Officially, there is not a way to put the Netgear CG3000DCR cable modem router used Comcast into "true" bridge mode. The official documentation offers a workaround that instructs you how to put the CG3000DCR into "pseudo-bridge mode" or, more appropriately, "IP passthrough mode". Either way, it would be nice if the Netgear CG3000DCR router supported true bridge mode so that a double NAT situation could be avoided. After some research and digging into forum responses I found a great bit of advice to get the CG3000DCR into true bridge mode. It is a hidden function built within the firmware of the router.
(These "hidden" webpages are not advertised or spoken of by Comcast or Netgear but they are accessed as follows):
To enable bridge mode (depending on how your CG3000DCR is addressed): http://x.x.0.1/RgNatControl.asp (In my case, http://192.168.0.1/RgNatControl.asp). Accessing this webpage turns bridge mode on and disables NAT.
Adversely, to disable bridge mode (depending on how your CG3000DCR is addressed): http://x.x.100.1/RgNatControl.asp (In my case, http://192.168.100.1/RgNatControl.asp). Accessing this webpage turns bridge mode off and NAT will thusly be re-enabled.
Notice the difference in IP addresses. One ends in "0.1" (to enable bridge mode) and the other ends in "100.1" (to disable bridge mode).
Cheers!