2021思科認(rèn)證考試題庫8節(jié)

2021思科認(rèn)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(diǎn)到點(diǎn)WAN鏈路上，下列哪個

設(shè)備室DCE設(shè)備

A.路由器

B.CSU/DSU

C用話局中心機(jī)房設(shè)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(jī)上執(zhí)行命令showspanning-tree時(shí)得到的輸出:請問下面

哪兩種有關(guān)這臺交換機(jī)的說法是正確的?()

A.這臺交換機(jī)是根網(wǎng)橋

B這臺交換機(jī)不是根網(wǎng)橋

C根網(wǎng)橋與這臺交換機(jī)之間有4臺交換機(jī)

D.這臺交換機(jī)運(yùn)行的是802.1W

E.這臺交換機(jī)運(yùn)行的是STPPVST+

答案：BD

下圖中如果允許/24和10.000/8的網(wǎng)絡(luò)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(guān)鍵字disable

D.使用命令licenseclear將許可證清除

答案：CD

2021思科認(rèn)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(jìn)入網(wǎng)絡(luò)的流量大幅增加。管理員清除了

計(jì)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(jié)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(wù)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(biāo)主要是電子郵件服

務(wù)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(jī)。以下哪些操作

時(shí)標(biāo)準(zhǔn)IPACL可配置來執(zhí)行的()

A.匹配準(zhǔn)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(biāo)IP地址

正確答案：AC

2021思科認(rèn)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(xué)習(xí)

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(luò)流量

B.它將拒絕源自主機(jī)62的流量

C.因?yàn)橥ㄅ浞诖a忽略了所有比特，所以對流量沒有影響

D.permitany選項(xiàng)使deny選項(xiàng)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(rèn)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(xiàng)不屬于分組交換技術(shù)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(rèn)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(dá)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(rèn)證考試題庫精選8節(jié)第6節(jié)

關(guān)于RIPV1和RIPV2,RIPV1報(bào)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(yùn)行配置。請問可能出現(xiàn)了什么問題?()

A.啟動路由器時(shí)使用的命令不對

B.NVRAM受損

G配置寄存器的設(shè)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(jìn)行TELNET

C.只允許對R1進(jìn)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(guān)于地址轉(zhuǎn)換，敘述正確的是0。

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

安全保護(hù)技術(shù)

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

地址，為了達(dá)到所有的內(nèi)部主機(jī)都可以連接Internet網(wǎng)絡(luò)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(rèn)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(guān)標(biāo)準(zhǔn)ACL和擴(kuò)展AC