Part IV gets into more detail about how networks with multiple LANs work. To deliver end user data between different LANs, networking devices called routers are used; these routers forward data based on TCP/IP addresses. Chapter 10 introduces the concepts of TCP/IP addressing and the basics of routing, and Chapter 11 provides more detail on the routing process. Chapter 12 describes the basics of how routers learn how to route packets by using something called a routing protocol. Finally, Chapter 13 explains how TCP/IP networks use names and how they are resolved into their corresponding numeric TCP/IP addresses.
Chapter 10: Delivering the Goods to the Right Street (IP) Address
Chapter 11: Knowing Where to Turn at Each Intersection (Router)
Chapter 12: Painting the Road Signs on Your Interstate (Internetwork)
Chapter 13: People Like Names, but Computers Like Numbers