Macbook connects to modem, internet works, but modem -> router, no internet
Disabling the WiFi Signal on the Netgear CG3000D WiFi Cable Modem 

You may have a standalone router that you would like to continue to use and are having problems with connecting to your router. The device may be causing a conflict because the router portion of the device is also active. You can turn off the WiFi network of the device, turning it into a modem only, and be able to use your router without an issue.

Completing this procedure disables the SSID for the Netgear CG3000D Home Device. This allows customers to use their own standalone wireless router.