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Ethernet Connection Limited to 100Mbps Instead of 1Gbps

Anonymous
2025-01-18T03:19:34+00:00

Hello!

I have a GA-B85M-D3PH motherboard that supports 1Gbps connections, but I've only been able to achieve that speed for two days. After that, my connection remains stuck at 100Mbps. I verified this both through speed tests and in the Ethernet properties.

I'm using Windows 10 Pro (fully updated), along with the Realtek driver version 10.73.815.2024. The "Speed & Duplex" setting is manually configured to 1Gbps, and I'm using a Cat5e cable.

From what I can tell, everything seems to be properly set up. I even tested the same cable and connection on a laptop running Windows 11, and it worked perfectly at 1Gbps. This leads me to believe the issue lies within Windows 10 (or maybe my ISP just doesn't like me).

I've already tried adjusting some registry settings (following tutorials and guidance from AI), but without success. Interestingly, the configurations I applied seemed to work temporarily, but once I shut down the computer and turned it back on the next day, the settings no longer forced the connection to 1Gbps.

Is there some "hidden" configuration I might be missing? Could this be a Windows-specific issue, or is there possibly a problem with my onboard network adapter?

Any advice would be greatly appreciated!

Thank you in advance!

Windows for home | Windows 10 | Internet and connectivity

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  1. Anonymous
    2025-01-24T06:01:55+00:00

    Sorry for the delayed response!
    I managed to identify the issue: apparently, the cable I was using had some kind of defect that was not externally visible, causing the connection speed to fluctuate. The connection behaved differently depending on the cable's position on different days. When I replaced it with a Cat 6 cable, the connection properties showed /1000, indicating the problem was resolved.
    Sometimes, we forget to do the simplest things (even though I had to buy a new cable and did so while waiting for the delivery).
    Anyway, thank you for your response!

    2 people found this answer helpful.
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  2. franco d'esaro 24,991 Reputation points Volunteer Moderator
    2025-01-24T10:22:31+00:00

    I'm glad you solved your problem.

    Thank you for letting me know.

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  3. franco d'esaro 24,991 Reputation points Volunteer Moderator
    2025-01-18T10:40:13+00:00

    Hi.

    First of all, Speed ​​and Duplex should remain set to Auto Negotiate.

    Ethernet speed stuck at 100 Mbps is usually caused by a hardware problem: a faulty or low-quality network cable, a faulty Ethernet connector, or a faulty Ethernet LAN socket on the PC or router/switch. The quickest test is to unplug/replug the network cable on both ends or try replacing the network cable.

    Are the router and PC in the same room or are they in different rooms or on different floors of the house?

    Is the PC's network cable directly connected to the router's LAN port or is it connected via the Ethernet wall socket or via some other network device?

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