How to Test a Failed Ethernet LAN Connectionby Stephen Lilley
If your Ethernet local area network (LAN) connection has failed and your computer has been disconnected from your network, you can test this failed connection using a native Windows tool called the "Network and Sharing Center." This utility will analyze your connection and attempt to not only figure out what when wrong, but also automatically fix it to get the Ethernet LAN connection up and operational once again.
Click "Control Panel."
Click "Network and Sharing Center."
Click "Change Adapter Settings."
Right-click on the "Local Area Connection" icon. This icon represents your Ethernet LAN connection. Click "Diagnose." The Windows operating system will analyze your failed connection. After a few seconds you will be presented with an explanation of the problem and a list of things you can try to fix it.