2021年度思科认证考试题库

CCNA640-802V13题库试题分析题库解说:吴教师(艾迪飞CCIE实验室首发网站:Whataretworeasonsthatanetworkadministratorwoulduseaccesslists?(Choosetwo.)tocontrolvtyaccessintoaroutertocontrolbroadcasttrafficthrougharoutertofiltertrafficasitpassesthrougharoutertofiltertrafficthatoriginatesfromtheroutertoreplacepasswordsasalineofdefenseagainstsecurityincursionsAnswer：AC解释一下:在VTY线路下应用ACL,可以控制从VTY线路进来telnet流量。也可以过滤穿越一台路由器流量。AdefaultFrameRelayWANisclassifiedaswhattypeofphysicalnetwork?point-to-pointbroadcastmulti-accessnonbroadcastmulti-accessnonbroadcastmultipointbroadcastpoint-to-multipointAnswer：C解释一下:在默认状况ド,帧中继为非广播多路访问链路。但是也可以通过子接口来修改她网络类型。Refertotheexhibit.Howmanybroadcastdomainsexistintheexhibitedtopology?A.oneB.twothreefourfivesixAnswer：C解释一下:广播域问题,在默认状况下,每个互换机是不能隔离广播域,因此在同一种区域所有互换机都在同一种广播域中,但是为了减少广播危害,将广播限制在ー种更小范畴,有/VLAN概念，VLAN表达是ー种虚拟局域网，而她作用就是隔离广播。因此被VLAN隔离了每个区域都表达ー种单独广播域，这样ー种VLAN中广播流量是不能传到其她区域，因此在上题中就有3个广播域J’。Asingle802.11gaccesspointhasbeenconfiguredandinstalledinthecenterofasquareoffice.Afewwirelessusersareexperiencingslowperformanceanddropswhilemostusersareoperatingatpeakefficiency.Whatarethreelikelycausesofthisproblem?(Choosethree.)mismatchedTKIPencryptionnullSSIDcordlessphonesmismatchedSSIDmetalfilecabinetsantennatypeordirectionAnswer：CEFThecommandframe-relaymapip102broadcastwasenteredontherouter.Whichofthefollowingstatementsistrueconcerningthiscommand?Thiscommandshouldbeexecutedfromtheglobalconfigurationmode.TheIPaddressisthelocalrouterportusedtoforwarddata.102istheremoteDLCIthatwillreceivetheinformation.ThiscommandisrequiredforallFrameRelayconfigurations.Thebroadcastoptionallowspackets,suchasRIPupdates,tobeforwardedacrossthePVC.Answer：E解释一下：关于命令frame-relaymapip102broadcast,这个命令用于手工静态添加一条映射,到达流量封装ー种DLCI号为102,并且这条PVC是支持广播流量,例如RIP更新包。由于在默认状况下,帧中继网络为非广播,而R1P在其上是无法发包。8.WhichofthefollowingareassociatedwiththeapplicationlayeroftheOSImodel?(Choosetwo.)pingTelnetC.FTPD.TCPE.IPAnswer：BC解释一下:在OSI7层模型中位于应用层应用有lelnel和ftp这两种应用。Forsecurityreasons,thenetworkadministratorneedstopreventpingsintothecorporatenetworksfromhostsoutsidetheinternetwork.Whichprotocolshouldbeblockedwithaccesscontrollists?IPICMPC.TCPD.UDPAnswer：B解释一下:PING命令运用ICMP合同echo,和echo・replay两个报文来检测链路与否连通。因此如果要制止PING流量到网络,就只要过滤掉ICMP应用就可以了。10.Refertotheexhibit.ThenetworkadministratorhascreatedanewVLANonSwitch1andaddedhostCandhostD.TheadministratorhasproperlyconfiguredswitchinterfacesFastEthemetO/13throughFastEthemetO/24tobemembersofthenewVLAN.However,afterthenetworkadministratorcompletedtheconfiguration,hostAcouldcommunicatewithhostB,buthostAcouldnotcommunicatewithhostCorhostD.Whichcommandsarerequiredtoresolvethisproblem?RouterItshoworoitfe5/245;24 51246124Router(config)#interfacefastethernet0/1.3Router(config-if)#encapsulationdotlq3Router(config-if)#ipaddressRouter(config)#routerripRouter(config-router)#networkRouter(config-router)#networkRouter(config-router)#networkSwitch1#vlandatabaseSwitchl(vlan)#vtpv2-modeSwitch1(vlan)#vtpdomainciscoSwitchl(vlan)#vtpserverSwitch1(config)#interfacefastethernet0/1Switch1(config-if)#switchportmodetrunkSwitch1(config-if)#switchporttrunkencapsulationislAnswer：A解释一下:这是・种多VLAN间通讯问题,虽然都同在一台互换机上,但是由于处在不同VLAN中,而导致了不同VLAN中主机是不能通讯。这时咱们就需要借助与trunk和三层路由功能了，在互换机和路由器之间封装TRUNK,这样可以容许互换机间二层通讯,但是由于两个VLAN是划分到不同网段中，因而需要借助路由器路由功能来实现三层可达，可以将VLAN中主机网关指定为路由器与该VLAN相连子接口地址,这样VLAN中数据包就都会发往网关,而由网关来进行进一步转发。在这个题中,题目给出了路由器子接口网段，而又给出了VLAN2与路由器相连接口IP地址,因此剩余ー种网段就是给VLAN3了,因此要在路由器上将与一种子接口划分到VLAN3,并给其分派另ー种网段中IP地址。这样就可以了。Whataretworecommendedwaysofprotectingnetworkdeviceconfigurationfilesfromoutsidenetworksecuritythreats?(Choosetwo.)AllowunrestrictedaccesstotheconsoleorVTYports.Useafirewalltorestrictaccessfromtheoutsidetothenetworkdevices.AlwaysuseTelnettoaccessthedevicecommandlinebecauseitsdataisautomaticallyencrypted.UseSSHoranotherencryptedandauthenticatedtransporttoaccessdeviceconfigurations.Preventthelossofpasswordsbydisablingpasswordencryption.Answer：BD解释一下:要保证外部安全站点オ可以访问我网络,这就涉及到了安全问题了,咱们可以使用防火墙来限制外网中来设备;也可以通过SSH或加密和认证来控制。Refertotheexhibit.TheaccesslisthasbeenconfiguredontheS0/0interfaceofrouterRTBintheoutbounddirection.Whichtwopackets,ifroutedtotheinterface,willbedenied?(Choosetwo.)access-list101denytcp25anyeqtelnetaccess-list101permitipanyanyTelnelServersourceipaddress：；destinationport：21sourceipaddress:»7destinationport：21sourceipaddress:,1destinationport：21sourceipaddress:,6destinationport：23sourceipaddress：6；destinationport：23sourceipaddress:,9destinationport：23Answer：DE解释一下:这个访问列表定义『两个语句:access-list101denytcp25anyeqtelnetaccess-list101permitipanyany在访问列表中匹配顺序是从上到下,如果匹配了某一句,就退出访问列表,如果没有就始终往下匹配，在访问列表中有一句隐含回绝所有。因此不论怎么样均有一句是能被匹配。在上题中，她定义第一句是回绝到从2-7发出任何telnet流量，然后第二句定义就是容许所有IP流量。并且要明确telnet流量使用是端口23,因此这个题答案就很明确了。Refertotheexhibit.Switch!hasjustbeenrestartedandhaspassedthePOSTroutine.HostAsendsitsinitialframetoHostC.Whatisthefirstthingtheswitchwilldoasregardspopulatingtheswitchingtable?HostBMAC-000A.8A47.E612 ム MAC-000B.DB95.2EE9IP- 導 IP-2HostDSwitch1willaddtotheswitchingtable.Switch1willadd2totheswitchingtable.Switch1willadd000A.8A47.E612totheswitchingtable.Switch1willadd000B.DB95.2EE9totheswitchingtable.Answer：C解释一下:互换机重新启动了，这个时候互换机MAC地址表是空,当主机A发送数据给主机C而通过互换机时,互换机依照她工作原理她要进行原MAC地址学习，而由于对于这个目MAC地址无记录，而将这个流量从除收到这个接口外所有接口泛洪出去。因此在最开始ー步中，互换机是记录下主机AMAC地址000A.8A47.E612到她MAC地址表中。heuserofHostlwantstopingtheDSLmodem/routerat54.BasedontheHostlARPtablethatisshownintheexhibit,whatwillHostldo?sendaunicastARPpackettotheDSLmodem/routersendunicastICMPpacketstotheDSLmodem/routersendLayer3broadcastpacketstowhichtheDSLmodem/routerrespondssendaLayer2broadcastthatisreceivedbyHost2,theswitch,andtheDSLmodem/routerAnswer：B解释ー下:在下面表中咱们可以看到ARP表中关于于54ARP条目,因此在这主机都只需要发送单播ICMP包到DSLmodem/router即可〇Refertotheexhibit.WhatisthemostefficientsummarizationthatR1canusetoadvertiseitsnetworkstoR2?/24/2428/25/24/24/2428/25/24/22/21/22/24/24/24/24/2528/25/24/24/24Answer：C解释一下:这还是ー种关于汇总问题。规定R1将所有网段用汇总条目发送给R2,由于这些条目网络位是相似都为172.1,因此在这需要汇总只是第3个八位,将4,4,5,6,7这些写成二进制形式,然后找出相似位数,则有相似位数字节就是她们掩码位数,而最小有相似位最小数字就是她们基数位,因此R1告示出去汇总条目为172.240/22。Refertotheexhibit.Assumethatallrouterinterfacesareoperationalandcorrectlyconfigured.Inaddition,assumethatOSPFhasbeencorrectlyconfiguredonrouterR2.HowwillthedefaultrouteconfiguredonRIaffecttheoperationofR2?A.AnypacketdestinedfbranetworkthatisnotdirectlyconnectedtorouterRIwillbedropped.AnypacketdestinedforanetworkthatisnotdirectlyconnectedtorouterR2willbedroppedimmediately.AnypacketdestinedforanetworkthatisnotdirectlyconnectedtorouterR2willbedroppedimmediatelybecauseofthelackofagatewayonRI.ThenetworksdirectlyconnectedtorouterR2willnotbeabletocommunicatewiththe,28,and4subnetworks.AnypacketdestinedforanetworkthatisnotreferencedintheroutingtableofrouterR2willbedirectedtoR1.R1willthensendthatpacketbacktoR2andaroutingloopwilloccur.Answer：E解释一下:在RI上产生了一种OSPF缺省路由,出接口指定为S0/0,这条缺省路由以5类LSA形式告示给J'R2,于是R2上也有了一条标记为〇・E/0出接口为SerialO/O路由。因此

R2收到任何路由表中没有目网段时,就将指定给R1,而RI依照缺省路山出接口又将数据包发往R2,这样就形成了一种路由环路。Anetworkinterfaceporthascollisiondetectionandcarriersensingenabledonasharedtwistedpairnetwork.Fromthisstatement,whatisknownaboutthenetworkinterfaceport?Thisisa10Mb/sswitchport.Thisisa100Mb/sswitchport.C.rPhisisanEthernetportoperatingathalfduplex.ThisisanEthernetportoperatingatfullduplex.ThisisaportonanetworkinterfacecardinaPC.Answer：C解释一下:一种接口有冲突检测和载波侦听,并且是使用双绞线网络,那么对于这个接口咱们可以推测出她是以太接口,并且是工作在半双工模式下。Refertothetopologyandrouterconfigurationshowninthegraphic.AhostontheLANisaccessinganFTPserveracrosstheInternet.Whichofthefollowingaddressescouldappearasasourceaddressforthepacketsforwardedbytheroutertothedestinationserver?TOC\o"1-5"\h\zinterfaceStriall «1ipaddress20022.18256266256262 2~—Ipnatoutsidet <ヽInterfaceFastEthemetO SI：8/30ipaddress255^55255.0 fjQ10I〇〇］ハ4開煙 Testinsideゆnatpooltest199999.40199593.62netmMk256255255224ゆnatInsidesourcelist1pooltestiprout«。。。〇00X)020022.17(acc•”粕11permit10.10000.0.0255A.B.C.3D.7E.7F.8Answer：D解释一下:这是个NAT地址转换题目,在这fi)/0接口连接下为私有地址,这些地址是不能同外网进行通讯,这时就借助NAT,将内网私有地址转换为可以在公网上通讯地址,咱们看到NATPOOL中定义转换后公有地址为0到2,则表达这段地址是我转换后内网全局地址，因此HOST想要穿过INTERNET访问FTP服务器,则需要转换为公有地址0到2之内地址，在上面答案中只有地址7满足条件，因此答案就是D了。AcompanyisinstallingIPphones.Thephonesandofficecomputersconnecttothesamedevice.Toensuremaximumthroughputforthephonedata,thecompanyneedstomakesurethatthephonetrafficisonadifferentnetworkfromthatoftheofficecomputerdatatraffic.Whatisthebestnetworkdevicetowhichtodirectlyconnectthephonesandcomputers,andwhattechnologyshouldbeimplementedonthisdevice?(Choosetwo.)hubrouterswitchSTPsubinterfacesF.VLANAnswer：CF解释一下:公司语音设备和办公设备都连在相似设备上,还要保证语音数据流在不同与公司办公数据流量,最佳网络设备固然是互换机了,然后运用VLAN技术就完全可以满足所有规定了。22.Refertotheexhibit.WhichstatementdescribesDLCI17?A.DLCI17describestheISDNcircuitbetweenR2andR3.DLCI17describesaPVConR2.ItcannotbeusedonR3orR1.DLCI17istheLayer2addressusedbyR2todescribeaPVCtoR3.DLCI17describesthedial-upcircuitfromR2andR3totheserviceprovider.Answer：C解释•下：DLCI是在Frame-relay中描述二层信息地址,她地位等同于以太网中MAC地址。咱们以R2上DLCI17来看,DLCI17描述是:从这个接口出去目地为R3接口这条PVC二层地址为17。Whichroutingprotocolbydefaultusesbandwidthanddelayasmetrics?A.RIPB.BGPC.OSPFD.EIGRPAnswer：D解释一下:在咱们路由合同中使用复合度量合同只有IGP和EIGPR,而她们在默认状况下是使用带宽和延时来计算度量。IntheimplementationofVLSMtechniquesonanetworkusingasingleClassCIPaddress,whichsubnetmaskisthemostefficientforpoint-to-pointseriallinks?A.B.40C.48D.52E.54Answer：D解释ー下:在点到点链路上由于只需要分派两个地址给两端就可以J’,因此加上网络地址和广播地址,这个网段也就只需要有4个地址了,因此网络位需要匹配30位,掩码就为52.Refertotheexhibit.ThenetworksconnectedtorouterR2havebeensummarizedasa/21routeandsenttoRI.WhichtwopacketdestinationaddresseswillRIforwardtoR2?(Choosetwo.)OtherOtherNetworksA.60B.1C.D.55E.F.5Answer：BE解释一下:这个题其实就是考察汇总问题,她说意思是R2发送了一种汇总路由/21给R1,哪两个包文目地R1仍将转发给R2。这还是汇总问题ー种反向考察,依照21位掩码位数可以推断在第3个八位字节前5位是相似,不同是背面3位，而将176写成二进制形式为10110000,因此可以看出来明细路由可以是176-183,因此在上面答案中可以很容易看到答案B和E是咱们明细路由。Refertotheexhibit.Switch-1needstosenddatatoahostwithaMACaddressof00b0,d056.efa4.WhatwillSwitch-1dowiththisdata?Switch-1#showmacaddress-tableTOC\o"1-5"\h\zDynamicAddressesCount 3SecureAddresses(User-defined)Count 0StaticAddresses(User-defined)Count 0SystemSelfAddressesCount 41TotalMad/却鱒芈s 156ユNon-staticAtidrSss wCDestinationAddressAddressTypeVLANDestinationPort0010OdeOe289 Dynamic 1 FastEttiemetO/100107b001540 Dynamic 2 FastEthernetO/300107boe1,1545 Dynamic 2 FastEthemetO/2Switch-1willdropthedatabecauseitdoesnothaveanentryforthatMACaddress.Switch-1willfloodthedataoutallofitsportsexcepttheportfromwhichthedataoriginated.Switch-1willsendanARPrequestoutallitsportsexcepttheportfromwhichthedataoriginated.Switch-1willforwardthedatatoitsdefaultgateway.Answer：B解释一下:一方面Switch1需要发送・种数据到MAC地址为00b0.d056.efa4主机,理解到目地后,就查看她MAC地址表,然后发当前MAC地址表中没有这个MAC地址条目存在。互换机在收到未知单播,组播和广播时,都采用是泛洪方式,往除收到数据这个接口外所有接口都发送。因此在这儿,Switch1也采用上泛洪方式。woroutersnamedAtlantaandBrevardareconnectedbytheirserialinterfacesasshownintheexhibit,butthereisnodataconnectivitybetweenthem.TheAtlantarouterisknowntohaveacorrectconfiguration.Giventhepartialconfigurationsshownintheexhibit,whatistheproblemontheBrevardrouterthatiscausingthelackofconnectivity?

AtlantaBrevardAtlanla^showintertacesMSerialOisupfAtlantaBrevardAtlanla^showintertacesMSerialOisupflineprotocolisupHaidwdreisHD6457Qレ’0・・Internetaddressis/24MTU1500bytes.BW1544Kbitreliablity255.255EncapsulationHDLC,loopbacknotsetKeepaliveset(10sec)Brevardflshowinterfacess1S»riatlisup.ineprotocolisupHm小・ioRHM4570InternetaddressH/24MTU1500bytes,BW56000Kbit.reliability255/255Enc4ip«iilationHDLC,loopbacknotsetKeepaliveset(10sec)Aloopbackisnotset.TheIPaddressisincorrect.Thesubnetmaskisincorrect.Theseriallineencapsulationsareincompatible.E.rrhemaximumtransmissionunit(MTU)sizeistoolarge.F.Thebandwidthsettingisincompatiblewiththeconnectedinterface.Answer：B解释一下:很明显错误啊,两台路由器串行接口地址配备错误,不是在相似网段,从而导致了不能通讯。WhichtwovaluesareusedbySpanningTreeProtocoltoelectarootbridge?(Choosetwo.)amountofRAMbridgepriorityIOSversionIPaddressMACaddressspeedofthelinksAnswer：BE解释一下:生成树选举问题,根桥选举是通过比较BID,而BID由桥优先级和MAC地址构成.因此在选根桥时候需要比较是桥优先级和MACaddressoRefertotheexhibit.Whichswitchprovidesthespanning-treedesignatedportroleforthenetworksegmentthatservicestheprinters?Switchl DistributionLay«r Switch?PiiiiteisPfiority4096：Switchl DistributionLay«r Switch?PiiiiteisPfiority4096：0010Jbcc.7320Piioiity32768MAC0010.7bcc.7347Piioiity8192MAC0010.7bcc.732dSwitch)aMPiioiity32768 ,MAC0010.7bcc.733aSwitch1Switch2Switch3Switch4Answer：C解释一下:这是个关于生成树选举问题,咱们ー方面需要找到根桥,而根桥选举是通过比较桥ID,并且是越小越优先,桥ID构成为桥优先级和MAC地址。因此咱们通过上图可以找到根桥为switch1〇然后在非根桥上选出根端口,通过比较到根桥耗费来选举,耗费最小就是根端口。由于上图中没有表达出链路带宽,因此无法比较她们耗费。下ー步咱们来选举指派端口。每条链路都需要有一种DP,先是比较耗费,如果耗费相似则比较BID（桥优先级）,仍是越小越优先,依照上图表识,咱们可以找到每条链路上DP,而连Printers链路上DP就为Switch3,由于她有更小MAC地址。32.Refertotheexhibit.WhywouldthenetworkadministratorconfigureRAinthismanner?F?A(corYflg)#accessdist2permit55RA(conflg)/linevty04RA(con1ig-line)tfaccess-class2intogivestudentsaccesstotheInternettopreventstudentsfromaccessingthecommandpromptofRAtopreventadministratorsfromaccessingtheconsoleofRAtogiveadministratorsaccesstotheInternettopreventstudentsfromaccessingtheInternettopreventstudentsfromaccessingtheAdminnetworkAnswer：B解释一下:在这儿,将ACL应用到VTY线路下,并且是IN方向,表达凡是被我ACL容许オ干lelnet到我.在RA上配备是permit55依照隐式denyany容许Admin网段中顾客可以記Inel到她,因此Swdcnl网段中顾客是被回绝.InordertoallowtheestablishmentofaTelnetsessionwitharouter,whichsetofcommandsmustbeconfigured?router(config)#lineconsole0router(config-line)#enablepasswordciscorouter(config)#lineconsole0router(config-line)#enablesecretciscorouter(config-line)#loginrouter(config)#lineconsole0router(config-line)#passwordciscorouter(config-line)#loginrouter(config)#linevty0router(config-line)#enablepasswordciscorouter(config)#linevty0router(config-line)#enablesecretciscorouter(config-line)#loginrouter(config)#linevty0router(config-line)#passwordciscorouter(config-line)#login解释一下:⑹nel是ー种应用层应用,她使用是vty线路,并且在默认状况下,是需要访问线路下设有密码。而在VTY线路下设立密码命令为passworks府〃g,而VTY线路下另ー种命令login则是默认,可写也可不写。如果想Telnet时在VTY线路下不设立密码也可以访问这个线路,可以在该VTY线路下输入命令nologin〇Refertotheexhibit.ThetwoexhibiteddevicesaretheonlyCiscodevicesonthenetwork.Theserialnetworkbetweenthetwodeviceshasamaskof52.Giventheoutputthatisshown,whatthreestatementsaretrueofthesedevices?(Choosethree.)HanchesS”sh'cdpeatry• 1-—… 貝支|nvndaDeviceID:LondバアZ^^^^Entryaddress(es):IPaddress:PlatforB：cisco2610,Capabilities:RouterIntelface:Serial10/0#PortID(outgoingport):SerlalO/1Holdtme:125sec<cucpucA.TheManchesterserialaddressis.B.TheManchesterserialaddressis.C.rrheLondonrouterisaCisco2610.TheManchesterrouterisaCisco2610.TheCDPinformationwasreceivedonportSerial0/0oftheManchesterrouter.TheCDPinformationwassentbyportSerial0/0oftheLondonrouter.解释一下:CDP是CISC0私有一种二层合同,但是她却可以发现三层IP信息,通过CDP可以发现邻居信息有:设备名称,IP地址,端口,能力,平台,对端holddowntime.在上图showcdpentry・命令显示可以看到信息有:设备名称:London；IP地址:；平台:cisco2610；能力:Router；端口:s0/1；holdtime：125S.Manchesteter收到这个CDP信息接口为S0/0.综合一下,这个题目答案就出来了.Anetworkadministratorhasconfiguredtwoswitches,namedLondonandMadrid,touseVTP.However,theswitchesarenotsharingVTPmessages.Giventhecommandoutputshowninthegraphic,whyaretheseswitchesnotsharingVTPmessages?1011*2sh«wvty>statusMadrids vt|istatusVTPVtnion:2VTPVmioti:2CtnigurationRation:0ConCguratxnRevKion:•MaximumVLAMs bcelly:64MaximamVLANssupportedlocallyNumberメ・xi的nqVLAN><y:5NunibtrofexMpgVLANt:SVTPOptfNoqMak：SwvtrVTPOHan.：LondonVTPDomaknflattw：MadridVTPPruningMode:DIsaModVTPPnifiln9Mode：OiBbledVTPV2Mole;DgbQdVTPV?;D&bl貝VTPTrap^G9neotionVTPTrap*G，ロ9：DisabledTheVTPversionisnotcorrectlyconfigured.TheVTPoperatingmodeisnotcorrectlyconfigured.TheVTPdomainnameisnotcorrectlyconfigured.VTPpruningmodeisdisabled.VTPV2modeisdisabled.VTPtrapsgenerationisdisabled.Answer：C解释一下:互换机间不能共享VTP信息,咱们就需要检查VTP状态,一方面需要检查是VTP域名,只有同一种域中オ也许互相学习,再来检查VTP模式,必要有一种server模式オ干有VTP学习过程,默认状况下VTP模式为Server。然后咱们检查图题目给出信息,可以看到两台互换机VTPdomain是不一致，因此这个就是问题所在Host1istryingtocommunicatewithHost2.TheeOinterfaceonRouterCisdown.Whichofthefollowingaretrue?(Choosetwo.)RouterCwilluseICMPtoinformHost1thatHost2cannotbereached.RouterCwilluseICMPtoinformRouterBthatHost2cannotbereached.RouterCwilluseICMPtoinformHost1,RouterA,andRouterBthatHost2cannotbereached.RouterCwillsendaDestinationUnreachablemessagetype.RouterCwillsendaRouterSelectionmessagetype.RouterCwillsendaSourceQuenchmessagetype.Answer：AD解释一下:连Host2接UEO/Odownj',那么最直接反映就发生在路由器C上，C路由表中这个条目就消失了,因而当Host1想要跟Host2建立连接时候,RouterC就发送ー种目网段不可达消息:如果是使用ping命令，那么RouterC就使用ICMP包文告诉Host1,Host2是不可打。Refertotheexhibit.Assumingthattherouterisconfiguredwiththedefaultsettings,whattypeofrouterinterfaceisthis?R!和howinieifacef«outpiiomitted»«outputomitted»is呼,LneprotocolisupHardwaic券Lxuice.adchtssis001Q^b80bfo6(bia0pl0.7bS0bfa6)MTU BWJOWQDKbit.t'LYWw沦 2T3,Hd1/255Enc&psulahoQARFA,loopbacksotset.keepdiveset(10tec)ARPtypeAFPA.XPPlimeout"OT0O.O(f«oulpntEthernetFastEthemetGigabitEthernetasynchronousserialsynchronousserialAnswer：B解释・下:这个题是需要依照图中提供信息来判断接口类型。可以看到接口MAC地址,表达这个接口必定不是串行接口,因此可以排除D和E选项。看带宽BW100000Kbit,表达是100M带宽,因此这是个FastEthernet接口。Onpoint-to-pointnetworks,OSPFhellopacketsareaddressedtowhichaddress?A.B.C.D.E.F.55Answer：E解释一下:在OSPF中Hello包发向是和这两个地址。人们在做OSPF实验时候,用debug命令是可以看到这两个个地址。Whiletroubleshootingaconnectivityproblem,anetworkadministratornoticesthataportstatusLEDonaCiscoCatalystseriesswitchisalternatinggreenandamber.Whichconditioncouldthisindicate?Theportisexperiencingerrors.Theportisadministrativelydisabled.Theportisblockedbyspanningtree.Theporthasanactivelinkwithnormaltrafficactivity.Answer：A解释一下:CISCO互换机端n状态批示灯是闪烁绿色和浅黄色,表达端口有操作问题——也许是过量错误或连接问题。Refertotheexhibit.ThenetworkshownintheexhibitisrunningtheRIPv2routingprotocol.Thenetworkhasconverged,andtheroutersinthisnetworkarefunctioningproperly.TheFastEthernetO/OinterfaceonRIgoesdown.Inwhichtwowayswilltheroutersinthisnetworkrespondtothischange?(Choosetwo.)A.Allrouterswillreferencetheirtopologydatabasetodetermineifanybackuproutestothenetworkareknown.RoutersR2andR3marktherouteasinaccessibleandwillnotacceptanyfurtherroutingupdatesfromR1untiltheirhold-downtimersexpire.Becauseofthesplit-horizonrule,routerR2willbepreventedfromsendingerroneousinformationtoR1aboutconnectivitytothenetwork.WhenrouterR2learnsfromRIthatthelinktothenetworkhasbeenlost,R2willrespondbysendingaroutebacktoRIwithaninfinitemetrictothenetwork.RIwillsendLSAstoR2andR3informingthemofthischange,andthenallrouterswillsendperiodicupdatesatanincreasedrateuntilthenetworkagainconverges.Answer：CD解释一下:这涉及到RIP关于环路避免几种机制了。在这里RI直连链路发生了变化,及时触发更新（触发更新）,发送flashupdate出去,将这个条目置为possibledown,设立最大跳数（路由毒性），R2收到这个flashupdate后,也回答一种flashupdate包（毒性逆转）,同步将这个条目也置为possibledown»设立最大跳数。WhichofthefollowingdescribetheprocessidentifierthatisusedtorunOSPFonarouter?（Choosetwo.）It