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Study Sheets

INTRO 2

ICND/CCNA 49


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GraphicSymbols

ComputingBasics

PCComponents

PCsarethebuildingblocksofnetworks.Theyhavemany

ofthesamepartsandsystemsas

othernetworkdevice

s,suchasroutersandswitches.You

shouldunderstandthefunctions

ofthefollowingcomponentsincasetheneedtotroubleshootarises.

Component

Function

Bus

Wiresthatconnecttheinternalcomponentstothe

CPU.

CD-ROMdrive

CompactDiscRead-OnlyMemory.

CentralProcessingU

nit(CPU)

Thecomputersbra

inwherenearlyall

calculationsareperformed.

Expansioncard

Aprintedcircuitboa

rdthatcanbeinsertedfor

additionalfunctionality.

Expansionslot

Anopeningintheco

mputerforexpansioncards.

Switch

Access

Server

Bridge

Router

NetworkSwitch

Multilayer

Switch

Hub

NetworkCloudor

BroadcastDomain

Personal

Computer

FileServer

WANCloud

M

odem

Ethernet

FastEthernet

SerialLine

CircuitSwitchedLine

DSU/CSU

DataServiceUnit/

ChannelServiceUnit

VLAN

ISDN

Switch

Component

Function

Floppydiskdrive

Adeviceforreadingandwritingtofloppydisks.

Harddiskdrive

Usedtostoreandretrievedatafromnonvolatile

storagemedia.

Microprocessor

AsiliconchipthatcontainsaCPU.

Motherboard

Thecomputersmaincircuitboard.Everythingelse

plugsintothemotherboardan

discontrolledbyit.

Printedcircuitboard

Athinplateonwhichintegrat

edcircuitsareplaced.

Memory

Internalstorage.

RandomAccessMemory(RAM)

Atemporarystorageplacefor

datawhileprograms

areinuse.Ifthecomputerlosespower,alldatain

RAMt

hatwasnotsavedislost.

Read-OnlyMemory(ROM)

Prerecordedorstartupmem

ory.

ErasableProgrammableRead-

OnlyMemory(EPROM)

Computermemoryunavailabl

etotheuser.It

usuallycontainsverybasicins

tructionsforthe

computersoperation.

Systemunit

Thecomputersmainbox.

Backplane

Alargecircuitboardthathassocketsforexpansion

cards.

Socket

Aconnectorforexpansioncards.

Interface

Adevicethatconnectstopiecesofequipment(a

mouseandcomputer,forexam

ple).

Networkcard

APCBthatprovidesnetwork

access.

Parallelport

Aninterfacethatcommunicatesmorethan1bitof

informationatatime.Usually

usedtoconnect

devicessuchasprinters.

Serialport

Aninterfacethatcancommun

icate1bitatatime.

UniversalSerialBus(USB)

Aninterfacethatallowsother

devicestobe

connectedanddisconnectedw

ithoutresettingthe

system.


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WANPhysicalLayerProtocols

Physicallayerprotocolsspecifytheelectrical,mechanical,operational,andfunctional

connectionforWAN

services.ThefiveserialstandardssupportedbyCiscodevicesareEIA/

TIA-232,EIA/TIA-44

9,V.35,X.21,andEIA/TIA-530.

WANDataLinkLayerProtocols

Datalinkprotocolso

perateoverpoint-to-point,multipoint,andmultiaccessswitched

services.Thefollowingarecommonencapsulationprotocols:

High-LevelData

Link

Control(HDLC)The

defaultencapsulation

typeonpoint-to-point,

dedicatedlinks,andcir-

cuit-switchedconnec-

tions.HDLCsho

uldbe

usedwhencomm

unicat-

ingbetweenCisc

o

devices.

Point-to-PointProtocol(PPP)Providesconnectionsbetweendevicesoverseveral

typesofphysicalinterfacessuchasasynchronousserial,HSSI,

ISDN,andsynchro-

nous.PPPworkswithman

ynetworklayerprotocols,includingIPandIPX.PPPuses

PAPandCHAPforbasics

ecurity.

X.25/LinkAccessProcedure,Balanced(LAPB)DefinesconnectionsbetweenDTEand

DCEforremoteterminalaccess.LAPBisadatalinklayerprotocolspecifiedbyX.25.

FrameRelayTheindustr

y-standard,switcheddatalinklayer

protocol.FrameRelay

(basedonX.25)canhandlemultiplevirtualcircuits.Asynchro

nousTransferMode

(ATM):Theinternational

standardforcellrelayusingfixed-length(53-byte)cellsfor

multipleservicetypes.Fixed-lengthcellsallowhardwareproce

ssing,whichgreatly

reducestransitdelays.ATM

takesadvantageofhigh-speedtran

smissionmediasuchas

E3,T3,andSONET.

WANSummary

TheInternetistheinterconnectionofthousandsoflargeandsmallnetworksallover

theworld.

AWANisusedtointerconnectLANsthatareseparatedbyalarg

egeographicdistance.

Dedicatedline,circuitswitc

hing,packetswitching,andcellswitchingaresomecommon

WANconnectiontypes.

WANdevicesincluderouters,WANswitches,modems,andac

cessservers.

WANphysicalprotocolsd

escribehowtoprovideelectrical,mechanical,operational,

andfunctionalconnection

forWANservices.

WANdatalinklayerprotocolsdescribehowframesarecarriedbetweensystemsona

singledatalink.

LineType

SignalStandard

BitRateCapacity

OC-3

SONET

155.54Mbps

OC-9

SONET

466.56Mbps

OC-12

SONET

622.08Mbps

OC-18

SONET

933.12Mbps

OC-24

SONET

1244.16Mbps

OC-36

SONET

1866.24Mbps

OC-48

SONET

2488.32Mbps

LeasedLine

Packet-Switched

Circuit-Switched

HDLC

,PPP

,SLIP

X.2

5,

Frame

Re

lay,

ATM

Service

Provider

PPP

,SLIP

,HDLC

Telephone

Company


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municationforlong-distancecommunication.Ciscoroutersuseaproprietary60-pincon-

nector,andthenetwo

rkendofthecablemustmatchtheservicehardware.

CablingRouters

forSerialConnectors

Whencablingrouters,

youneedtodetermin

eif

youneedadataterminal

equipment(DTE)con

nec-

tororadatacircuit-

terminatingequipment

(DCE)connector:

DTEistheendpoint

oftheusersdevice

ontheWANlink

.

DCEisthepoint

whereresponsibilityfordeliveryofda

tapassesintothehandsoftheISP.

Ifyouconnectrouter

sback-to-back,oneoftheroutersis

aDTE,andtheotherisaDCE.

RouterPorts

Routerscanhavefixedormodularports:

Withfixedports,eachpor

thasaporttypeandnumber,sucha

sEthernet0.

Withmodularports,each

porthasaporttype,slotnumber,an

dportnumber,such

asserial1/0.

ConfiguringDevices

Youmustestablishaconnection

viaaconsoleporttoconfigurea

Ciscodevice.Somedevicesuse

arollovercabletoconnecta

consoleporttoaPC.Tosetup

theconnection,dothefollowing

:

Step1

Cablethedeviceusingarollovercable.YoumightneedanadapterforthePC.

Step2

Configuretheterminalemulationapplicationwiththefo

llowingCOMport

settings:9600bps,8

databits,noparity,1stopbit,and

noflowcontrol.

WANSpecifications

andConnectionsSummary

WANsuseserialtransmiss

ionforlong-distancecommunication.

Ciscoroutersuseaproprietary60-pinconnectoronserialports.

ADTE/DCEisthepointw

heretheserviceproviderassumesresponsibilityforthe

WAN.ADCEprovidesclo

cking.

Routershaveeitherfixedormodularports.Thesyntaxyouus

etoconfigureeach

interfacedependsonthetypeofport.

Rollovercablesareusedtosetupaconsoleconnection.

SharedLANTechno

logy

EarlyLANsused10BASE5(thicknet)cables.Thesecableswereeve

ntuallyreplacedby

thinnet,whichwascheaperand

easiertoworkwith.SomethicknetLANsweretappedinto

andextendedusingthinnetcab

les.

DTE

DCE

DTE

DCE

DCE

DTEM

odem

CSU/DSU

S

SS

S S

S

Thicknet(10BASE5)

Thinnet(10BASE2)(

Cheapnet)

Relativelyexpensiveandlarge

in

diameter

Lessexpensiveandrequireslessspacethan

thicknet

Requiresrepeatersevery500m

Requiresrepeatersevery185m

Devicewith

Console

RJ-45-to-R

J-45

Ro

llover

Ca

ble

RJ-45-to-D

B-9

Adap

ter

(La

be

ledTerm

ina

l)

PC


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ThisfigureshowsaV

LAN

design.NotethatVLANsare

definedbyuserfunctions

ratherthanlocations.

VLANOperation

EachVLANonaswitch

behavesasifitwereaseparate

physicalbridge.Theswitch

forwardspackets(including

unicasts,multicasts,and

broadcasts)onlytop

orts

assignedtothesame

VLAN

fromwhichtheyorig

inated.

Thisdrasticallycutsdownon

networktraffic.

VLANsrequireatrunkor

physicalconnectionf

oreachVLANto

spanmultipleswitches.Eachtrunkcan

carrytrafficformultipleVLANs.

VLANAssignment

Aportcanbeassigne

d(configured)toa

givenVLAN.VLANmembershipcanbe

eitherstaticordynam

ic.

Staticassignmen

tTheVLANport

isstaticallyconfi

guredbyanadmin-

istrator.

Dynamicassignm

ent

TheswitchusesaVMPS

(VLANMembershipPolicy

Server).TheVM

PSisa

databasethatma

psMAC

addressestoVLA

Ns.A

portcanbelongtoonly

oneVLANatatime.

Multiplehostscanexist

onasingleportonlyifthe

yareallassignedtothesameVLAN

.VLANscanalsobe

assignedbasedonMACaddresses.Thismethodoffersflexibilitybutincreasesswitching

overhead(computerproce

ssingrequirements).

VLANmembershipdescribesh

owaportonaswitchisassignedto

aparticularVLAN:

Port-drivenmembershipis

basedontheportagivenworkstationplugsinto.

MACaddressmembership

usestheMACaddresstodynamica

llyassigntheend

stationtoaVLAN.

Layer3-basedmembershipusesinformationcontainedintheIPheadertodetermine

VLANmembership.

Trunking

TheIEEE802.1Qprotocolisu

sedtodefineVLANtopologiesand

toconnectmultiple

switchesandrouters.Ciscosup

ports802.1QtrunkingoverFastEthernetandGigabit

Ethernetlinks.802.1Qdefines

howtocarrytrafficfrommultipleV

LANsoverasingle

point-to-pointlink.

Inter-SwitchLink(ISL)

ISLisaCisco-proprietaryprotoco

l

formoftrunkingdesignedto

manageVLANtrafficbetween

switches.ISLprovidespoint-to

-

pointlinksinfullorduplex

mode.ISLisperformedwith

ASICs,whichoperateatwire

speedsandenableVLANsto

spanthebackbone.

Inter-VLANRouting

VLANscreateLayer2seg-

ments.Endstationsindifferentsegments(broadcastdomains)cann

otcommunicatewith

3rdFloor

2ndFloor

1stFloor

SALES

HR

ENG

GreenVLAN

GreenVLAN

SwitchA

Red

VLAN

Black

VLAN

Green

VLAN

StaticVLAN

DynamicVLAN

VMPS

1111.1111.1111=vlan10

MAC=1111.1111.1111

Trun

k

VLAN5

VLAN10

Porte0/4

Porte0/9

VLANTagAddedBy

IncomingPort

Inter-SwitchLink

CarriesVLANIdentifier

VLANTagStrippedBy

ForwardingPort


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Three-WayHandshake

Thesynchronization

requires

eachsidetosenditso

wninitial

sequencenumberand

to

receiveaconfirmationofitin

acknowledgment(AC

K)from

theotherside.

Step1

HostAsen

dsaSYN

segmentwith

sequence

number10

0.

Step2

HostBsen

dsan

ACKandconfirms

theSYNitreceived.HostBalsosendsaSYN.

NotethattheACKfieldinHost

Bisnowexpectingtohearsequence101.

Step3

Inthenextsegment,HostAsendsdata.Notethatthesequencenumberinthis

stepisthe

sameastheACKinStep2.

TCPSequencea

ndAcknowledgmentNumbers

TCPusesforwardreferenceacknowledgments.Eachdata

gramisnumberedsothatatthe

receivingendTCPreassemblesthesegmentsintoacompletemessage.Ifasegmentisnot

acknowledgedwithin

agiventimeperiod,itisresent.

TCPWindowing

Windowingensuresthatone

sideofaconnectionisnot

overwhelmedwithdataitcan-

notprocess.Thewindowsize

fromoneendstationtellsthe

othersideoftheconnection

howmuchitcanacceptatone

time.Withawindowsizeof1,

eachsegmentmustbeacknowl-

edgedbeforeanothersegment

issent.Thisistheleast-efficient

useofbandwidth.

Step1

Thesendersends

threepacketsbefore

expectinganACK.

Step2

Thereceivercanhan

dleawindowsizeofonly2.Soitdro

pspacket3,specifies3

asthenextpacket,a

ndspecifiesawindowsizeof2.

Step3

Thesendersendsthenexttwopacketsbutstillspecifiesitswindowsizeof3.

Step4

Thereceiverrepliesbyrequestingpacket5andspecifyin

gawindowsizeof2.

ATCP/IPsessioncanhavedifferentwindowsizesforeachnode.

TCP/IPOverviewSu

mmary

Thetransportlayerprovidestransportservicefromthesourcehosttothedestinationhost.

ThetwoprimaryprotocolsareTCPandUDP.

TheTCPthree-wayhand

shakeisasynchronizationprocess.

Sequencenumbersandacknowledgments(ACKs)areusedtoestablishconnections.

TCPwindowingisaflow-controlmechanism.

TCP/IPInternetLayerOverview

TCP/IPDatagrams

TCP/IPinformationissentviadatagrams.Onemessagemaybebro

kenintoaseriesofdat-

agramsthatmustbereassembledatthedestination.Threelayersareassociatedwiththe

TCP/IPprotocolstack:

Hos

tA

Hos

tB

SYNRece

ive

d

SYNRece

ive

d

SendSYN

(seq=100ctl=SYN)

Established

(seq=101ack=301

ctl=ack)

SendSYN,ACK

(seq=300ack=101

ctl=syn,ack)

1 3

2

Sender

Receiver

Windowsize=3

Send1

Windowsize=3

Send2

Windowsize=3

Send3

Windowsize=3

Send3

Windowsize=3

Send4

Packet3is

Dropped

ACK3

Windowsize=2

ACK5

Windowsize=2


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RankingRoutes

withAdministrativeDistan

ce

Severalroutingprotoc

ols

canbeusedatthesame

timeinthesamenetwork.

Whenthereismorethana

singlesourceofrouting

information,therouter

usesanadministrativ

edis-

tancevaluetorateth

e

trustworthinessofeach

routinginformation

source.Theadministrative

distancemetricisanin

teger

from0to255.Ingen

eral,

aroutewithalowernum-

berisconsideredmore

trustworthyandismore

likelytobeused.

RoutingOverviewS

ummary

Routersoperateatthenetworklayer.Packetsareencapsulated

andde-encapsulated

eachtimethepacketpasse

sthrougharouter.

Routersmakeadecisionregardingthebestpathforapacketthroughthenetwork.

Routedprotocolsdefineth

eaddressformatandfieldswithina

packet.

Routersuseroutingprotocolstodeterminepaths,maintainan

dshareroutingtable

information,anddirecttra

ffic.

Routingalgorithmsusedifferentmetricstodeterminethebestpaththroughthenetwork.

RoutingProtocols

Routingprotocolsdetermineth

epaththroughthenetworkforpackets.Routingprotocols

aredividedintotwoclassesbasedonhowtheyinteractwithotherautonomoussystems:

ExteriorGatewayProtocols(EGPs)andInteriorGatewayProtocols(IGPs).

IGPandEGP

Anautonomoussystemreferstoagroupofnetworksunderacommonadministrative

domain.InteriorGatewayProtocols(IGPs)exchangeroutinginform

ationwithinanauton-

omoussystem.ExamplesincludeRoutingInformationProtocol(RIP),InteriorGateway

RoutingProtocol(IGRP),EnhancedInteriorGatewayRoutingProtocol(EIGRP),Open

ShortestPathFirst(OSPF),and

IntermediateSystem-to-IntermediateSystem(IS-IS).

ExteriorGatewayProtocols(EGPs)connectbetweenautonomoussystems.BorderGate-

wayProtocol(BGP)isanexam

pleofanEGP.

DefaultDistanceV

alues

RouteSource

DefaultDistance

Connectedinterface

0

Staticrouteaddress

1

EIGRP

5

BGP

20

InternalEIGRP

90

IGRP

100

IS-IS

115

RIP

120

EGP

140

ODR

160

ExternalEIGRP

170

InternalBGP

200

Unknown

255

RoutedProtocol:IP

E0

S0

10.120.2.0

172.16.1.0

Network

Protocol

Destination

Network

Exit

Interface

Connected

Learned

10.120.2.0

172.16.1.0

E0

S0

IGPs:RIP,IGRP

EGPs:BGP

AutonomousSystem100

AutonomousSystem200


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PrimaryRateInterface(PRI)InNorthAmericaandJap

an,PRIhas23Bchannelsand

oneDchannel(allch

annelsare64kbps).InEurope,aPR

Ihas30BchannelsandoneD

channel.PRIiswrittenas23B+D.

PPP

Point-to-PointProtoc

ol(PPP)providesconnectionsbetweendevicesoverseveraltypesof

physicalinterfaces,su

chasasynchronousserial,HSSI,ISD

N,andsynchronous.PPPworks

withseveralnetwork

layerprotocols,includingIPandIPX.PPPusesPAPandCHAPfor

basicsecurity.

PPPusesaNetworkC

ontrolProtocol(NCP)componenttoencapsulatemultipleprotocolsand

theLinkControlProtocol(LCP)tosetupandnegotiatecon

troloptionsonthedatalink.

HDLC

HDLCisadata-linkprotocolusedonsynchronousserialdatalinks.HDLCcannotsup-

portmultipleprotocolsonasinglelinkbecauseitlacksamechanismtoindicatewhich

protocolitiscarrying.

TheCiscoversionofHDLCuses

aproprietaryfieldthatactsasa

protocolfield.Thisfieldmakes

it

possibleforasingleseriallinkto

accommodatemultiplenetwork-layerprotocols.CiscosHDLCisa

point-to-pointproto-

colthatcanbeusedonleasedlinesbetweentwoCiscodevices.PPP

shouldbeusedwhen

communicatingwithnon-Cisco

devices.

DialupAccessSummary

ISDNprovidesanintegrat

eddata,voice,andvideocapabilitythatusesthepublic

switchednetwork.

WANencapsulationformatsincludePPPandHDLC.

HDLCisthedefaultencap

sulationforseriallinesintheCisco

IOSSoftware.


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LEDsonthefrontpaneloftheswitchprovideinformationonswitchstatusduringstartup,

normaloperation,an

dfaultconditions.Pressingthemod

ebutton(showninthefigure,

whichshowsaCatalyst1900)togglesthroughtheLEDd

isplaymodes:

Portstatus

Bandwidthutiliz

ation

Full-duplexsupp

ort

Thefollowingtabled

etailsswitchLEDstatusindications

fortheCatalyst1900.

Catalyst1900S

witchLEDs

FortheCatalyst2900series,theLEDindicatorsaresligh

tlydifferent.

Catalyst2900SwitchLEDs

GettingHelp

SeveralcommandsbuiltintoIO

Sprovidehelpwhenyouenterconfigurationcommands:

?displaysalistofcommonlyusedcommands.

-More-appearsatthebott

omofthescreenwhenmoreinforma

tionexists.Displaythe

nextavailablescreenbypr

essingtheSpacebar.DisplaythenextlinebypressingEnter.

Pressanyotherkeytoretu

rntotheuser-modeprompt.

s?listsallcommandsthat

startwiths.

show?listsallvariantsof

theshowcommand.

LED

Status

System

GreenSystempoweredandoperational

AmberSystemmalfunction

Redundantpower

supply(RPS)

GreenRPSoperational

AmberRPSinstalledbutnotoperational

FlashingamberTheinternalpowersupplyandRPShave

power,andtheinternalpowersupplyispoweringtheswitch

Portstatus(STAT)

GreenLinkpresent

FlashinggreenActivity

Alternatinggreenandamber

Linkfault

AmberPortnotforwarding

Bandwidthutilizatio

n

(UTL)

1to8LEDson0.1toeeeennnnaaaabbbblllleeee

RouterA#ccccoooonnnnffffiiiigggg

tttteeeerrrrmmmm

RouterA(config)#iiiinnnntttt

sssseeeerrrr0000

RouterA(config-if)#iiiipppp

aaaaddddddddrrrreeeessssssss

111177772222....11110000....111122222222....33330000

RouterA(config-if)#eeeennnnccccaaaappppssssuuuullllaaaattttiiiioooonnnn

ffffrrrraaaammmmeeee----rrrreeeellllaaaayyyy

cccciiiissssccccoooo

RouterA(config-if)#iiiinnnntttteeeerrrrffffaaaacccceeee

sssseeeerrrriiiiaaaallll0000....3333

ppppooooiiiinnnntttt----ttttoooo----ppppooooiiiinnnntttt

RouterA(config-if)#ffffrrrraaaammmmeeee----rrrreeeellllaaaayyyy

iiiinnnntttteeeerrrrffffaaaacccceeee----ddddllllcccciiii

111122220000

RouterA(config-if)#eeeexxxxiiiitttt

RouterA(config)#eeeexxxxiiiitttt

RouterA#

Theframe-relayinterface-dlcidlcicommandisrequiredforallpoin

t-to-pointconfigura-

tionsandmultipointsubinterfa

cesforwhichInverseARPisenabled.Donotusethiscom-

mandonphysicalinterfaces.

ConfiguringFrameRelaySubinterfaces

Splithorizondoesnotallo

wroutingupdatesreceivedononeinterfacetobefor-

wardedoutthesameinterface.

Routingupdatesreceivedononesubinterfacecanbesentoutanothersubinterface

configuredonthesameph

ysicalinterface.

Virtualcircuitscanbeconfiguredaspoint-to-pointconnections

allowingsubinterfaces

toactlikeleasedlines.

Subinterfacescanbeconfiguredtosupportpoint-to-multipointorpoint-to-pointcon-

nectiontypes.

Aphysicalinterfaceisalwaysamultipointinterface.

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