reply to juniiflow You can change the routers IP address under Setup/Networking. SO if your ISP modem is 192.168.0.1, just change the 655 IP address from .0.1 to .1.1. Should work there.
It's recommended to bridge the ISP modem if possible and let the 655 handle the NAT and PPPoE connection if your on DSL. If the ISP modem can't be bridged, use the DMZ on the ISP modem and input the IP address the WAN side gets from the ISP modem into the modems DMZ. This should prevent any double NAT from happening.