I recently moved into a new house and had 1 Gbps internet installed. The connection is consistently fast on my phones, TVs, and other devices, usually reaching around 900 Mbps to 1 Gbps. However, my desktop's wired connection is extremely unstable.
The PC is connected directly to the router with an Ethernet cable, but the connection frequently drops to 0 Mbps in Task Manager. Web pages often fail to load or take a very long time. I've checked that no applications are using excessive bandwidth, installed Windows and Ethernet adapter updates, restarted both the PC and modem several times, and confirmed that no VPN is active. I even temporarily disabled the Windows firewall, but nothing helped.
I'm considering wiping and reinstalling Windows because the installation is several years old, though I'd prefer to troubleshoot the issue first. Could a faulty Ethernet cable, router port, or network adapter be responsible, and what should I try next?
2 Answers
Start by testing with a different Ethernet cable, preferably a known-good Cat5e or Cat6 cable. Cables can fail over time even if they worked previously, and a damaged cable can cause an unstable link or repeated speed negotiation. Also try another LAN port on the router and check the adapter's negotiated link speed in Windows.
Make sure the cable is plugged into one of the router's LAN ports, not the modem or the router's Internet/WAN port. If another cable and LAN port produce the same problem, test the PC with a different network adapter, such as a USB Ethernet adapter, to determine whether the desktop's built-in Ethernet hardware is failing.
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