Posted 20 May 2012 - 03:13 PM
Basically, bridged means your router becomes part of the ISP's network. For example, in a bridged network your modem would "pass-along" the public IP address given by the ISP to the router. If it's not bridged and double NAT is being used then your modem is assigned the public IP address, and the modem assigns the router a private (for example, 192.168.0.2) IP address. Your router then assigns your PC a different private IP (ex: 192.168.1.2) and since it's going through two "layers" of private IP addressing (NAT) it's "Double NATed".
The easiest way to tell if your connection is bridged or not is to look in the router's control panel and see what type of IP address has been assigned to it's WAN interface. If it was assigned a 192.x.x.x, 10.x.x.x, then it's not operating in bridged mode and may be double NAT'd.