Appendix.docx
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Appendix.docx
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Appendix
PartVII:
Appendix
AppendixAAnswerstoEndofChapterExercises
AnswerstoChapter1ReviewQuestions
1:
Whatistheppsratefora100BaseXnetwork?
Calculateitfortheminimumandmaximumframesizes.
A:
Becauseallofthebittimevaluesareonetenththatof10MbpsEthernet,theppsfor100MbpsEthernetis10timesthe10Mbpsppsvalues.SoFastEthernetsupportsupto148,800ppsfor64byteframesand8,120ppsfor1518byteframes.
2:
Whataretheimplicationsofmixinghalf-duplexandfull-duplexdevices?
Howdoyoudoit?
A:
Youneedtoensurethatyourfull-duplexdevicesattachtofull-duplexhubs.Otherwise,thefull-duplexdevicesneedtoruninhalf-duplexmode.Alwaysattachfullduplextogetherandhalfduplextogether.
Anotherissueconcernsbandwidth.Thefull-duplexdeviceseffectivelyhave200Mbpsbandwidth,whereasthehalf-duplexrun100Mbps.Infact,thehalfduplexmightbeevenlessthan100Mbpsifthedeviceattachestoasharedhub.Therefore,communicationsbetweenthefull-duplexandhalf-duplexdeviceislimitedbythebandwidthofthehalf-duplexattachment.
3:
IntheopeningsectiononFastEthernet,wediscussedthedownloadtimeforatypicalmedicalimageoverasharedlegacyEthernetsystem.Whatisanapproximatedownloadtimefortheimageoverahalf-duplex100BaseXsystem?
Overafull-duplex100BaseXsystem?
A:
Themedicalfilesizewas100Megabytes.Ifthesystemishalfduplex,itmightberunningonasharedhub.Assumethatthestationhasaneffectivesharedbandwidth,then,of20Mbps.Inreality,itmightbelessormore.Thenthetransfertimeisabout40seconds.100MB×8/20Mbps=40seconds.
Full-duplexoperationscanprovide100Mbpsbandwidthinthereceivedirection.Therefore,theapproximatetransfertimeis100MB×8/100Mbps=8seconds.
Bothmodelsassumethattheserverscangeneratetrafficatthatrate.
4:
Whatdisadvantagesarethereinhavinganentirenetworkrunningin100BaseXfull-duplexmode?
A:
Onedisadvantagecanbecost.Everyfull-duplexdeviceneedstoattachtoitsowndedicatedswitchport.Youcannothavemultiplefull-duplexdevicesattachedtothesameport.Ifyouhavemanydevices,youneedmanyports,whichequatestoincreasedcost.
Anotherdisadvantagecanbecongestionattheservers.Asyouincreasethenumberofdevicesoperatinginfull-duplexmode,higheramountsofbandwidthhityourservers.Thisamountcangreatlyexceedthebandwidthcapacityoftheserverconnection.
5:
CanaClassIIrepeatereverattachtoaClassIrepeater?
Whyorwhynot?
A:
YoushouldnotattachaClassIrepeatertoaClassIIrepeaterbecausethisviolatesthelatencyrulesofFastEthernet.WhenyouhaveaClassIrepeater,therecanbeonlyonerepeater.
6:
WhatisthesmallestGigabitEthernetframesizethatdoesnotneedcarrierextension?
A:
TheneedforthecarrierextensionbytesisdrivenbytheslotTime.GigabitEthernetusesaslottimefor4096bits.Thisequatesto512bytes.Therefore,anyframesof512bytesorlargerdonotneedcarrierextension,whereasallframeslessthan512MUSThavecarrierextension.
AnswerstoChapter2ReviewQuestions
RefertothenetworksetupinFigure2-15toanswerQuestions1and2.
1:
ExamineFigure2-15.Howmanybroadcastandcollisiondomainsarethere?
A:
Thereare14collisiondomains.Eachportonabridge,router,andswitchdefineanewbroadcastdomain.Youcannoteasilytellhowmanybroadcastdomainsexistinthenetworkduetothepresenceoftheswitch.Aswitchcancreateoneormanybroadcastdomains,dependinguponhowyouconfigureit.Iftheswitchisconfiguredasonebroadcastdomain,therearetwobroadcastdomains.Thisisnotarecommendedsolution,becausebothsidesoftherouterattachedtotheswitchandbridgebelongtothesamebroadcastdomain.Thisisnotgood.Ontheotherhand,theswitchcanhavemanybroadcastdomainsdefined.
2:
InFigure2-15,howmanyLayer2andLayer3addresspairsareusedtotransmitbetweenStations1and2?
A:
ForStation1tocommunicatewithStation2,twoLayer2addresspairsareneeded.OneMACpairisusedonthetopsegment,andtheotherontheothersideoftherouter.However,onlyoneLayer3addresspairisneededendtoend.
RefertothenetworksetupinFigure2-16toanswerQuestion3.
3:
WhatistheproblemwiththenetworkinFigure2-16?
A:
Twoissuesinthisnetworkneedattention.ThemostcriticalproblemisthattwoportsontheCatalyst,whichbelongtodifferentVLANs,attachtoastandardbridge.ThismergesthetwoVLANsintoacommonbroadcastdomainanddefeatsthepurposeoftheCatalysthavingtwoormorebroadcastdomains.
AnadditionalissueinvolvesSpanningTree.AlthoughSpanningTreeisnotdiscusseduntilChapters6and7,aloopexistsinVLAN1.ThismightbeintentionalforresiliencyandcanbecontrolledbySpanningTree.Butifunintentional,itcanforceyournetworktotransmitframesoveralessdesirablepaththanyoumightexpect.
4:
Ifyouattachamultiportrepeater(hub)toabridgeport,howmanybroadcastdomainsareseenonthehub?
A:
Legacyhubshaveallportsinthesamecollisionandbroadcastdomains,regardlessoftheinternetworkingdevicetheyattachto.
5:
Canalegacybridgebelongtomorethanonebroadcastdomain?
A:
Generally,allportsonalegacybridgebelongtothesamebroadcastdomain.
AnswerstoChapter3ReviewQuestions
1:
IfaRIFispresentinasource-routedframe,doesasource-routeswitcheverexaminetheMACaddressofaframe?
A:
No,theswitchpassestheframetothebridgewithoutlookingatthedestinationMACaddress.
2:
TohowmanyVLANscanaTrBRFbelong?
A:
ATrBRFbelongstoonlyoneVLAN
3:
Thetransparent-bridgelearningprocessaddsentriestothebridgingtablebasedonthesourceaddress.Sourceaddressesarenevermulticastaddresses.YetwhenexaminingtheCatalystbridgetable,itispossibletoseemulticast.Why?
A:
Somemulticastaddressesareidentifiedassystemaddresses.Forexample,andframeswith01-00-0C-CC-CC-CCaredirectedtotheSupervisormodule.Itisalsopossibletoforcesomemulticastaddressesoutadministratordefinedinterfaces.Thisoverridesthenormalfloodingprocesses.
4:
TwoCiscoroutersattachtoaCatalyst.Ononerouteryoutypeshowcdpneighbor.Youexpecttoseetheotherrouterlistedbecausecdpannouncesonamulticastaddress01-00-0c-cc-cc-cc,whichisfloodedbybridges.ButyouseeonlytheCatalystasaneighbor.Suspectingthattheotherrouterisn'tgeneratingcdpannouncements,youentershowcdpneighborontheCatalyst.Youseebothrouterslistedverifyingthatbothroutersaregeneratingannouncements.Whydidn'tyouseethesecondrouterfromthefirstrouter?
(Hint:
neitherroutercanseetheother.)
A:
CDPannouncementsuse01-00-0C-CC-CC-CCasthedestinationaddress.TheCatalystreceivestheseannouncementsandterminatesthemintheSupervisormodule.Itdoesnotforwardthemtootherinterfaces.Carefulexaminationoftherouter'scdpneighbordisplaywillshowonlyoneneighbor,theCatalystsinceitgeneratescdpannouncements.
AnswerstoChapter4ReviewQuestions
1:
WhathappensifyoureplacetheactiveSupervisormodule?
A:
Ifyoureplacetheactivemodule,thestandbybecomestheactiveSupervisormodule.Iftheconfigurationfilesdifferbetweenthetwo,thenowactiveSupervisorupdatestheconfigurationonthereplacementmodule.Likewise,ifanysoftwareimagesdiffer,thenowactivemoduleupdatesthereplacementunit.
2:
IfyourredundantSupervisorenginesarerunningsoftwareversion4.1,theuplinkportsonthestandbyenginearedisableduntilitbecomestheactivesupervisor.Whatstrategiesmightyouneedtoemploytoensurethatfailoverworksfortheuplinks?
A:
ReferringtoFigureA-1,ifyouconnecttheuplinkportsfromtheactivesupervisormoduleonCat-AtotheactivesupervisoronCat-B,everythingworkswelluntiloneofthesupervisorsfail.ThenowactiveuplinksonthestandbymoduleofCat-AareconnectedtotheinactiveuplinksonthestandbymoduleofCat-B.Connectivitymightbelost,SpanningTreereconverges.Therefore,youmightwanttocrossconnectmodulesasinFigureA-2orFigureA-3.ThestrategyofFigureA-2enablesonlyonelinktobeactiveatatime,whereasthestrategyofFigureA-3allowstwolinkstobeactiveatatime.AnotheralternativeistonotusetheSupervisorportsforuplinks,butusethemforhostconnectionsinstead.
FigureA-1UplinkStrategiesforFailover
FigureA-2CrossConnectStrategy1
FigureA-3CrossConnectStrategy2
3:
Table4-4showshowtorecallandeditacommandfromthehistorybuffer.HowwouldyourecallandeditthefollowingcommandsothatyoumovetheportsfromVLAN3toVLAN4?
setvlan32/1-10,3/12-21,6/1,5,7
A:
Youcannotsimplyusetheedit^3^4becausethischangesnotjusttheVLAN,buttheportlisttoo.Ports3/12-21become4/12-21.Rather,youcouldusethecommand^vlan3^vlan4andbemorespecificaboutthestringyouaremodifying.ThischangesonlytheVLANassignmentwithoutmodifyingtheportvalues.
4:
WhathappensifyouconfiguretheSupervisorconsoleportassl0,andthenyoudirectlyattachaPCwithaterminalemulatorthroughthePCserialport?
A:
ThePCcannotattachtotheconsole,becausetheCatalystexpectsSLIP-basedIPconnectionsthroughtheinterface.Thesl0configurationmeansthatyouaccesstheCatalystconsoleportbytreatingtheseriallineasanIPdevice.WhenyouattachaPCthroughtheserialportanddonotusetheIPmode,thePCdoesnotattempttouseitsIPstacktobuildtheconnection.
5:
TheCatalyst5500supportsLS1010ATMmodulesinthelast5slots
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