Tài liệu học CCNA kỳ 2 mod1 wansrouters

Module 1 – WANs and RoutersOverview Students completing this module should be able to: • Identify organizations responsible for WAN standards • Explain the difference between a WAN and L

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Module 1 – WANs and Routers

Overview

Students completing this module should be able to:

• Identify organizations responsible for WAN standards

• Explain the difference between a WAN and LANand the type of

addresses each uses

• Describe the role of a routerin a WAN

• Identify internal components of the routerand describe their functions

• Describe the physical characteristicsof the router

• Identify common ports on a router

• Properly connect Ethernet, serial WAN, and console ports

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NIIT-ICT Hanoi info@niithanoi.vn 3

Introduction to WANs

These are the major characteristics of WANs:

• They connect devices that are separated by wide geographical

areas

• They use the services of carriers such as the Regional Bell

Operating Companies (RBOCs), Sprint, MCI, VPM Internet Services,

Inc., and Altantes.net

• They use serial connections of various types to access bandwidth

over large geographic areas

- A WAN differs from a LAN in several ways For example, unlike a LAN, which

connects workstations, peripherals, terminals, and other devices in a single

building or other small geographic area, a WAN makes data connections

across a broad geographic area Companies use a WAN to connect various

company sites so that information can be exchanged between distant offices.

- A WAN operates at the physical layer and the data link layer of the OSI

reference model It interconnects LANs that are usually separated by large

geographic areas WANs provide for the exchange of data packets and frames

between routers and switches and the LANs they support.

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• Routers offer many services, including internetworking and WAN interface

ports

• Switches in the WAN provide connectivity for voice, data, and video

communication

• Modems include interface voice-grade services, channel service units/digital

service units (CSU/DSUs) that interface T1/E1 services, and Terminal

Adapters/Network Termination 1 (TA/NT1s) that interface Integrated Services

Digital Network (ISDN) services

• Communication servers concentrate dial-in and dial-out user communication

• WAN data link protocols describe how frames are carried between systems on a single

data link.

• They include protocols designed to operate over dedicated point-to-point, multipoint,

and multi-access switched services such as Frame Relay.

• WAN standards are defined and managed by a number of recognized authorities,

including the following agencies:

– International Telecommunication Union-Telecommunication Standardization Sector (ITU-T),

formerly the Consultative Committee for International Telegraph and Telephone (CCITT).

– International Organization for Standardization (ISO).

– Internet Engineering Task Force (IETF).

– Electronic Industries Association (EIA).

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Router Introduction

• A router is a special type of computer It has the same basic components

as a standard desktop PC It has a CPU, memory, a system bus, and

various input/output interfaces.

• Just as computers need operating systems to run software applications,

routers need the Internetwork Operating System software (IOS) to run

configuration files.

RAM, also called dynamic RAM (DRAM), has the following

characteristics and functions:

Stores routing tables

Holds ARP cache

Holds fast-switching cache

Performs packet buffering (shared RAM)

Maintains packet-hold queues

Provides temporary memory for the configuration file of

the router while the router is powered on

Loses content when router is powered down or restarted

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NVRAM Non-Volatile RAM

NVRAM has the following characteristics and

functions:

Provides storage for the startup configuration file

Retains content when router is powered down or

restarted

Flash

Flash memory has the following characteristics and

functions:

Holds the operating system image (IOS)

Allows software to be updated without removing and

replacing chips on the processor

Retains content when router is powered down or

restarted

Can store multiple versions of IOS software

Is a type of electronically erasable, programmable ROM

(EEPROM)

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Read-only memory (ROM) has the following characteristics

and functions:

Maintains instructions for power-on self test (POST)

diagnostics

Stores bootstrap program and basic operating system

software

Requires replacing pluggable chips on the motherboard

for software upgrades

Interfaces

Interfaces have the following characteristics and

functions:

Connect router to network for frame entry and exit

Can be on the motherboard or on a separate

module

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Router LANs and WANs

• Smaller broadcast domains

• Connecting Layer 3 networks

Router LANs and WANs

• Routers are the backbone devices of large intranets and of the Internet

• They operate at Layer 3of the OSI model, making decisions based on

network addresses

• The two main functions of a router are the selection of best pathfor

and the switching of framesto the proper interface

• Routers accomplish this by building routing tables and exchanging

network information with other routers

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WAN & OSI model

Physical Layer

Data Link

Layer

EIA/TIA-232 EIA/TIA-449 V24 V35 HSSI G.703 EIA-530

HDLC PPP SDLC

MAC sublayer

Network Layer

Router role in a WAN

• The WAN physical layer describes the interface between the data

terminal equipment (DTE) and the data circuit-terminating equipment

(DCE)

• Generally, the DCE is the service provider and the DTE is the attached

device In this model, the services offered to the DTE are made

EIA/TIA-232, EIA/TIA-449, V.24, V.35, X.21, G.703, EIA-530, ISDN, T1, T3, E1, and E3, xDSL, SONET (OC-3, OC-12, OC-48, OC-192) ,

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External CSU/DSU

• For digital lines, a channel service unit (CSU)and a data service

unit (DSU)are required

– We won’t go into the differences here

• The two are often combined into a single piece of equipment, called

the CSU/DSU

To router

To T1 circuit

Router role in a WAN

• The primary WAN roles of a router are therefore not routing, but

providing connections to and between the various WAN physical and

data-link standards

• For example, a router may have an ISDN interface using PPP

encapsulation and a serial interface terminating a T1 line using Frame

Relay encapsulation

HDLC, Frame Relay, PPP, SDLC, SLIP, X.25, ATM, LAPB, LAPD, LAPF,

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Academy approach to hands-on labs

• In the academy lab, devices that make up the WAN cloud

are simulated by the connection between the back-to-back

DTE-DCE cables

• One of the routers will provide the clock rate (later).

Router physical characteristics

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Router external connections

• The three basic types of connections on a router are LAN interfaces,

WAN interfaces, and management ports.

• LAN interfaces allow the router to connect to the Local Area Network

media.

• Wide Area Network connections provide connections through a

service provider to a distant site or to the Internet.

• The management ports provide text-based connections for the

configuration and troubleshooting of the router.

Management port connections

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Management port connections

router modem modem terminal

Connecting console interfaces

When connected using the console interface, the computer is acting

as a “dumb terminal”.

<Router Output>

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Connecting console interfaces

roll-over cable

9600 baud

8 data bits

No parity

1 stop bit

No flow control

router terminal

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Connecting LAN interfaces

Connecting WAN interfaces

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• What is the type of connection to the Cisco device? Cisco routers may use different

connectors for the serial interfaces The interface on the left is a Smart Serial interface

The interface on the right is a DB-60 connection This makes the selection of the serial

cable connecting the network system to the serial devices a critical part in setting up a

WAN.

• Is the network system being connected to a DTE or DCE device? DTE and DCE are the

two types of serial interfaces that devices use to communicate The key difference

between these two is that the DCE device provides the clock signal for the

communications on the bus The device documentation should specify whether it is

DTE or DCE.

What signaling standard does the device require? For each different device, a

different serial standard could be used Each standard defines the signals on the

cable and specifies the connector at the end of the cable Device documentation

should always be consulted for the signaling standard

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Is a male or female connector required

on the cable? If the connector has visible projecting pins, it is male If the connector has sockets for projecting pins, it is female

Summary

An understanding of the following key points should have

been achieved:

• WAN and LAN concepts

• Role of a router in WANs and LANs

• WAN protocols

• Configuring encapsulation

• The identification and description of the internal

components of a router

• The physical characteristics of a router

• The common ports on a router

• How to connect router console, LAN, and WAN ports

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