CCNA2 M1 WANs and Routers

8/14/2019 CCNA2 M1 WANs and Routers

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CCNA Semester2

Module 1

WANs and Routers

Objectives

WANs characteristics

Describe the role of a router in a WAN Router components

Router connections


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WANs

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

They use serial connections of

various types to accessbandwidth over large geographic

areas.


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A WAN operates at the physical layer and the

data link layerof the OSI reference model.

It interconnects LANs that are usually separatedby large geographic areas.

WANs provide for the exchange of data packets

and frames between routers and switches and

the LANs they support.

WAN Devices


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WAN Standards

WAN physical layerprotocols describe how to

provide electrical, mechanical, operational, and

functional connections for WAN services

WAN data link protocols describe how frames arecarried between systems on a single data link.

WAN standards and OSI model

Physical

Layer

Data Link

Layer

OSI model WAN Specifications

SMDS

X21bis

EIA/TIA-232

EIA/TIA-449

V24 V35

HSSI G.703

EIA-530

LAP

B

Frame

Relay

X25PLP

HDLC

PP

P

SDL

C

MAC

sublayer

LLC

sublayer

Network

Layer


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WAN: Physical Layer standards

Describes the interface

between the DTE and the DCE

EIA/TIA-232, V.24 (DB25)

EIA/TIA-449 (DB37) EIA-530 (DB25)

V.35 (DB34)

X.21 (DB15)

G.703 (BNC)

www.connectworld.net

WAN Standards: Protocols


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Typical WAN Layer 2 Links

Circuit-switched

PPP, SLIP, HDLC

Telephone

Company

Packet-switched

X.25, Frame Relay, ATM

Service

Provider

Leased LineHDLC, PPP, SLIP

WAN: Data Link Layer standards HDLC

High-Level Data Link Control

IEEE standard from SDLC

Point-to-point and multipoint links

Operates over sync. links

LAPB

Link Access Procedure Balanced used by X.25 protocol

LAPD

Link Access Procedure D-channel ISDN D-Channel for control signal

LAPF Link Access Procedure Balanced Used in Frame Relay for fast frame

switching over high-quality digitalfacilities

SLIP

Serial Line Interface Protocol

Designed to carry IP packets

Being replaced by PPP

PPP

Point-to-Point Protocol

Support multiple network layerprotocols (IP, IPX, DecNET)

Operates over sync. or async. links

SDLC

Synchronous Data Link Control

Protocol IBM designed protocol

Point-to-point & multipoint links

Operates over sync. links


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A typical WAN setup

Point-to-point or

circuit-switchedconnection

CO Switch

Customer PremisesEquipment

Demarcation

Local Loop

WAN service provider toll network

Trunks and switches

S S

S SS

S S

Internetwork with router

Consistent end-to-end addressing

Addresses that represent network topologies

Best path selection

Dynamic or static routing

Switching


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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.

Routers


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Introduction to routers in a WAN

A router is a special type ofcomputer. It has a CPU, memory,a system bus, and various

input/output interfaces. Routers need the Internetwork

Operating System software (IOS)to run configuration files.

Configuration files contain theinstructions and parameters thatcontrol the flow of traffic in andout of the routers.

Router Component: CPU

The Central Processing Unit (CPU) executes

instructions in the operating system. Among

these functions are system initialization, routing

functions, and network interface control.

The CPU is a microprocessor. Large routers

may have multiple CPUs.


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Router Component: RAM

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

following functions:

Stores routing tables

HoldsARP cache

Holds fast-switching cache

Performs packet buffering (shared RAM)

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

Router Component: RAM

RAM provides run time space for executable

Cisco IOS software and its subsystems.

RAM is usually logically divided into main

processor memory and shared input/output (I/O)

memory.

RAM can be upgraded by adding additional DualIn-Line Memory Modules (DIMMs).


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Router Component: NRAM

NVRAM has the following characteristics and

functions:

Provides storage for the startup configuration file Retains content when router is powered down or restarted

In some devices it is implemented in the same

flash device.

Router Component: Flash

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)

Adding or replacing the flash Single In-Line Memory

Modules (SIMMs) or PCMCIA cards can upgrade the

amount of flash.


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Router Component: ROM

Maintains instructions forpower-on self test

(POST) diagnostics

Stores bootstrap program and basic operatingsystem software, load Cisco IOS software from

Flash ro RAM

Some routers also have a scaled down version

of the IOS that can be used as an alternative

boot source.

Requires replacing pluggable chips on the

motherboard for software upgrades

Router Component: Interfaces

Three types of interfaces are local-area network

(LANs), wide-area network (WANs), and

Console/AUX.

Connect router to network forframe entry and

exit, or connect to terminal forconfiguration

Can be on the motherboard or on a separatemodule (fixed or modular card)


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Router Component: Interfaces

LAN interfaces (Ethernet, FDDI, ATM..) and WAN

interfaces(serial, ISDN, CSUs..) have controller

chips that provide the logic for connecting thesystem to the media.

The Console/AUX ports are serial ports used

primarily for the initial configuration of the

router.

Router Component: Power Supply

The power supply provides the necessary power

to operate the internal components.

Larger routers may use multiple or modular

power supplies.

In some of the smaller routers the power supply

may be external to the router.


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2600 External Connection

Management Ports

Provides a text-based connection for the

configuration, monitoring and troubleshooting

of the router

The common management interfaces are the

console and auxilliary ports. These are EIA-232

asynchronous serial ports. Computer must run a terminal emulation

program to provide a text-based session with

the router.


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Management Ports Connections

Management Ports Connections

The console port is preferred because it

displays router startup, debugging, and error

messages by default.

The console port can also be used when the

networking services have not been started or

have failed. Therefore, the console port can beused fordisasterand password recovery

procedures.


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Connecting console interfaces

Configure terminalemulation software onthe PC for with theappropriate com portand settings.

Connect the RJ-45connector of therollover cable to therouter console port.

Connect the other endof the rollover cable tothe RJ-45 to DB-9

adapter. Attach the female DB-9adapter to a PC

Summary


WANs standards and protocols

Router internal components

Router functions

Router management ports Router LAN and WAN connection


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CCNA2 Module1

CCNA2 M1 WANs and Routers

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