The C4000 series modem/WiFi router comes in two models, each with different specifications. The one you use will depend on the type of internet service you have.
Regardless of the specific model, the status LED ring on the front of the modem will function in the same way. This single status light replaces the multiple lights (Ethernet, Internet, WAN, etc.) found on earlier modems. If you have a C4000BG/BZ or LG/LZ model, you will also see a DSL status light on the back of the modem.