Concept Exercise Chapter 10 Name:
Date: Class:

Cisco Exercises - Semester 1 - Networking Fundamentals
Chapter 10 Layer 3: Routing and Addressing

Introduction

The network layer interfaces to networks and provides the best end-to-end
packet delivery services to its user, the transport layer. The network layer
sends packets from the source network to the destination network.

Routers are devices that implement the network service. They provide interfaces
for a wide range of links and subnetworks at a wide range of speeds. Routers
are active and intelligent network nodes and thus can participate in managing
the network. Routers manage networks by providing dynamic control over
resources and supporting the tasks and goals for networks: connectivity,
reliable performance, management control, and flexibility.

In addition to the basic switching and routing functions, routers have
implemented a variety of value-added features that help to improve the
cost-effectiveness of the network. These features include sequencing traffic
based on priority and traffic filtering.

Typically, routers are required to support multiple protocol stacks, each with
its own routing protocols, and to allow these different environments to operate
in parallel. In practice, routers also incorporate bridging functions and can
serve as a limited form of hub.

IP addressing makes it possible for data passing over the network media of the
Internet to find its destination. Because each IP address is a 32-bit value,
that means that there are four billion different IP address possibilities. IP
addresses are hierarchical addresses like phone numbers and zip codes. They
provide a better way to organize computer addresses than MAC addresses, which
are flat addresses like social security numbers. IP addresses may be set in
software and are thus flexible. MAC addresses are burned into hardware. Both
addressing schemes are important for efficient communications between
computers.

Concept Questions

Demonstrate your knowledge of these concepts by answering the following
questions in the space provided.

Path determination occurs at the network layer. Routers are another type of
internetworking device. These devices pass data packets between networks based
on network protocol or Layer 3 information. Explain how this process works.

Routers have the ability to make intelligent decisions as to the best path for
delivery of data on the network. What criteria do they use to make these
decisions?





IP addresses are 32-bit values written as four octets separated with periods.
To make them easier to remember, IP addresses are usually written in dotted
notation using decimal numbers. IP addresses are used to identify a machine on
a network and the network to which it is attached. What do each of the numbers
mean?






Hexadecimal is a Base 16 numbering system that is used to represent MAC
addresses. It is referred to as Base 16 because it uses 16 symbols;
combinations of these symbols can then represent all possible numbers. Since
there are only 10 symbols that represent digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9),
and the Base 16 requires 6 more symbols, the extra symbols are the letters A,
B, C, D, E, and F.

The position of each symbol, or digit, in a hex number represents the base
number 16 raised to a power, or exponent, based on its position. Moving from
right to left, the first position represents 160, or 1; the second position
represents 161, or 16; the third position 162 or 256; and so on.

Example
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
1 2 3 4 5 6 7 8 9 A B C D E F 10

4176A = (4 x 163)+ (F[15] x 162)+ (6 x 161)+ (A[10] x 160)

Convert decimal to hex

Converting from decimal to binary is done with a procedure called the remainder
method. This method uses successive divisions of the base number of the system.
You can use the same method to convert decimal into hex, or Base 16.

Example

24,032 / 16 = 16 into 24,032 is 1502, with a remainder of 0
1502 /16 = 16 into 1502 is 93, with a remainder of 14, or E
93 /16 = 16 into 93 is 5, with a remainder of 13, or D
5 /16 = 16 into 5 is 0, with a remainder of 5

By collecting all the remainders backward, we have the hex number 5DE0.

Convert the following decimal numbers to binary:

32,014 Hex number =

56,432 Hex number =

57,845 Hex number =

98,764 Hex number =

54,462 Hex number =

Convert hex to decimal

Convert hexadecimal numbers to decimal numbers by multiplying the hex digits by
the base number of the system, in this case Base 16, raised to the exponent of
the position.

Example
Convert the hex number 3F4B to decimal (Work from right to left.)

B x 163 = 12,288
F(15) x 162 = 3840
4 x 161 = 64
B(11) x 160 = 11
16,203 = decimal equivalent

Convert the following hex numbers to decimal:

23F6 Decimal =

6AB7 Decimal =

5FE3 Decimal =

87CE Decimal =

59AC Decimal =