CCNA640-802V13+题库详解(50-100)

51.WhatcananetworkadministratorutilizebyusingPPPLayer2encapsulation?(Choosethree.)A.VLANsupportB.compressionC.authenticationD.slidingwindowsE.multilinksupportF.qualityofserviceAnswer:BCE解释一下：PPP协议是能支持认证的，包括PAP和CHAP；PPP还支持压缩功能和差错校验，还可实现多链路捆绑。而他们的这些功能都是HDLC所没有的。52.Refertotheexhibit.Whatisthemeaningofthetermdynamicasdisplayedintheoutputoftheshowframe-relaymapcommandshown?A.TheSerial0/0interfaceispassingtraffic.B.TheDLCI100wasdynamicallyallocatedbytherouter.C.TheSerial0/0interfaceacquiredtheIPaddressof172.16.3.1fromaDHCPserver.D.TheDLCI100willbedynamicallychangedasrequiredtoadapttochangesintheFrameRelaycloud.E.ThemappingbetweenDLCI100andtheendstationIPaddress172.16.3.1waslearnedthroughInverseARP.Answer:E解释一下：这是个关于MAP的知识。在图中可以看到这个MAP是dynamic的，因此是通过inverseARP学习到的。而ip172.16.3.1dlci100表示的是DLCI100映射的地址为172.16.3.1。就像是以太网中的MAC和IP的映射一样，通过DLCI100可以找到IP172.16.3.1。53.WhatisthefunctionoftheCiscoIOScommandipnatinsidesourcestatic10.1.1.5172.35.16.5?A.ItcreatesaglobaladdresspoolforalloutsideNATtransactions.B.Itestablishesadynamicaddresspoolforaninsidestaticaddress.C.ItcreatesdynamicsourcetranslationsforallinsidelocalPATtransactions.D.Itcreatesaone-to-onemappingbetweenaninsidelocaladdressandaninsideglobaladdress.E.Itmapsoneinsidesourceaddresstoarangeofoutsideglobaladdresses.Answer:D解释一下：ipnatinsidesourcestatic10.1.1.5172.35.16.5这条命令是静态创建一个一对一的地址转换。他把内部本地地址10.1.1.5转换为全局地址172.35.16.5。54.Refertotheexhibit.Whatistheeffectoftheconfigurationthatisshown?A.ItconfiguresSSHgloballyforalllogins.B.IttellstherouterorswitchtotrytoestablishanSShconnectionfirstandifthatfailstouseTelnet.C.Itconfiguresthevirtualterminallineswiththepassword030752180500.D.ItconfiguresaCisconetworkdevicetousetheSSHprotocolonincomingcommunicationsviathevirtualterminalports.E.ItallowssevenfailedloginattemptsbeforetheVTYlinesaretemporarilyshutdown.Answer:D解释一下：使用telnet进行远程设备维护的时候，由于密码和通讯都是明文的，易受sniffer侦听，所以应采用SSH替代telnet。SSH(SecureShell)服务使用tcp22端口，客户端软件发起连接请求后从服务器接受公钥，协商加密方法，成功后所有的通讯都是加密的。Cisco设备目前只支持SSHv1，不支持v2。Cisco实现SSH的目的在于提供较安全的设备管理连接，不适用于主机到主机的通讯加密。Cisco推荐使用IPSEC作为端对端的通讯加密解决方案55.Refertotheexhibit.WhenPC1sendsanARPrequestfortheMACaddressofPC2,networkperformanceslowsdramatically,andtheswitchesdetectanunusuallyhighnumberofbroadcastframes.Whatisthemostlikelycauseofthis?A.Theportfastfeatureisnotenabledonallswitchports.B.ThePCsareintwodifferentVLANs.C.SpanningTreeProtocolisnotrunningontheswitches.D.PC2isdownandisnotabletorespondtotherequest.E.TheVTPversionsrunningonthetwoswitchesdonotmatch.Answer:C解释一下：PC1发出一个ARPrequest的数据报，并且是以广播的形式发送出去的。当ARP报文传到switch2，交换机对广播的流量是以泛洪的形式处理的，报文就从除了连接PC1的接口外的所有接口都发出去了。Switch1收到广播后也泛洪，因此一个广播环路就产生了，所以在感觉网络性能很差，因为广播的流量占有了很大的带宽。而我们阻断二层环路是通过生成树来实现的，在图中有环路存在因此就说明没有运行生成树了。56.Anadministratorissuesthecommandping127.0.0.1fromthecommandlinepromptonaPC.Ifareplyisreceived,whatdoesthisconfirm?A.ThePChasconnectivitywithalocalhost.B.ThePChasconnectivitywithaLayer3device.C.ThePChasadefaultgatewaycorrectlyconfigured.D.ThePChasconnectivityuptoLayer5oftheOSImodel.E.ThePChastheTCP/IPprotocolstackcorrectlyinstalled.Answer:E解释一下：地址127.0.0.0是一个私有的保留地址段，他是一个回环的地址，一般用于测试，测试TCP/IP协议栈是否起来了。在一台PC上能ping通127.0.0.1说明这个PC的TCP/IP协议栈是正确安装的。57.Host1hasjuststartedupandrequestsawebpagefromwebserver2.WhichtwostatementsdescribestepsintheprocessHost1usestosendtherequesttowebserver2(choosetwo)?A.Host1addressestheframestotheMACaddressofrouterR1B.Host1looksinitsARPcachefortheMACaddressofrouterR1C.Host1addressestheframestotheMACaddressofwebserver2D.Host1sendsthepacketstorouterR1tobeforwardedtowebserver2E.Host1sendsabroadcastARPrequesttoobtaintheMACaddressofwebserver2.Answer:CE解释一下：Host1的Ip为192.168.1.106/24webserver2的ip地址为192.168.1.10/24host1和webserver2在同一子网中（网络号都为192.168.1.0）host1直接将数据发送到网络中即可，不需要路由器转发。所以host1的打包封桢的时候目的mac应该是webserver2的mac地址，而不是路由器的mac地址。host1需要使用arp协议解析webserver2的mac地址。58.Refertotheexhibit.Whichtwostatementsabouttheconfigurationoftheswitchinterfacearecorrect?(Choosetwo)A.TheswitchportbelongsonlytoVLAN2B.Interfacefa0/0willbeinbothVLAN1(bydefault)andVLAN2C.Theexhibitshowsinterfacefa0/0tobedynamicallymappedtoVLAN2D.Anetworkhostcanbeconnectedtothisinterface.Answer:AD解释一下：这样配置后，这个接口肯定是属于vlan2了，并且只能属于vlan2。一般情况下划分VLAN的接口是连接主机的，可以把划分VLAN的接口叫做主机接口。59.Refertotheexhibit.Thenetworkadministratorrequireseasyconfigurationoptionsandminimalroutingprotocoltraffic.Whattwooptionsprovideadequateroutingtableinformationfortrafficthatpassesbetweenthetworoutersandsatisfytherequestsofthenetworkadministrator?(Choosetwo.)A.adynamicroutingprotocolonInternetRoutertoadvertiseallroutestoCentralRouter.B.adynamicroutingprotocolonInternetRoutertoadvertisesummarizedroutestoCentralRouter.C.astaticrouteonInternetRoutertodirecttrafficthatisdestinedfor172.16.0.0/16toCentralRouter.D.adynamicroutingprotocolonCentralRoutertoadvertiseallroutestoInternetRouter.E.adynamicroutingprotocolonCentralRoutertoadvertisesummarizedroutestoInternetRouter.F.astatic,defaultrouteonCentralRouterthatdirectstraffictoInternetRouter.Answer:CF解释一下：因为在这个图中,internetRouter要访问内网172.16.0.0/16只能通过路由器CentralRouter.所以只需要在InternetRou