ZyXEL P-660HN-T1H firmware with IPv6 support, as stated in the name, packed in a 5.23 MB RAR. The hardware version is not given, so check the router label and compare it with any notes inside the archive. Such firmware is used to add features, fix bugs or recover a modem with damaged firmware, either through the web interface, bootloader console or by writing the flash chip directly. Save the original flash first and confirm the image suits the chip capacity.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @biosarchive. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.
Back up your own chip before writing any dump, and match the full board number and revision. Flashing guide →