21年思科认证考试历年真题精选9章.docx

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1、21年思科认证考试历年真题精选9章21年思科认证考试历年真题精选9章 第1章 某台PC，能ping通路由器，但不能telnet到路由器，可能的原因是（）A.PC的IP地址设置错误B.路由器端口IP设置错误C.路由器端口处于关闭状态D.telnet密码未设置正确答案：D 查看路由表的命令是：()A.show interfaceB.show runC.show ip routeD.show table正确答案：C IP地址为：192.168.50.70，掩码为：255.255.255.248，则该IP地址所在子网的广播地址为（）A.192.168.50.32B.192.168.80.64C.192

2、.168.50.96D.192.168.50.71正确答案：D Which of the following are types of flow control? (Choose three)ABufferingBCut-throughCWindowingDCongestion avoidanceELoad balancing正确答案：ACD解析：Explanation:Datatransmissionflowcontroloccursatlayer4withthehelpofbuffering,windowingandcongestionavoidance. Ezonexam is migr

3、ating to a private IP addressing scheme. Which of the following describe the use of private IP addresses? (Choose two)AAddresses chosen by E to communicate with the Internet.BAddresses that cannot be routed through the public Internet.CAddresses that can be routed through the public Internet.DA sche

4、me to conserve public addresses.EAddresses licensed to enterprise or ISPs by an Internet registry organization.正确答案：BD解析：Explanation:Private IP address space has been allocated via RFC 1918. This means the addresses are available for any use by anyone and therefore the same private IP addresses can

5、be reused. However they are defined as not routable on the public Internet. They are used extensively in private networks due to the shortage of publicly registered IP address space and therefore network address translation is required to connect those networks to the Internet. 两个VLAN之间要想通信，应该使用的设备是

6、（）A.集线器B.二层交换机C.路由器D.PC机正确答案：C21年思科认证考试历年真题精选9章 第2章 下图中如果允许192.168.1.0/24和10.0.0.0/8的网络之间通信，必须要配置的两条命令是什么()A.A(config)iproute 10.0.0.0 255.0.0.0 172.16.40.2B.A(config)iproute 10.0.0.0 255.0.0.0 S0/0/0C.A(config)iproute 10.0.0.0 255.0.0.0 10.0.0.1D.B(config)iproute 192.168.1.0 255.255.255.0 172.16.40

7、.1E.B(config)iproute 192.168.1.0 255.255.255.0 172.16.40.2F.Biproute 192.168.1.0 255.255.255.0 192.168.1.1正确答案：AD What value is primarily used to determine which port becomes the root port on each nonroot switch in a spanning-tree topology?A. path costB. lowest port MAC addressC. VTP revision number

8、D. highest port priority numberE. port priority number and MAC addressF. None of the above正确答案：AA 解析：Explanation:At the conclusion of the root bridge election process, the switches move on to selecting Root Ports. The Root Port of a bridge is the port that is closest to the Root Bridge in terms of P

9、ath Cost. Every non-Root Bridge must select one Root Port. Again, bridges use the concept of cost to measure closeness. As with some routing metrics, the measure of closeness using STP is not necessarily reflected by hop count. Specifically, bridges track what is referred to as Root Path Cost, which

10、 is the cumulative cost of all links to the Root Bridge. Why is full-duplex Ethernet superior to its single-duplex counterpart? (Select two answer choices.)AIt uses inexpensive hubsBIt operates without collisionsCIt operates on switchesDIt provides faster data transferEIt utilizes fewer wiring pairs

11、正确答案：BD解析：Explanation:Full duplex Ethernet allows concurrent sending and receiving, which allows the full bandwidth to be used for both sending and receiving. The result is a collision free network with increased throughput.Incorrect Answers:A, C. These are incorrect because full duplex doesnt requi

12、re hubs or switches. Full duplex operation can be used on switch and router ports, as well as PC hosts.E. This is incorrect because full duplex actually uses more wiring pairs. In full duplex, both wire pairs are used. Half duplex uses only a single pair. A Ezonexam router boots up in ROMMON mode. W

13、hat is ROM Monitor (ROMMON)?A. A memory component for storing the saved configuration fileB. A memory management toolC. An operating system used for hardware troubleshooting and for password recoveryD. Temporary storage space for the router operating filesE. The source of the primary Cisco IOS softw

14、are imageF. None of the above正确答案：CC 解析：Explanation:The ROM Monitor is a very limited code set that enables you to perform. elementary functions to manually get the router or switch back to a functioning state. You can perform. low-level diagnostics and even copy a new IOS file to the Cisco device o

15、ver the console port. It is also used after the break sequence is issued during bootup for password recovery use. 路由器中时刻维持着一张路由表，这张路由表可以是静态配置的，也可以是什么协议产生的()A.生成树协议B.链路控制协议C.被承载网络层协议D.动态路由协议正确答案：D 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：21年思科认证考试历年真题精选9章 第3章 In which circumstance a

16、re multiple copies of the same unicast frame. likely to be transmitted in the Ezonexam Switched LAN?A. During high traffic periodsB. In an improperly implemented redundant topologyC. After broken links are re-establishedD. When upper-layer protocols require high reliabilityE. When a dual ring topolo

17、gy is in useF. None of the above正确答案：BB 解析：Explanation:A redundant topology eliminates single points of failure, but it also causes broadcast storms, multiple frame. copies, and MAC address table instability problems. Multiple Frame. Copies-when a new switch is added, the other switches may not have

18、 learned its correct MAC address. The host may send a unicast frame. to the new switch. The frame. is sent through several paths at the same time. The new switch will receive several copies of the frame. This causes MAC database instability. MAC database instability results when multiple copies of a

19、 frame. arrive on different ports of a switch. Layer 2 has no mechanism to stop the loop. This is the main reason for the Spanning Tree Protocol(STP) IEEE 802.1d which was developed to prevent routing loops.If multiple connections between switches are created for redundancy purposes, network loops c

20、an occur iin an imprperly designed topology. Spanning Tree Protocol (STP) is used to stop network loops while still permitting redundancy. 下列关于RIP的说法，哪些是正确的（）。A.RIPv1采用广播形式发送报文，RIPv2有广播和多播两种方式B.RIPv2多播地址为224.0.0.9C.RIPv2多播地址为224.0.0.10D.缺省情况下，接口运行RIPv1，只能接收和发送RIPv1正确答案：AB 常见的LSA有几种类型()A.4B.5C.6D.7正确

21、答案：C Which type of cable should be used to make a connection between the Fa0/0 port on a router and the Fa0/0 port switch?ARollover cableBConsole cableCCrossover cableDStraight-through cableESerial cable正确答案：D解析：Explanation:Straight-throughcablesareusedtoconnecthosttoswitch(orhub)androutertoswitch(o

22、rhub). A new Ezonexam switch is installed into an existing LAN and a new VTP trunk is set up with an existing switch. Which VLANs will be allowed on this new trunk?AAll defined VLANs are allowed on the trunk by default.BEach VLAN, or VLAN range, that is specified with the switchport mode command.CEa

23、ch VLAN, or VLAN range, that is specified with the vtp domain command.DEach VLAN, or VLAN range, that is specified with the vlan database command.ENone of the above正确答案：A解析：Explanation:The question does not state that there are multiple VTP Domains meaning that all defined VLANs are allowed on the t

24、runk until a vtp domain command is issued. Which command on router EzonexamA will assign the last usable IP address from the 192.168.32.128/28 subnetwork to a router interface?A. EzonexamA(config-if) ip address 192.168.32.142 255.255.255.240B. EzonexamA(config-if) ip address 192.168.32.143 255.255.2

25、55.240C. EzonexamA(config-if) ip address 192.168.32.158 255.255.255.240D. EzonexamA(config-if) ip address 192.168.32.145 255.255.255.240E. EzonexamA(config-if) ip address 192.168.32.144 255.255.255.240F. EzonexamA(config-if) ip address 192.168.32.158 255.255.255.240G. None of the above正确答案：AA 解析：Exp

26、lanation:The last usable IP address would be 128 + (16-2) = 142 because only the last 4 bits of the last octet are used for host addressing.21年思科认证考试历年真题精选9章 第4章 以下哪些答案列出了一个可用于标准编号IPACL的有效数字（）A.1987B.2187C.187D.87正确答案：AD Which of the following correctly describe the various functions and virtues of

27、a router? (Select all valid answer choices)A. Packet switchingB. Collision prevention on a LAN segment.C. Packet filteringD. Broadcast domain enlargementE. Broadcast forwardingF. Internetwork communicationG. None of the above正确答案：ACFA,C,F 解析：Explanation:The main function of a router is to connect di

28、fferent, separated networks together. In doing so, switching packets from one network to another is a primary function, along with providing for communication between networks. As an additional feature, routers are capable of providing filtering on a network address and application port level, so ch

29、oice C is also correct.Incorrect Answers:B. Routers can indeed be used to segment a network separate a collision domain, since routers do not forward LAN broadcasts and multicasts to other interfaces. However, routers alone can not prevent all collisions from occurring on any given LAN segment.D. Ro

30、uters actually segment LANs into smaller broadcast domains.E. Routers do not forward broadcast and multicast traffic out the additional interfaces by default. Unless bridging or IP helpers are configured on the router, LAN broadcasts are blocked at the router level. 请参见图示。主机A无法访问Internet。此问题的原因是什么A.

31、主机A的IP地址不正确B.主机A的默认网关不正确C.两台路由器的Fa0/1接口配置了不同的子网D.R1Fa0/0的子网掩码不正确正确答案：C你使用命令copy runningconfig startupconfig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：C 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.EIGR

32、PD.IGRP正确答案：C 请参见图示。公司的新安全策略允许来自工程部LAN的所有IP流量访问Internet，但对于来自营销部LAN的流量，则只允许其中的web流量访问Internet。为实施新的安全策略，可在营销部路由器的Serial0/1接口的出站方向上应用哪一ACL()A.access-list 197 permit ip 192.0.2.0 0.0.0.255 any access-list 197 permit ip 198.18.112.0 0.0.0.255 any eq wwwB.access-list 165 permit ip 192.0.2.0 0.0.0.255 an

33、y access-list 165 permit tcp 198.18.112.0 0.0.0.255 any eq www access-list 165 permit ip any anyC.access-list 137 permit ip 192.0.2.0 0.0.0.255 any access-list 137 permit tcp 198.18.112.0 0.0.0.255 any eq wwwD.access-list 89 permit 192.0.2.0 0.0.0.255 any access-list 89 permit tcp 198.18.112.0 0.0.0

34、.255 any eq www正确答案：C21年思科认证考试历年真题精选9章 第5章 关于RIPV1和RIPV2，下列说法哪些正确()A.RIPV1报文支持子网掩码B.RIPV2报文支持子网掩码C.RIPV2缺省使用路由聚合功能D.RIPV1只支持报文的简单口令认证，而RIPV2支持md5认证正确答案：BC 下列选项中不属于数据链路层的广域网通信协议的是()。A.HDLCB.PPPC.ICMPD.Frame-Relay正确答案：C Ezonexam is migrating to a private IP addressing scheme. Which of the following de

35、scribe the use of private IP addresses? (Choose two)AAddresses chosen by E to communicate with the Internet.BAddresses that cannot be routed through the public Internet.CAddresses that can be routed through the public Internet.DA scheme to conserve public addresses.EAddresses licensed to enterprise

36、or ISPs by an Internet registry organization.正确答案：BD解析：Explanation:Private IP address space has been allocated via RFC 1918. This means the addresses are available for any use by anyone and therefore the same private IP addresses can be reused. However they are defined as not routable on the public

37、Internet. They are used extensively in private networks due to the shortage of publicly registered IP address space and therefore network address translation is required to connect those networks to the Internet. 为了阻止交换机环路，交换机上所采用的技术为（）A.水平分割B.生成树协议C.触发更新D.地址学习正确答案：B 在路由表中到达同一网络的路由有：静态路由、RIP路由、IGRP路

38、由，OSPF路由，则路由器会选用哪条路由传输数据：()A.静态路由B.RIP路由C.IGRP路由D.OSPF路由正确答案：A802.1d定义了哪些端口状态?()A.阻断B.丢弃C.侦听D.学习E.转发F.替代答案：ACDE21年思科认证考试历年真题精选9章 第6章下面哪个命令显示路由器当前运行的IOS版本?()A.sh IOSB.sh flashC.sh versionD.sh protocols答案：C Which of the following addresses can be assigned to a host when using a subnet mask of 255.255.

39、254.0? (Select three)A. 113.10.4.0B. 186.54.3.0C. 175.33.3.255D. 26.35.2.255E. 152.135.7.0F. 17.35.36.0正确答案：BDEB,D,E 解析：Explanation:These are all valid host IP addresses within the /23 subnet.Incorrect Answers:A. This is the network address for the 113.10.4.0/23 subnet.C. This is the broadcast addre

40、ss for the 175.33.2.0/23 subnet.F. This is the network address for the 17.35.36.0/23 subnet. What will cause a Ezonexam router to enter setup mode? (Choose two)A. The configuration file is missing in NVRAM.B. The configuration register is set to 0x2100.C. Boot system commands are misconfigured in th

41、e running-configuration.D. The setup command was issued from the privileged mode prompt.E. The IOS is missing.F. The IOS is corrupt.正确答案：ADA,D 解析：Explanation:When router boots up, it checks the valid configuration into NVRAM and tries to load the configuration. If there is not configuration router a

42、utomatically goes into setup dialog. From setup dialog, you able to configuration the basic configuration. As well you can run the setup command manually from privileged mode using the setup command.网络管理员想升级路由器的IOS,但又不希望当前安装的映像被删除。因此,他需要查看当前IOS映像占用的闪存空间,并确定闪存是否有足够的空间同时存储当前映像和新映像。为此,他可使用哪个命令?()A.show

43、 versionB.show flashC.show memoryD.show buffersE.show running-config答案：B 关于矢量距离算法以下那些说法是错误的()A.矢量距离算法不会产生路由环路问题B.矢量距离算法是靠传递路由信息来实现的C.路由信息的矢量表示法是(目标网络，metric)D.使用矢量距离算法的协议只从自己的邻居获得信息正确答案：A 把指定端口添加到VLAN的命令是：()A.vlanB.vlan-member shipC.vtpD.switch port正确答案：D21年思科认证考试历年真题精选9章 第7章 一个AS由多个组织行政下控制的网络组成。此题为

44、判断题(对，错)。正确答案： After working all night and successfully configuring a Cisco router for the Ezonexam network you save your changes on the startup config, reboot the router, and go out for a cigarette. When you return, none of your changes are active and the router boots to the initial configuration m

45、ode! Which of the choices below indicates the source of your problem?AHardware failure in NVRAM prevents the router from loading the configBStartup-config in flash is corrupt and cannot be analyzedCRouter configuration-register set to bypass startup configurationDStartup-config in NVRAM is corrupt a

46、nd cannot be analyzedENone of the above正确答案：C解析：Explanation:The default configuration-register setting of 0x2102 loads the IOS from flash and the configuration from NVRAM.However, for password recovery, you can set the register to 0x2142 and the startup-config file in NVRAM will be bypassed. The pro

47、blem described here is that the config register was not changed back to 0x2102 before the router was rebooted, so the active configuration is bypassed. Simply setting the config register back to 0x2102 will fix this problem.Incorrect Answers:A, B, D. All of these describe hardware or software errors. In the event that this is the problem, errors will be