21年思科认证历年真题5辑

21年思科认证历年真题5辑第1辑

HDLC是一种面向()的链路层协议。

A.希

B比特

C信元

D.数据包

正确答案：B

请参见图示1040.0网络发生故障哪种机制可防止R2接收有关网络

的错误更新信息()

A.水平分割

B.抑制计时器

C.路由毒化

D.触发更新

正确答案：A

都是NAT的地址转换方式()。

A静态地址转换

B.动态地址转换

C.复用动态地址

D.端口地址转换

正确答案：ABD

GiventhatyouhaveaclassBIPaddressnetworkrange,whichofthesubnet

masksbelowwillallowfor100subnetswith500usablehostaddressesper

subnet?

A.

B.

C.

D.

E.24

正确答案：c

解析:Explanation:

Usingthe2n-2formulaforhostaddresses,29-2=510hostaddress,soa9-bit

subnetmaskwillprovidetherequirednumberofhostaddresses.Ifthese9bits

areusedforthehostsinaclassBnetwork,thentheremaining7bitsareusedfor

thenumberofnetworks.

Againusingthe2n-2formula,wehave2n-2=126networksthatareavailable.

IncorrectAnswers:

A.Thiswillprovideforonly1networkwith216-2=65534hosts

B.Thisw川providefor6networkswith8190hostaddresses.

D.Thiswillprovide254networksand254hosts.

E.Thiswillprovide2046differentnetworks,buteachnetworkwillhaveonly30

hosts.

TheEzonexamnetworkadministratorhasjustissuedthe"switchporttrunk

nativevlan998"commandonswitchVE2.Whatisthefunctionofthiscommand?

A.ItdesignatesVLAN998asthedefaultforallunknowntaggedtraffic

B.ItdesignatesVLAN998foruntaggedtraffic

C.ItblocksVLAN998trafficfrompassingonthetrunk

D.ItcreatesaVLAN998interface

E.Noneoftheabove

正确答案：B

RIP路由协议每隔()秒进行路由更新。

A.30

B.60

C.120

D.180

正确答案：A

下面哪个命令将新的思科IOS版本复制到路由器?()

A.copyflashftp

B.copynvramflash

C.copyflashtftp

D.copytftpflash

答案：D

21年思科认证历年真题5辑第2辑

默认情况下，RIP定期发送路由更新的时间是()

A.15S

B.30S

C.60S

D.90S

正确答案：B

RIP路由协议采用哪些方法来避免路由环路？()

A.水平分割

B.毒性逆转

C.最大跳数

D.触发更新

正确答案：ABCD

在OSI七层模型中，介质工作在哪一层()

A传输层

B.会话层

C物壬醺

D.应用层

正确答案：C

路由器下"特权用户模式”的标识符是：（）

A.>

B.!

C.

D.(config-if)

正确答案：C

AsaCCNAcandidate,youmustknowthevariouslayersoftheOSImodel.At

whichlayersoftheOSIModeldoWideAreaNetworksoperatein?(Choosetwo)

A.PhysicalLayer

B.DatalinkLayer

C.NetworkLayer

D.SessionLayer

E.TransportLayer

F.PresentationLayer

G.ApplicationLayer

正确答案：AB

A,B解析:Explanation:

AWANisadatacommunicationsnetworkthatcoversarelativelybroad

geographicareaandthatoftenusestransmissionfacilitiesprovidedbycommon

carriers,suchastelephonecompanies.WANtechnologiesgenerallyfunctionat

thelowertwolayersoftheOSIreferencemodel:thephysicallayerandthedata

linklayerasshownbelow.

OSIlayersWANspecificallon*

NetworK

layerc

n

d

eln

x

2d2

o0d

d口

dHS

MACE

sublayer

EIA/TIA232

PhysicalEIA/TIA449

layerV24V35

为HSSIG.7O3

L

7EIA-530

X

Note:OccasionallyWAN'swouldalsobeconsideredtooperateatlayer3,but

sincethisquestionaskedforonly2chopiceslayers1and2arebetterchoices.

帧中继环境中，在物理端口上，建立子接口的命令是（）

A.create

B.interface

C.encapsulation

D.ipaddress

正确答案：B

在路由表中到达同一网络的路由有：静态路由、RIP路由、IGRP路由，OSPF

路由，则路由器会选用哪条路由传输数据：（）

A.静态路由

B.RIP路由

C.IGRP路由

D.OSPF路由

正确答案：A

21年思科认证历年真题5辑第3辑

以下特殊区域中哪一个没有自动下发缺省路由（）

A.末梢区域

B.完全末梢区域

C.NSSA区域

D.完全NSSA区域

正确答案：D

YouwishtosegmentyourLANintomultiplebroadcastdomains.Which

technologymethodshouldyouimplementinordertodothis?

A.Transparentbridging

B.Cut-throughswitching

C.Fragment-freeswitches

D.VirtualLANs

E.Store-and-forwardswitching

F.Noneoftheabove

正确答案：D

D解析：Explanation:

ThecreationofVLANsinaswitchwillprovideseparateBroadcastdomains.By

default,allportsinaCatalystswitchbelongtoVLAN1.Bycreatingadditional

VLANs,theLANwillbelogicallysegmentedintoseparatebroadcastdomains.

IncorrectAnswers

A.TransparentbridgingiscalledTransparentbecausetheendpointsdevicesdo

notneedtoknowthatthebridgesexists.Itwillnotplayanyroleforcreating

separatebroadcastdomain

B,E.Bothoftheseareswitchingmethods.

C.Thishasnothingtodowiththecreationofmultiplebroadcastdomains.

请参见图示。主机A无法访问Internet。此问题的原因是什么

A.主机A的IP地址不正确

B.主机A的默认网关不正确

C.两台路由器的FaO/1接口配置了不同的子网

D.RlFaO/O的子网掩码不正确

正确答案：C

EzonexamisusingIPaddressingaccordingtoRFC1918.Whichthreeaddress

rangesareusedforinternalprivateaddressblocksasdefinedbyRFC1918?

(Chooseallthatapply)

A.to255.255.255

B.to55

C.to55

D.to55

E..to55

F.to55

G.to55

正确答案：BDF

B,D,F解析：Explanation:

RFC1918definesthreedifferentIPaddressrangesasprivate,meaningthatthey

canbeusedbyanyprivatenetworkforinternaluse,andtheserangesarenotto

beusedintheInternet.TheclassAprivaterangeisto55.

TheclassBaddressrangeisto55.TheclassCprivateIP

addressrangeisto55.

IncorrectAnswers:

A.Thenetworkaddressisinvalidandcannotbeused.

C.Thecorrectaddressrangeis172.16.X.Xthrough172.31.X.X

E.TheaddressisreservedfortheinternalloopbackIPaddress,butthe

entire127.X.X.XrangeisnotdefinedinRFC1918asaprivateaddressrangefor

networks.

G.ThisaddressrangedescribestheclassDmulticastaddressrange.

交换机工作在OSI七层模型的哪一层()

A.物理层

B.数据链路层

C.网络层

D.传输层

正确答案：B

要将许可证复制到闪存，可使用哪个命令?()

A.copytftpflash

B.savelicenseflash

C.licensesaveflash

D.copylicenseflash

答案：C

Whenyoucomparethedifferencesbetweenhalf-duplexandfull-duplex

Ethernet,whichofthefollowingcharacteristicsareexclusivetohalf-duplex?

(Selecttwoanswerchoices)

A.Half-duplexEthernetoperatesinasharedcollisiondomain.

B.Half-duplexEthernetoperatesinanexclusivebroadcastdomain.

C.Half-duplexEthernethasefficientthroughput.

D.Half-duplexEthernethaslowereffectivethroughput.

E.Half-duplexEthernetoperatesinanexclusivecollisiondomain.

正确答案：AD

解析：Explanation:

Asingledevicecouldnotbesendingaframe,andreceivingaframe,atthesame

timebecauseitwouldmeanthatacollisionwasoccurring.So,devicessimply

chosenottosendaframe,whilereceivingaframe.Thatlogiciscalledhalf­

duplexlogic.

Ethernetswitchesallowmultipleframestobesentoverdifferentportsatthe

sametime.Additionally,ifonlyonedeviceisconnectedtoaswitchport,thereis

neverapossibilitythatacollisioncouldoccur.So,LANswitcheswithonlyone

devicecabledtoeachportoftheswitchallowtheuseoffull-duplexoperation.

FullduplexmeansthatanEthernetcardcansendandreceiveconcurrently.

IncorrectAnswers:

B.Fullduplexeffectivelydoublesthethroughputofhalf-duplexoperation,

becausedatacanbebothsentandreceivedatthefull10/100speed.

C,E.Inhalfduplexoperation,thenetworkissharedbetweenalldevicesinthe

collisiondomain.

21年思科认证历年真题5辑第4辑

IP扩展访问列表的数字标示范围是多少（）。

A.0-99

B.1-99

C.100-199

D.101-200

正确答案：C

Whiletroubleshootingaconnectivityproblemonthenetwork,youissuethe

pingcommandfromyourPCcommandprompt,buttheoutputshows"request

timesout."

AtwhichOSIlayeristhisproblemassociatedwith?

A.Thedatalinklayer

B.Theapplicationlayer

C.Theaccesslayer

D.Thesessionlayer

E.Thenetworklayer

正确答案：E

解析:Explanation:

TCP/IPincludesICMP,aprotocoldesignedtohelpmanageandcontrolthe

operationofaTCP/IPnetwork.TheICMPprotocolprovidesawidevarietyof

informationaboutanetwork'shealthandoperationalstatus.Controlmessageis

themostdescriptivepartofaname.ICMPhelpscontrolandmanageIP'swork

andthereforeisconsideredpartofTCP/IP'snetworklayer.

对于使用链路状态路由协议的路由器如何选择最佳路线到达子网，下列哪项是

正确的（）

A.路由器会发现链路状态数据库中的最佳路由

B.通过针对链路状态数据库中的信息运行SPF算法，路由器会计算出最佳路由

C.路由器将比较每个邻居接收到的更新中为子网列出的标准，并挑选最佳标准

路由

D.路由器会使用具有最低条数的路径

正确答案：B

WhichofthefollowingcomponentsmustbeelectedbeforetheSpanning

TreeProtocolcanconvergeinaswitchedLAN?

A.Designatedports.

B.Duplexoperatingmode.

C.Fastmodeports.

D.Rootbridge.

E.Rootports.

F.BDPUpriority.

正确答案：ADE

A,D,E解析:Explanation:

Designatedport:Eitherarootportoraportthathasbeendeterminedashaving

thebest(lower)cost-adesignatedportwillbemarkedasaforwardingport.

Rootbridge:TherootbridgeisthebridgewiththebestbridgeID.WithSTP,the

keyisforalltheswitchesinthenetworktoelectarootbridgethatbecomesthe

focalpointinthenetwork.Allotherdecisionsinthenetwork-likewhichportisto

beblockedandwhichportistobeputinforwardingmode-aremadefromthe

perspectiveofthisrootbridge.

Rootport:Alwaysthelinkdirectlyconnectedtotherootbridge,ortheshortest

pathtotherootbridge.Ifmorethanonelinkconnectstotherootbridge,thena

portcostisdeterminedbycheckingthebandwidthofeachlink.Thelowestcost

portbecomestherootport.

Sothesethreecomponentsmustbeelectedbeforethespanningtreeprotocol

canconvergeinaswitchedLAN

命令ipnatpoolaaa0netmask的作用是()

A.指定可访问地址

B.定义地址池

C.指定路由

D.定义哪些地址可以进行地址转换

正确答案：B

OSPF协议中，ABR的不同端口可能运行在不同的area中，其中一定有接口

运行在（）当中.

A.areaO

B.areal

C.arealO

D.arealOO

正确答案：A

Showcdpinterface命令是用于显示以下哪一项的（）

A.CDP的时间值和接口状态

B.邻居路由器的接口配置

C.邻居设备的IP地址

D.CDP保持时间

正确答案：A

21年思科认证历年真题5辑第5辑

YouaretryingtoconnectdirectlyintotheLANprotofaEzonexamrouter.

YouwanttotelnettothelocalCiscorouterusingTCP/IPbutcannotcreatea

session.

Whatshouldyoudotoresolvetheproblem?

A.Useastraight-throughcabletoconnectyourcomputer'sCOMporttothe

router'sconsoleport.

B.Useacrossovercabletoconnectyourcomputer'sCOMporttothe

router'sconsoleport.

C.Useastraight-throughcabletoconnectyourcomputer'sCOMporttothe

router'sEthernetport.

D.Useacrossovercabletoconnectyourcomputer'sEthernetporttothe

router'sEthernetport.

E.Usearollovercabletoconnectyourcomputer'sEthernetporttothe

router'sEthernetport.

F.Useastraight-throughcabletoconnectyourcomputer'sEthernetportto

therouter'sEthernetport.

G.Noneoftheabove

正确答案：D

D解析:Explanation:

Inordertoconnectdirectlytoarouterviatelnet,youmustconnecttotherouter

viaoneoftheLANports.WhenconnectingdirectlytotheEthernetportwithaPC

withouttheuseofaswitchorhub,acrossovercablemustbeused.

IncorrectAnswers:

A,B,C.InordertotelnetdirectlyintotherouterviaaTCP/IPconnection,the

COMportofthePCcannotbeused.TheCOMportisusedfordirectterminal

emulationprogramssuchasHyperTerminal.

E.Rollovercablesareusedforconsoleconnectionsintotherouter,notforTCP/IP

connections.

F.Straightthroughcablesareusedforconnectionsintoaswitchorhubfromthe

PC.ItwillnotworkfordirectEthernetconnectionsintotherouter.

WhichofthefollowingareVLANframe,encapsulationtypesthatmaybe

configuredonaCatalystswitch?(Choosetwo.)

A.VTP

B.ISL

C.CDP

D.802.1Q

E.802.1p

F.LLC

正确答案：BD

B,D解析：Explanation:

ThetwoVLANtrunkingencapsulationtypesare:

Inter-SwitchLink(ISL):ThisisproprietarytoCiscoswitches,andit'susedforFast

EthernetandGigabitEthernetlinksonly.ISLroutingcanbeusedonaswitchport,

routerinterfaces,andserverinterfacecardstotrunkaserver.ISLletsyou

explicitlytagVLANinformationontoanEthernetframe.Thistagginginformation

allowsVLANstobemultiplexedoveratrunklinkthroughanexternal

encapsulationmethod,whichallowstheswitchtoidentifytheVLANmembership

ofaframe,overthetrunkedlink.

IEEE802.1Q:CreatedbytheIEEEasastandardmethodofframe,tagging,this

actuallyinsertsafieldintotheframe,toidentifytheVLAN.Ifyou'retrunking

betweenaCiscoswitchedlinkandadifferentbrandofswitch,youhavetouse

802.1Qforthetrunktowork.

AstheEzonexamnetworkadministrator,youarerequiredtohaveafirm

understandingoftheOSImodel.Whydoesthedatacommunicationindustryuse

thelayeredOSIreferencemodel?(Choosetwo)

A.Itenablesequipmentfromdifferentvendorstousethesameelectronic

components,thussavingresearchanddevelopmentfunds

B.Itencouragesindustrystandardizationbydefiningwhatfunctionsoccur

ateachlayerofthemodel

C.Itdividesthenetworkcommunicationprocessintosmallerandsimpler

components;thusaidingcomponentdevelopment,designandtroubleshooting

D.Itprovidesameansbywhichchangesinfunctionalityinonelayer

requirechangesinotherlayers

E.Itsupportstheevolutionofmultiplecompetingstandardsandthus

providesbusinessopportunitiesforequipmentmanufacturers

正确答案：BC

解析:Explanation:

TheOSI(OpenSystemInterconnection)referencemodelwascreatedasa

referencepointforcommunicationsdevices.Alayeredapproachisusedto

segmenttheentiretelecommunicationsprocessintoaseriesofsmallersteps.

Aiscorrectbecauseitencouragesalevelofstandardizationbyencouragingthat

functionsbecomparedtoknownlayers.

Disalsocorrectbecauseitallowsengineerstofocusonthedevelopment,

refining,andperfectionofsimplercomponents.

交换机的三大功能为(