properties and event log on the other server. It too was getting disconnected regularly.  The NIC was set to autonegotiate, but was only running at 100/full.  I removed the APC Ethernet surge protector from that server’s network connection.  The NIC autonegotiated to gigabit and was no longer getting disconnected.