Sybex CCNA 640-802
Chapter 2: Ethernet Networking and Data
Encapsulation
Instructor & Todd Lammle
Chapter 2 Objectives
• The CCNA Topics Covered in this chapter
include:
– Use the OSI and TCP/IP models and their associated
protocols to explain how data flows in a network
– Select the appropriate media, cables, ports, and
connectors to connect switches to other network
devices and hosts
– Explain the technology and media access control
method for Ethernet networks
– Explain network segmentation and basic traffic
management concepts
– Select the appropriate media, cables, ports, and
connectors to connect routers to other network
devices and hosts
2
Ethernet Networking
• Ethernet is a contention media access method that
allows all hosts on a network to share the same
bandwidth of a link.
• Ethernet is popular because it’s readily scalable,
meaning that it’s comparatively easy to integrate
new technologies, such as Fast Ethernet and
Gigabit Ethernet, into an existing network
infrastructure.
• It’s also relatively simple to implement in the first
place, and with it, troubleshooting is reasonably
straightforward.
3
Ethernet Collision Detection
CSMA/CD
4
Half and Full Duplex
Half-duplex Ethernet is defined in the original 802.3
Ethernet; Cisco says it uses only one wire pair with a
digital signal running in both directions on the wire.
But full-duplex Ethernet uses two pairs of wires instead of
one wire pair like half duplex. And full duplex uses a
point-to-point connection between the transmitter of the
transmitting device and the receiver of the receiving
device.
Full-duplex Ethernet can be used in three situations:
• With a connection from a switch to a host
• With a connection from a switch to a switch
• With a connection from a host to a host using a
crossover cable
5
Ethernet Addressing
The MAC, or hardware, address is a 48-bit (6-byte) address
written in a hexadecimal format.
6
Binary Addressing
Binary to Decimal Memorization Chart
10000000
128
11000000
192
11100000
224
11110000
240
11111000
248
11111100
252
11111110
254
11111111
255
Conversion Example
BINARY
128
64
32
16
8
4
2
1
DECIMAL
10000100
1
0
0
0
0
1
0
0
132
11010010
1
1
0
1
0
0
1
0
210
10111000
1
0
1
1
1
0
0
0
184
10100110
1
0
1
0
0
1
1
0
166
7
Ethernet at the Physical Layer
The IEEE 802.3 and original Ethernet Physical layer
specifications.
8
Ethernet Cabling
Ethernet cabling is an important discussion, especially if you
are planning on taking the Cisco exams.
Three types of Ethernet cables are available:
• Straight-through cable
• Crossover cable
• Rolled cable
We will look at each in the following sections.
9
Straight Through
The straight-through cable is used to connect
• Host to switch or hub
• Router to switch or hub
10
Crossover Cable
The crossover cable can be used to connect
• Switch to switch
• Hub to hub
• Host to host
• Hub to switch
• Router direct to host
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Rolled Cable
Although rolled cable isn’t used to connect any Ethernet
connections together, you can use a rolled Ethernet cable to
connect a host to a router console serial communication (com)
port.
12
Using Hyper Terminal
Notice the settings for Hyper Terminal
13
What type of cable is used?
14
What type of cable is used for
each connection?
15
Data Encapsulation
When a host transmits data across a
network to another device, the data
goes through encapsulation:
• It is wrapped with protocol
information at each layer of the OSI
model.
• Each layer communicates only with
its peer layer on the receiving
device.
16
Data Encapsulation
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PDU
18
Port Numbers
The Transport layer uses port numbers to define both the virtual
circuit and the upper-layer process.
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Cisco’s Three-Layer Model
The following are the three layers and their typical functions:
• The core layer: backbone
• The distribution layer: routing
• The access layer: switching
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Written Labs and Review
Questions
– Open your books and go through all the
written labs and the review questions.
– Review the answers in class.
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