Tenda often releases country-specific firmware versions for the D303 to match local DSL standards, VLAN settings, and ISP parameters. on a unit intended for India — it can break ADSL sync.
To update the Tenda D303 firmware specifically for use in India, you must download the correct regional file and upload it through the router’s web management page. The Tenda D303 is an "All-in-One" N300 ADSL2+/3G modem router that includes pre-built configurations for major Indian ISPs like Step 1: Download the Correct Firmware tenda d303 firmware update for india work
If you are using this device merely as a Wi-Fi access point for a fiber connection: tenda d303 firmware update for india work