Gigabit ethernet adaptor Realtek PCIe GbE Family Controller throttling from 1000Mbps to 100mbps

Question

Gigabit ethernet adaptor Realtek PCIe GbE Family Controller throttling from 1000Mbps to 100mbps

CB 0

Hello,

Im having an issue where my internet is being throttled down to 100mbps. Ive tried a usb to ethernet adaptor and with that I am able to get gigabit download speeds however when i plug the same ethernet cable into the port on my laptop, my connection turns into 100mbps. I have tried uninstalling and reinstalling drivers, uninstalling the device, going into advance properties for the controller and changing settings as per some online forums however nothing seems to work. Visual inspection of the ethernet port on the laptop doesnt show anything abnormal. Please help this is very frustrating. Running windows 11 current update as of 5/5/2026

CB 0 Reputation points

2026-05-05T19:17:48.6666667+00:00

Im getting this message in the event log of my ethernet adaptor-

Device settings for PCI\VEN_10EC&DEV_8168&SUBSYS_13B61462&REV_15\01000000684CE00000 were not migrated from previous OS installation due to partial or ambiguous device match.

could this have anything to do with the issue? It was all working fine yesterday, could it be a windows update gone wrong?
Jeronimo Fuerte 46,170 Reputation points Independent Advisor

2026-05-05T19:50:03.6333333+00:00
In your case, the important detail is this: the same cable gives gigabit speed through a USB Ethernet adapter, but only 100 Mbps through the laptop’s built-in Realtek PCIe GbE port. That could point to one of these:

The Realtek driver/settings were changed or corrupted after an update.

A power-saving option is forcing bad negotiation.

Go to Device Manager > Network adapters > Realtek PCIe GbE Family Controller > Properties > Driver and check whether Roll Back Driver is available.

1 answer

Your answer

CB 0 Reputation points

2026-05-05T19:17:48.6666667+00:00

Im getting this message in the event log of my ethernet adaptor-

Device settings for PCI\VEN_10EC&DEV_8168&SUBSYS_13B61462&REV_15\01000000684CE00000 were not migrated from previous OS installation due to partial or ambiguous device match.

could this have anything to do with the issue? It was all working fine yesterday, could it be a windows update gone wrong?
Jeronimo Fuerte 46,170 Reputation points Independent Advisor

2026-05-05T19:50:03.6333333+00:00

In your case, the important detail is this: the same cable gives gigabit speed through a USB Ethernet adapter, but only 100 Mbps through the laptop’s built-in Realtek PCIe GbE port. That could point to one of these:

The Realtek driver/settings were changed or corrupted after an update.

A power-saving option is forcing bad negotiation.

Go to Device Manager > Network adapters > Realtek PCIe GbE Family Controller > Properties > Driver and check whether Roll Back Driver is available.

Answer 1

Since the same cable and router give gigabit speeds through a USB–Ethernet adapter, the issue is isolated to the built‑in Realtek PCIe GbE controller or its configuration in Windows.

Try these steps on the Windows 11 PC, in order:

Run the built‑in network troubleshooter
1. Select Start > Settings > Network & internet.
2. Select Status (Windows 10) or use the Network & internet troubleshooters in Windows 11 via Get Help.
3. Run the Network troubleshooter and apply any fixes it suggests.
Uninstall and reinstall the Ethernet adapter driver This forces Windows to reload a clean driver, which can fix speed/negotiation issues.
1. Select Search on the taskbar, type Device Manager, and open Device Manager.
2. Expand Network adapters and locate the Realtek PCIe GbE Family Controller.
3. Right‑click it and select Uninstall device.
4. Check Attempt to remove the driver for this device if available, then select Uninstall.
5. Select Start > Power > Restart.
6. After restart, Windows will automatically reinstall the Ethernet driver. Test the link speed again.
7. If Windows does not reinstall it, install the backup driver downloaded from the laptop or motherboard manufacturer on another PC and copied via USB.
Use Network Reset (last resort) If the adapter still negotiates only 100 Mbps, reset all network components in Windows.
1. Select Start, type settings, then open Settings > Network & internet.
2. On Windows 11, select Advanced network settings > Network reset.
3. Select Reset now > Yes to confirm.
4. Wait for the PC to restart and test the Ethernet speed again.
Notes:
- Network reset removes and reinstalls all network adapters and resets their settings to defaults.
- Afterward, VPN clients, virtual switches (Hyper‑V, etc.), and Wi‑Fi profiles might need to be reconfigured.
Hardware/port check If, after driver reinstall and network reset, the built‑in port still only links at 100 Mbps while the same cable and router port give 1 Gbps through a USB adapter, the laptop’s Ethernet PHY/port is likely degraded or damaged and limited to Fast Ethernet. In that case, continuing to use the USB–Ethernet adapter is the practical workaround, or the laptop’s Ethernet port would need hardware repair.

References:

Fix Ethernet connection problems in Windows