There is no such thing as "30-30-30 RULE METHOD" for RouterBoards. What you should try is this:
1. Press reset button, power on the device and immidiately release the reset button. This will hopefully start the router with backup bios. If it boots up, you should upgrade your firmware.
2. If the above procedure does not do anything, try to reinstall the router with netinstall. Press and hold reset button, power on the router. Does the ACT led start to blink after holding the button for a few seconds? If it does not, it is probably a hardware failure, if it blinks, do a fresh install with netinstall. If you can not get an ethernet link during netinstall, it is most definitely ethernet hardware problem.
I tried, but nothing happened (all eth ports are still inactive)
Only PWR Led is on.
Did you try the 30 rule? It work for me. Just keep on trying at least 3 times. Here is more info.:
Hard Reset ("30/30/30 reset")
Holding down the reset-button while plugging in the router achieves a different goal than the thirty second reset
. Here the bootloader is in charge, so getting it to clear the memory for you may have different results. Some platforms will completely empty the nvram and depend on another stage of the bootloader or firmware to repopulate it.
On some less-supported hardware this may have unpleasant results, so use the following two reset methods cautiously.
How to do a "30/30/30 reset"
To do a "hard reset for anyone not knowing OP or otherwise, hold the reset button with the power on, for 30 seconds, then while continuing to hold the reset button, unplug the router, continuing to hold the red button in the back for 30 seconds, and while still holding it in, plug in the power again and keep holding the reset button for an additional 30 seconds. This will wipe the nvram out.
Keep in mind with hard resets the routers can be touchy I had to do it three times till it fully cleared out the nvram on mine" I think this forum poster actually meant that it will reset back to firmware/factory defaults, but as stated above, it could have unpleasant results "on some less-supported hardware".