CCNA考试实践题库-选择题.pdf

exam a question 1 refer to the exhibit what will router1 do when it receives the data frame shown choose three a router1 will strip off the source mac address and replace it with the mac address 0000 0c36 6965 b router1 will strip off the source ip address and replace it with the ip address 192 168 40 1 c router1 will strip off the destination mac address and replace it with the mac address 0000 0c07 4320 d router1 will strip off the destination ip address and replace it with the ip address of 192 168 40 1 e router1 will forward the data packet out interface fastethernet0 1 f router1 will forward the data packet out interface fastethernet0 2 correct answer acf section part 1 explanation explanation reference 考点 数据通信过程源目ip mac地址的变化 age min 下面 为本地端口 a 源mac替换为f0 2口的mac 正确 b 替换源ip 错误 c 替换目的mac为下一跳入口的mac 正确 d 替换目的ip 错误 e 从f0 1转发数据 错误 f 正确 鸿鹄论坛 question 2 refer to the exhibit which three statements correctly describe network device a choose three ccna考试交流1000人qq群 150429991 a with a network wide mask of 255 255 255 128 each interface does not require an ip address b with a network wide mask of 255 255 255 128 each interface does require an ip address on a unique ip subnet c with a network wide mask of 255 255 255 0 must be a layer 2 device for the pcs to communicate with each other d with a network wide mask of 255 255 255 0 must be a layer 3 device for the pcs to communicate with each other e with a network wide mask of 255 255 254 0 each interface does not require an ip address correct answer bde section part 1 explanation explanation reference 如图 哪三个选项正确的描述了网络设备a 考点分析 这题考的是子网掩码的问题 使用掩码255 255 255 128和255 255 255 0时 两台主机的ip地址 属于两个网段 所以a要用路由器 三层设备 才能通信 所以a设备每个接口需要设置ip地址 使用掩码 255 255 254 0是 两台主机属于同一个网段 所以a要使用switch或hub就能通信 且不需要ip地址 question 3 which layer in the osi reference model is responsible for determining the availability of the receiving program and checking to see if enough resources exist for that communication a transport b network c presentation d session e application correct answer e section part 1 explanation explanation reference osi中那一层负责决定一个进程的可用性并查看是否有可用的资源分给该进程 考点分析 osi七层参考模型中负责决定一个进程的可用性并查看是否有可用的资源分给该进程是第七层应 用层 question 4 which of the following describes the roles of devices in a wan choose three a a csu dsu terminates a digital local loop b a modem terminates a digital local loop ccna考试交流1000人qq群 150429991 c a csu dsu terminates an analog local loop d a modem terminates an analog local loop e a router is commonly considered a dte device f a router is commonly considered a dce device correct answer ade section part 1 explanation explanation reference su dsu是用于连接终端和数字专线的设备 属于dce设备 modem用于数字信号和模拟信号的转换 属于dce设备 路由器一般是dte设备 question 5 refer to the exhibit host a pings interface s0 0 on router 3 what is the ttl value for that ping a 253 b 252 c 255 d 254 correct answer a section part 1 explanation explanation reference 默认是255 每经过一个路由器减1 question 6 a network administrator is verifying the configuration of a newly installed host by establishing an ftp connection to a remote server what is the highest layer of the protocol stack that the nework administrator is using for this operation ccna考试交流1000人qq群 150429991 a application b presentation c session d transport e internet f data link correct answer a section part 1 explanation explanation reference http ftp telnet snmp dns等服务都是在应用层 question 7 refer to the exhibit after hosta pings hostb which entry will be in the arp cache of hosta to support this transmission a b c ccna考试交流1000人qq群 150429991 d e f correct answer d section part 1 explanation explanation reference 问 当主机a ping 主机b之后 下面那个arp缓存条目会支持此次通讯 考题分析 这道题考的是局域网arp的请求 host a要ping host b 首先host a需要封装ping包 而封装 ping包需要host a和host b的二 三层地址的信息 然而host a不知道host b的二层地址 这样host a就会 向局域网发送arp请求 来请求host b的二层地址 网关收到host a的arp请求后 发现host b是其他网段的 地址 这样网关会启用代理arp的功能 将自己的二层地址应答给host a host a收到应答包后会对本地的 arp缓存进行更新 将应答方的ip和mac地址存储在arp缓存中 同时完成ping包的封装 网关在收到ping 包后会自动完成二层地址的重定向 所以答案是d 此题考查的是pc的arp表 不要和包的目的地址 源地址弄混了 在以太网寻址的时候 依靠的事mac地址 每一个网段都需要寻找到自己的下一条 gateway 以自己的 mac作为source gateway的mac作为destination封装frame 然后将frame转发出去 但是数据包是不会进 行变化的 也就是packet的头部信息不会发生改变 所以ip包头的source和des地址是不会变更的 鸿鹄论坛 question 8 a network interface port has collision detection and carrier sensing enabled on a shared twisted pair network from this statement what is known about the network interface port a this is a 10mb s switch port b this is a 100mbs switch port c this is an ethernet port operating at half duplex d this is an ethernet port operating at full duplex e this is a port on a network interface card in a pc correct answer c section part 1 explanation explanation reference 考点 考查冲突域的概念 在半双工网络中才存在冲突域 综上所述选c question 9 a receiving host computes the checksum on a frame and determines that the frame is damaged the frame is then discarded at which osi layer did this happen a session b network c physical d data link e transport ccna考试交流1000人qq群 150429991 correct answer d section part 1 explanation explanation reference 帧的处理是在二层 question 10 which of the following correctly describe steps in the osi data encapsulation process choose two a the transport layer divides a data stream into segments and may add reliability and flow control information b the data link layer adds physical source and destination addresses and an fcs to the segment c packets are created when the network layer encapsulates a frame with source and destination host addresses and protocol related control information d packets are created when the network layer adds layer 3 addresses and control information to a segment e the presentation layer translates bits into voltages for transmission across the physical link correct answer ad section part 1 explanation explanation reference 传输层将数据分段 并且加入flow control等信息 在网络层就将数据进行打包 并加上ip包头 链路层 将 包进行成frame 封装二层头部 鸿鹄论坛 question 11 refer to the graphic host a is communicating with the seiver what will be the source mac address of the frames received by host a from the server a the mac address of the seiver network interface b the mac address of host a c the mac address of router interface e 1 d the mac address of router interface e0 ccna考试交流1000人qq群 150429991 correct answer d section part 1 explanation explanation reference host a收到server的帧的源mac地址是host a的网关的mac question 12 refer to the exhibit what two results would occur if the hub were to be replaced with a switch that is configured with one ethernet vlan choose two a the number of collision domains would decrease b the number of collision domains would increase c the number of broadcast domains would remain the same d the number of collision domains would remain the same e the number of broadcast domains would increase correct answer bc section part 1 explanation explanation reference hub不可以隔离冲突域 所有端口同一个冲突域中 交换机可以隔离冲突域 每个端口在不同冲突域中 故换成交换机冲突域个数会增加 大小会减小 而hub 交换机都不可隔离广播域 所有端口都在同一个广播 域中 故广播域数量不变 a 冲突域数量减少 b 冲突域数量增加 c 广播域数量不变 d 冲突域数量不变 e 广播域数量增加 question 13 which three statements accurately describe layer 2 ethernet switches choose three a microsegmentation decreases the number of collisions on the network b if a switch receives a frame for an unkown destination it uses arp to resolve the address c spanning tree protocol allows switches to automatically share vlan information d in a properly functioning network with redundant switched paths each switched aegment will contain ccna考试交流1000人qq群 150429991 one root bridge with all its ports in the forwarding state all other switches in that broadcast domain will have only one root port e establishing vlans increases the number of broadcast domains f switches that are configured with vlans make forwarding decisions based on both layer 2 and layer 3 address information correct answer ade section part 1 explanation explanation reference a为分割减少冲突的数量 这里是冲突并不是冲突域 正确 b收到未知目的帧会产生泛洪 c这是vtp的特性 不是stp的 d在一个能够正常运行的网络冗余交换路径 每一个交换网段将包括一个跟桥 所有端口都在转发状态 其 他本广播域的交换机有一个根端口 正确 e vlan增加了广播域 正确 f vlan使转发基于二层和三层ip 题目要求对2层交换机的描述 二层交换机不能基于3层ip转发 question 14 where does routing occur within the dod tcp ip reference model a application b internet c network d transport correct answer b section part 1 explanation explanation reference 路由发生在dod模型的哪一层 注意是dod模型不是osi模型 question 15 which destination addresses will be used by host a to send data to host c choose two a the ip address of switch 1 b the mac address of switch 1 c the ip address of host c d the mac address of host c e the ip address of the router s e0 interface f the mac address of the router s e0 interface ccna考试交流1000人qq群 150429991 correct answer cf section part 1 explanation explanation reference 数据包在转发的过程中 源目ip不变 源目mac会变化 目的地不在同一个网段 数据先发送到网关 question 16 for what two purposes does the ethernet protocol use physical addresses choose two a to uniquely identify devices at layer 2 b to allow communication with devices on a different network c to differentiate a layer 2 frame from a layer 3 packet d to establish a priority system to determine which device gets to transmit first e to allow communication between different devices on the same network f to allow detection of a remote device when its physical address is unknown correct answer ae section part 1 explanation explanation reference 考点 考查mac地址的作用 a 在二层唯一确定一台设备 正确 b 是设备在不同的网络中通信 错误 不同网络通信需要通过ip地址确定 c 区别二层和三层帧 错误 d 确定设备的优先级 错误 没有这个功能 e 是同一网络的不同设备可以通信 正确 f 当不知道远程设备的物理地址时可以查询 错误 不能跨网段 鸿鹄论坛 question 17 refer to the exhibit based on the information given which switch will be elected root bridge and why a switch a because it has the lowest mac address b switch c because it has the lowest priority c switch b because it has the highest mac address d switch c because it is the most centrally located switch e switch a because it is the most centrally located switch f switch d because it has the highest priority correct answer b section part 1 ccna考试交流1000人qq群 150429991 explanation explanation reference 选跟桥先比较优先级 优先级相同再比较mac地址大小 question 18 what value is primarily used to determine which port becomes the root port on each nonroot switch in a spanning tree topology a lowest port mac address b port priority number and mac address c vtp revision number d highest port priority number e path cost correct answer e section part 1 explanation explanation reference 此处为选举跟端口 先要比较到跟桥的cost 如果是选跟桥 先比较优先级 question 19 refer to the exhibit switch 1 needs to send data to a host with a mac address of 00b0 d056 efa4 what will switch 1 do with this data a switch 1 will drop the data because it dose not have an entry for that mac address b switch 1 will flood the data out all of its port from which the data originated c switch 1 will forward the data to its default gateway d switch 1 will send an arp request out all its ports except the port from which the data originated correct answer b section part 1 explanation explanation reference 答案 b 没有mac地址会泛红 根据下图 switch 1需要往一台mac地址为00b0 d056 efa4的主机发数据 switch 1会如何处理这些数据 ccna考试交流1000人qq群 150429991 a switch 1 will drop the data because it does not have an entry for that mac address switch 1会丢弃该 数据 因为它没有该mac地址条目 b switch 1 will flood the data out all of its ports except the port from which the data originated switch 1会 泛洪该数据到所有的接口 除了该数据的源接口 c switch 1 will send an arp request out all its ports except the port from which the data originated switch 1会发送arp请求到所有的接口 除了该数据的源接口 d switch 1 will forward the data to its default gateway switch 1会往默认网关发送该数据 question 20 what is the function of the command switchport trunk native vlan 999 on a switch a it designates vlan 999 for untagged traffic b it blocks vlan 999 traffic from passing on the trunk c it creates a vlan 999 interface d it designates vlan 999 as the default for all unkown tagged traffic correct answer a section part 1 explanation explanation reference 设置vlan999为本征vlan 交换机默认本征vlan为vlan1 此题正确答案为a question 21 which two protocols are used by bridges and or switches to prevent loops in a layer 2 network choose two a 802 1d b vtp c 802 1q d stp e sap correct answer ad section part 1 explanation explanation reference 考点分析 这道题考的是生成树协议 能防止二层环路的当然是生成树协议 生成树协议 有stp 802 1d 和rstp 802 1w question 22 which switch would stp choose to become the root bridge in the selection process a 32768 11 22 33 44 55 66 b 32768 22 33 44 55 66 77 c 32769 11 22 33 44 55 65 d 32769 22 33 44 55 66 78 correct answer a section part 1 explanation explanation reference stp选举跟桥首先比较优先级大小 然后比较mac地址大小 question 23 a switch is configured with all ports assigned to vlan 2 with full duplex fastethernet to segment existing departmental traffic what is the effect of adding switch ports to a new vlan on the switch ccna考试交流1000人qq群 150429991 a more collision domains will be created b ip address utilization will be more efficient c more bandwidth will be required than was needed previously d an additional broadcast domain will be created correct answer d section part 1 explanation explanation reference 一个交换机把所有的端口以全双工的模式加到一个vlan里 把一个端口加入到一个新的vlan里会对此交换机 产生什么影响 考点分析 这道题考的是vlan的概念 将一个交换的端口加入一个新vlan代表一个新的广播域产生了 因为 vlan有隔离广播域的作用 question 24 what are three benefits of implementing vlans choose three a a more efficient use of bandwidth can be achieved allowing many physical groups to use the same network infrastructure b broadcast storms can be mitigated by decreasing the number of broadcast domains thus increasing their size c a higher level of network security can be reached by separating sensitive data traffic from other network traffic d port based vlans increase switch port use efficient thanks to 802 1q trunks e a more efficient use of bandwidth can be achieved allowing many logical networks to use the same network infrastructure f broadcast storms can be mitigated by increasing the number of broadcast domains thus reducing their size g vlans make it easier for it staff to configure new logical groups because the vlans all belong to the same broadcast domain correct answer cef section part 1 explanation explanation reference a错 不是通过物理上组合 而是逻辑上的 b错 应该是增加广播域的数量 c一个更高的层次网络安全可以实现 以分离的敏感数据从其他网络 正确 d thanks to 802 1q trunks不正确 e正确 logical是逻辑的意思 f正确 g错误 是vtp的作用不是vlan的 鸿鹄论坛 question 25 which ieee standard protocol is initiated as a result of successful dtp completion in a switch over fastethernet a 802 3ad b 802 1w c 802 1q d 802 1d correct answer c section part 1 explanation ccna考试交流1000人qq群 150429991 explanation reference 动态中继协议dtp 是 vlan 组中思科的私有协议 主要用于协商两台设备间链路上的中继过程及中继 封装 802 1q 类型 question 26 which of the following are benefits of vlans choose three a they increase the size of collision domains b they allow logical grouping of users by function c they can enhance network security d they increase the size of broadcast domains while decreasing the number of collision domains e they increase the number of broadcast domains while decreasing the size of the broadcast domains f they simplify switch administration correct answer bce section part 1 explanation explanation reference 考查vlan的特点 a 增加冲突域的大小 错误 b 允许逻辑划分网段 正确 c 增强网络安全 正确 不同vlan不能直接通信 d 当减少冲突域时增加广播域的大小 错误 e 减少广播域的大小时增加了广播域个数 正确 f 简化交换机管理 答非所问 鸿鹄论坛 question 27 refer to the exhibit a technician has installed swithchb and needs to configure it for remote access from the management workstation connected switcha which set of commands is required to accomplish this task a switchb config interface fastethernet 0 1 switchb config ip address 192 168 8 252 255 255 255 0 switchb config no shutdown b switchb config ip default gateway 192 168 8 254 ccna考试交流1000人qq群 150429991 switchb config interface vlan 1 switchb config ip address 192 168 8 252 255 255 255 0 switchb config no shutdown c switchb config interface vlan 1 switchb config ip address 192 168 8 252 255 255 255 0 switchb config ip default gateway 192 168 8 254 255 255 255 0 switchb config no shutdown d switchb config ip default network 192 168 8 254 switchb config interface vlan 1 switchb config ip address 192 168 8 252 255 255 255 0 switchb config no shutdown correct answer b section part 1 explanation explanation reference 想要远程管理交换机需要在交换机上的配置 b正确 question 28 in an ethernet network under what two scenarios can devices transmit choose two a when they receive a special token b when there is a carrier c when they detect no other devices are sending d when the medium is idle e when the server grants access correct answer cd section part 1 explanation explanation reference 在以太网网络 在什么情况下可以两种设备可以传输 考点分析 这题考的是以太网的基本概念csma cd 题目问在两种情况下设备才会开始传输数据 当然是 当它检测到没有其他设备在传输数据或传输介质是空闲的时才开始传输数据 鸿鹄论坛 question 29 which two states are the port states when rstp has converged choose two a blocking b learning c discarding d forwarding e listening correct answer cd section part 1 explanation explanation reference 在rstp中只有三种端口状态 discarding leaning和forwarding 汇聚之后的状态只有discarding forwarding question 30 which two commands can be used to verify a trunk link configurationt status on a given cisco switch choose two ccna考试交流1000人qq群 150429991 a show interfaces interface b show interfaces trunk c show interfaces switchport d show ip interface brief e show interfaces vlan correct answer bc section part 1 explanation explanation reference 查看trunk命令 show interface trunk和show interface switchport 只能选bc question 31 which command enables rstp on a switch a spanning tree mode rapid pvst b spanning tree uplinkfast c spanning tree backbonefast d spanning tree mode mst correct answer a section part 1 explanation explanation reference 启用rstp的命令 question 32 which of the following statements describe the network shown in the graphic choose two a there are two broadcast domains in the network b there are four broadcast domains in the network c there are six broadcast domains in the network d there are four collision domains in the network e there are five collision domains in the network f there are seven collision domains in the network correct answer af section part 1 ccna考试交流1000人qq群 150429991 explanation explanation reference 路由器一个端口一个广播域 交换机一个端口一个冲突域 集线器一个冲突域 左边是集线器 右边是交换机 路由器有两个端口 所以有两个广播域 右边交换机有6个端口加上左边集线器一共7个冲突域 question 33 refer to the exhibit all switch ports are assigned to the correct vlans but none of the hosts connected to switcha can communicate with