How do I test an Ethernet network interface card (NIC)?
A. Most NICs or network adapters come with one or more floppy disks containing drivers, etc. for various operating systems. These floppies also usually include a diagnostic program to test the NIC. Many of these programs are DOS-Based and must be run by booting the computer to DOS or from a DOS window in Windows. Unless you have a loopback plug installed, the loopback test will probably fail. A loopback plug directs signals from the NIC’s transmitter back to it’s receiver. An indicator that a NIC and cabling is functioning is to check the LINK (sometimes labeled LNK, etc.) and Activity (ACT, etc.) LEDs, if there are any, on the NIC and on the device at the other end of the cable. The LINK should be solid with no flickering and the ACTIVITY should be blinking, which indicates, of course, network activity. This indication is not as thorough a test as the diagnostics program and it is not foolproof (see Why would the Link (or LNK) LEDs be on solid, if there is a faulty cable connecting tw
