Routers are located on layer 3 the network layer of the OSI model. Routers provides the capability to forward packets end to end through a network. In a network LAN or a WAN, the router connects to the LAN switch and some WAN link. The WAN link is like my central offices at the Sheriff's Office and our remote sites like the different sectors. Chapter 17, Figure 17.1 and 17.2 shows how the router plays a part in setting up an enterprise network showing a pictorial view of the setup. This can be very simple or very complex with one or more routers in the network. Again as you exam these networks you will see that there is a Leased line between both CSU/DSU (Channel Service Unit/ Data Service Unit) that converts a digital data frame from a LAN and converts it to something a WAN can use. As we move along in the class we will break out each of the sections of the LAN and the WAN with the focus on the router. As we are here look up some of the protocols that a router used to communicate with in an enterprise network.