2021思科认证考试真题6节.pdf

2021思科认证考试真题6 节 第 1 节下列哪项OSI第 2 层功能是由PPP协议标准规范，但使用CISCO专有的HDLC报头字段实现A成帧B.寻址G错误检测D识别帧内的协议类型正确答案：DCHAP验证时，将对方的主机名HOST作为自己的用户名USER。此题为判断题（对，错）。正确答案：VYou have set up an Internet based FTP server,where people can upload anddownload files.In terms of the OSI model,what is the highest layer used duringthe FTP sessions.A.ApplicationB.PresentationC.SessionD.TransportE.InternetF.Data LinkG.Physical正确答案：AA 解 析：Explanation:The application layer is the highest layer(layer 7)of the OSI model,and isreserved for end user applications.Since FTP is itself an application,layer 7 is thehighest layer used.Incorrect Answers:B,C,D,E,F,G.In any given FTP session,all of these layers will be used at somepoint but they are incorrect because the question asked for the highest layerused by FTP.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下列哪两项用于在配置OSPF路由进程时确定路由器ID()A.第一个快速以太网接口的IP 地址B.任何逻辑接口的最大IP 地址C.任何物理接口的最大IP 地址D.默认网关的IP 地址E.优先级为1 的任何物理接口正确答案：BC2021思科认证考试真题6 节 第 2 节某网络中，拟设计10子 网,每个子网中放有14台设备，用 IP 地址段为199.41.10.X,请问符合此种规划的子网掩码是()A.255.255.255.0B.255.255.240.0C.255.255.255.240D.255.248.0.0正确答案：COSPF在同一区域内，下列说法正确的是（）A.每台路由器生成的LSA都是相同的B.每台路由器的LSDB（链路状态数据库）都是相同的C.每台路由器根据该LSDB计算出的最短路径树都是相同的D.每台路由器根据该最短路径树计算出的路由都是相同的正确答案：B以下哪个命令让路由器在show之后显示有效的参数列表A.sh?B.show?C.show?D.show help正确答案：CThe Ezonexam network Topology is displayed in the exhibit below:ingSwitchVlan2 Vlan3 Vlan4A switch has been configured for three different VLANs:VLAN 2,VLAN 3,and VLAN 4.For the purposes of communication between VLANs a router is to beadded.Host from one VLAN should be able to reach the hosts in the otherVLANs.Based on this requirement,what type of connection is acceptable betweenthe router and switch?(Select all valid answers)A.10 Mbps EthernetB.56 kbps serialC.100 Mbps EthernetD.1,544 Mbps serialE.1000 Mbps Ethernet正确答案：CE解 析:Explanation:Forallhoststobeabletoreacheachother,inter-VLANroutingwillneedtobeconfigured.Inordertoprovidelnter-VLANroutingbetweentherouterandtheswitch,atrunkwillneedtobesetup.ThistrunkcanbeeitherISLor802.1Q.Onarouter,theinterfacethatistobeusedasthetrunkcanbel00MbpsEthernet,GigabitEthernet,orlOGigabitEthernet.Therefore,onlychoicesCorEarecorrect.With regard to Ethernet media access methods,which of the following aretrue?(Choose all that apply.)A.A device waits for an electronic signal before transmitting.B.A device listens and waits until the media is not busy before transmitting.C.All devices on an Ethernet segment see data that passes on the networkmedium.D.Only the sender and the receiver devices see data that passes on thenetwork medium.E.Ethernet networks allow you to configured devises with highertransmission priority.正确答案：BC解 析:Explanation:Ethernet uses the CSMA/CD access method.CSMA/CD logic helps prevent collisions and also defines how to act when acollision does occur.The CSMA/CD algorithm words like this:1.A device with a frame,to send listens until the Ethernet is not busy.2.When the Ethernet is not busy,the sender begins sending the frame.3.The sender listens to make sure that no collision occurred.4.Once the senders hear the collision,they each send a jamming signal,toensure that all stations recognize the collision.5.After the jamming is complete,each sender randomizes a timer and waits thatlong.6 When each timer expires,the process starts over with Step 1.So,all devices on the Ethernet need to use CSMA/CD to avoid collisions and torecover when inadvertent collisions occur.2021思科认证考试真题6节 第3节0sl七层模型中，数据链路层的数据封装名称为（）A上 匕 特B.帧C.包D.段正确答案：BAfter working all night and successfully configuring a Cisco router for theEzonexam network you save your changes on the startup config,reboot therouter,and go out for a cigarette.When you return,none of your changes areactive and the router boots to the initial configuration mode!Which of thechoices below indicates the source of your problem?A.Hardware failure in NVRAM prevents the router from loading the configB.Startup-config in flash is corrupt and cannot be analyzedC.Router configuration-register set to bypass startup configurationD.Startup-config in NVRAM is corrupt and cannot be analyzedE.None of the above正确答案：C解 析：Explanation:The default configuration-register setting of 0 x2102 loads the IOS from flash andthe configuration from NVRAM.However,for password recovery,you can set the register to 0 x2142 and thestartup-config file in NVRAM will be bypassed.The problem described here isthat the config register was not changed back to 0 x2102 before the router wasrebooted,so the active configuration is bypassed.Simply setting the configregister back to 0 x2102 will fix this problem.Incorrect Answers:A,B,D.All of these describe hardware or software errors.In the event that this isthe problem,errors will be generated and the router will fail to boot properly.Inthese cases,the router will not return to the initial startup configuration.混合型协议既具有“距离矢量路由协议”的特性，又具有“链路状态路由协议”的特 性，下列协议中属于混合型协议的是：（）A.RIPB.OSPFC.EIGRPD.IGRP正确答案：C下列哪一设备工作时，要用到OSI的七个层（一层到七层）（）A.PCB.网管机C.WEB服务器D.交换机E.路由器正确答案：ABC配 置 LACP时,在要使用的接口上必须将哪三个参数配置得完全相同?（）A虚 拟 MAC地址B.端口速度C双工模式D.PortFastE.VLAN信息答 案：BCE2021思科认证考试真题6 节 第 4 节The Ezonexam network administrator has just issued the switchport trunknative vlan 998 command on switch VE2.What is the function of this command?A.It designates VLAN 998 as the default for all unknown tagged trafficB.It designates VLAN 998 for untagged trafficC.It blocks VLAN 998 traffic from passing on the trunkD.It creates a VLAN 998 interfaceE.None of the above正确答案：B下列哪项OSI第 2 层功能是由PPP协议标准规范，但使用CISCO专有的HDLC报头字段实现A成帧B.寻址U错误检测D识别帧内的协议类型正确答案：D下列路由协议中，属于链路状态路由协议的是（）A.RIPB.EIGRPC.IGRPD.OSPF正确答案：DEzonexam is using IP addressing according to RFC 1918.Which three addressranges are used for internal private address blocks as defined by RFC 1918?(Choose all that apply)A.0.0.0.0 to 255.255.255B.10.0.0.0 to 10.255.255.255C.172.16.0.0 to 172.16.255.255D.172.16.0.0 to 172.31.255.255E.127.0.0.0.to 127.255.255.255F.192.168.0.0 to 192.168.255.255G.224.0.0.0 to 239.255.255.255正确答案：BDFB,D,F 解 析：Explanation:RFC 1918 defines three different IP address ranges as private,meaning that theycan be used by any private network for internal use,and these ranges are not tobe used in the Internet.The class A private range is 10.0.0.0 to 10.255.255.255.The class B address range is 172.16.0.0 to 172.31.255.255.The class C private IPaddress range is 192.168.0.0 to 192.168.255.255.Incorrect Answers:A.The 0.0.0.0 network address is invalid and can not be used.C.The correct address range is 172.16.X.X through 172.31.X.XE.The 127.0.0.1 address is reserved for the internal loopback IP address,but theentire 127.X.X.X range is not defined in RFC 1918 as a private address range fornetworks.G.This address range describes the class D multicast address range.为将当前运行的配置复制到TFTP服务器上，需要哪个命令？（）A.copy running-configtftpB.copy startup-configtftpC.copy tftp running-configD.copy tftp startup-config正确答案：A2021思科认证考试真题6节 第5节In a switched LAN network,what is the Spanning-Tree algorithm used for?A.It is used to provide a mechanism for routing updates in switchedenvironments.B.It is used to prevent routing loops in networks with redundant routes.C.It is used to prevent switching loops in networks with redundant switchedroutes.D.It is used to manage,the addition,deletion,and naming of VLANs acrossmultiple switches.E.It is used to segment a network into multiple collision domains.F.None of the above.G.All of the above are functions of STP.正确答案：CC 解 析：Explanation:To avoid loops,all bridging devices,including switches,use STP.STP causes eachinterface on a bridging device to settle into a blocking state or a forwarding state.Blocking means that the interface cannot forward or receive data frames.Forwarding means that the interface can send and receive data frames.By havinga correct subset of the interfaces blocked,a single currently active logical pathwill exist between each pair of LANs.STP resides at the data link layer,so it isused to prevent loops within a switched network.It is not used to prevent routingloops;that is the function of the mechanisms within a routing protocol.当拓扑信息完成交换,相邻路由器具有相同的LSDB时，下列哪项OSPF邻居状态是希望得到的()A.2-WAYB.FULLC.Exchange0.Loading正确答案：B关 于 PPP和 HDLC的说法中，错误的是（）A.PPP是通用协议，HDLC是 CISCO私有协议B.PPP有验证功能,HDLC无验证功能C.PPP效率低，HDLC效率高D.在配置ISDN时，广域网协议不能封装成PPP，但可以封装成HDLC正确答案：D关于静态NAT,下 面（）说法是正确的。A.静 态 NAT转换在缺省情况下24小时后超时B.静 态 NAT转换从地址池中分配C.静 态 NAT将内部地址一对一静态映射到内部全局地址D.CISCO路由器缺省使用了静态NAT正确答案：CCDP is being used throughout the Ezonexam network.What are two reasonswhy the Ezonexam network administrator would use CDP?（Choose two）A.To determine the status of network services on a remote deviceB.To obtain the IP Address of a connected device in order to telnet to thedeviceC.To verify the type of cable interconnecting two devicesD.To verify Layer 2 connectivity between two devices when Layer 3 failsE.To obtain VLAN information from directly connected swticehsF.To determine the status of the routing protocols between directlyconnected routersG.To support automatic network failover during outages正确答案：BDB,D2021思科认证考试真题6节 第6节Ezonexam users have noticed extremely slow network performance,intermittent connectivity,and connection losses.After entering the showinterfaces command,you notice that the Ethernet interface is configured as 100Mbps full-duplex and that there is evidence of late collisions.What could be thecause of this problem?A.Duplex mismatchB.A routing loopC.Trunking mode mismatchD.Improperly configured root bridgeE.Improperly configured static VLANF.None of the above正确答案：AA 解 析：Explanation:A duplex mismatch may result in performance issues,intermittent connectivity,and loss of communication.When troubleshooting NIC issues,verify that the NICand switch are using a valid configuration.Some third-party NIC cards may fallback to half-duplex operation mode,even though both the switchport and NICconfiguration have been manually configured for 100 Mbps,full-duplex.This behavior,is due to the fact that NIC autonegotiation link detection is stilloperating when the NIC has been manually configured.This causes duplexinconsistency between the switchport and the NIC.Symptoms include poor portperformance and frame,check sequence(FCS)errors that increment on theswitchport.To troubleshoot this issue,try manually configuring the switchport to 100 Mbps,half-duplex.If this action resolves the connectivity problems,you may be runninginto this NIC issue.Try updating to the latest drivers for your NIC,or contact yourNIC card vendor for additional support.扩 展 ACL和标准ACL的区别（）。A.标准的ACL在禁止和允许方面比扩展的ACL更高的精度B.扩展的ACL核查数据包的源地址和目标地址和端口号C.他们都可以查端口号D.他们都可以查特殊协议和其他参数正确答案：BStudy the Exhibit below carefully:London#show vtpVTP Version:2Configuration Revision:0Maximum VLANs supported locally:64Number of existing VLANs:5VTP Operating Mode:ClientVTP Domain Name:LondonVTP Pruning Mode:DisabledVTP V2 Mode:DisabledVTP Traps Generation:DisabledBased on the information given above,what is the VTP function of thisparticular switch?A.Learn and save VTP configuration in the running configuration.B.Create and change VLANs.C.Forwards information about VTP configuration.D.VTP is disabled on this device.E.VTP is not saved to NVRAM.正确答案：C解 析：Explanation:FromtheoutputthisswitchisoperatingmerelyasVTPclient,soitbasicallydoesastheVTPserversays,andpassesoninformationaboutVTPconfigurationtothenextswitchinline.IncorrectAnswers:A.Thisisincorrectbecausethefunctionisredundant.B.ThisincorrectbecausetheswitchmustbeinserverortransparentmodetocreateandchangeVLANs.D.ThisisincorrectbecauseifX/TPwouldbedisabledJtwouldntappearonthecommandoutput.E.Ifthisweretrue,theVTPconfigurationinformationwouldnotbedisplayedafterbeingpoweredon.你使用命令copy running-config startup-config保存路由器的配置，并重启路由器，但路由器启动后没有任何运行配置。请问可能出现了什么问题?()A.启动路由器时使用的命令不对B.NVRAM 受损C.配置寄存器的设置不正确D.新升级到的IOS与路由器硬件不兼容E.保存的配置与硬件不兼容答 案：CWhich of the following are types of flow control?(Choose three)A.BufferingB.Cut-throughC.WindowingD.Congestion avoidanceE.Load balancing正确答案：ACD解 析：Explanation:Datatransmissionflowcontroloccursatlayer4withthehelpofbuffering/windowingandcongestionavoidance.