About the Transparent Bridge Mode
The transparent bridge mode is one of the transparent modes you can configure for the proxy functions of the appliance if you do not want to use an explicit mode.
In this mode, the clients are unaware of the appliance and need not be configured to direct their web traffic to it. The appliance is usually placed between a firewall and a router, where it serves as an invisible bridge.
The following diagram shows a configuration in transparent bridge mode.