Quick answer
If the LAN cable is not connecting, the most common culprits are a faulty cable, a loose or damaged port, a disabled network adapter or incorrect IP configuration. First check the port LEDs and replace the cable, then in Windows check whether the adapter is enabled and whether it obtains an IP address automatically. If that does not help either, the problem is probably in the router, driver or the port itself.
How to recognize the problem
- The LED on the LAN port does not light up or blink
- Windows shows "Network cable unplugged" or "No internet access"
- The network icon has a red X or a yellow exclamation mark
- The computer does not obtain an IP address (169.254.x.x)
- The connection speed is 100 Mbps instead of 1 Gbps or the connection keeps dropping
Most common causes
Faulty or damaged cable
The cable may be physically damaged, bent or have a poorly attached connector. Try another cable that is known to work.
Loose or damaged port
The connector may not be fully inserted into the port on the computer or router, or the port may be dusty and oxidized. Clean it and firmly plug in the cable.
Network adapter is disabled or has no driver
In Windows the adapter may be manually disabled or the driver is not installed. Check in Device Manager and in the list of network connections.
Incorrect IP configuration
If a manual IP address from the wrong range is set or DHCP is disabled, the computer will not obtain an address. Set automatic IP address assignment.
Problem on the router or switch
The port on the router may be inactive and the DHCP server disabled. Restart the router and check whether another device works on the same port.
Step-by-step fix
- 1
Check the port LEDs
Look at the LEDs next to the LAN port on the computer and on the router. If they do not light up, the cable is not connected or the port has no power. Try unplugging and reinserting the cable until it clicks.
- 2
Replace the cable and port
Take another LAN cable and connect the computer directly to another port on the router. If it works then, the old cable or port is faulty. Avoid cables longer than 100 m and those with damaged insulation.
- 3
Restart the router and computer
Unplug the router from power for 30 seconds, then plug it back in. Wait for it to boot, then restart the computer. This resolves temporary DHCP server and network driver hangs.
- 4
Check whether the adapter is enabled
Press
Win + R, typencpa.cpland pressEnter. If the Ethernet adapter is disabled, right-click it and selectEnable. Make sure airplane mode is not on. - 5
Set automatic IP address assignment
In the same window, right-click the Ethernet adapter and select
Properties. SelectInternet Protocol Version 4 (TCP/IPv4), clickPropertiesand selectObtain an IP address automaticallyandObtain DNS server address automatically. Confirm withOK. - 6
Reset network settings
Open
Settings > Network & internet > Advanced network settings > Network resetin Windows 11, orSettings > Network & internet > Status > Network resetin Windows 10, and clickReset now. Before resetting, write down Wi-Fi passwords and VPN settings or back up network profiles, because the reset removes that data. The computer will restart and return network components to default. This does not delete personal files. - 7
Check the network adapter driver
Right-click
Startand selectDevice Manager. ExpandNetwork adapters, right-click the Ethernet adapter and selectUpdate driver > Search automatically for drivers. If that does not help, download the latest driver from the computer or network card manufacturer's website. - 8
Test another device and cable
Connect a laptop or another computer with the same cable to the same port. If it also has a problem, the fault is in the cable, port or router. If the other device works, the problem is in the network card or software of the first computer.
If nothing helps: advanced check
If you have tried another cable, another port and a network reset, and the connection still does not work, check whether a MAC filter is used for that port on the router or whether the port is administratively disabled. In that case, log in to the router and review the list of connected devices. Also, in Windows open the command line (cmd) and type ipconfig /all to see whether the adapter is obtaining an IP address at all. If the output says the media is disconnected (Media disconnected), Windows does not see the cable, which indicates a hardware fault of the network card or port. For older computers, check whether the network card is properly inserted in the PCI or PCIe slot. If it is a laptop, a motherboard fault is possible and then the repair is more expensive than buying a USB LAN adapter.
How to prevent it
- Use quality cables and do not bend them at sharp angles
- Regularly update the network card drivers
- Do not forcibly unplug the router from power and keep it in a dry place
- Label cables and ports to make faults easier to find
When to call a professional
If you have tried another cable, another port and a network reset, and the computer still does not see the network, contact IT support. A hardware fault of the network card or port on the router is possible, which requires diagnostics beyond home conditions.
IT infrastructure maintenance · Servers, networks, backup, security and helpdeskFAQ
Why is the LED on the LAN port not lighting up?
The LED does not light up if the cable is not properly inserted, if the cable is broken or if the port has no power. Try another cable and another port on the router. If it still does not light up, a network card fault is possible.
How do I know whether the problem is in the cable or the computer?
Connect the same cable to another device. If the other device works, the problem is in the computer. If it does not work, the problem is in the cable, port or router.
Does a network reset delete my files?
No, a network reset in Windows deletes only network settings and returns adapters to default. Personal files and installed applications remain intact, but saved Wi-Fi passwords and VPN profiles are removed.