Computer is Online with USB Cable but Cannot with Modem LAN Port

Today I received a call from one of my friends to discuss a strange network issue. He can access the Internet on his computer using USB cable connected to his modem but it is not working when he tried to use Ethernet cable to connect his computer to the modem. His modem has router feature with 4 LAN ports and he decided to use them to connect his second computer. So he removed the USB connection and connected his computer to the LAN port with Ethernet cable. However, his computer failed to access the Internet and he has no clue. This tutorial explains how to deal with such a situation and I tried my best to make it easy to understand and follow.


In case if you have troubles to go online when connecting your computer to the LAN port (Ethernet Port) but can go online with the USB port of the modem, follow the procedure below.

1. Check the LED on your modem And at Computer LAN Port
   
   If there is no light on your modem (LED near the LAN Port) or at an Ethernet port on the computer, it shows no active connection between your computer and modem. Possible reasons can be;
   
   
   • Loose connection- Unplug the cable from both ends and connect back
   • Modem LAN Port issue - connect the cable to another LAN Port
   • Faulty Ethernet Cable - Try a different cable
   • Faulty Computer LAN card
   
   
2. Check Computer IP Address
   
   If Static IP address is assigned to your computer, you must use obtain an IP address automatically option. It is because if your computer static IP address does not match the network address of the modem DHCP, your computer will not go online.
   How to Set Your Computer to Receive IP Address From Modem DHCP Server
   
   
3. Power cycle the modem
   
   In this step, you need to disconnect the power cable from the modem and wait for 1 minute. After one minute power on the modem and wait till all the lights are steady.
   How to perform Power Cycle
   
   
   
4. Uninstall LAN Card Driver and Reinstall
   
   Corrupted LAN card adapter prevents you from accessing the Internet. You may uninstall the current adapter driver and install the latest version of adapter driver.
   How to Update Adapter Driver
   
   
5. Disable Firewall and check for the issue
   
   It is advised to disable the firewall protection on your computer and check for the issue.
   
   
6. Connect your computer to another modem
   
   To rectify the issues with the LAN port of the computer/LAN port of your modem
   either connect a different computer or Laptop to the modem or connect your computer to another modem.

The last step isolates the culprit port. If the issue is with the modem port, you need to contact your ISP. If your computer LAN port is defective, contact your hardware vendor.

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