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.