Never download firmware from third-party “driver download” websites. They often bundle malware or corrupted files.
Incorrect firmware can "brick" your router (turn it into a useless piece of plastic). Follow these preparatory steps religiously. 300m mimo wireless-n broadband router firmware download
If the manufacturer’s site is gone (e.g., for brands like “Netcore” or “TotoLink”), try: for brands like “Netcore” or “TotoLink”)