My PC lost internet access after a brief outage. The Ethernet cable is detected, but Windows shows "Unidentified network" and reports that Ethernet does not have a valid IP configuration and that the default gateway is unavailable. The connection briefly started working again for about two hours, then failed once more.
I have restarted the router, tried another Ethernet cable and router port, released and renewed the IP address, reset the Windows network stack, disabled the adapter's power-saving option, and updated and reinstalled the network driver. Renewing the address reports that Windows cannot contact the DHCP server, and manually assigning a fixed IP did not help. Flushing DNS also made no difference.
What else can I try? Could the router be failing to assign an address, and is there a way to fix that without immediately contacting my internet provider?
4 Answers
Try booting the computer from a Linux live USB and test the same Ethernet connection. If Linux gets an IP address and internet access, the problem is likely specific to Windows. If Linux also receives no address, focus on the router, network hardware, or the connection between the PC and router.
The 169.254.x.x address shown by ipconfig /all is a self-assigned Windows address. It means the PC is not receiving a response from the router’s DHCP server, so this is probably not a DNS problem. Fully power off the router, unplug it for a few minutes, then start it again and check whether other wired devices can obtain an address. If you use powerline adapters or a mesh system, restart and resync those as well. If other devices also fail, the router or the provider’s connection is the likely cause.
Flushing DNS would not normally fix this particular symptom because the computer does not yet have a valid IP address or default gateway. The DHCP failure needs to be resolved first.
Updating the network adapter driver and manually assigning an IP can sometimes help, but neither will solve a router that is not answering DHCP requests. Since the cable and port have already been changed and the connection worked intermittently, the router may be stuck after the outage or malfunctioning. Check its DHCP settings and connected-device status if you can access its administration page; otherwise, the provider may need to run a remote diagnostic or replace the router.
I confirmed that the PC is receiving a 169.254 address. I have already restarted and unplugged the router several times, but I’ll check whether other devices are affected and contact the provider if DHCP still does not return.