Once you understand the operations of the various devices and their roles in the network, it's time to put the pieces together. In this section, a review of collision and broadcast domains will be followed by a more complete description of the three-layer Cisco hierarchical model.
A broadcast domain is a set of devices that will receive one another's broadcast packets. If these devices have physical connectivity with one another and are in the same subnet, they are in the same broadcast domain. One of the main functions of routers is to separate or create broadcast domains. In Figure 10.13, the router has four interfaces, and each interface is a separate broadcast domain.