2021思科認(rèn)證歷年真題和解答8篇第1篇

Areceivinghosthasfailedtoreceiveallofthesegmentsthatitshould

acknowledge.

Whatcanthehostdotoimprovethereliabilityofthiscommunication

session?

A.StartanewsessionusingUDP

B.ObtainanewIPaddressfromtheDHCPserver

C.Useadifferentsourceportforthesession

D.Decreasethesequencenumber

E.Decreasethewindowsize

正確答案：E

解析:Explanation:

ATCPwindowtheamountofoutstanding(unacknowledgedbytherecipient)

dataasendercansendonaparticularconnectionbeforeitgetsan

acknowledgmentbackfromthereceiverthatithasgottensomeofit.

ForexampleifapairofhostsaretalkingoveraTCPconnectionthathasaTCP

windowsizeof64KB(kilobytes),thesendercanonlysend64KBofdataandthen

itmuststopandwaitforanacknowledgmentfromthereceiverthatsomeorall

ofthedatahasbeenreceived.Ifthereceiveracknowledgesthatallthedatahas

beenreceivedthenthesenderisfreetosendanother64KB.

OnewaytoimprovethereliabilityoftheTCPconnectionistoreducethewindow

sizethatthereceiverneedstoreceivebeforesendinganacknowledgement.

However,thiswillreducethroughputasmoresegmentsandacknowledgements

willneedtobesentinordertotransferthesameamountofdata.

請(qǐng)參見(jiàn)圖示。訪問(wèn)列表已應(yīng)用于R2上S0/0/0接口的入站流量。以下哪兩種

類型的流量可以到達(dá)服務(wù)器（）

724Z24

access-list101permittcp0host0eq80

A.來(lái)自主機(jī)0的IP流量

B.來(lái)自主機(jī)A的Web流量

C.來(lái)自主機(jī)的IP流量

D.來(lái)自網(wǎng)絡(luò)10.120的UDP流量

E.來(lái)自網(wǎng)絡(luò)的HTTP流量

正確答案：BD

當(dāng)配置一個(gè)CISCO的路由器時(shí)，缺省的DR和BDR優(yōu)先級(jí)是（）。

A.O

B.l

C.16

D.255

正確答案：B

屬于私有IP段的是()

A.-55

B.-55

C.-55

D.-55

E.-55

正確答案：ABD

幀中繼環(huán)境中，CIR的含義是()

A.提高線路速率

B.保證線路速率

C.降低線路速率

D酒己置線路速率

正確答案：B

2021思科認(rèn)證歷年真題和解答8篇第2篇

WhatistheIEEEstandardassociatedwithGigabitEthernet?(Selecttwo

answerchoices)

A.802.11

B.802.5

C.8023ab

D.8023ae

E.802.3z

F.802.3u

正確答案：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命令是用于顯示以下哪一項(xiàng)的()

A.CDP的時(shí)間值和接口狀態(tài)

B.鄰居路由器的接口配置

C.鄰居設(shè)備的IP地址

D.CDP保持時(shí)間

正確答案：A

要顯示路由器支持的技術(shù)包許可證和功能許可證以及多個(gè)狀態(tài)變量,可使用哪個(gè)命

令?()

A.showlicense

B.showlicensefeature

C.showlicenseudi

D.showversion

答案：B

將路由器的許可證刪除包括哪兩步?()

A.使用命令eraseflash:license

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

禁止RIP協(xié)議的路由聚合功能的命令是()

A.norip

B.no-summany

C.noauto-summany

D.nonetwork

正確答案：C

2021思科認(rèn)證歷年真題和解答8篇第3篇

Whichtwooftheaddressesbelowareavailableforhostaddressesonthe

Ezonexamsubnet9/28?(Selecttwoanswerchoices)

A.7

B.4

C.9

D.6

E.1

F.Noneoftheabove

正確答案：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.

距離-向量路由算法最優(yōu)路徑計(jì)算的復(fù)雜度要比鏈路-狀態(tài)路由算法最優(yōu)路徑計(jì)

算的復(fù)雜度大。

此題為判斷題（對(duì)，錯(cuò)）。

正確答案：X

FTP工作在OSI哪一層（）

A會(huì)話層

B.表示層

C.傳輸層

D.應(yīng)用層

正確答案：D

為了便于網(wǎng)絡(luò)的管理，人為地將互聯(lián)網(wǎng)劃分成若干自治系統(tǒng)，每一個(gè)自治系統(tǒng)

由運(yùn)行同一路由協(xié)議的路由器組成。

此題為判斷題（對(duì)，錯(cuò)）。

正確答案：V

在配置幀中繼子接口時(shí)，在物理接口上應(yīng)該配置的內(nèi)容是：（）

A.配置IP地址

B.封裝幀中繼協(xié)議

C.指定子接口類型

D.設(shè)定子接口

E.配置密碼

正確答案：BCD

2021思科認(rèn)證歷年真題和解答8篇第4篇

EzonexamhasimplementedtheuseoftheVirtualTrunkingProtocol(VTP).

Whichstatementbelowaccuratelydescribesabenefitofdoingthis?

A.VTPwillallowphysicallyredundantlinkswhilepreventingswitching

loops

B.VTPwillallowswitchestoshareVLANconfigurationinformation

C.VTPwillallowasingleporttocarryinformationtomorethanoneVLAN

D.VTPwillallowforroutingbetweenVLANs

E.Noneoftheabove

正確答案：B

以下封裝協(xié)議使用CHAP或者PAP驗(yàn)證方式的是()。

A.PPP

B.HDLC

C.SDLC

D.SLIP

正確答案：A

下列哪個(gè)network命令會(huì)告知此路由器開(kāi)始使用IP地址為.

和的接口上的OSPF()

A.networkarea0

B.network55area0

C.network55area0

0.network55area0

正確答案：B

VLAN主干協(xié)議VTP的默認(rèn)工作模式是()

A.服務(wù)器模式

B.客戶端模式

C.透明模式

D.以上三者都不是

正確答案：A

下列哪一^^通配符掩碼與子網(wǎng)/27的所有主機(jī)匹配（）。

A.

B.

C.1

D.55

正確答案：C

2021思科認(rèn)證歷年真題和解答8篇第5篇

osi七層模型中，物理層的數(shù)據(jù)封裝名稱為（）

A.比特

B幀

C包

D段

正確答案：A

命令confreg0x2142有何作用?()

A用于重啟路由器

B.用于忽略NVRAM中的配置

C.用于進(jìn)入ROM監(jiān)視器模式

D.用戶查看遺忘的密碼

答案：B

以下ACL將對(duì)路由器的流量產(chǎn)生何種影響()

Access-list1deny192.168.19.1620.0.0.0

AccessTist1permitany

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(duì)流量沒(méi)有影響

D.permitany選項(xiàng)使deny選項(xiàng)失效

正確答案：B

為了查看路由器的E0端口上，是否掛接了訪問(wèn)權(quán)限表，應(yīng)該使用的命令是

()

A.showaccess-list

B.showinterfaceeO

C.showipinterfaceeO

D.showeO

正確答案：B

HowcouldtheEzonexamcorporationbenefitfromusingVLANsontheir

network?

(Selectthreeanswerchoices.)

A.VLANsallowaccesstonetworkservicesbasedondepartment,not

physicallocation.

B.VLANsutilizepacketfilteringtoenhancenetworksecurity.

C.VLANsprovidealow-latency,highbandwidthinternetworkingalternative.

D.VLANsprovideamethodofcommunicationbetweenIPaddressesinlarge

networks.

E.VLANsestablishsegmentedbroadcastdomainsinswitchednetworks.

F.VLANscangreatlysimplifyadding,moving,orchanginghostsonthe

network.

正確答案：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思科認(rèn)證歷年真題和解答8篇第6篇

當(dāng)配置一個(gè)CISCO的路由器時(shí)，缺省的DR和BDR優(yōu)先級(jí)是（）。

A.0

B.1

C.16

D.255

正確答案：B

以下哪一項(xiàng)不是有關(guān)虛電路交換方式的正確描述。()

A.分組需要包含虛電路標(biāo)識(shí)符

B.某條虛電路對(duì)應(yīng)的轉(zhuǎn)發(fā)項(xiàng)只給出該虛電路經(jīng)過(guò)的兩個(gè)端口之間的關(guān)聯(lián)

C.虛電路標(biāo)識(shí)符用于建立終端間傳輸路徑與終端間傳輸?shù)臄?shù)據(jù)之間的綁定

D.虛電路是指終端間傳輸路徑

參考答案：A

已知某臺(tái)路由器的路由表中有如下兩個(gè)表項(xiàng)假如該路由器要轉(zhuǎn)發(fā)目的地址為

的報(bào)文，則下列說(shuō)法中正確的是()

A.選擇第一項(xiàng)，因?yàn)镺SPF協(xié)議的優(yōu)先級(jí)高

B.選擇第二項(xiàng)，因?yàn)镽IP協(xié)議的花費(fèi)值(Metric)小

C.選擇第二項(xiàng)，因?yàn)槌隹谑荅thternetO,比Serial。速度快

D.選擇第二項(xiàng),因?yàn)樵撀酚身?xiàng)對(duì)于目的地址9.145來(lái)說(shuō)，是更精確的匹配

正確答案：D

Whencomparingandcontrastingthesimilaritiesanddifferencesbetween

bridgesandswitches,whichofthefollowingarevalidstatements?Chooseallthe

validanswerchoices)

A.Bridgesarefasterthanswitchesbecausetheyhavefewerports.

B.Aswitchisamultiportbridge,

C.BridgesandswitcheslearnMACaddressesbyexaminingthesourceMAC

addressofeachframe,received.

D.Abridgewillforwardabroadcastbutaswitchwillnot.

E.Bridgesandswitchesincreasethesizeofacollisiondomain.

F.Noneoftheabovestatementsaretrue.

正確答案：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.

正確答案：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思科認(rèn)證歷年真題和解答8篇第7篇

假設(shè)有這樣的組網(wǎng)實(shí)例:兩個(gè)路由器（假設(shè)為RTA和RTB）通過(guò)串口相連接，其

中RTA的串口IP地址是/30,RTB的串口IP地址/30,RTA

通過(guò)以太口連接的本地局域網(wǎng)的IP地址是/16,RTB通過(guò)以太口連接的

本地局域網(wǎng)IP地址是/16,在上面所有的接口上都啟動(dòng)RIPV1（僅僅

RIPVD協(xié)議，那么，下列說(shuō)法正確的是（）

A.在RTA的本地局域網(wǎng)上的計(jì)算機(jī)可以訪問(wèn)在RTB本地局域網(wǎng)上的計(jì)算機(jī)

B.在RTB的本地局域網(wǎng)上的計(jì)算機(jī)可以訪問(wèn)在RTA本地局域網(wǎng)上的計(jì)算機(jī)

C.在RTA的本地局域網(wǎng)上的計(jì)算機(jī)不能訪問(wèn)在RTB本地局域網(wǎng)上的計(jì)算機(jī)

D.在RTB的本地局域網(wǎng)上的計(jì)算機(jī)不能訪問(wèn)在RTA本地局域網(wǎng)上的計(jì)算機(jī)

正確答案：CD

路由器上"水平分割”的功能是：（）

A.分離端口

B,阻止路由環(huán)路

C.簡(jiǎn)化配置

D.方便故障處理

正確答案：B

以下特殊區(qū)域中哪一個(gè)沒(méi)有自動(dòng)下發(fā)缺省路由（）

A.末梢區(qū)域

B.完全末梢區(qū)域

C.NSSA區(qū)域

D.完全NSSA區(qū)域

正確答案：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

正確答案：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

正確答案：ACD

A,C,D

2021思科認(rèn)證歷年真題和解答8篇第8篇

一臺(tái)運(yùn)行OSPF的路由器，它的兩個(gè)正常工作的接口一個(gè)屬于區(qū)域0,另一個(gè)

屬于區(qū)域9,并且重分布5條靜態(tài)路由進(jìn)入OSPF,則該路由器一定會(huì)始發(fā)哪些

LSA()

A.RouterLSA(Type=l)；

B.NetworkLSA(Type=2)；

C.NetworkSummaryLSA(Type=3);

D.ASBRSummaryLSA(Type=4);

E.ASExternalLSA(Type=5)；

正確答案：ACDE

Ezonexamusershavenoticedextremelyslownetworkperformance,

intermittentconnectivity,andconnectionlosses.Afterenteringthe"show

interfaces"command,younoticethattheEthernetinterfaceisconfiguredas100

Mbpsfull-duplexandthatthereisevidenceoflatecollisions.Whatcouldbethe

causeofthisproblem?

A.Duplexm