2021思科認證考試題庫精選8節(jié)第1節(jié)

在相距幾百英里的路由器之間使用租用線路的點到點WAN鏈路上，下列哪個

設備室DCE設備

A.路由器

B.CSU/DSU

C用話局中心機房設備

D.路由器處理器上的芯片

正確答案：B

下面是你在一臺交換機上執(zhí)行命令showspanning-tree時得到的輸出:請問下面

哪兩種有關這臺交換機的說法是正確的?()

A.這臺交換機是根網(wǎng)橋

B這臺交換機不是根網(wǎng)橋

C根網(wǎng)橋與這臺交換機之間有4臺交換機

D.這臺交換機運行的是802.1W

E.這臺交換機運行的是STPPVST+

答案：BD

下圖中如果允許/24和10.000/8的網(wǎng)絡之間通信,必須要配置的

兩條命令是什么()

/8

「B一

A.A(config)iproute

B.A(config)iprouteS0/0/0

C.A(config)iproute

D.B(config)iproute

E.B(config)iproute

F.Biproute192.168.1,0

正確答案：AD

Whichoneofthefollowingcharacteristicsistrueregardingtheuseofhubs

andswitches?

A.HubscanhavetheirportsbeconfiguredwithVLANs

B.Usinghubsiscostlywithregardtobandwidthavailability.

C.Switchescannotforwardbroadcasts.

D.Switchesaremoreefficientthanhubsinprocessingframes.

E.Switchesincreasethenumberofcollisiondomainsinthenetwork.

正確答案：E

解析：

Explanation:Switchesincreasesthenumberofcollisionsdomainsinthenetwork.Switch

esthatareconfiguredwithVLANswillreducethesizeofthecollisiondomainsbyincreasin

gthenumberofcollisiondomainsinanetwork,butmakingthemsmallerthanthatofoneb

ig,flatnetwork.IncorrectAnswers:A.SwitchesarecapableofVLANconfigurations,buth

ubsarenot.B.Hubsaregenerallytheleastcostlymethodpossibletoconnectmultipledev

icestogetherinanetwork.C.Switchesforwardbroadcastsandmulticasts,bydefault,toall

portswithinthesameVLAN.Onlyroutersblockallbroadcasttrafficbydefault.D.Switches

andhubscanbeequallyefficientinprocessingframes,intheory.Inpractice,switchesareg

enerallymoreefficientastheyusuallyhavemoreCPUanclmemoryallocatecltothem,and

aregenerallymuchmoreexpensivethanasimplehub.

將路由器的許可證刪除包括哪兩步?()

A.使用命令eraseflashJicense

B.重啟系統(tǒng)

C.使用命令licenseboot,并在末尾指定關鍵字disable

D.使用命令licenseclear將許可證清除

答案：CD

2021思科認證考試題庫精選8節(jié)第2節(jié)

SplithorizonhasbeenenabledwithintheEzonexamroutednetwork.Which

oneofthefollowingstatementsbestexplainsthesplithorizonrule?

A.Onlyrouterscansplitboundaries(horizons)betweennetworksin

separateASnumbers.

B.EachASmustkeeproutingtablesconvergedtopreventdeadroutes

frombeingadvertisedacrossboundaries.

C.Oncearouteisreceivedonaninterface,advertisethatrouteas

unreachablebackoutthesameinterface.

D.Informationaboutarouteshouldneverbesentbackinthedirection

fromwhichtheoriginalupdatecame.

E.Noneoftheabove

正確答案：D

解析:Explanation:

Thesplithorizonrulestates:

*Neveradvertisearouteoutoftheinterfacethroughwhichyoulearnedit.

Forinstance,inFigure4abelow,ifRouterOneisconnectedtoRoutersTwoand

Threethroughasinglemultipointinterface(suchasFrame.Relay),andRouter

OnelearnedaboutNetworkAfromRouterTwo,itwillnotadvertisetherouteto

NetworkAbackoutthesameinterfacetoRouterThree.Routeroneassumesthat

RouterThreewouldlearnaboutNetworkAdirectlyfromRouterTwo.

IncorrectAnswers:

A:Thereisnosuchrequirement

B:Distancevectorprotocolsupdatesroutingtableatregularintervalsinsteadof

Topologychanges

C:Thisisthedefinitionofthepoisonreverserule,notthesplithorizonrule.

請參見圖示。管理員注意到從ISP處進入網(wǎng)絡的流量大幅增加。管理員清除了

計數(shù)器。幾分鐘之后，管理員又檢查access-list表。從圖中的輸出可得出什么結論

0

R2*showaccess-lists

ExtendedIPaccesslists175

10denyicmpanyanyecho(1786matches)

20permittcpanyhost45eqwww(21matches)

30permittcpanyhost43eqpop3(189matches)

40permittcpanyhost43eqsmtp(133matches)

A.少量HTTP流量表明web服務器未正確配置

B.較高的POP3流量（與SMTP流量相比）表明企業(yè)中POP3電子郵件客戶端

的數(shù)量比SMTP客戶端數(shù)量多

C.大量ICMP流量在接口處被拒絕，這是受到DoS攻擊的跡象

D.較高的電子郵件流量（與web流量相比）表明攻擊目標主要是電子郵件服

務器

正確答案：C

AEzonexamEthernetswitchreceivesaunicastframe,withadestinationMAC

thatislistedintheswitchtable.Whatwillthisswitchdowiththeframe?

A.Theswitchwillforwardtheframe,toaspecificport

B.Theswitchwillforwardtheframe,toallportsexcepttheportonwhichit

wasreceived

C.Theswitchwillreturnacopyoftheframe,outthesourceport

D.Theswitchwillnotforwardunicastframes

E.TheswitchwillremovethedestinationMACfromtheswitchtable

F.Noneoftheabove.

正確答案：A

A解析：Explanation:

HowDoestheSwitchFindHostMACs?

Let'susethediagrambelowtohelpusunderstandhowaddresslearningprocess

takesplace.

DataLinkAddressLearning

Mactable

FEO/O:0000.74a3.0023

/FE0/11:0000.43C5.334C

Let'sassumethatwehavejustpoweredontheswitch.IthasnothinginitsMAC

table.Weconnectthecablesfromthehostsontheswitchinterfacesasshownin

thediagram.HostAinitiatesaconnectiontowardsHostD,andthefollowing

takesplace:

1.HostA(interfacefeO/O)sendsaframe,toHostD(MAC

address:0000.43c5.334c).

2.TheswitchinspectstheSourceAddressintheframe,andnotesinitstablethe

MACaddressofHostAalongwiththeInterfacenumberfromwhichtheframe,

originated.

3.TheswitchinspectstheDestinationAddressintheframe.Sinceitdoesnot

haveHostsDMACaddressinitstable,itconstructsabroadcastframe,and

forwardsoutallinterfacesexcepttheinterfacefromwheretheoriginalframe,

arrived.

4.HostDidentifiesitselfastheexpectedrecipientandrespondsbacktoHostA.

Theswitchreceivestherespondframe,oninterfacefeO/11andplacestheSAin

itstablealongwiththeinterfacenumberwheretheframe,camefrom.

5.Fromnowon,furthercommunicationbetweenthetwohostswillbeswitched

totheappropriateinterfacesbasedontheMACtablesentries.

Thisprocesstakesplaceeverytimeanewhostisattachedontheswitchand

initiatestraffic.TheswitchtriestokeepitsMACtableup-to-date,thereforeif

somehostsdonotinitiatetrafficforacertainamountoftime,theswitchremoves

themfromitstableandreinsertsthemwhentheybeginsendingtraffic.

YouneedsubnetaEzonexamnetworksegment.Howmanysubnetworksand

hostsareavailablepersubnetifyouapplya/28masktotheclassC

network?

A.30networksand6hosts.

B.6networksand30hosts.

C.8networksand32hosts.

D.32networksand18hosts.

E.16networksand14hosts.

F.Noneoftheabove

正確答案：E

E解析：Explanation:

A28bitsubnetmask(11111111.11111111.11111111.11110000)appliedtoaclass

Cnetworkusesa4bitsfornetworks,andleaves4bitsforhosts.Usingthe2n-2

formula,wehave24-2(or2x2x2x2-2)whichgivesus14forthenumberofhosts,

andthenumberofnetworksis24=16.

IncorrectAnswers:

A.Thiswouldbetheresultofa/29(48)network.

B.Thiswouldbetheresultofa/27(24)network.

C.Thisisnotpossible,aswemustsubtracttwofromthesubnetsandhostsfor

thenetworkandbroadcastaddresses.

D.Thisisnotapossiblecombinationofnetworksandhosts.

Barney是子網(wǎng)/24中一個具有IP地址1QLL1的主機。以下哪些操作

時標準IPACL可配置來執(zhí)行的()

A.匹配準確的源IP地址

B.使用一個access-list命令匹配IP地址到,而不匹配其他IP

地址

C.使用一個access-list命令匹配Barney的子網(wǎng)中的所有IP地址，而不匹配其

他IP地址

D.僅匹配包的目標IP地址

正確答案：AC

2021思科認證考試題庫精選8節(jié)第3節(jié)

802.1d定義了哪些端口狀態(tài)?()

A.阻斷

B.丟棄

C偵聽

D學習

E.轉(zhuǎn)發(fā)

F.替代

答案：ACDE

AEzonexamswitchisconfiguredwithallportsassignedtoVLAN2.In

addition,allportsareconfiguredasfull-duplexFastEthernet.Whatistheeffectof

addingswitchportstoanewVLANonthisswitch?

A.Theadditionswillcreatemorecollisionsdomains.

B.IPaddressutilizationwillbemoreefficient.

C.Morebandwidthwillberequiredthanwasneededpreviously.

D.Anadditionalbroadcastdomainwillbecreated.

E.Thepossibilitythatswitchingloopswilloccurwillincreasedramatically.

正確答案：D

解析:Explanation:

AVLANisagroupofhostswithacommonsetofrequirementsthat

communicateasiftheywereattachedtothesamewire,regardlessoftheir

physicallocation.AVLANhasthesameattributesasaphysicalLAN,butitallows

forendstationstobegroupedtogethereveniftheyarenotlocatedonthesame

LANsegment.

Networksthatusethecampus-wideorend-to-endVLANslogicallysegmenta

switchednetworkbasedonthefunctionsofanorganization,projectteams,or

applicationsratherthanonaphysicalorgeographicalbasis.Forexample,all

workstationsandserversusedbyaparticularworkgroupcanbeconnectedtothe

sameVLAN,regardlessoftheirphysicalnetworkconnectionsorinteractionwith

otherworkgroups.

Networkreconfigurationcanbedonethroughsoftwareinsteadofphysically

relocatingdevices.CiscorecommendstheuseoflocalorgeographicVLANsthat

segmentthenetworkbasedonIPsubnets.Eachwiringclosetswitchisonitsown

VLANorsubnetandtrafficbetweeneachswitchisroutedbytherouter.The

reasonsfortheDistributionLayer3switchandexamplesofalargernetwork

usingboththecampus-wideandlocalVLANmodelswillbediscussedlater.

AVLANcanbethoughtofasabroadcastdomainthatexistswithinadefinedset

ofswitches.PortsonaswitchcanbegroupedintoVLANsinordertolimit

unicast,multicast,andbroadcasttrafficflooding.Floodedtrafficoriginatingfrom

aparticularVLANisonlyfloodedoutportsbelongingtothatVLAN,including

trunkports,soaswitchthatconnectstoanotherswitchwillnormallyintroduce

anadditionalbroadcastdomain.

以下ACL將對路由器的流量產(chǎn)生何種影響（）

Access-!ist1deny192.168.19.1620.0.0.0

Access-!ist1permitany

A.它將允許所有源自的網(wǎng)絡流量

B.它將拒絕源自主機62的流量

C.因為通配符掩碼忽略了所有比特，所以對流量沒有影響

D.permitany選項使deny選項失效

正確答案：B

下列靜態(tài)路由配置正確的是0

A.iprouteserial0/0

B.iproute/24

C.iproute

D.iproute

正確答案：D

Afterloggingintoarouterandtypinginafewshowcommands,youpress

theuparrowkey.Whatwillthisdo?

A.Itwillrecallthepreviouscommandline

B.Itwillmovethecursoronelineup

C.Itwillredisplaythecurrentcommandline

D.Itwillcapitalizethecommandline

E.Noneoftheabove

正確答案：A

解析:Explanation:

Theuparrowkeyisusedtorecallthepreviouscommandlineentry.The

commandsthatwereenteredpreviouslycanbedisplayedbyrepeatedlypressing

theuparrowkey,orbyenteringthe"showhistory"command.

2021思科認證考試題庫精選8節(jié)第4節(jié)

Usingasubnetmaskof24,whichoftheIPaddressesbelow

canyouassigntothehostsonthissubnet?(Selectallthatapply)

A.3

B.59

C.3

D.6

E.7

F.92

正確答案：CDE

C,D,E解析：Explanation:

Sincethesubnetmaskis24,thenumberofnetworkhoststhatis

availableis30.Everynetworkboundarywillbeamultipleof32.Thismeansthat

everysubnetwillbeamultiple(0,32,64,96,128,160,192,224)andthe

broadcastaddressforeachofthesesubnetswillbeonelessthisnumber(31,63,

95,127,159,191,223).

Therefore,anyIPaddressthatdoesnotendinoneofthesenumberswillbea

validhostIPaddress.

C.ValidHostinsubnetwork2(4to5)

D.ValidHostinsubnetwork1(2to3)

E.ValidHostinsubnetwork2(4to5)

IncorrectAnswers:

A.Thiswillbethebroadcastaddressforthe2/27network.

B.Thiswillbethebroadcastaddressforthe28/27network

F.Thiswillbethenetworkaddressforthe92/27network.

路由表中，某條路由的"路由代碼為D”,則表明該路由為()

A.直連路由

B.靜態(tài)路由

C.IGRP路由

D.EIGRP路由

正確答案：D

下列選項不屬于分組交換技術的廣域網(wǎng)通信協(xié)議有()。

A.X.25

B.幀中繼

C.ATM

D.PSTN

正確答案：D

Whichtypeofcableshouldbeusedtomakeaconnectionbetweenthe

Fa0/0portonarouterandtheFa0/0portswitch?

A.Rollovercable

B.Consolecable

C.Crossovercable

D.Straight-throughcable

E.Serialcable

正確答案：D

解析：Explanation:Straight-

throughcablesareusedtoconnecthosttoswitch(orhub)androutertoswitch(orhub).

Youhavejustpurchasedabrandnewrouterandwishtohavetherouter

promptyouthroughtheinitialconfigurationcommands.Whichroutermode

doesthisdescribe?

A.ROMMonitormode

B.SETUPmode

C.Autoflashmode

D.RXBOOTmode

E.Noneoftheabove

正確答案：B

解析:Explanation:

Setupmodeisaconvenientmodethatwalksyouthroughthesetupprocedure

bypromptingyouwithspecificquestionsandoptionsonebyone.

2021思科認證考試題庫精選8節(jié)第5節(jié)

EzonexamhasaClassCnetworkandyouneedtensubnets.Youwishtohave

asmanyaddressesavailableforhostsaspossible.Whichoneofthefollowing

subnetmasksshouldyouuse?

A.92

B.24

C.40

D.48

E.Noneoftheabove

正確答案：c

解析:Explanation:Usingthe2n-

2formula,wewillneedtouse4bitsforsubnetting,asthiswillprovidefor24-

2=14subnets.Thesubnetmaskfor4bitsisthen40.IncorrectAnswers:A.Th

iswillgiveusonly2bitsforthenetworkmask,whichwillprovideonly2networks.B.Thiswill

giveus3bitsforthenetworkmask,whichw川provideforonly6networks.D.Thisw川use5bi

tsforthenetworkmask,providing30networks.However,itwillprovideforonlyfor6hosta

ddressesineachnetwork.soCisabetterchoice.

什么是路由環(huán)路()

A.數(shù)據(jù)包在路由器的兩個環(huán)回接口之間來回傳遞

B.從目的地返回的路徑與出發(fā)路徑不同而形成"環(huán)路"的情況

C.數(shù)據(jù)包在一系列路由器間不斷傳輸卻始終無法到達其真正的目的地的情況

D.路由從一種路由協(xié)議到另一種路由協(xié)議的分布

正確答案：C

WhichLayer4protocolisusedforaTelnetconnectionbetweentwo

Ezonexamrouters?

A.IP

B.ICMP

C.DNS

D.TCP

E.UDP

F.RTP

正確答案：D

D解析：Explanation:

TCPisareliableconnection-orientedprotocol.TCPusesacknowledgments,

sequencing,andflowcontroltoensurereliability.TelnetusesTCPport23.

Youareexperiencingintermittentissuesrelatingtocongestionwithinthe

Ezonexamnetwork.WhatarethepossiblecausesofcongestiononthisLAN?

(Chooseallthatapply)

A.Abroadcastdomainwithtoomanyhosts.

B.Fullduplexoperation.

C.Broadcaststorms.

D.Multicasting.

E.NetworkSegmentation.

F.Lowbandwidth.

正確答案：ACF

A,C,F解析：Explanation:

ALANsegmentwithtoomanyhostscanmeanthattherearealargenumberof

stationscontendingforbandwidth.Itcanalsomeananincreaseinthenumberof

collisionsonthesegment,whichcancausefurthercongestionissues.

Broadcaststormsaretheresultofalargenumberofbroadcastssentoverthe

LAN.Becauseeachstationlistenstothesebroadcastmessages,congestioncan

occurquickly.Finally,lowbandwidthcansimplymeanthattheLANcannot

processalloftheLANtrafficthatisbeingsent.ThiscanmeanthatTCPsessions

areretransmitted,whichcanleadtoadditionalcongestion.

IncorrectAnswers:

B.Thiscanalleviatecongestion,asdatacanbesentandreceivedatthesame

time.Inaddition,collisionsarenotpossibleinafullduplexLAN.

D.Multicastingcanactuallyalleviatecongestionissues,assinglestreamsof

informationcanreachmultiplehostsatthesametime,insteadofusingaseries

ofpointtopoint

connections.

E.SegmentationbreaksupalargeLANintomultiple,smallerLANS.Thiswill

meanfewerhostsperbroadcastdomain.

在路由器上，可以使用的命令有：0

A.ping

B.showinterfaces

C.showiproute

D.ipconfig

E.wincfg

正確答案：ABC

2021思科認證考試題庫精選8節(jié)第6節(jié)

關于RIPV1和RIPV2,RIPV1報文支持子網(wǎng)掩碼，RIPV2不支持子網(wǎng)掩碼。

此題為判斷題(對，錯)。

正確答案：x

你使用命令copyrunning-configstartup-config保存路由器的配置，并重啟路由

器，但路由器啟動后沒有任何運行配置。請問可能出現(xiàn)了什么問題?()

A.啟動路由器時使用的命令不對

B.NVRAM受損

G配置寄存器的設置不正確

D.新升級到的IOS與路由器硬件不兼容

E.保存的配置與硬件不兼容

答案：C

對于以下ACL語句描述正確的是()

RI(config)#ipaccess-liststandardTELNET

RI(config-stdmacl)#permit192.168.4.20.0.0.0

R1#1ineytv04

RI(config-1ine)#access-classTELNETin

A.只允許的數(shù)據(jù)流穿過RI

B.只允許192,168.4.2對RI進行TELNET

C.只允許對R1進行TELNET并拒絕其它流量

D.只允許/24網(wǎng)段的數(shù)據(jù)流穿過R1

正確答案：B

下面關于地址轉(zhuǎn)換，敘述正確的是0。

A.NAT技術不可以有效的隱藏內(nèi)部局域網(wǎng)中的主機，但卻是一種有效的網(wǎng)絡

安全保護技術

B.一個局域網(wǎng)內(nèi)部有很多主機，可是不能保證每臺主機都擁有合法的公網(wǎng)IP

地址，為了達到所有的內(nèi)部主機都可以連接Internet網(wǎng)絡的目的,可以使用地址轉(zhuǎn)

換

C.地址轉(zhuǎn)換是在IP地址日益短缺的情況下提出的

D.NAT可以按照用戶的需要,在局域網(wǎng)內(nèi)部提供給外部FTP.WWW.Telnet

正確答案：BCD

Youhavejustpurchasedabrandnewrouterandwishtohavetherouter

promptyouthroughtheinitialconfigurationcommands.Whichroutermode

doesthisdescribe?

A.ROMMonitormode

B.SETUPmode

C.Autoflashmode

D.RXBOOTmode

E.Noneoftheabove

正確答案：B

解析:Explanation:

Setupmodeisaconvenientmodethatwalksyouthroughthesetupprocedure

bypromptingyouwithspecificquestionsandoptionsonebyone.

2021思科認證考試題庫精選8節(jié)第7節(jié)

AfterworkingallnightandsuccessfullyconfiguringaCiscorouterforthe

Ezonexamnetworkyousaveyourchangesonthestartupconfig,rebootthe

router,andgooutforacigarette.Whenyoureturn,noneofyourchangesare

activeandtherouterbootstotheinitialconfigurationmode!Whichofthe

choicesbelowindicatesthesourceofyourproblem?

A.HardwarefailureinNVRAMpreventstherouterfromloadingtheconfig

B.Startup-configinflashiscorruptandcannotbeanalyzed

C-Routerconfiguration-registersettobypassstartupconfiguration

D.Startup-configinNVRAMiscorruptandcannotbeanalyzed

E.Noneoftheabove

正確答案：C

解析:Explanation:

Thedefaultconfiguration-registersettingof0x2102loadstheIOSfromflashand

theconfigurationfromNVRAM.

However,forpasswordrecovery,youcansettheregisterto0x2142andthe

startup-configfileinNVRAMwillbebypassed.Theproblemdescribedhereis

thattheconfigregisterwasnotchangedbackto0x2102beforetherouterwas

rebooted,sotheactiveconfigurationisbypassed.Simplysettingtheconfig

registerbackto0x2102willfixthisproblem.

IncorrectAnswers:

A,B,D.Allofthesedescribehardwareorsoftwareerrors.Intheeventthatthisis

theproblem,errorswillbegeneratedandtherouterwillfailtobootproperly.In

thesecases,therouterwillnotreturntotheinitialstartupconfiguration.

Whichthreeoftheprotocolsbelowbelongtotheapplicationlayer?(Select

threeanswerchoices)

A.ARP

B.HTTPS

C.SMTP

D.CDP

E.TFTP

F.ICMP

正確答案：BCE

B,C,E解析：Explanation:

TheapplicationlayeristhehighestOSIlayer,andprotocolsatthislayerareend-

useroriented.HTTPSsopeoplecangetinformationontheinternet,SMTPso

peoplecanmanagenetworks,andTFTPsopeoplecandownloadfiles.

IncorrectAnswers:

A,D,F.ARP,CDP,ICMPareprotocolsthatequipmentlikeroutersandswitches

usetocommunicatewiththemselves,andbelongtolowerlevelsonthemodel.

下列有關標準ACL和擴展AC