It's preferred to bridge the ISP modem, presuming this modem is a DSL modem with built in router. Once you bridge the DSL modem, it effectively shuts off the internal router and WiFi. So you really don't need to use it's WiFi to bridge to the 655. You'll need to use the PPPoE information on the 655 to set up the Internet Connection. After you do this, power off everything, turn on the DSL modem and let it sync, then power on the 655 router. Should have internet after that.