Ethernet speed capped at 100 Mbps instead of 1 Gbps (1000 Mbps)
Paying for 300Mbps to 1Gbps internet but Windows Ethernet link speed shows capped at 100/100 Mbps.
Internal desktop parts run on harmless 12V DC voltage and cannot shock you. Simply unplug the wall power cable first, then touch the unpainted metal case frame to ground static electricity.
Common Symptoms & Tells
- Windows Network Properties shows 'Link speed (Receive/Transmit): 100/100 (Mbps)'
- Speed test never exceeds 94-95 Mbps on a 500Mbps+ fiber plan
- Ethernet port LED shows amber/orange instead of green
Interactive Fix Checklist
0 of 3 steps completedInspect and replace damaged Cat5/Cat5e Ethernet cable
Gigabit Ethernet (1000 Mbps) requires all 8 copper pins to negotiate properly. If even one pin is bent or severed, Windows falls back to 4-pin Fast Ethernet (100 Mbps). Swap cable for a certified Cat6 patch cable.
Disable Energy Efficient Ethernet and Green Ethernet
Open Device Manager -> Network adapters -> right-click your Intel/Realtek Ethernet controller -> Properties -> Advanced tab. Set 'Energy Efficient Ethernet', 'Green Ethernet', and 'Gigabit Lite' to 'Disabled'.
Force Speed & Duplex to 1.0 Gbps Full Duplex
In the same Advanced tab, find 'Speed & Duplex'. If set to 'Auto Negotiation' and negotiating 100 Mbps, test setting it explicitly to '1.0 Gbps Full Duplex'. Click OK.
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