2021思科认证历年真题和解答8篇

2021思科认证历年真题和解答8篇第1篇

Areceivinghosthasfailedtoreceiveallofthesegmentsthatitshould

acknowledge.

Whatcanthehostdotoimprovethereliabilityofthiscommunication

session?

A.StartanewsessionusingUDP

B.ObtainanewIPaddressfromtheDHCPserver

C.Useadifferentsourceportforthesession

D.Decreasethesequencenumber

E.Decreasethewindowsize

正确答案：E

解析:Explanation:

ATCPwindowtheamountofoutstanding(unacknowledgedbytherecipient)

dataasendercansendonaparticularconnectionbeforeitgetsan

acknowledgmentbackfromthereceiverthatithasgottensomeofit.

ForexampleifapairofhostsaretalkingoveraTCPconnectionthathasaTCP

windowsizeof64KB(kilobytes),thesendercanonlysend64KBofdataandthen

itmuststopandwaitforanacknowledgmentfromthereceiverthatsomeorall

ofthedatahasbeenreceived.Ifthereceiveracknowledgesthatallthedatahas

beenreceivedthenthesenderisfreetosendanother64KB.

OnewaytoimprovethereliabilityoftheTCPconnectionistoreducethewindow

sizethatthereceiverneedstoreceivebeforesendinganacknowledgement.

However,thiswillreducethroughputasmoresegmentsandacknowledgements

willneedtobesentinordertotransferthesameamountofdata.

请参见图示。访问列表已应用于R2上S0/0/0接口的入站流量。以下哪两种

类型的流量可以到达服务器（）

724Z24

access-list101permittcp0host0eq80

A.来自主机0的IP流量

B.来自主机A的Web流量

C.来自主机的IP流量

D.来自网络10.120的UDP流量

E.来自网络的HTTP流量

正确答案：BD

当配置一个CISCO的路由器时，缺省的DR和BDR优先级是（）。

A.O

B.l

C.16

D.255

正确答案：B

属于私有IP段的是()

A.-55

B.-55

C.-55

D.-55

E.-55

正确答案：ABD

帧中继环境中，CIR的含义是()

A.提高线路速率

B.保证线路速率

C.降低线路速率

D酒己置线路速率

正确答案：B

2021思科认证历年真题和解答8篇第2篇

WhatistheIEEEstandardassociatedwithGigabitEthernet?(Selecttwo

answerchoices)

A.802.11

B.802.5

C.8023ab

D.8023ae

E.802.3z

F.802.3u

正确答案：CE

C,E用星析：Explanation:

TheIEEE802.3zstandarddescribes1000BASE-SX.

ThelOOOBaseTstandardwasreleasedinJune1999,definedbyIEEE802.3ab.

IncorrectAnswers:

A.Thisdescribesthestandardusedforwirelessnetworks.

B.Thisisthestandardfortokenringnetworks.

D.OnJune17,2002theIEEE802.3aespecificationfor10GigabitEthernetwas

approvedasanIEEEstandardbytheIEEEStandardsAssociation(IEEE-SA)

StandardsBoard.

F.IEEE802.3udescribesthestandardfor100BASE-TX.

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

要显示路由器支持的技术包许可证和功能许可证以及多个状态变量,可使用哪个命

令?()

A.showlicense

B.showlicensefeature

C.showlicenseudi

D.showversion

答案：B

将路由器的许可证删除包括哪两步?()

A.使用命令eraseflash:license

B.重启系统

C.使用命令licenseboot,并在末尾指定关键字disable

D.使用命令licenseclear将许可证清除

答案：CD

禁止RIP协议的路由聚合功能的命令是()

A.norip

B.no-summany

C.noauto-summany

D.nonetwork

正确答案：C

2021思科认证历年真题和解答8篇第3篇

Whichtwooftheaddressesbelowareavailableforhostaddressesonthe

Ezonexamsubnet9/28?(Selecttwoanswerchoices)

A.7

B.4

C.9

D.6

E.1

F.Noneoftheabove

正确答案：AC

A,C解析：Explanation:

Thenetworkusesa28bitsubnet(40).Thismeansthat4bitsare

usedforthenetworksand4bitsforthehosts.Thisallowsfor14networksand14

hosts(2n-2).Thelastbitusedtomake240isthe4thbit(16)thereforethefirst

networkwillbe6.

Thenetworkwillhave16addresses(butrememberthatthefirstaddressisthe

networkaddressandthelastaddressisthebroadcastaddress).Inotherwords,

thenetworkswillbeinincrementsof16beginningat6/28.TheIP

addresswearegivenis9.Thereforetheotherhostaddressesmust

alsobeonthisnetwork.ValidIPaddressesforhostsonthisnetworkare:

7-0.

IncorrectAnswers:

B.Thisisnotavalidaddressforthisparticular28bitsubnetmask.Thefirst

networkaddressshouldbe6.

D.Thisisthenetworkaddress.

E.Thisisthebroadcastaddressforthisparticularsubnet.

距离-向量路由算法最优路径计算的复杂度要比链路-状态路由算法最优路径计

算的复杂度大。

此题为判断题（对，错）。

正确答案：X

FTP工作在OSI哪一层（）

A会话层

B.表示层

C.传输层

D.应用层

正确答案：D

为了便于网络的管理，人为地将互联网划分成若干自治系统，每一个自治系统

由运行同一路由协议的路由器组成。

此题为判断题（对，错）。

正确答案：V

在配置帧中继子接口时，在物理接口上应该配置的内容是：（）

A.配置IP地址

B.封装帧中继协议

C.指定子接口类型

D.设定子接口

E.配置密码

正确答案：BCD

2021思科认证历年真题和解答8篇第4篇

EzonexamhasimplementedtheuseoftheVirtualTrunkingProtocol(VTP).

Whichstatementbelowaccuratelydescribesabenefitofdoingthis?

A.VTPwillallowphysicallyredundantlinkswhilepreventingswitching

loops

B.VTPwillallowswitchestoshareVLANconfigurationinformation

C.VTPwillallowasingleporttocarryinformationtomorethanoneVLAN

D.VTPwillallowforroutingbetweenVLANs

E.Noneoftheabove

正确答案：B

以下封装协议使用CHAP或者PAP验证方式的是()。

A.PPP

B.HDLC

C.SDLC

D.SLIP

正确答案：A

下列哪个network命令会告知此路由器开始使用IP地址为.

和的接口上的OSPF()

A.networkarea0

B.network55area0

C.network55area0

0.network55area0

正确答案：B

VLAN主干协议VTP的默认工作模式是()

A.服务器模式

B.客户端模式

C.透明模式

D.以上三者都不是

正确答案：A

下列哪一^^通配符掩码与子网/27的所有主机匹配（）。

A.

B.

C.1

D.55

正确答案：C

2021思科认证历年真题和解答8篇第5篇

osi七层模型中，物理层的数据封装名称为（）

A.比特

B帧

C包

D段

正确答案：A

命令confreg0x2142有何作用?()

A用于重启路由器

B.用于忽略NVRAM中的配置

C.用于进入ROM监视器模式

D.用户查看遗忘的密码

答案：B

以下ACL将对路由器的流量产生何种影响()

Access-list1deny192.168.19.1620.0.0.0

AccessTist1permitany

A.它将允许所有源自的网络流量

B.它将拒绝源自主机62的流量

C.因为通配符掩码忽略了所有比特，所以对流量没有影响

D.permitany选项使deny选项失效

正确答案：B

为了查看路由器的E0端口上，是否挂接了访问权限表，应该使用的命令是

()

A.showaccess-list

B.showinterfaceeO

C.showipinterfaceeO

D.showeO

正确答案：B

HowcouldtheEzonexamcorporationbenefitfromusingVLANsontheir

network?

(Selectthreeanswerchoices.)

A.VLANsallowaccesstonetworkservicesbasedondepartment,not

physicallocation.

B.VLANsutilizepacketfilteringtoenhancenetworksecurity.

C.VLANsprovidealow-latency,highbandwidthinternetworkingalternative.

D.VLANsprovideamethodofcommunicationbetweenIPaddressesinlarge

networks.

E.VLANsestablishsegmentedbroadcastdomainsinswitchednetworks.

F.VLANscangreatlysimplifyadding,moving,orchanginghostsonthe

network.

正确答案：AEF

A,E,F解析：Explanation:

VLANsestablishbroadcastdomainsinswitchednetworks,sobyvirtueofhaving

theoptiontocreatemanyefficientbroadcastdomains,congestionisreduced

andnetworkthroughputisgreatlyenhanced.VLANsallownetworkstobe

dividedbydepartmentorresourceneeds,ratherthenbyphysicallocation.When

peoplemovedepartments,leaveadepartment,orjoinadepartment,

administrationiseasyandconvenientwithafewkeystrokes.

IncorrectAnswers:

B,D.Thesewouldberouterfunctionsatlayer3.SwitchesandVLANsoperateat

layer2oftheOSImodel.

C.TheuseofVLANsmayactuallyincreasethelatencyinsomecases,astraffic

fromoneVLANtotheotherwillneedtoberouted.

2021思科认证历年真题和解答8篇第6篇

当配置一个CISCO的路由器时，缺省的DR和BDR优先级是（）。

A.0

B.1

C.16

D.255

正确答案：B

以下哪一项不是有关虚电路交换方式的正确描述。()

A.分组需要包含虚电路标识符

B.某条虚电路对应的转发项只给出该虚电路经过的两个端口之间的关联

C.虚电路标识符用于建立终端间传输路径与终端间传输的数据之间的绑定

D.虚电路是指终端间传输路径

参考答案：A

已知某台路由器的路由表中有如下两个表项假如该路由器要转发目的地址为

的报文，则下列说法中正确的是()

A.选择第一项，因为OSPF协议的优先级高

B.选择第二项，因为RIP协议的花费值(Metric)小

C.选择第二项，因为出口是EthternetO,比Serial。速度快

D.选择第二项,因为该路由项对于目的地址9.145来说，是更精确的匹配

正确答案：D

Whencomparingandcontrastingthesimilaritiesanddifferencesbetween

bridgesandswitches,whichofthefollowingarevalidstatements?Chooseallthe

validanswerchoices)

A.Bridgesarefasterthanswitchesbecausetheyhavefewerports.

B.Aswitchisamultiportbridge,

C.BridgesandswitcheslearnMACaddressesbyexaminingthesourceMAC

addressofeachframe,received.

D.Abridgewillforwardabroadcastbutaswitchwillnot.

E.Bridgesandswitchesincreasethesizeofacollisiondomain.

F.Noneoftheabovestatementsaretrue.

正确答案：BC

B’C解析：Explanation:

Bothbridgesandswitchesbuildthebridgetablebylisteningtoincomingframes

andexaminingthesourceMACaddressintheframe.

Switchesaremultiportbridgesthatallowyoutocreatemultiplebroadcast

domains.Eachbroadcastdomainislikeadistinctvirtualbridgewithinaswitch.

IncorrectAnswers:

A.Switchesaregenerallyfasterthanbridges.Bridgesalsodonotnecessarilyhave

fewerportsthanswitches.

D.Bothbridgesandswitcheswillforwardbroadcastandmulticasttraffic,

assumingthatthetrafficremainsinthesameVLAN.

E.TheuseofVLANsinaswitchcandecreasethesizeofthecollisiondomain,by

creatingadditional,smallercollisiondomains.

Onahalf-duplexEthernetLAN,twohostsattempttosenddata

simultaneously,resultinginacollision.Followingthiscollision,whatwillthehosts

do?(Selectallvalidanswers)

A.Thedestinationhostsendsarequesttothesourceforretransmission.

B.Thejamsignalindicatesthatthecollisionhasbeencleared.

C.Thehostswillattempttoresumetransmissionafteratimedelayhas

expired.

D.Anelectricalpulseindicatesthatthecollisionhascleared.

E.Therouteronthesegmentwillsignalthatthecollisionhascleared.

F.Thehostswilldonothing,asthehigherlayersareresponsiblefordata

errorcorrectionandre-transmission.

正确答案：C

C解析:Explanation:

WhenahostonanEthernetLANhasinformationtosend,thefollowingstepsare

taken:

1.Adevicewithaframe,tosendlistensuntilEthernetisnotbusy.

2.WhentheEthernetisnotbusy,thesenderbeginssendingtheframe.

3.Thesenderlistenstomakesurethatnocollisionoccurred.

4.Oncethesendershearthecollision,theyeachsendajammingsignal,to

ensurethatallstationsrecognizethecollision.

5.Afterthejammingiscomplete,eachsenderrandomizesatimerandwaitsthat

long.

6.Wheneachtimerexpires,theprocessstartsoverwithstep1.

2021思科认证历年真题和解答8篇第7篇

假设有这样的组网实例:两个路由器（假设为RTA和RTB）通过串口相连接，其

中RTA的串口IP地址是/30,RTB的串口IP地址/30,RTA

通过以太口连接的本地局域网的IP地址是/16,RTB通过以太口连接的

本地局域网IP地址是/16,在上面所有的接口上都启动RIPV1（仅仅

RIPVD协议，那么，下列说法正确的是（）

A.在RTA的本地局域网上的计算机可以访问在RTB本地局域网上的计算机

B.在RTB的本地局域网上的计算机可以访问在RTA本地局域网上的计算机

C.在RTA的本地局域网上的计算机不能访问在RTB本地局域网上的计算机

D.在RTB的本地局域网上的计算机不能访问在RTA本地局域网上的计算机

正确答案：CD

路由器上"水平分割”的功能是：（）

A.分离端口

B,阻止路由环路

C.简化配置

D.方便故障处理

正确答案：B

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

WhiletroubleshootingaconnectivityissuefromaPCyouobtainthe

followinginformation:

LocalPCIPaddress:5/24

DefaultGateway:

RemoteServer:50/24

YouthenconductthefollowingtestsfromthelocalPC:

Ping-Unsuccessful

Ping5-Successful

Ping-Unsuccessful

Ping50-Unsuccessful

Whatistheunderlyingcauseofthisproblem?

A.TCP/IPnotcorrectlyinstalled

B.Localphysicallayerproblem

C.NICnotfunctioning

D.Remotephysicallayerproblem

E.Noneoftheabove

正确答案：A

解析：Explanation:

EveryWindowsbasedPCusestheasthelocalloopbackIPaddress.

EveryPCwillrespondtothislocalIPaddressiftheTCP/IPstackiscorrectly

installedandrunningonthemachine.Ifyoucannotpingtheloopbackaddressof

,thensomethingiswrongwiththeTCP/IPprotocolstack.

Asanetworkadministrator,youw川needtodecideontheappropriate

networkdevicestouse.Whichofthefollowingcorrectlydescribestherolesof

devicesinaWAN?(Choosethree)

A.ACSU/DSUterminatesadigitallocalloop.

B.ArouteriscommonlyconsideredaDCEdevice.

C.Amodemterminatesananaloglocalloop.

D.ArouteriscommonlyconsideredaDTEdevice.

E.Amodemterminatesadigitallocalloop.

F.ACSU/DSUterminatesananaloglocalloop.

G.AmodemisusedtoterminateaT1

正确答案：ACD

A,C,D

2021思科认证历年真题和解答8篇第8篇

一台运行OSPF的路由器，它的两个正常工作的接口一个属于区域0,另一个

属于区域9,并且重分布5条静态路由进入OSPF,则该路由器一定会始发哪些

LSA()

A.RouterLSA(Type=l)；

B.NetworkLSA(Type=2)；

C.NetworkSummaryLSA(Type=3);

D.ASBRSummaryLSA(Type=4);

E.ASExternalLSA(Type=5)；

正确答案：ACDE

Ezonexamusershavenoticedextremelyslownetworkperformance,

intermittentconnectivity,andconnectionlosses.Afterenteringthe"show

interfaces"command,younoticethattheEthernetinterfaceisconfiguredas100

Mbpsfull-duplexandthatthereisevidenceoflatecollisions.Whatcouldbethe

causeofthisproblem?

A.Duplexm