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CCNA Bootcamp
Chapter 1: Internetworking
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Chapter 1 Objectives
The CCNA Topics Covered in this chapter include:
Internetworking Basics
Layered Models
The OSI Model
Ethernet Networking Data Encapsulation
Ciscos Three-Layer Model
Chapter 1 Written Labs and Review Questions
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Internetworking Basics
How would you say the PC named Bobcommunicates with the PC named Sally?
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Internetworking Basics
Switches can replace the hub, breaking up collision domains.
Keep in mind that the hub used in the figure just extended the onecollision domain from the switch port.
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Internetworking Basics
Heres a list of some of the things that commonly causeLAN traffic congestion:
Too many hosts in a broadcast domain Broadcast storms Multicasting
Low bandwidth Adding hubs for connectivity to the network A bunch of ARP or IPX traffic (IPX is a Novell
protocol that is like IP, but really, really chatty.Typically not used in todays networks.)
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Internetworking Basics
Routers create an internetwork.
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Internetworking Basics
There are two advantages of using routers in yournetwork:
They dont forward broadcasts by default. They can filter the network based on layer 3 (Network
layer) information (e.g., IP address).
Four router functions in your network can be listed asfollows:
Packet switching Packet filtering
Internetwork communication Path selection
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Internetworking Basics
Internetworking devices
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Internetworking Basics
Switched networks creating an internetwork
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Layered Models
The Layered Approach
A reference model is a conceptual blueprint of howcommunications should take place.
It addresses all the processes required for effectivecommunication and divides these processes intological groupings called layers.
When a communication system is designed in thismanner, its known as layered architecture.
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The OSI Model
The OSI isnt a physical model. Rather, its a set ofguidelines that application developers can use to createand implement applications that run on a network.
It also provides a framework for creating andimplementing networking standards, devices, and
internetworking schemes.
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The OSI Model
The upper layers
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The OSI Model
The lower layers
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The OSI Model
The Layer Functions
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The OSI Model
Connection-Oriented Communication
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The OSI Model
Windowing
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The OSI Model
Network Layer Routing Table used in a router
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The OSI Model
Router in an internetwork
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The OSI Model
Data Link Layer
Provides the physical transmission of the data and handles errornotification, network topology, and flow control Ensure that messages are delivered to the proper device on a LAN using
hardware addresses and will translate messages from the Network
layer into bits for the Physical layer to transmit.
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Binary Addressing
Binary to Decimal Memorization Chart10000000 12811000000 19211100000 22411110000 24011111000 24811111100 25211111110 25411111111 255
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 00
184
10100110 1 0 1 0 0 1 1 0 166
Conversion Example
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Hexadecimal Addressing [1]
Hex is short for hexadecimal, which is a numbering systemthat uses the first six letters of the alphabet (A through F) to
extend beyond the available 10 digits in the decimal system.Hexadecimal has a total of 16 digits.
Hex Value Binary Value Decimal Value
0 0000 01 0001 1
2 0010 2
3 0011 34 0100 4
5 0101 5
6 0110 6
7 0111 7
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Hexadecimal Addressing [2]
Hex Value Binary Value Decimal Value
8 1000 89 1001 9
A 1010 10
B 1011 11
C 1100 12
D 1101 13
E 1110 14
F 1111 15
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The OSI Model
A hub in an network
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The OSI Model
A Switch in an network
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Ethernet Networking
Ethernet is a contention media access method that allowsall hosts on a network to share the same bandwidth of alink.
Ethernet is popular because its readily scalable, meaningthat its comparatively easy to integrate new technologies,
such as Fast Ethernet and Gigabit Ethernet, into anexisting network infrastructure.
Its also relatively simple to implement in the first place,
and with it, troubleshooting is reasonably straightforward.
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Ethernet Collision Detection
CSMA/CD
Carrier Sense Multiple Access with
Collision Detection (CSMA/CD),a protocol that helps devices share thebandwidth evenly without having twodevices transmit at
the same time on the network medium
CSMA/CD was created to overcomethe problem of those
collisions that occur when packets aretransmitted simultaneously fromdifferent nodes.
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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 inboth directions on the wire.
But full-duplex Ethernet uses two pairs of wires instead of one wirepair like half duplex. And full duplex uses a point-to-pointconnection 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
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Ethernet Addressing
The MAC, or hardware, address is a 48-bit (6-byte)address written in a hexadecimal format.
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Ethernet at the Physical Layer
The IEEE 802.3 and original Ethernet Physical layer
specifications.
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Ethernet Cabling
Ethernet cabling is an important discussion, especially ifyou 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.
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Straight Through
The straight-through cable is used to connect Host to switch or hub
Router to switch or hub
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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 isnt used to connect any Ethernet connectionstogether, you can use arolled Ethernet cable to connect a host to a
router console serial communication (com) port.
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Using Hyper Terminal
Notice the settings for Hyper Terminal
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What type of cable is used?
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Data Encapsulation [1]
When a host transmits data across a network to another device, thedata goes through encapsulation:
It is wrapped with protocol information at each layer of the OSImodel.
Each layer communicates only with its peer layer on the receivingdevice.
To communicate and exchange information, each layer uses ProtocolData Units (PDUs). These hold the control information attached tothe data at each layer of the model. They are usually attached to theheader in front of the data field but can also be in the trailer, or end,of it.
Each PDU attaches to the data by encapsulating it at each layer of theOSI model, and each has a specific name depending on theinformation provided in each header. This PDU information is readonly by the peer layer on the receiving device. After its read, its
stripped off and the data is then handed to the next layer up.
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Data Encapsulation [2]
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PDU
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Port Numbers
The Transport layer uses port numbers to define both the virtualcircuit and the upper-layer process.
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Ciscos 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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Review Question
Hub Hub
How many broadcast domains are shown?
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Review Question
Hub HubHub HubHub Hub
Switch Switch
How many collision domains are shown?
Which of the hosts can transmit simultaneously
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Which of the hosts can transmit simultaneouslywithout causing collisions?
HubSwitch
How many collision and broadcast domains are show?
A FEDB C
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Written Labs and Review Questions
Open your books and go through all the writtenlabs and the review questions.
Review the answers in class.
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Thank You
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