Help configuring Fortigate 30D behind Comcast gateway

[hboswell]

We have Comcast Business Class, and an SMC D3G modem/gateway. We would like to turn off the router function in the SMC, and use our Fortigate 30D instead. I' ve read about putting the SMC in bridge mode, and I' ve looked at how to set up the Fortigate, including the Fortigate cookbook, but I' m not getting it to work. Can someone help me understand where I might be going wrong? Thanks, Harry