Hardware version v2.1 needs a firmware version 188.8.131.52K or higher!
You can find the how to on the firmware flash instruction page.
Note: flash firmware is at your own risk!
Original for CN hardware
Original for international hardware
Modified for CN hardware
Additional features are added to this firmwares (RTSP, FTP, telnet, timezone, …)
How to use the different additional features is described on the instruction page.