My newly built Windows PC recognizes the Ethernet connection, but it always shows "Unidentified Network" and assigns itself a 169.254.x.x address. The router works normally with another computer, and this PC is connected directly to the router. I've already tried resetting Winsock and TCP/IP, renewing the IP configuration, reinstalling and updating the Ethernet driver, resetting Windows networking, changing IPv4 between automatic and manual settings, disabling and enabling the adapter, restarting the PC, power-cycling the modem and router, replacing the Ethernet cable with a new Cat6 cable, and resetting the PC. Windows reports that no DHCP server can be found. For now, I'm using USB tethering, but I'd like to determine whether the problem is the onboard network adapter, its driver or BIOS settings, or something else.
4 Answers
Since the router gives another computer an address, check the new PC’s Ethernet driver and BIOS settings next. Download the correct LAN driver from the motherboard manufacturer using another device and install it manually. You can also test with a USB 3.0 Gigabit Ethernet adapter; if that works immediately, the onboard network interface or its configuration is probably defective.
Make sure the manual settings are based on the working computer’s configuration rather than guessed values. Compare its IPv4 address, subnet mask, default gateway, and DNS settings, then choose an unused address in the same range for testing. If the Ethernet adapter’s link lights are missing while connected, try another router port as well.
A 169.254.x.x address is an APIPA address. Windows assigns it when the adapter cannot obtain a usable address from DHCP, so it usually points to a connection, adapter, driver, or router-port problem. Restart the network equipment in order, beginning with the modem or primary router, waiting a few minutes between each device, then restart the PC. Also confirm the cable is plugged directly into the router rather than a wall jack or another device.
I restarted everything in that order, but the PC still receives the same 169.254.x.x address.
Try assigning a temporary static IPv4 address that matches the router’s network, along with the correct subnet mask and router address. If the PC works with a static address, DHCP is the likely issue. If it still cannot communicate with the router, the problem is more likely the adapter, cable path, router port, driver, or motherboard configuration. Use the working PC to check its IP range before choosing the address.
I’m going to try a USB Gigabit Ethernet adapter. If it works, that should help confirm the onboard adapter is the problem.