Network link is disconnected

You get a new device that has a 1Gb ethernet card (mine has the I219-LM) and you start getting random network disconnects. Been there and it is frustrating. There are a couple of reasons why this could happen (faulty drivers, faulty hardware, more than 100m from router) but in my case, it was a faulty cable that was easily identified with a ethernet cable continuity checker. I have a router far away from my machine. Both devices support gigabit connectivity, but they were auto negotiating and connecting at 100Mbps due to the faulty patch cable.  The problem was that from time to time the network connectivity dropped, just like if someone pulled the plug. 

In the event viewer in the system log, I could see the following sequence of events from the e1dexpress source: 

• Warning: Network link is disconnected.
• Information: Network link has been established at 100Mbps full duplex. 

As a workaround till I get a new patch panel, I disabled the auto negotiation feature of my network card and hardcoded the connectivity to 100Mbps full duplex. Probably will drop it to even less if I observe more disconnects. To do that 

1. Right-click Start menu button.
2. Click Device Manager. 
3. Expand Network Adapter.
4. Right-click on the ethernet adapter that is disconnecting
5. Click Properties. 
6. Click Advanced tab. 
7. Click "Speed & Duplex" from the list of properties
8. Select 100 Mbps Half Duplex or even less. 
9. Click OK. 

Hope this helps