In this chapter, you will

• Learn about network structures

• Discover the role of routers

• Learn how to configure a router

• Review the role of firewalls and network security

• Discover static and dynamic routing protocols

In this chapter we will examine how to connect multiple machines in subnets and how to connect subnets to form local area networks (LANs) through routers. Inter-router connection allows the formation of wide area networks (WANs), and ultimately the Internet. Communication between different machines, through the transmission of data packets, can only take place through the process of routing. Routing involves finding a route between two hosts, whether they exist on the same network or are separated by thousands of miles and hundreds of intermediate hosts. Fortunately, the basic principles are the same in both cases. However, for security reasons, many sites on the Internet have installed packet filters, which deny certain packet transmissions on a host or port basis. In this chapter we will examine static and dynamic methods for configuring routes between hosts, and examine the mechanisms of IP filtering and firewalls.