Scenario 2-1: Routing IP on Cisco Routers

In this scenario, you configure two Cisco routers for IP routing using a Class B (/16) network address,, with a Class C subnet mask (, or /24). You learn how to build a small network up from the physical layer and build an IP routing table using one serial link between the two routers, R1 and R2. You also configure a number of loopback interfaces to populate the IP routing table.


A loopback interface is a software interface. You can ping it and communicate with it. Most importantly, it never goes down, and you can use it as a tool to populate routing tables.

Figure 2-2 shows the network for this scenario.

Figure 2-2. Routing IP with Directly Connected Networks

Routing IP ...

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