The concept of bridge in ROS has nothing to do with hardware … it’s the same also on devices without switch chips (e.g. CCR1xxx). So you have to try to understand the concept. And layering (e.g. port vs. interface), the two major functions of bridge (interface which allows CPU to interact with connected devices vs. switch-like device which connects ports), the different details of each of these functions, how they interact, what part of bridge config is actually about which detail. Etc.