Log in to your router (usually 192.168.0.1 ) and look for the hardware version in the top-right corner or the "Device Info" section. 2. Official DWR-921 Firmware Download Sources

Always download firmware from official D-Link support portals to ensure file integrity. Index of /pub/Router/DWR-921/Firmware - D-Link FTP Index of /pub/Router/DWR-921/Firmware. ftp.dlink.ru [OpenWrt Wiki] D-Link DWR-921

You download the firmware that matches your specific hardware version (e.g., B1, C1, or C3). Installing the wrong version can permanently damage (brick) your router.

Look at the sticker on the bottom of the device for "H/W Ver:" followed by a letter and number (e.g., C3).