Ethernet Not Working on Windows 11 (Fix)

Open Device Manager and expand Network adapters. If your Ethernet controller has a yellow triangle, right-click it, Properties, check the error code. Code 10 means the driver failed to start — uninstall the device, check “Delete the driver software for this device,” restart, and Windows will reinstall a clean copy. Code 31 or 39 means Windows loaded a corrupted or incompatible driver, same fix. If the adapter isn’t listed at all, click Action at the top, Scan for hardware changes. Still nothing means the port is disabled in BIOS or the hardware is dead.

The Intel I225-V and I226-V 2.5 Gigabit controllers are on every mid-to-high-end motherboard sold in the last three years — Z590, Z690, B660, Z790, B760 — and they’ve had more driver bugs than any Ethernet controller I can remember. The original I225-V hardware revision B1 had packet loss and disconnection problems baked into the silicon that no driver update could fully fix. Intel released the B2 and B3 revisions to address it, but if you bought a Z590 board in 2021 or early 2022, yours is probably B1. Check by opening Device Manager, double-clicking the Intel Ethernet adapter, Details tab, choose “Hardware IDs” from the dropdown — if it ends in REV_03, that’s B3 (fine). REV_02 is B2 (mostly fine). REV_01 is B1 and you may just be stuck with occasional drops that no driver version permanently fixes.

A customer’s brand new Z790 build wouldn’t get an IP address on Ethernet. Link light on, Windows showed “Identifying…” forever, never got past it. His WiFi worked fine on the same router, same cable worked fine plugged into his old machine. Opened Device Manager — Intel I226-V, no yellow triangle, driver looked healthy. Went to Intel’s download center, pulled their latest LAN driver (28.3, released early 2026), installed it over the top. Immediately connected. The driver that Windows Update had pushed was 27.x from mid-2025, and it had a known DHCP timing bug with certain router chipsets — the handshake would start but the adapter wouldn’t wait long enough for the router’s response. Eight minutes from “no internet” to fully connected.

Driver and Windows Update Problems

If Ethernet died right after a Windows Update, roll back the driver first. Device Manager, double-click the Ethernet adapter, Driver tab, Roll Back Driver. If that’s greyed out, Windows didn’t keep the previous version — you need to manually download one. For Intel, go to intel.com/support and search your controller model. For Realtek, go to realtek.com/Download — their RTL8111/8168 (1Gb) and RTL8125B (2.5Gb) are the two most common. For Killer Ethernet (common in gaming laptops), use the Intel driver instead — Killer was acquired by Intel and the standalone Killer Suite caused more problems than it solved.

Don’t install the driver through Device Manager’s “Update driver” wizard — it picks from Microsoft’s catalog which is always months behind and sometimes the exact version causing the problem. Download the .exe or .inf directly from the manufacturer and run the installer.

The Realtek RTL8125B on AMD B550 and B650 boards has a specific power management issue. Device Manager, double-click the adapter, Power Management tab, uncheck “Allow the computer to turn off this device to save power.” Then go to Advanced tab, find “Energy Efficient Ethernet” and set it to Disabled. EEE puts the adapter into micro-sleep states between packets to save a few watts, but the RTL8125B’s implementation on certain board BIOS versions causes the adapter to not wake up properly. The link stays up but no data flows — the worst kind of failure because Windows still shows “Connected” while nothing actually works.

If you’re only getting 100Mbps instead of your expected gigabit, and speed tests confirm it, the auto-negotiation is stuck. Advanced tab in the adapter properties, find “Speed & Duplex,” change it from “Auto Negotiation” to “1.0 Gbps Full Duplex” (or 2.5 Gbps if your adapter supports it). Auto-negotiation fails when the cable is marginal — technically functional but with just enough signal degradation that the handshake settles on a lower speed as a safety fallback. This is a symptom that your cable is starting to fail even if it still “works.”

Physical Layer

The link light on the back of your PC where the cable plugs in tells you more than Device Manager does. No light at all means no electrical connection — the cable is bad, the port is dead, or the other end isn’t plugged into an active switch/router port. Solid amber usually means 100Mbps link (should be green for gigabit). Blinking green means active gigabit traffic, which is what you want.

Swap the cable before anything else. Ethernet cables go bad more often than people think, especially if they’re bent sharply around furniture legs or run through walls where rodents chew on them. Cat5e handles gigabit up to 100 meters but only if the cable is intact — one damaged pair inside drops it to 100Mbps or kills it entirely. If you’re buying a new cable, Cat6 is worth the extra dollar. If you’re running through walls, Cat6a.

Try a different port on your router too. Consumer routers have 4 LAN ports and I’ve seen individual ports die while the others work fine. Plug into port 2 instead of port 1. If that works, port 1 is dead — on a $40 router it’s not worth fixing, just use a different port.

Settings Nobody Checks

Large Send Offload is the first one. Device Manager, adapter properties, Advanced tab, find “Large Send Offload v2 (IPv4)” and “Large Send Offload v2 (IPv6)” — disable both. LSO lets the adapter handle TCP segmentation instead of Windows, which theoretically saves CPU time but in practice causes some adapters to freeze under sustained load. This is the fix for Ethernet that works fine for browsing but drops during large file transfers or sustained downloads.

Wake-on-LAN can cause phantom connection states. If your PC wakes from sleep and shows Ethernet connected but with no internet, WoL might be holding the adapter in a half-initialized state. Advanced tab, disable Wake on Magic Packet, Wake on Pattern Match, and Wake on Link Settings. This costs you remote wake capability but eliminates the sleep-wake connection failures.

If nothing software-side works and the adapter shows up healthy in Device Manager with no errors, try booting a Linux live USB. If Ethernet works in Linux, the problem is Windows-side — do a full netsh int ip reset and netsh winsock reset, restart, and if that doesn’t work, network reset in Settings. If Ethernet doesn’t work in Linux either, the NIC is dead. A USB 3.0 Ethernet adapter costs $12-15 and works immediately — plug and play, no drivers needed, genuine gigabit. For WiFi issues or if you’re having DNS problems alongside the Ethernet failure, those are different diagnostic paths. If the adapter is confirmed dead or you’re stuck on intermittent drops you can’t pin down, our network diagnostic covers the full NIC and routing stack remotely.