Asus RT-N66W - Manual (Page 7)

1.3 Your wireless router
Power LED
Off: No power.
On: Device is ready.
Flashing slow: Rescue mode
Flashing quick: WPS is processing.
LAN LED
Off: No power or no physical connection.
On: Has physical connection to a local area network (LAN).
Flashing: Transmitting or receiving data via wireless connection.
WAN LED
Off: No power or no physical connection.
On: Has physical connection to a wide area network (WAN).
Flashing: Transmitting or receiving data via wireless connection.
2.4GHz LED / 5GHz LED
Off: No 2.4GHz or 5GHz signal.
On: Wireless system is ready.
Flashing: Transmitting or receiving data via wireless connection.