How to connect DVR via internet when using Comcast cable Internet access?

[jlask01]

I have read this entire thread and cannot believe my problem has not come up. My iSP is Comcast. The internet connection goes into their modem which has ethernet ports on it. I have admin access to it. I then have my own router plugged into one of the ethernet ports. I have my DVR configured to work thru my local router just fine, however, how do I configure the cable modem to allow remote internet access and send that to the DVR thru my router? I have all the IP addresses involved (Internet IP, modem to router and router to DVR).