Scenarios

The following scenarios and questions are designed to draw together the content of the chapter and to exercise your understanding of the concepts. There is not necessarily a right answer. The thought process and practice in manipulating the concepts are the goals of this section. The answers to the scenario questions are found at the end of this chapter. The information used in these scenarios was adapted from the Cisco web page, "Cisco Configuration Guidelines."

Scenario 4-1

The multinational company Gargantuan, Inc., has a private network addressed using the 10.0.0.0/8 space. Figure 4-3 shows the addressing scheme.

Figure 4-3. Diagram for Scenario 4-1

The network is experiencing timeouts and network crashes. In addition, EIGRP appears to be losing routes from its routing tables, which is adding to the problem.

Review the Gargantuan, Inc., addressing scheme and answer the following questions:

1.	What changes to addressing or EIGRP could affect the route drops and network problems? State the configuration commands necessary to activate this solution on Router A.
2.	The WAN is a Frame-Relay cloud, and Router A is the hub in the hub-and-spoke configuration. Each VC is 56 kbps. Give the commands to configure Router A for EIGRP over this NBMA cloud.
3.	Give the commands to configure Router B for EIGRP over this NBMA cloud.

Scenario 4-2

Given the configuration of EIGRP in Example 4-12, perform the tasks and answer the questions listed. The WAN has light user traffic and is a hub-and-spoke configuration, as shown in Figure 4-4.

Example 4-12. Scenario 4-2 Configuration for Router A

Router#show config
interface Serial 0
   encapsulation frame-relay

   interface Serial 0.1 point-to-point
   bandwidth 25
   ip bandwidth-percent eigrp 123 90

   interface Serial 0.2 point-to-point
   bandwidth 25
   ip bandwidth-percent eigrp 123 90

   ...

Figure 4-4. Diagram for Scenario 4-2

The 256-kbps access line to the hub has 56-kbps access lines to each of ten spoke sites. Each link has a Frame Relay CIR of 56 kbps. The access line to each router reflects the CIR. The access line to the hub router, Router A, is 256 kbps, but the CIR of the hub is the same as its access line.

From a Frame Relay perspective, a circuit is considered oversubscribed when the sum of CIRs of the remote circuits is higher than the CIR of the hub location. With ten links, each with a CIR of 56 kbps, this circuit is oversubscribed.

1.	How much bandwidth has each circuit been allocated? Why was this value chosen by the administrator?

2.	What bandwidth utilization is available to EIGRP? Why was this value chosen by the administrator?
3.	If Router A fails, what would the effect be on the network?
4.	Is summarization possible only on the routers entering the WAN cloud, or is it possible on the networks not shown in the figure that are on the other side of the routers? Give reasons for your answers.