No internet access even when router is plugged into fiber optic cable

If your internet does not work when a fiber optic cable is connected to your router, the issue is often due to modem/router configuration, IP assignment, or ISP setup.Check the Fiber Modem/ONT SetupMost fiber connections require an Optical Network Terminal (ONT) provided by your ISP. Ensure the fiber cable is connected to the ONT, not directly to the router, unless your router has a dedicated fiber port (SFP or WAN labeled for fiber) . Power on the ONT and wait for the status lights to stabilize, which can take 2–5 minutes .Connect the Router CorrectlyUse an Ethernet cable to connect the ONT's Ethernet/LAN port to your router's WAN port. Make sure the router is compatible with fiber input. After connecting, power on the router and check the indicator lights for a successful connection .Verify IP ConfigurationFiber connections may require static IP addresses or specific settings from your ISP. If your router is set to auto-detect and selects dynamic IP incorrectly, manually configure the router with the IP, gateway, DNS, and MAC address provided by your ISP . Incorrect IP settings can prevent the router from obtaining an external IP, resulting in no internet access .Check for Gateway ConflictsIf your ISP's fiber gateway is not in bridge mode, it may conflict with your router's IP range (commonly 192.168.1.x), preventing access to devices on your network . You may need to either:Enable bridge mode on the ISP gateway, orChange your router's LAN IP range to avoid conflicts .Basic Troubleshooting StepsRestart devices: Power cycle the ONT, router, and connected devices .Inspect cables and connectors: Ensure fiber and Ethernet cables are undamaged, clean, and securely connected .Check router firmware: Update to the latest firmware to avoid compatibility issues .Test direct connection: Connect a computer directly to the ONT to verify the ISP connection works .When to Contact Your ISPIf the above steps fail, the issue may be on the ISP's end, such as incomplete provisioning, IP assignment errors, or a non-bridged gateway . Contact your ISP and provide details about your router model, IP configuration, and the steps you have already tried. By following these steps, you can identify whether the problem is due to hardware, configuration, or ISP setup, and take appropriate action to restore internet access.