Foundation Summary

10 Mar

Foundation Summary
The “Foundation Summary” section of each chapter lists the most important facts from the chapter. Although this section does not list every fact from the chapter that will be on your exam, a wellprepared candidate should, at a minimum, know all the details in each “Foundation Summary” before going to take the exam.

The following is a list of the commands explained in this chapter. This list is not intended to teach the use of the commands, but to remind you of the options available.

The commands in Table 7-12 are configuration commands.
Table 7-12 OSPF Configuration Command Summary

OSPF Configuration

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Table 7-13 The show Command Options for OSPF

Command Options for OSPF

Q&A

As mentioned in the introduction, “All About the CCNP, CCDP, and CCIP Certifications,” you have two choices for review questions. The questions that follow next give you a bigger challenge than the exam itself by using an open-ended question format. By reviewing now with this more difficult question format, you can exercise your memory better and prove your conceptual and factual knowledge of this chapter. The answers to these questions are found in Appendix A.

For more practice with examlike question formats, including questions using a router simulator and multichoice questions, use the exam engine on the CD.

1. What command is used to manually determine which router on a LAN will become the DR?
2. What parameter is used to calculate the default metric of a route in OSPF on a Cisco router?
3. It is possible to have more than one OSPF process on a router. How would you do this?
4. Explain the command ip ospf network non-broadcast .
5. In which of the NBMA configuration choices is it necessary to state the neighbors manually? Why is this necessary?
6. In a Frame Relay environment, which is fully meshed, which OSPF configurations might be chosen? Give reasons for your choice.
7. The Cisco solution point-to-point mode does not require the configuration of DR and BDR. Explain briefly why.
8. The address 192.100.56.10/21 has been allocated to an interface on the router. This interface alone is to be included in the OSPF process. State the command that would start the process on this interface.
9. The metric used by OSPF is cost. How would you change the metric on an interface?
10. If the command ip ospf network non-broadcast is used, what additional statement is necessary?
11. What command shows which router on a LAN is the BDR?
12. Explain briefly what show ip ospf database will reveal.
13. What command is used to show the state of adjacencies?
14. Which command is used to show OSPF packets being sent and received in real time?
15. How would you show the OSPF process ID of the router?
16. What makes debug a dangerous command for your router?
17. What is the sequence number and where is it held?
18. In the show ip ospf command, there is a field called the SPF schedule delay. What is the purpose of this field, and what is the default time?
19. What is the advantage of the command show ip ospf interface in troubleshooting?

Scenarios
The following scenario 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 is the goal of this section. The answers to the scenario questions are found at the end of this chapter.

Scenario 7-1
The company Jackanory.com is charged with configuring the Los Angeles site for OSPF. Figure 7-2 is a network diagram for this network. You must first understand the design requirements for the entire network. As the figure shows, Jackanory.com intends to use Frame Relay to connect the different sites. The company also has decided to use the private address of 10.0.0.0. The Los Angeles site is to be allocated 10.1.0.0 255.255.0.0, which can be subdivided. Referring to Figure 7-2, answer the following questions.

Figure 7-2 Network Diagram for Scenario 7-1

Scenario

1. Design the addressing scheme for the site so that summarization can be implemented at a later stage.
2. Determine the configuration that will be implemented across the Frame Relay cloud.
3. State the configuration commands required to implement OSPF on the routers. Note that all the routers are to be in Area 0.
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Scenario Answers
The answers provided in this section are not necessarily the only possible answers to the questions. The questions are designed to test your knowledge and to give practical exercise in certain key areas. This section is intended to test and exercise skills and concepts detailed in the body of this chapter.

If your answer is different, ask yourself whether it follows the tenets explained in the answers provided. Your answer is correct not if it matches the solution provided in the book, but rather if it has included the principles of design laid out in the chapter.

In this way, the testing provided in these scenarios is deeper: It examines not only your knowledge, but also your understanding and ability to apply that knowledge to problems.

If you do not get the correct answer, refer back to the text and review the subject tested. Be certain to also review your notes on the question to ensure that you understand the principles of the subject.

Scenario 7-1 Answers
1. Design the addressing scheme for the site so that summarization can be implemented at a later stage.
An addressing scheme for the Los Angeles site could be as shown in Figure 7-3.

Scenario 7-1 Answer

2. Determine the configuration that will be implemented across the Frame Relay cloud.

The Frame Relay configuration is a hub-and-spoke topology. Because Los Angeles is the central hub of the company, it is logical that it is also the network hub.

The configuration in Frame Relay would therefore be a point-to-multipoint one. This avoids the DR/BDR election process, because it treats all the PVC links as a collection of point-to-point links, forming adjacencies across each link even though they are not separate point-to-point subinterfaces. Having separate links removes the need for the DR/BDR. This is a good solution if three different companies have a multivendor environment, because it conforms to the RFC standards.

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Example 7-13 shows a configuration that could be implemented.
Example 7-13 Answer to Scenario 7-1 Configuration Question 2

Answer to Scenario

Example 7-14 Answer to Scenario 7-1 Configuration Question 2 (Continued)

Configuration Question

Note that the Frame Relay cloud is a continuation of Area 0. This is a logical first step; it is advisable to change this configuration when OSPF is being run throughout the organization. When the other sites are up and running OSPF, the Los Angeles site could become another area. This would allow the summarization of routes across the Frame Relay cloud, which would reduce the traffic, cost, and possibility for congestion.

3. State the configuration commands required to implement OSPF on the routers. Note that all the
routers are to be in Area 0.

The configuration on the Los Angeles routers, not including the Frame Relay configuration, is shown in Example 7-15.

Example 7-15 Answer to Scenario 7-1 Configuration Question 3

Angeles routers,

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Example 7-15 Answer to Scenario 7-1 Configuration Question 3 (Continued)

Answer to Scenario

Note that Router A has been given a priority of 10, ensuring that it becomes the DR. Although this is not essential, it is a clear configuration and is advisable because this router is a larger system and is very reliable. For the same reasons, it is also considered good system management to define the priority for the BDR.

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