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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.