The router will upload the file and reboot automatically. during this process, as it can "brick" the device, making it unusable. Alternative: Checking for Auto-Updates
If you must search online (forums, tech sites): Zte F670 Firmware Update
Most F670 routers are configured to update automatically from the ISP's server. The router will upload the file and reboot automatically
New software versions often fix bugs that cause Wi-Fi drops or system freezes, especially in high-traffic environments. as it can "brick" the device
Some enthusiasts modify ZTE F670 firmware to unlock: