IP Routing Principles
The topics in this chapter are the basis of the BSCI course that feeds the BSCI exam. It is
therefore the ﬁrst chapter of the book, as all remaining chapters build from the subjects
This chapter describes the different types of routing protocols for IP, explains how to read the
routing table and keep it current, and compares the routing and switching functions.
The concepts of routing with IP and the mechanics of the routing process are dealt with
generically in this chapter as a foundation for the subsequent chapters, which deal with the
individual routing protocols.
The topics presented here will directly reﬂect questions on the BSCI exam. If you do not
understand the contents of this chapter, it will be impossible for you to pass the exam. The
subsequent chapters assume the comprehension of the subjects covered in this chapter.
“Do I Know This Already?” Quiz
The purpose of the “Do I Know This Already?” quiz is to help you decide what parts of this
chapter to use. If you already intend to read the entire chapter, you do not necessarily need to
answer these questions now.
The 12-question quiz, derived from the major sections in the “Foundation Topics” portion of the
chapter, helps you to determine how to spend your limited study time.
Table 1-1 outlines the major topics discussed in this chapter and the “Do I Know This Already?”
quiz questions that correspond to those topics.
“Do I Know This Already?” Foundation Topics Section-to-Question Mapping.
NOTE: The goal of self-assessment is to gauge your mastery of the topics in this chapter. If you do not know the answer to a question or are only partially sure of the answer, you should mark this question wrong for purposes of the self-assessment. Giving yourself credit for an answer you correctly guess skews your self-assessment results and might provide you with a false sense of security.
1- Which of the following criteria would select a route as the preferred path to a destination
network to be added to the routing table?
a. The route is the only available path to the destination network.
b. The route has one interface conﬁgured for IP.
c. The route has the lowest administrative distance.
d. The route has the lowest metric.
2- Which of the following best describes a routing protocol?
a. A set of rules that describes how Layer 3 routing devices will send updates between each
b. other about available networks and build a routing table
The mechanism by which a router describes the autonomous system
c. The means by which a router learns about the Internet
d. The rules that state how a router builds a routing table
3- What is the forwarding process?
a. The means by which a datagram is selected to be in the routing table
b. The process that determines which path to select from the routing table
c. How networks are forwarded between autonomous systems
d. The switching process using the memory cache
4- What is the purpose of the command ip classless ?
a. To force a classful routing protocol to send the subnet mask in its routing updates
b. To allow VLSM to be conﬁgured on directly connected interfaces
“Do I Know This Already?” Quiz 7
c. To allow the redistribution of OSPF subnets into RIPv1
d. To allow the router to ignore the classful boundaries of the networks in its routing table
and simply route to the longest preﬁx match it can ﬁnd
5- Which of the following statements characterizes classless routing protocol?
a. Within the same IANA classful network address, subnets are exchanged between the rout-
ers without the subnet mask.
b. Router interfaces using the same IANA classful network address can have different subnet
c. IGRP and EIGRP are the only distance vector routing protocols that can be conﬁgured as
classless routing protocols.
d. Within the same IANA classful network address, subnets are exchanged between the
6- Which of the following two statements is a characteristic of a classful routing protocol?
a. Routes exchanged between foreign networks are summarized to the IANA classful
b. Within the same network (IANA network number), different subnet masks can be conﬁg-
c. All the interfaces on all the routers within an IANA network number must share the same
d. All interfaces on a router must share the same subnet mask.
7- Which of the following is an instance of when a static route is used?
a. On a slow speed dialup link
b. On networks where surge protectors are not in use
c. When there are many links to the Internet
d. On unstable networks
8- What does 0.0.0.0 signify in an IP routing table?
a. Indicates the router whose routing table is being displayed
b. Indicates that the router has no directly connected interfaces
c. Indicates that no routing protocol is running
d. Shows the default route for the routing table
9- What is the command syntax to empty the Cisco routing table of all its routes?
a. clear ip route *
b. clear ip route table
c. reset ip route *.*.*.*
d. clear ip route 0.0.0.0
10- Cisco makes a distinction between the routing function and the switching function of a router. Which of the following best describes the routing function?
a. Moving data to the end destination that is in cache
b. Load balancing
c. Moving the datagram across the router
d. Path determination
11- What information is found in the routing table in order to process switch a packet?
a. The address of the neighboring router that will forward the trafﬁc
b. The MAC address of the remote network
c. The destination address of a static route
d. The path with the lowest administrative distance
12- Which of the following questions are asked by the routing function when trying to route a datagram?
a. If the destination network is not in the routing table, is there a default network conﬁgured?
b. Is fast switching enabled?
c. Which is the best path to that remote network?
d. Are there multiple equal-cost paths?
The answers to the “Do I Know This Already?” quiz are found in Appendix A, “Answers to Chapter
‘Do I Know This Already?’ Quizzes and Q&A Sections.” The suggested choices for your next step
are as follows:
■ 6 or less overall score—Read the entire chapter. This includes the “Foundation Topics” and
“Foundation Summary” sections, the “Q&A” section, and the “Scenarios” at the end of the chapter.
■ 7–9 overall score—Begin with the “Foundation Summary” section, and then go to the “Q&A”
section and the “Scenarios” at the end of the chapter. If you have trouble with these exercises,
read the appropriate sections in “Foundation Topics.”
■ 10 or more overall score—If you want more review on these topics, skip to the “Foundation
Summary” section, and then go to the “Q&A” section and the “Scenarios” at the end of the
chapter. Otherwise, move to the next chapter.