Before we jump into the management of routing tables, let’s take a more detailed look at how the tables are used. Consider the network shown in Exhibit A.
Exhibit A Example network
Router R1 connects the two Ethernets, and router R2 connects one of the nets to the outside world. (For now, we’ll assume that R1 and R2 are UNIX computers rather than dedicated routers.) Let’s look at some routing tables and some specific packet forwarding scenarios. First, host A’s routing table:
A% netstat -rnRouting tablesDestination Gateway Flags Refs Use If127.0.0.1 127.0.0.1 UH 6 563131 lo0 ...