Member Avatar for Helltech

So on my friend's computer, his RJ45 jack stopped working. I thought maybe it got shut off in the BIOS, even though it just stopped working while using the computer. Its not the cord it self as when he plugs it into his xbox 360 he geting connectivity. When he tries a different ethernet cord he still doesn't get anything. So he brought it to my house, and plugged it in here still nothing. I really don't know what to do at all.

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Dani AI

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Useful next steps and diagnostics that complement , and without repeating the driver/disable advice already suggested.

Start with the firmware and hardware level

  • Enter the BIOS/UEFI (Del/F2 or vendor key at POST) and confirm the on‑board LAN or integrated NIC setting is enabled. If the machine had any recent power event, try a full power drain: shut down, unplug the PC, press and hold the power button ~15–30 seconds, then power back on. If comfortable doing so, visually inspect the motherboard and the RJ45 jack for burnt components, cracked solder joints, or bulging capacitors near the LAN area. Take ESD precautions and avoid forcing anything if still under warranty.

Use an alternate OS to isolate Windows vs hardware

  • Boot a Linux live USB (Ubuntu, SystemRescue, etc.) and look for the NIC at the PCI/hardware level and for kernel messages. This helps decide whether the chipset is still visible to the system (hardware) or only missing under Windows (software/driver).
  • Example commands to run from a live environment or an elevated Windows command prompt:
# Linux (from live USB)
lspci -nn | grep -i ethernet
dmesg | grep -i -E 'eth|link|r816|e100'

# Windows (admin cmd)
ipconfig /all
getmac

What to infer from results

  • If the NIC does not appear in lspci or produces no kernel messages, it is almost certainly a hardware/PHY/magnetics failure on the motherboard. If it appears to the OS but never establishes a link under any cable/switch, look for BIOS/firmware settings or intermittent board damage.

Short-term fixes and final options

  • A cheap USB-to-Ethernet adapter is a quick way to restore connectivity for testing and use. If the board is under warranty, contact the motherboard vendor; if not, replacement options are PCI/PCIe NICs or professional repair (RJ45/magnetics replacement) if worth the cost.

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Member Avatar for baltazar

Do the orange and green lights on the RJ45 work? i.e do they flash or are they solid?

Have you tried disabling and enabling the Ethernet adapter?
Network Connections -> Right-click on Local Area Connection -> Disable. Then do the same and select enable.

If that doesn't work, you can also remove the driver and re-install it.
1. Download the latest driver for the Ethernet adapter from the manufacturer's website.
2. Right-click My Computer -> Manage. Select the Ethernet card from under Network Adapters and un-install the driver.
3. Re-boot your machine and run the setup file for the driver you previously downloaded.
(You can also try running Windows update after rebooting and it will automatically find a driver for you, but I personally don't like doing that.)

Member Avatar for Helltech

Ill try that right away, but no the lights don't come on. Also its just the ethernet port that came with the mobo, not like on a pci card.

Member Avatar for baltazar

Ok, then you need to download the latest motherboard drivers from the manufacturer's website.

Member Avatar for caperjack

and if that doesn't work ,then i suggest going out and buying and installing a pci nic card

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