These are just a few things to try to help figure out if it is your cable, ethernet card, router, or some other problem.
- start the troubleshooting process by making sure that everything (routers,switches, hubs, modems, and computers) is firmlyplugged in.
- If your computer is on and the other end of the Ethernet cable isconnected to a network device, the link or activity LED should light.If the light remains dark after you plug in the cable, replace thecable. If replacing the cable gives the same result (no green light), then go to the next step.
- Once you’ve eliminated cabling as a source of the problem, it’s time tolook to your computer. Start by making sure that your computer is able toaccess your Ethernet card. A good tool for doing this, and subsequentnetwork troubleshooting, is the command prompt.
- Select Start, All Programs, Accessories, and then Command Prompt. When the Command Prompt window opens, type ipconfig –alland press ENTER. Various lines of information will display, dependingon how your system is configured. Look for a section labeled EthernetAdapter Local Area Connection. This section should include a linelabeled Description, which should be a description of your Ethernetcard. If you see it, then your computer knows about your Ethernet cardand has successfully loaded the necessary drivers. If the Descriptionline is blank or missing, you will need to reinstall the drivers foryour Ethernet card.
- Your Ethernet card doesn’t detect a connection to the Ethernet cable. Open a command prompt, type ipconfig –all,and press ENTER. If the section that starts with Ethernet adapter LocalArea Connection contains a line labeled Media, with a status of MediaDisconnected, then your computer is unable to detect that a link hasbeen made from your Ethernet card through the Ethernet cable to anothernetwork device, such as your computer or router. Recheck the cabling.Use a known good cable to connect your computer to a known good networkdevice and then perform the check again. If the status is still MediaDisconnected, and you are sure that the cable and the network devicethe cable connects to are good, then you may have a bad Ethernet card.Reinstall the Ethernet card. If the problem continues, you may need toreplace the card.
- Other things to check:
- Bad connection, bad cable, or wrong cable. The ports on arouter, hub, switch, wireless access point, and print server can, likeany other device, go bad. However, the most common problem is not a badport but a bad or loose connection, a bad Ethernet cable, or the wrongtype of cable. Refer to the Cabling section above, to eliminate thesepossibilities.
- Wrong port. One possible cause of Ethernet port problems isusing the wrong port on a network device. For example, routers have WAN(wide-area network) and LAN ports. These ports accept the same Ethernetcabling but are not interchangeable. The same is true of hubs andswitches that have uplink ports, which are specially wired LAN portsthat allow easy cascading of multiple hubs and switches. In some cases,the uplink port is also a normal LAN port controlled by a switch on thedevice. If you’re using the uplink port as a normal LAN port, make surethe device is configured properly for this type of use.
If aport doesn’t appear to be working, you can use the link light toconfirm it. Port link lights should always be lit when a good cable isconnected between the port and another working network device. If youuse known good cable and a known good network device to test the portbut the link light isn’t lit, you may have a bad port. You can eitherreplace the network device, or in the case of a hub/switch, add a hubor switch to gain more LAN ports.
- You cannot connect to other computers or router/Internet. Whenother computers in your LAN can connect to each other, as well as tothe Internet or other services, and your computer cannot, this may bean indication that your computer did not receive an IP (InternetProtocol) assignment when you booted.
- Open a command prompt, type ipconfig –all, and press ENTER. Inthe section labeled Ethernet adapter Local Area Connection, look forthe line labeled IP. If it starts with 169, you have a self-assignedIP, which indicates that your computer was not able to acquire an IPassignment from the DHCP (Dynamic Host Configuration Protocol) server.
Test your access to the DHCP server by using the ping command. Open a command prompt and type pingfollowed by the IP address of the DHCP server. Your DHCP server isprobably the same as your router. For example, if your router’s IP is192.168.1.1, then type ping 192.168.1.1 and press ENTER. Youshould see four lines of text, starting with Reply From 192.168.1.1:Bytes 32, followed by time values that indicate how much time elapsedbetween the ping command and the router’s response. If you see fourlines that say Request Timed Out, then your computer cannot reach yourrouter/DHCP server.
Make sure the router is plugged in,turned on, and properly configured to provide DHCP services.