ccna chapter1

Sybex CCNA

CCNA Course Contents

• Prerequisite : Good Knowledge in Computer Networking

– Introduction to Internetworking.

– TCP/IP Fundamentals.

– Subnetting , Variable length Subnetting.

– IP Routing.

– EIGRP and OSPF Protocols.

– Layer 2 Switching and Spanning Tree Protocol (STP).

– Virtual LANs (VLANs).

– Security and Access Lists.

– Network Address Translation (NAT).

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Chapter 1

Internetworking

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Chapter 1 Objectives

• The Topics Covered in this chapter include:– Internetworking Basics– Layered Models– The OSI Model– Ethernet Networking– Data Encapsulation– Cisco’s Three-Layer Model– Chapter 1 Written Labs and Review

Questions

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Internetworking Basics

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How would you say the PC named Bob communicates with the PC named Sally?


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Switches can replace the hub, breaking up collision domains.

Keep in mind that the hub used in the figure just extended the one collision domain from the switch port.


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Here’s a list of some of the things that commonly cause LAN traffic congestion:

•Too many hosts in a broadcast domain

•Broadcast storms

•Multicasting

•Low bandwidth

•Adding hubs for connectivity to the network


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Routers create an internetwork.


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There are two advantages of using routers in your network:

•They don’t 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 as follows:

•Packet switching

•Packet filtering

•Internetwork communication

•Path selection


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Internetworking devices


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Switched networks creating an internetwork

Layered Models

The Layered Approach

• A reference model is a conceptual blueprint of how communications should take place.

• It addresses all the processes required for effective communication and divides these processes into logical groupings called layers.

• When a communication system is designed in this manner, it’s known as layered architecture.

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The OSI Model

• The OSI isn’t a physical model. Rather, it’s a set of guidelines that application developers can use to create and implement applications that run on a network.

• It also provides a framework for creating and implementing networking standards, devices, and internetworking schemes.

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The OSI Model

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The upper layers

The OSI Model

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The lower layers

The OSI Model

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The Layer Functions

The OSI Model

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Connection-Oriented Communication

The OSI Model

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Windowing

The OSI Model

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Network LayerRouting Table used in a router

The OSI Model

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Router in an internetwork

The OSI Model

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Data Link Layer

Binary Addressing

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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 0 0 184

10100110 1 0 1 0 0 1 1 0 166

Conversion Example

The OSI Model

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A hub in an network

The OSI Model

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A Switch in an network

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.

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Ethernet Collision Detection

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CSMA/CD

Half and Full Duplex

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Half-duplex Ethernet is defined in the original 802.3 Ethernet; 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

Ethernet Addressing

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The MAC, or hardware, address is a 48-bit (6-byte) address written in a hexadecimal format.

Ethernet Cabling

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Ethernet cabling is an important discussion.

Three types of Ethernet cables are available:

• Straight-through cable• Crossover cable• Rolled cable

We will look at each in the following sections.

Straight Through

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The straight-through cable is used to connect• Host to switch or hub

• Router to switch or hub

Crossover Cable

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The crossover cable can be used to connect• Switch to switch• Hub to hub• Host to host• Hub to switch• Router direct to host

Rolled Cable

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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.

What type of cable is used?

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What type of cable is used for each connection?

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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.

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PDU= Protocol Data Unit

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FCS= Frame Check Sequence

Port Numbers

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The Transport layer uses port numbers to define both the virtualcircuit and the upper-layer process.

Cisco’s Three-Layer Model

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The following are the three layers and their typical functions:• The core layer: backbone• The distribution layer: routing• The access layer: switching

Review Question

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Hub Hub

How many broadcast domains are shown?

Review Question

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Hub HubHub HubHub Hub

Switch Switch

How many collision domains are shown?

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Which of the hosts can transmit simultaneously without causing

collisions?

HubSwitch

How many collision and broadcast domains are show?

A FEDB C

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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ccna chapter1

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