Troubleshooting Your Network Interface Card (NIC). One end of the Ethernet cable (RJ-45 cable) that came in your installation kit should be connected to your modem, while the other end should be connected to the Ethernet jack in the back of your computer. If you have a laptop computer, the Ethernet jack may be on the side of your computer.
Typical Ethernet Connection
The Ethernet jack in your computer is part of your Network Interface Card (NIC), also known as an Ethernet adapter. If the Ethernet cable is plugged in and your computer is on, you should see a green light next to the Ethernet jack.
If you cannot access the Internet and the light is off: