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C H A P T E R 7

Advanced Routing

Protocol Topics

In Chapters 5 and 6, you read about the concepts and configuration of the four interior routing protocols covered on the ICND exam—RIP, IGRP, EIGRP, and OSPF. Those chapters focused on the details specific to each routing protocol.

This chapter covers several topics related to designing a network’s IP subnetting scheme, with considerations for the routing protocol’s capabilities. For instance, you must consider whether the routing protocol will support variable-length subnet masking (VLSM). If the routing protocol does not support VLSM, you need to pick a single subnet mask for the entire network—and as a result, you might waste a lot of IP addresses in each subnet.

This chapter describes several concepts related to IP subnetting design. VLSM is covered in the first section, along with route summarization. Route summarization requires VLSM support in the routing protocol, so these two topics are covered in the same section. The second section describes classful and classless routing protocols. These terms are used in many different ways, and this section clears up their meanings.

“Do I Know This Already?” Quiz

The purpose of the “Do I Know This Already?” quiz is to help you decide if you need to read the entire chapter. If you intend to read the entire chapter, you do not necessarily need to answer these questions now.

The eight-question quiz, derived from the major sections in the “Foundation Topics” section, helps you determine how to spend your limited study time.

Table 7-1 outlines the major topics discussed in this chapter and the “Do I Know This Already?” quiz questions that correspond to those topics.

Table 7-1 “Do I Know This Already?” Foundation Topics Section-to-Question Mapping

 

Questions Covered in This

Foundations Topics Section

Section

 

 

Route Summarization and Variable-Length Subnet Masks

1–4, 8

 

 

Classless Routing Protocols and Classless Routing

5–7

 

 

220 Chapter 7: Advanced Routing Protocol Topics

CAUTION The goal of self-assessment is to gauge your mastery of the topics in this chapter. If you don’t know the answer to a question or you’re only partially sure of the answer, you should mark this question as wrong for purposes of the self-assessment. Giving yourself credit for an answer you guess correctly skews your self-assessment results and might give you a false sense of security.

1.Which of the following summarized subnets is the smallest summary route that includes subnets 10.1.55.0, 10.1.56.0, and 10.1.57.0, mask 255.255.255.0?

a.10.0.0.0 255.255.255.0

b.10.1.0.0 255.255.0.0

c.10.1.55.0 255.255.255.0

d.10.1.48.0 255.255.240.0

e.10.1.32.0 255.255.224.0

2.Which of the following summarized subnets is not a valid summary that includes subnets 10.1.55.0, 10.1.56.0, and 10.1.57.0, mask 255.255.255.0?

a.10.0.0.0 255.0.0.0

b.10.1.0.0 255.255.0.0

c.10.1.55.0 255.255.255.0

d.10.1.48.0 255.255.240.0

e.10.1.32.0 255.255.224.0

3.What does the acronym VLSM stand for?

a.Variable-length subnet mask

b.Very long subnet mask

c.Vociferous longitudinal subnet mask

d.Vector-length subnet mask

e.Vector loop subnet mask

“Do I Know This Already?” Quiz 221

4.Imagine a router that lists three routes to subnets in network 10.0.0.0. Assume that VLSM is in use. How many times does the show ip route command list mask/prefix information about routes in network 10.0.0.0?

a.1

b.2

c.3

d.4

e.5

5.Which routing protocol(s) perform(s) autosummarization by default?

a.RIP-1

b.IGRP

c.EIGRP

d.OSPF

6.Which of the following routing protocols are classless?

a.RIP-1

b.IGRP

c.EIGRP

d.OSPF

7.Which of the following is affected by whether a router is performing classful or classless routing?

a.When to use a default route

b.When to use masks in routing updates

c.When to convert a packet’s destination IP address to a network number

d.When to perform queuing based on the classification of a packet into a particular queue

222Chapter 7: Advanced Routing Protocol Topics

8.Which of the following routing protocols support route summarization?

a.RIP-1

b.IGRP

c.EIGRP

d.OSPF

The answers to the “Do I Know This Already?” quiz appear in Appendix A. The suggested choices for your next step are as follows:

6 or less overall score—Read the entire chapter. This includes the “Foundation Topics,”

“Foundation Summary,” and “Q&A” sections.

7 or 8 overall score—If you want more review on these topics, skip to the “Foundation Summary” section and then go to the “Q&A” section. Otherwise, move to the next chapter.