Foundation Topics

The Need for Routing and Routing Tables

Suppose you’re at your desk and want to access a website on the far side of the continent. You enter a URL and your browser locates a DNS server that can translate the URL into its corresponding IP address (more about this later in Chapter 5, “Installing and Configuring Domain Name System (DNS)”). But, your network only knows about local IP addresses. However, you’ve configured your TCP/IP properties with an IP address for the default gateway (or the network DHCP server has supplied this address for you). This address is that of your network router, and it knows that it must send your message onward. But, there’s a veritable maze of networks and routers out there. Without some kind of directing authority, your message could bounce around these routers forever. Figure 3-1 gives you an idea of the type of problem each message packet must face in its journey to the destination.