CCNA ITN 第 7 章考试

诶了我累了目录第二章网络通信P2-8第三章应用层功能及协议P9-14 第四章 OSI 传输层 P15-20第五章 OSI 网络层 P21-27第六章网络编址-IPv4 P28-34第七章数据链路层P35-40第八章 OSI 物理层 P41-45第九章以太网P46-51第十章网络规划和布线P52-61 第十一章配置和测试网络P62-70 第一学期末考试P71-91文档末尾返回目录第二章网络通信001 TCP/IP 网络接入层有何作用路径确定和数据包交换数据表示、编码和控制可靠性、流量控制和错误检测详细规定构成物理链路的组件及其接入方法将数据段划分为数据包2下列哪些陈述正确指出了中间设备在网络中的作用（选择三项）确定数据传输路径发起数据通信重新定时和重新传输数据信号发送数据流管理数据流数据流最后的终止点003 下列哪三项陈述是对局域网(LAN) 最准确的描述（选择三项）LAN 通常位于一个地域内。

此类网络由由一个组织管理。

LAN 中的不同网段之间一般通过租用连接的方式连接。

此类网络的安全和访问控制由服务提供商控制。

LAN 为同一个组织内的用户提供网络服务和应用程序访问。

此类网络的每个终端通常都连接到电信服务提供商(TSP)。

004 什么是PDU传输期间的帧损坏在目的设备上重组的数据因通信丢失而重新传输的数据包特定层的封装005 OSI 模型哪两层的功能与TCP/IP 模型的网络接入层相同（选择两项）网络层传输层物理层数据链路层会话层6请参见图示。

所示网络属于哪一类型WANMANLANWLAN7以下哪种特征正确代表了网络中的终端设备管理数据流发送数据流重新定时和重新传输数据信号确定数据传输路径008 第 4 层端口指定的主要作用是什么标识本地介质中的设备标识源设备和目的设备之间的跳数向中间设备标识通过该网络的最佳路径标识正在通信的源终端设备和目的终端设备标识终端设备内正在通信的进程或服务9请参见图示。

•考试结果•试题反馈报告Introduction to Networks (版本6.00) - ITN 第7 章考试以下是针对您未获得满分的试题给出的反馈。

某些交互式试题可能不显示您的答案。

分项分数：1 IPv4 地址由多少位组成？1IPv4 地址由多少位组成？•正确响应您的响应•o256o64o128o32IPv4 地址由 4 个二进制八位数组成，每个数字包含 8 个位，从而构成一个32 位地址。

此试题参考以下领域的内容：Introduction to Networks•7.1.1 二进制和十进制的转换2 十进制数232 的二进制表示是什么？2十进制数232 的二进制表示是什么？•正确响应您的响应•o11000110o10011000o11110010o11101000232 在二进制中表示为 11101000。

128+64+32+8 = 232 此试题参考以下领域的内容：Introduction to Networks•7.1.1 二进制和十进制的转换3 二进制数10010101 的十进制表示是什么？3二进制数10010101 的十进制表示是什么？•正确响应您的响应•o157o168o149o192二进制 10010101 可映射为十进制的 149。

128+16+4+1 = 149此试题参考以下领域的内容：Introduction to Networks•7.1.1 二进制和十进制的转换4 下列哪两项是IPv4 地址的组成部分？（请选择两项。

）4下列哪两项是IPv4 地址的组成部分？（请选择两项。

）•正确响应您的响应•o子网部分o逻辑部分o网络部分o主机部分o广播部分o物理部分IPv4 地址分为两个部分：网络部分 - 用于识别主机所在的特定网络，主机部分 - 用于识别网络中的特定主机。

子网掩码用于识别各个部分的长度。

此试题参考以下领域的内容：Introduction to Networks•7.1.2 IPv4 地址结构5 IP 地址172.17.4.250/24 代表什么？5IP 地址172.17.4.250/24 代表什么？•正确响应您的响应•o广播地址o主机地址o网络地址o组播地址/24 表明，网络地址为 172.17.4.0。

答案：1、D 2、AE 3、BC 4、E 5、B 6、D 7、AEF 8、A 9、A 10、B 11、D 12、B 13、A 14、D 15、AD 16、A 17、ABF 18、BF 19、B 20、C1收集症状以排查网络故障时，哪个步骤可能会牵涉到外部管理员？缩小范围收集可疑设备的症状分析现有症状确定所有权2逻辑网络图中一般有哪两项要素？（选择两项。

）接口标识符连接器类型操作系统版本电缆类型虚电路3请参见图示。

在创建网络文档的过程中应该进行哪两个步骤？（选择两项。

）记录仅在园区网络中发现的设备的相关信息。

记录在整个网络中（包括远程站点）发现的设备的相关信息。

将网络配置表中与拓扑图所示组件相关的任何设备信息记录下来。

仅将网络配置表中与拓扑图所示组件相关的第2 层和第3 层设备信息记录下来。

将网络配置表中与拓扑图所示组件相关的在网络使用高峰期收集的的设备信息记录下来。

4请参见图示。

图中的图表来自HR-1，它是HR 部门使用的唯一一台应用程序服务器。

基线数据收集开始于8 月1 日。

从图表中可确定什么有用信息？HR-1 上的CPU 资源失衡。

需要调整处理周期。

有两个明显的周末处理周期，它们始于周六夜晚，止于周日早上。

基线图表显示HR-1 明显具有处理问题（尽管问题本质尚不清楚）。

HR-1 上的处理负载重复再现，因此可预测。

HR-1 上的CPU 负载因某种原因受到明显影响，但由于信息不足，无法确定是否存在问题。

5请参见图示。

服务器HR 上的一个应用程序不再响应任何客户端请求。

每件事务都取决于数据中心中的多台服务器。

数据中心内的服务器上运行的为全公司提供服务的应用程序均无问题。

员工没有解决此类故障的经验，且对各种应用程序的了解也有限。

哪些初始故障排除步骤体现了自上而下的故障排除方法？检查所有服务器的电缆连接。

检查每块网卡上的连接指示灯是否为绿色。

Ping 每台服务器的本地地址，然后Ping 相关服务器和典型客户端的地址。

CCNA认证基础-习题分析讲义第一部分第一章1. Convert the binary number 10111010 into its hexadecimal equivalent. Select thecorrect answer from the list below. （3）1) 852) 903) BA4) A15) B36) 1C2. Convert the Hexadecimal number A2 into its Base 10 equivalent. Select thecorrect answer from the list below. （4）1) 1562) 1583) 1604) 1625) 1646) 1663. Which binary number is a representation of the decimal number 248? （3）1) 111010002) 111101003) 111110004) 111110104. Which of the following will test the internal loopback of a node? （3）1) ping 10.10.10.12) ping 192.168.1.13) ping 127.0.0.14) ping 223.223.223.2235) ping 255.255.255.2555. What can be verified by successfully pinging the reserved loopback address ona host? （2）1) Connectivity exists between two hosts on the LAN.2) The TCP/IP stack of the local host is configured correctly.3) A connection exists between a host and the default gateway.4) The route a packet takes from the local host to a remote host is valid.6. Which of the following commands could be used on a Windows-basedcomputer to view the current IP configuration of the system? (Choose two.) （3，4）1) configip2) ifconfig3) ipconfig4) winipcfg5) Winipconfig7.Refer to the exhibit. What must be configured on Host B to allow it to communicate withthe Host C? (Choose three.) （2，4，6）1)the MAC address of RTA router interface connected to Switch 12) a unique host IP address3)the IP address of Switch 14)the default gateway address5)the MAC address of Host C6)the subnet mask for the LAN8. What are important characteristics to consider when purchasing a networkinterface card? (Choose two.) （2，3）1) security used on the network2) media used on the network3) system bus used on the computer4) software installed on the network5) diagnostic tools installed on the network第二章1. Select the necessary information that is required to compute the estimated timeit would take to transfer data from one location to another. (Choose two.) （1，5）1) file size2) data format3) network in use4) type of medium5) bandwidth of the link2. Using the data transfer calculation T=S/BW, how long would it take a 4MB file tobe sent over a 1.5Mbps connection? （2）1) 52.2 seconds2) 21.3 seconds3) 6.4 seconds4) 2 seconds5) 0.075 seconds6) 0.0375 seconds3. What are features of the TCP/IP Transport layer? (Choose two.) （3，5）1) path determination2) handles representation, encoding and dialog control3) uses TCP and UDP protocols4) packet switching5) reliability, flow control and error correction4. Which of the following is the Layer 4 PDU? （4）1) bit2) frame3) packet4) Segment5. What is important to remember about the data link layer of the OSI model whenconsidering Peer to Peer communication? (Choose three.) （3，4，5）1) It links data to the transport layer.2) It encapsulates frames into packets.3) It provides a service to the network layer.4) It encapsulates the network layer information into a frame.5) Its header contains a physical address which is required to complete the datalink functions.6) It encodes the data link frame into a pattern of 1s and 0s (bits) for transmissionon the medium.6. Which statement describes a star topology? （2）1) Each host in the network is connected to a backbone cable that is terminated atboth ends.2) Each host is connected to a hub or switch, either of which acts as a central pointfor all network connections.3) Each host is directly connected to two other hosts to form a long chain of hosts.4) Each host has a connection to all other hosts in the network.7. Which statements describe the logical token-passing topology? (Choose two.)（2）1) Network usage is on a first come, first serve basis.2) Computers are allowed to transmit data only when they possess a token.3) Data from a host is received by all other hosts. Electronic tokens are passedsequentially to each other.4) Token passing networks have problems with high collision rates.8. Which technologies are considered to be LAN technologies? (Choose two.) （2，5）1) DSL2) Token Ring3) Frame Relay4) ISDN5) Ethernet9.Refer to the exhibit. Host A wants to send a message to host B. Place the following stepsin the correct order so that the message can be sent. （4）A - add network layer addressesB - transmit bitsC - create application dataD - add data link layer addresses1) B, A, D, C2) D, A, C, B3) A, D, A, B4) C, A, D, B5) C, D, A, B6) C, B, A, D10.After an uns u ccessful ping to the local router, the technician decides to investigate therouter. The technician observes that the lights and fan on the router are not operational.In which layer of the OSI model is the problem most likely occurring? （4）1) transport2) network3) data link4) physical11. Refer t o the exhibit. What is the order of the TCP/IP Protocol Data Units as datais moved as indicated through the OSI model? （3）1) data, segments, frames, packets, bits2) data, packets, segments, frames, bits3) data, segments, packets, frames, bits4) data, packets, frames, segments, bits第三章1. Which combinations of charges will be repelled by electric force? (Choose two.)（4，6）1) neutral and neutral2) neutral and positive3) neutral and negative4) positive and positive5) positive and negative6) negative and negative2. Which of the following are considered the best media for use in data networkcommunications? (Choose three.) （2，3，6）1) glass2) fibers3) copper4) gold5) plastic6) silicon7) Silver3. Which of the following wireless standards increased transmission capabilitiesto 11 Mbps? （2）1) 802.11a2) 802.11b3) 802.11c4) 802.11d4. What is attenuation? （3）1) opposition to the flow of current2) measurement of electrical signals relative to time3) degradation of a signal as it travels along the medium4) amount or volume of traffic that is flowing on the medium5. Which cable specifications are indicated by 10BASE-T? （3）1) 10 Mbps transmission speed, baseband signal, 500 meter cable length, coaxialcable2) 10 Mbps transmission speed, broadband signal, 100 meter cable length, coaxialcable3) 10 Mbps transmission speed, baseband signal, 100 meter cable length,twisted-pair cable4) 10 Gbps transmission speed, broadband signal, 500 meter cable length,twisted-pair cable6. For which Ethernet installations would fiber optic rather than Cat5 UTP be abetter media choice? (Choose two.) （2，4）1) a 3 meter connection between two 10BASE-T hubs2) an environment with many potential sources of EMI and RFI3) a peer to peer connection between two NICs with RJ45 connectors4) an installation between two buildings that are located 500 meters apart5) a single building installation where installation costs are the major concern7. Refer to the exhibit. Which type of UTP cable should be used to connect Host Ato Switch1? （4）1) rollover2) console3) crossover4) straight-through8. Refer to the exhibit. Which type of Category 5 cable is used to make an Ethernetconnection between Host A and Host B? （3）1) coax cable2) rollover cable3) crossover cable4) straight-through cable第四章1. During cable testing, which of the following are used to calculate theinformation carrying capacity of a data cable? (Choose two.) （2，5）1) bit speed2) attenuation3) wire map4) saturation limit5) analog bandwidth2. What type of wiring problem is depicted in this sample of a cable tester? （3）1) a fault2) a short3) an open4) a split a good map3. In a new network installation, the network administrator has decided to use amedium that is not affected by electrical noise. Which cable type will best meet this standard? （5）1) coaxial2) screened twisted pair3) shielded twisted pair4) unshielded twisted pair5) fiber optic4. How does network cable length affect attenuation? （3）1) Category 5 cable that is run in metal conduit has the highest attenuation in theshortest distance.2) Shorter cable lengths have greater signal attenuation.3) Longer cable lengths have greater signal attenuation.4) The length of the cable has no effect on signal attenuation.第五章1. The highest capacity Ethernet technologies should be implemented in whichareas of a network? (Choose three.) （3，4，5）1) between workstation and backbone switch2) between individual workstations3) between backbone switches4) between enterprise server and switch5) on aggregate access links2. What device must be used between an AUI port of a networking device and themedia to which it is being connected? （3）1) a transducer2) a transmitter3) a transceiver4) a transponder5) a port replicator3. An ISDN Basic Rate Interface (BRI) is composed of how many signalingchannels? （1）1) 12) 23) 34) 44. Which layer of the OSI model covers physical media? （1）1) Layer 12) Layer 23) Layer 34) Layer 45) Layer 56) Layer 65. What type of network cable is used between a terminal and a console port? （3）1) cross-over2) straight-through3) rollover4) patch cable6. What is the recommended maximum number of workstations configured on apeer-to-peer network? （3）1) 252) 153) 104) 55) 27. Which of the following increases the potential for a collision to occur? （4）1) the use of an active hub instead of an intelligent hub2) the use of an intelligent hub instead of an active hub3) a reduction in the number of devices attached to the hub4) an increase in the number of devices attached to the hub8. What is the maximum length of a media segment used for 100BASE-TX? （1）1) 100 meters2) 185 meters3) 400 meters4) 500 meters9. Which cable diagram displays the end to end pinout for a crossover cable usedwith Cisco devices? （3）1) Cable A2) Cable B3) Cable C4) Cable D第六章1. What does the "10" in 10Base2 indicate about this version of Ethernet? （2）1) The version uses Base10 numbering within the frames.2) The version operates at a transmission rate of 10 Mbps.3) Frames can travel 10 meters unrepeated.4) The maximum frame length is 10 octets.2. How is a MAC address represented? （4）1) four groups of eight binary digits separated by a decimal point2) four Base10 digits separated by a decimal point3) six hexadecimal digits4) twelve hexadecimal digits5) twenty-four Base10 digits3. Which of the following statements are correct about CSMA/CD? (Choose three.)（1，3，6）1) It is a media access method used in LANs.2) It is a media access method used in FDDI WANs.3) When a device needs to transmit, it checks to see if the media is available.4) A device sends data without checking media availability because all deviceshave equal access.5) Multiple devices can successfully transmit simultaneously.6) Only one device can successfully transmit at a time.4. Which devices shown in the graphic must have a MAC address? （5）1) only PC2) only router3) PC and router4) PC, hub, and router5) PC, printer, and router第七章1. Which of the following items are common to all 100BASE technologies?(Choose three.) （1，4，5）1) frame format2) media3) connectors4) timing5) multi-part encoding2. Which of the following does 1000BASE-T use to accomplish gigabit speeds onCat 5e cable? （4）1) the use of four conductors in full-duplex mode2) the use of two multiplexed pairs of wires, simultaneously3) the use of three pairs of wires for data and the fourth for stabilization andforward error correction4) the use of all four pairs of wires in full-duplex mode, simultaneously3. For which of the following is Ethernet considered the standard? (Choose three.)（1，4，5）1) inter-building connection2) mid-length voice3) video conferencing4) vertical wiring5) horizontal wiring6) diagonal wiring4. To make sure timing limitations are not violated when implementing a 10 MbpsEthernet network involving hubs or repeaters, a technician should adhere to which rule? （4）1) the 4-5-3 rule2) the 6-4-2 rule3) the 3-4-5 rule4) the 5-4-3 rule5. What is the maximum distance that 10BASE-T will transmit data before signalattenuation affects the data delivery? （1）1) 100 meters2) 185 meters3) 300 meters4) 500 meters6. When using Category 5 UTP cable, which RJ-45 pin pairs are used to exchangedata between hosts on an Ethernet network? （2）1) 1 and 2; 4 and 52) 1 and 2; 3 and 63) 3 and 6; 7 and 84) 4 and 5; 7 and 8第八章1. John has been hired as the network administrator of a local company and hasdecided to add more hubs to the company's existing network. Which of the following has been caused by John's inexperience? （1）1) collision domain extended2) an increased number of collision domains3) increased network performance4) increased bandwidth5) extended bandwidth2. "CompA" is trying to locate a new computer named "CompB" on the network.Which of the following does "CompA" broadcast to find the MAC address of "CompB"? （2）1) MAC request2) ARP request3) ping4) Telnet5) proxy ARP3. Which of the following is a term associated with replacing hubs with switchesto increase the number of collision domains? （3）1) encapsulation2) latency3) segmentation4) layered model5) broadcast domain6) Extended4. The accumulation of traffic from which of the following can cause a networkcondition called broadcast radiation? (Choose three.) （3，5，6）1) anonymous FTP servers2) telnet sessions3) video over IP applications4) NAS services5) ARP requests6) RIP updates5. Which of the following describes the use of Spanning Tree Protocol (STP)? （4）1) resolve routing loops2) eliminate Split Horizon errors3) limit collisions4) resolve switching loops6. Which term describes the delay in time that occurs when a frame leaves itssource device and reaches its destination? （4）1) collision2) backoff3) attenuation4) latency5) broadcast7. Based on the graphic above, which of the following occurs as each host systemcomes on line in the topology? （2）1) The switch sends its MAC address to each host.2) The switch adds MAC address to the bridge table as each host sends a frame.3) Each host exchanges MAC addresses with each other.4) The switch listens for data traffic to block since the switch lacks an IP address. 8. Which devices segment collision domains? (Choose two.) （2，3）1) transceiver2) router3) switch4) hub5) media9. Which protocol is used to eliminate switching loops? （3）1) Transmission Control Protocol2) Routing Information Protocol3) Spanning Tree Protocol4) Interior Gateway Routing Protocol5) Internetworking Protocol10. Refer to the exhibit. A network associate needs to establish an Ethernetconnection between Host A and Host B. However, the distance between the two hosts is further than the cabling standards allow. Which two devices that operate at the physical layer of the OSI can be used to allow Host A and Host B to communicate? （2，5）1) switch2) hub3) bridge4) router5) repeater第九章1. Which term describes an ARP response by a router on behalf of a requestinghost? （3）1) ARP2) RARP3) Proxy ARP4) Proxy RARP2. Which protocol functions at the internet layer of the TCP/IP protocol suite? （4）1) File Transfer Protocol (FTP)2) Trivial File Transfer Protocol (TFTP)3) Transmission Control Protocol (TCP)4) Internet Protocol (IP)5) User Datagram Protocol (UDP)6) Simple Mail Transport Protocol (SMTP)3. Which of these workstation installation and setup tasks are concerned withnetwork access layer functions? (Choose two.) （2，4）1) configuring the e-mail client2) installing NIC drivers3) configuring IP network settings4) connecting the network cable5) using FTP to download application software updates4. Which part of an IP address identifies a specific device on a network? （4）1) first two octets2) third and fourth octets3) network portion4) host portion5) only the fourth octet5. Which of the following are features of the Internet Protocol (IP)? (Choose two.)（1，3）1) It is the most widely implemented global addressing scheme.2) It allows two hosts to share a single address on a local area network.3) It is a hierarchical addressing scheme allowing addresses to be grouped.4) It is only locally significant, used primarily on local area networks.6. Which of the following are useable Class A IP addresses with a default subnetmask? (Choose three.) （2，3，5）1) 127.0.39.12) 111.9.28.303) 123.1.2.1324) 128.50.38.25) 105.1.34.16) 0.23.92.37. Which application layer protocols use UDP at the transport layer? (Choose two.)（2，4）1) FTP2) SNMP3) Telnet4) DHCP5) SMTP第十章1. Which OSI layer encapsulates data into packets? （3）1) session2) transport3) network4) data link2. Which OSI layer defines the functions of a router? （3）1) physical2) data link3) network4) transport5) session3. Which of the following are Cisco proprietary routing protocols? (Choose two.)（2，6）1) RIPv22) IGRP3) OSPF4) BGP5) RIPv16) EIGRP4. A company with a Class B license needs to have a minimum of 1,000 subnetswith each subnet capable of accommodating 50 hosts. Which mask below is the appropriate one? （4）1) 255.255.0.02) 255.255.240.03) 255.255.255.04) 255.255.255.1925) 255.255.255.2245. A small company has a class C network license and needs to create five usablesubnets, each subnet capable of accommodating at least 20 hosts. Which of the following is the appropriate subnet mask? （3）1) 255.255.255.02) 255.255.255.1923) 255.255.255.2244) 255.255.255.2406. When a network administrator applies the subnet mask 255.255.255.248 to aClass A address, for any given subnet, how many IP addresses are available to be assigned to devices? （6）1) 10222) 5103) 2544) 1265) 306) 67. Host A is assigned the IP address 10.18.97.55 /21. How many more networkdevices can be assigned to this subnetwork if Host A is the only one that has an IP address assigned so far? （4）1) 2542) 5093) 10214) 20455) 40946) 81908.Refe r to the exhibit. The network administrator wants to create a subnet for thepoint-to-point connection between the two routers. Which subnetwork mask would provide enough addresses for the point-to-point link with the least number of wasted addresses?1) 255.255.255.1922) 255.255.255.2243) 255.255.255.2404) 255.255.255.2485) 255.255.255.2529. What is the correct number of usable subnetworks and hosts for the IP networkaddress 192.168.35.0 subnetted with a /28 mask?1) 6 networks / 64 hosts2) 14 networks / 32 hosts3) 14 networks / 14 hosts4) 30 networks / 64 hosts10. Which subnet masks would be valid for a subnetted Class B address? (Choosetwo.) （5，6）1) 255.0.0.02) 255.254.0.03) 255.224.0.04) 255.255.0.05) 255.255.252.06) 255.255.255.19211. Refer to the exhibit. How will the Fohi router dynamically learn routes to the192.168.16.16/28, 192.168.16.32/28, and 192.168.16.48/28 subnetworks? （3）1) with a static route2) with a routed protocol3) with a routing protocol4) with a directly connected route12. How many broadcast domains are shown in the diagram? （1）1) three2) four3) five4) six5) seven6) eight13. How many collision domains are shown in the diagram? （5）1) three2) four3) five4) six5) seven6) eight14. A router interface has been assigned an IP address of 172.16.192.166 with amask of 255.255.255.248. To which subnet does the IP address belong?1) 172.16.0.02) 172.16.192.03) 172.16.192.1284) 172.16.192.1605) 172.16.192.1686) 172.16.192.17615. Refer to the exhibit. Host A is sending data to Host B. Once R2 determines thatdata from Host A must be forwarded to R1 to reach Host B, which layer of the OSI model will R2 use to address and build the frames destined for R1?1) physical2) data link3) network4) transport5) session6) presentation16. Which type of address is 192.168.170.112/28?1) host address2) subnetwork address3) broadcast address4) multicast address17. Which type of address is 223.168.17.167/29?1) host address2) multicast address3) broadcast address4) subnetwork address18. Which combination of network id and subnet mask correctly identifies all IPaddresses from 172.16.128.0 through 172.16.159.255?1) 172.16.128.0 255.255.255.2242) 172.16.128.0 255.255.0.03) 172.16.128.0 255.255.192.04) 172.16.128.0 255.255.224.05) 172.16.128.0 255.255.255.19219. Refer to the exhibit. The internetwork in the exhibit has been assigned the IPaddress 172.20.0.0. What would be the appropriate subnet mask to maximize the number of networks available for future growth?1) 255.255.224.02) 255.255.240.03) 255.255.248.04) 255.255.252.05) 255.255.254.06) 255.255.255.0第十一章1. If a network administrator needed to download files from a remote server, whichprotocols could the administrator use to remotely access those files? (Choose two.) （3，5）1) NFS2) ASCII3) TFTP4) IMAP5) FTP6) UDP2. What is established during a connection-oriented file transfer betweencomputers? (Choose two.) （2，5）1) a temporary connection to establish authentication of hosts2) a connection used for ASCII or binary mode data transfer3) a connection used to provide the tunnel through which file headers aretransported4) a command connection which allows the transfer of multiple commands directlyto the remote server system5) a control connection between the client and server3. Which of the following protocols are used for e-mail transfer between clientsand servers? (Choose three.) （3，4，5）1) TFTP2) SNMP3) POP34) SMTP5) IMAP46) postoffice4. Which type of institution does the domain suffix .org represent? （4）1) government2) education3) network4) non-profit5. Which of the following services is used to translate a web address into an IPaddress? （1）1) DNS2) WINS3) DHCP4) Telnet6. Which part of the URL http://www.awsb.ca/teacher gives the name of thedomain? （4）1) www2) http://3) /teacher4) awsb.ca7. Which protocols are TCP/IP application layer protocols? (Choose two.) （2，4）1) UDP2) FTP3) IP4) SMTP5) TCP8. What are three characteristics of the TCP protocol? (Choose three.) （3，4，6）1) has less overhead than UDP2) is used for IP error messages3) forces the retransmission undelivered packets4) creates a virtual session between end-user applications5) carries the IP address of destination host in the TCP header6) is responsible for breaking messages into segments and reassembling9. Two peer hosts are exchanging data using TFTP. During the current session, adatagram fails to arrive at the destination. Which statement is true regarding the retransmission of the datagram? （2）1) Datagram retransmission requires user authentication.2) Datagram retransmission is controlled by the application.3) Datagram retransmission relies on the acknowledgements at transport layer.4) Datagram retransmission occurs when the retransmission timer expires in thesource host.案例学习1. 子网计算练习：Answer2. 子网号及广播地址计算练习Answer3. 子网规划练习：已知：给定一个C类地址201.16.5.0/24。

第一章：正确答案：2.4.5•解析：由于不需要使用网络设备和专用服务器，对等网络易于创建，复杂性更低，且成本更少。

而且对等网络也没有集中管理。

这种网络安全性更低，不可扩展，而且那些同时充当客户端和服务器的设备可能性能更差正确答案：1解析：正确答案： 3.5解析：选择网络介质的条件包括：所选介质可以成功传送信号的距离、要安装所选介质的环境、必须传输的数据量和速度以及介质和安装的成本。

正确答案：3和4解析：终端设备上的应用程序可以生成数据，更改数据内容并且负责启动封装过程。

正确答案：1和4解析：终端设备会发出通过网络传输的数据。

中间设备会在链路发生故障时通过备用路径传输数据，并且会过滤数据传输以增强安全性。

网络介质提供网络消息的传输通道。

正确答案：4解析：外联网是公司外部的人或企业合作伙伴访问数据的网络区域。

内部网只描述通常仅供内部人员访问的网络区域。

当设备连接到有线网络时，有线LAN 会受BYOD（自带设备）影响。

使用大学无线LAN 的设备多为平板电脑和智能手机。

大学生主要使用无线WAN 来访问他们的手机运营商网络。

.正确答案：2解析：由于通过Internet 可以联系在线供应商，所以家庭用户通过Internet 进行网上购物。

内联网基本上是仅供内部使用的局域网。

外联网是外部合作伙伴访问组织内部特定资源的网络。

家庭用户并不一定使用LAN 来访问Internet。

例如，PC 可以通过调制解调器直接连接到ISP。

正确答案：1解析：内部网这个术语用于表示一个组织的私有局域网和广域网连接。

内部网的设计旨在仅允许该组织的成员、员工或其他获得授权的人员进行访问。

正确答案：2和4解析：电缆和DSL 均能实现高带宽、始终联网，并提供到主机计算机或LAN 的以太网连接。

10正确答案：2和3解析：移动电话连接需要使用移动电话网络。

卫星连接通常用于家庭或企业外部不便使用物理布线的位置。

11正确答案：2解析：当对网络资源的请求超出了可用容量时，网络就会变得拥堵。

ccna考试题库最新版CCNA（Cisco Certified Network Associate）认证是全球范围内最受欢迎的网络工程师认证之一，具备CCNA认证可以证明一个人在建立、规划、运行、安装和配置中等规模的局域网和广域网方面的专业知识。

为了帮助广大考生顺利通过CCNA考试，不断更新的CCNA考试题库至关重要。

以下是最新版本的CCNA考试题库，希望对考生们有所帮助。

第一部分：网络基础知识1. 什么是OSI七层模型？简要介绍每一层的功能。

2. TCP和UDP之间有哪些区别？请分别举例说明。

3. 什么是IP地址？IP地址的类型有哪些？请列举并简要介绍各自的特点。

4. 什么是子网掩码？为什么在网络中使用子网掩码？5. 简述常见的网络设备有哪些，以及各自的功能与作用。

第二部分：路由和交换技术1. 路由器和交换机之间有何区别？请进行比较并指出各自的优势和劣势。

2. 什么是VLAN？VLAN的作用及在网络中的应用场景是什么？3. OSPF和EIGRP是两种常见的路由协议，请比较它们的特点并举例说明。

4. 请解释静态路由和动态路由的概念以及在网络中的应用。

5. 交换机在网络中扮演什么角色？交换机的MAC地址表是如何工作的？第三部分：网络安全和管理1. 网络安全的重要性是什么？请列举几种常见的网络安全威胁并介绍应对策略。

2. 什么是ACL（访问控制列表）？ACL的作用是什么？请给出一个ACL的配置示例。

3. VPN是什么？VPN的工作原理及在企业网络中的应用。

4. SNMP是网络管理中常用的协议，它的作用是什么？请解释SNMP中的几个重要概念。

5. 如何保护无线网络的安全？请列举几种方法。

第四部分：WAN技术1. 什么是WAN？WAN的主要特点是什么？2. PPP协议和HDLC协议分别是什么？请比较它们的异同。

3. 什么是Frame Relay？Frame Relay的工作原理及在WAN中的应用。

4. 请解释T1和E1的概念，以及它们在传输速率和应用方面的差异。

1当设备从一个网络或子网移至另一个网络或子网时，下列哪两项陈述是正确的？（选择两项）必须重新分配第 2 层地址。

不应改变默认网关地址。

设备使用同一个第 2 层地址仍可正常工作。

需要将其它端口号分配给应用程序和服务。

必须重新分配第 3 层地址才能与新的网络通信。

2请参见图示。

假设图示中的网络已收敛，即路由表和ARP 表均完整，主机 A 将在发往www 以太网帧目的地址字段中放入以下哪个MAC 地址？00-1c-41-ab-c0-0000-0c-85-cf-65-c000-0c-85-cf-65-c100-12-3f-32-05-af3数据链路层帧尾有何主要作用？定义逻辑拓扑提供介质访问控制支持帧错误检测传送帧的路由信息4请参见图示。

PC 正在向笔记本电脑发送帧。

离开RouterB 时，帧中包括的源MAC 地址和源MAC - PC源MAC - RouterA 的S0/0源MAC - RouterB 的Fa0/1源IP - PC源IP - RouterA 的S0/0源IP - RouterB 的Fa0/15在网络中实现第2 层协议时应该考虑哪三个因素？（选择三项）所选的第 3 层协议网络的地址范围传输层定义的PDU物理层实现要连接的主机数量网络层编址？介质共享应用进程逻辑拓扑中间设备的功能7以太网帧中的前导码有何作用？作为数据的填充位用于同步计时用于标识源地址。

用于标识目的地址。

8请参见图示。

流量从PC 路由到笔记本电脑时，会进行多少次CRC 计算？12468169有关物理拓扑和逻辑拓扑的陈述，下列哪一项正确？逻辑拓扑始终与物理拓扑相同。

物理拓扑与网络传输帧的方法有关。

物理信号路径是按数据链路层协议定义的。

逻辑拓扑由节点之间的虚拟连接组成。

10网络管理员有责任以图形精确表示公司网络线路和设备在建筑内的位置。

这种图是什么？逻辑拓扑物理拓扑电缆路径线路网接入拓扑11请参见图示。

下列哪项陈述描述了图示网络使用的介质访问控制方法？三个网络全部采用CSMA/CA。

CCNA思科考试答案（全）第 1 章考试1一家拥有10 名员工的小型公司使用单个LAN 在计算机之间共享信息。

哪种类型连接适合此公司？由当地电话服务提供商提供的拨号连接能够使公司方便且安全地连接员工的虚拟专用网络通过当地服务提供商建立的私有专用线路通过当地服务提供商提供的宽带服务（如DSL）答案：4解析：对于这种小型办公室，比较适合通过被称为数字用户线路(DSL) 的常见宽带服务实现Internet 连接，这种服务由当地的电话服务提供商提供。

由于员工人数很少，带宽的问题并不突出。

如果公司较大，在远程站点有分支机构，则专用线路会更加适合。

如果公司员工需要通过Internet 与公司联系，则采用虚拟专用网。

2哪种网络情况需要使用WAN？员工工作站需要获取动态分配的IP 地址。

员工在出差时需要通过VPN 连接到公司电子邮件服务器。

分支机构的员工需要与同一园区网络上的另一座建筑物内的公司总部共享文件。

员工需要访问托管在其建筑物内DMZ 中的公司Web 服务器上的网页。

答案：2解析：当出差的员工需要通过WAN 连接到公司电子邮件服务器时，VPN 将通过WAN 连接在员工笔记本电脑与公司网络之间创建一个安全隧道。

通过DHCP 获取动态IP 地址是LAN 通信的功能。

在企业园区的不同建筑物之间共享文件可通过LAN 基础设施来实现。

DMZ 是企业LAN 基础设施内一个受保护的网络。

3以下哪项描述了WAN 的特征？WAN 和LAN 在同一地理范围内运行，但有串行链路。

WAN 网络归运营商所有。

所有串行链路均被视为WAN 连接。

WAN 可提供到园区主干网的终端用户网络连接。

答案：2解析：WAN 可用于将企业LAN 互连到远程分支机构站点LAN 和远程工作人员站点。

WAN 归运营商所有。

虽然WAN 连接一般通过串行接口实现，但并不是所有串行链路均连接至WAN。

LAN（而非WAN）可在组织中提供终端用户网络连接。

4电路交换WAN 技术的两个常见类型是什么？（请选择两项。

1Refer to the exhibit. If all routers are running RIP version 2, why is there nothe 192.168.1.32/27 network?Rip version 2 does not send subnet masks in its updates.Router A is not setup with RIP as a routing protocol.Rip version 2 will auto summarize routes by default.Router B is not setup to advertise the 192.168.1.64/30 network.2Refer to the exhibit. Which command on which router will allow Router1 to lethe 192.168.0.0/20 network?Router1(config)# ip classlessRouter1(config-router)# no passive-interface serial 0/1/1Router2(config-router)# version 2Router2(config-router)# neighbor 10.0.0.23 What are two reasons to implement RIP version 2 rather than RIP version 1two.)RIP version 2 supports VLSM.RIP version 2 supports more than 16 routers.RIP version 2 supports classful (and not classless) routingRIP version 2 supports routing update authentication.RIP version 2 supports multi-areas.RIP version 2 uses the Dijkstra algorithm rather than the Bellman-Ford4 How are RIP v1 and RIP v2 similar to one another? (Choose three.)They both use hop count as a metric.They both have the same metric value for infinite distance.They both broadcast their updates to their neighbors.They both send subnet mask information in their updates.They both provide for authentication of update sources.They both use split horizon to prevent routing loops.5Refer to the exhibit. Routers East and West are configured using RIPv1. Boare sending updates about their directly connected routes. The East routerthe West router serial interface and West can ping the serial interface of EaHowever, neither router has dynamically learned routes from the other. Whlikely the problem?A gateway of last resort is required.Subnetting is not supported by RIPv1.VLSM is not supported by RIPv1.One of the routers needs a clock rate on the serial interface.6Refer to the exhibit. Which command will allow Router2 to learn about the192.168.16.0/28 network?Router1(config)# ip classlessRouter1(config-router)# network 192.168.16.0Router1(config-router)# no passive-interface serial 0/1/1Router2(config-router)# version 2Router2(config-router)# neighbor 10.0.0.27Refer to the exhibit. All routers are running RIP version 2. JAX is configuredadvertise the 10.0.0.0/24 network. CHI is configured to advertise the 172.16network. A network administrator enters the commands shown in the exhibchanges will occur in this network?The JAX router will ignore updates for the 172.16.0.0/16 network due tohorizon issues.The CHI router will install a route to the 192.168.0.0/16 network in its rouThe routing table for CHI will have the 192.168.0.0/16 route but it will hanext to the route.The ORL router will apply a 255.255.0.0 subnet mask to all networks inupdates it forwards.8Refer to the exhibit. A technician needs to add a new loopback interface to tfunctionality and network design. The technician enters the following set ofcommands on the router:Sanford(config)# interface loopback1Sanford(config-if)# ip address 192.168.6.62 255.255.255.252Why does the router respond with an error?The router does not allow loopback interface configurations.This mask can not be used with this class of addresses.Classless routing must be configured before this address can be addedThe network address for Loopback1 overlaps with an already configureaddress.The router is over the limit for the maximum paths that can be providedrouting table.9 What is the maximum network diameter permitted by the default metric of R15 hops16 hops100 hops120 hops255 hops10 What are two functions of the network command used when configuring roprotocols? (Choose two.)identifies which networks will be included in the routing updatesidentifies the hosts addresses that can be summarized in the networkused to list all addresses for remote and local networksdetermines which subnet mask to apply to routing updatesdetermines which interfaces can send and receive routing updates11Refer to the exhibit. What can be concluded from the output shown in the eThe routing table is limited to 2 routes.The LAN interfaces are participating in the routing process.One update has been sent out of each serial interface and 2 have beenThe no auto-summary has not been configured on this router.12 A network administrator has been told that the company IP address infrastrmust adhere to RFC 1918. What three IP address ranges from RFC 1918 cadministrator use on the network? (Choose three.)10.0.0.0/8127.0.0.0/8169.254.0.0/16172.16.0.0/12192.168.0.0/16209.165.201.0/2713Refer to the exhibit. All routers are running RIPv1. What changes will occurrouting table of router B if a loopback interface with an address of 10.16.1.1configured on router B?Routes to the 10.16.1.0/27, 10.16.1.64/27, and 10.16.1.128/27 networkadded.A connected route to the 10.16.1.128/27 network is added.A third route to the 10.0.0.0/8 network with RIPv1 as the source is addeThe 10.0.0.0/8 route is dropped immediately from the routing table after is configured.14 A network administrator installed four new routers that are running RIPv2. Ra boundary router in the RIPv2 network and has a default route configured.network has converged, the network administrator enters Router1(config-rodefault-information originate on Router1. How will this affect the networkprevents Router1 from forwarding updates about networks that are notconnectedcauses all routers in the network to synchronize routing updates with Rforces Router1 to become the primary or designated router (DR) for updpropagates the default route to all routers in the network15Refer to the exhibit. The exhibited network contains a mixture of Cisco androuters. The command debug ip rip was entered on the JAX router. All rourunning the same version of RIP. Router CHI and Router ORL are not ablethe 192.168.1.16/28 network. What is a possible solution to this problem?Enable split horizon in the network.Configure RIPv2 on routers.Add network 192.168.1.0 to the RIP configuration on the JAX router.Configure JAX Fa0/0 as a passive interface.Enable the Serial0/0/0 interface on the JAX router.Change the IP address on the Fa0/0 interface of the JAX router to 192.1 16 What field was added to the RIP message header by RFC 1723 to add supVLSM and CIDR?subnet maskdestination port numberaddress family identifiersource and destination IP addresses17Refer to the exhibit. What effect will the commands that are shown have onupdates for Router1?Only version 2 updates are sent to 255.255.255.255.Only version 2 updates are sent to 224.0.0.9.Both version 1 and version 2 updates are sent to 224.0.0.9.Both version 1 and version 2 updates are sent to 255.255.255.255.18Refer to the exhibit. RIPv1 is configured as the routing protocol for the netwshown. The following commands are used on each router:router ripnetwork 10.0.0.0network 172.16.0.0When this configuration is complete, users on the LAN of each router are uaccess the remote LANs. Why?The network statements are configured incorrectly.A routing loop has been created.RIPv1 is unable to route to discontiguous subnets of a major network.RIPv1 is unable to route networks with a /24 subnet mask.19RIPv2 is the configured routing protocol on the routers in a network. The co Router(config-router)# no version 2 is entered on the routers. What effectentering this command have on routing updates?Subnet masks will be added to the routing updates.Routing updates will be sent out using multicast address 224.0.0.9.Version 1 and 2 updates will be received and the version 2 updates willsent.The RIP routing process will be removed from the router and routing upnot be forwarded.Scoring RuleFor: correctnessof response。

第7章机器学习参考答案7-6 设训练例子集如下表所示：序号属性分类x1x21 T T +2 T T +3 T F -4 F F +5 F T _6 F T _请用ID3算法完成其学习过程。

解：设根节点为S，尽管它包含了所有的训练例子，但却没有包含任何分类信息，因此具有最大的信息熵。

即：H(S)= - (P(+)log2 P(+) + P(-)log2 P(-))式中P(+)=3/6，P(-)=3/6分别是决策方案为“+”或“-”时的概率。

因此有H(S)= - ((3/6)log2(3/6) + (3/6)log2(3/6))=1按照ID3算法，需要选择一个能使S的期望熵为最小的一个属性对根节点进行扩展，因此我们需要先计算S关于每个属性的条件熵：H(S|x i)= ( |S T| / |S|)* H(S T) + ( |S F| / |S|)* H(S F)其中，T和F为属性x i的属性值，S T和S F分别为x i=T或x i=F时的例子集，|S|、| S T|和|S F|分别为例子集S、S T和S F的大小。

下面先计算S关于属性x1的条件熵：在本题中，当x1=T时，有：S T={1，2，3}当x1=F时，有：S F={4，5，6}其中，S T和S F中的数字均为例子集S中的各个例子的序号，且有|S|=6，| S T |=| S F |=3。

由S T可知，其决策方案为“+”或“-”的概率分别是：P ST(+)=2/3P ST (-)=1/3因此有：H(S T)= - (P ST (+)log2 P ST (+) + P ST (-)log2 P ST (- ))= - ((2/3)log2(2/3) + (1/3)log2(1/3))=0.9183再由S F可知，其决策方案为“+”或“-”的概率分别是：P SF (+)=1/3P SF (-)=2/3则有：H (S F)= - (P SF (+)log2 P SF (+) + P SF (-)log2 P SF (- ))= - ((1/3)log2(1/3)+ (2/3)log2(2/3))=0.9183将H(S T)和H (S F)代入条件熵公式，有：H(S|x1)=(|S T|/|S|)H(S T)+ (|S F|/|S|)H(S F)=(3/6)﹡0.9183 + (3/6)﹡0.9183=0.9183下面再计算S关于属性x2的条件熵：在本题中，当x2=T时，有：S T={1，2，5，6}当x2=F时，有：S F={3，4}其中，S T和S F中的数字均为例子集S中的各个例子的序号，且有|S|=6，| S T |=4，| S F |=2。

25. QuestionWhat is the binary equivalent of the decimal number 232?o 11101000o 11000110o 10011000o 1111001026. QuestionWhat is the decimal equivalent of the binary number 10010101?o149o 157o 168o 1921. QuestionHow many bits are in an IPv4 address?o32o 64o 128o 2562. QuestionWhich two parts are components of an IPv4 address? (Choose two.)o subnet portiono network portiono logical portiono host portiono physical portiono broadcast portion3. QuestionWhat does the IP address 172.17.4.250/24 represent?o network addresso multicast addresso host addresso broadcast address4. QuestionWhat is the purpose of the subnet mask in conjunction with an IP address?o to uniquely identify a host on a networko to identify whether the address is public or privateo to determine the subnet to which the host belongso to mask the IP address to outsiders5. QuestionWhat subnet mask is represented by the slash notation /20?o 255.255.255.248o 255.255.224.0o 255.255.240.0o 255.255.255.0o 255.255.255.1926. QuestionA message is sent to all hosts on a remote network. Which type of message isit?o limited broadcasto multicasto directed broadcasto unicast7. QuestionWhat are three characteristics of multicast transmission? (Choose three.)o The source address of a multicast transmission is in the range of 224.0.0.0 to 224.0.0.255.o A single packet can be sent to a group of hosts.o Multicast transmission can be used by routers to exchange routing information.o The range of 224.0.0.0 to 224.0.0.255 is reserved to reach multicast groups on a local network.o Computers use multicast transmission to request IPv4 addresses.o Multicast messages map lower layer addresses to upper layer addresses.8. QuestionWhich three IP addresses are private ? (Choose three.)o 10.1.1.1o 172.32.5.2o 192.167.10.10o 172.16.4.4o 192.168.5.5o 224.6.6.69. QuestionWhich two IPv4 to IPv6 transition techniques manage the interconnection of IPv6 domains? (Choose two.)o trunkingo dual stacko encapsulationo tunnelingo multiplexing10. QuestionWhich of these addresses is the shortest abbreviation for the IP address:3FFE:1044:0000:0000:00AB:0000:0000:0057?o 3FFE:1044::AB::57o 3FFE:1044::00AB::0057o 3FFE:1044:0:0:AB::57o 3FFE:1044:0:0:00AB::0057o 3FFE:1044:0000:0000:00AB::57o 3FFE:1044:0000:0000:00AB::005711. QuestionWhat type of address is automatically assigned to an interface when IPv6 is enabled on that interface?o global unicasto link-localo loopbacko unique local12. QuestionWhat are two types of IPv6 unicast addresses? (Choose two.)o multicasto loopbacko link-localo anycasto broadcast13. QuestionWhat are three parts of an IPv6 global unicast address? (Choose three.)o an interface ID that is used to identify the local network for a particular hosto a global routing prefix that is used to identify the network portion of the address that has been provided by an ISPo a subnet ID that is used to identify networks inside of the local enterprise siteo a global routing prefix that is used to identify the portion of the network address provided by a local administratoro an interface ID that is used to identify the local host on the network14. QuestionAn administrator wants to configure hosts to automatically assign IPv6 addresses to themselves by the use of Router Advertisement messages, but also to obtain the DNS server address from a DHCPv6 server. Which address assignment method should be configured?o SLAACo stateless DHCPv6o stateful DHCPv6o RA and EUI-6415. QuestionWhich protocol supports Stateless Address Autoconfiguration (SLAAC) for dynamic assignment of IPv6 addresses to a host?o ARPv6o DHCPv6o ICMPv6o UDP16. QuestionWhich two things can be determined by using the ping command? (Choose two.)o the number of routers between the source and destination deviceo the IP address of the router nearest the destination deviceo the average time it takes a packet to reach the destination and for theresponse to return to the sourceo the destination device is reachable through the networko the average time it takes each router in the path between source and destination to respond17. QuestionWhat is the purpose of ICMP messages?o to inform routers about network topology changeso to ensure the delivery of an IP packeto to provide feedback of IP packet transmissionso to monitor the process of a domain name to IP address resolution 18. QuestionWhat is indicated by a successful ping to the ::1 IPv6 address?o The host is cabled properly.o The default gateway address is correctly configured.o All hosts on the local link are available.o The link-local address is correctly configured.o IP is properly installed on the host.19. QuestionA user is executing a tracert to a remote device. At what point would a router,which is in the path to the destination device, stop forwarding the packet?o when the router receives an ICMP Time Exceeded messageo when the RTT value reaches zeroo when the host responds with an ICMP Echo Reply messageo when the value in the TTL field reaches zeroo when the values of both the Echo Request and Echo Reply messages reach zero20. QuestionWhat field content is used by ICMPv6 to determine that a packet has expired?o TTL fieldo CRC fieldo Hop Limit fieldo Time Exceeded field21. QuestionFill in the blank.The decimal equivalent of the binary number 10010101is 149 .22. QuestionFill in the blank.The binary equivalent of the decimal number 232 is 1110100023. QuestionFill in the blank.What is the decimal equivalent of the hex number 0x3F? 63。

ccna考试题及答案1. 以下哪项是网络层的功能？A. 路由选择B. 错误检测C. 流量控制D. 封装数据包答案：A2. 在OSI模型中，哪一层负责在网络中传输数据？A. 应用层B. 传输层C. 会话层D. 网络层答案：D3. 以下哪个协议是用于在IP网络中发现网络设备的？A. ARPB. RARPC. ICMPD. OSPF答案：A4. 在TCP/IP模型中，哪一层与OSI模型的传输层相对应？A. 应用层B. 互联网层C. 网络接口层D. 传输层答案：D5. 以下哪个地址是一个有效的IPv4地址？A. 192.168.1.256B. 192.168.1.1C. 10.0.0.0D. 172.16.300.1答案：B6. 在配置路由器时，以下哪个命令用于进入全局配置模式？A. enableB. configure terminalC. privileged execD. user exec答案：B7. 以下哪个命令用于在Cisco设备上显示当前配置？A. show running-configB. show startup-configC. show configD. show current-config答案：A8. 在Cisco设备上，以下哪个命令用于保存当前的配置到启动配置文件？A. copy running-config startup-configB. copy startup-config running-configC. save running-configD. save startup-config答案：A9. 以下哪个命令用于在Cisco设备上查看所有接口的状态？A. show interfacesB. show ip interface briefC. show interface statusD. show running-config interface答案：B10. 在Cisco设备上，以下哪个命令用于关闭接口？A. shutdownB. no shutdownC. disableD. no enable答案：A11. 以下哪个命令用于在Cisco设备上启用接口？A. shutdownB. no shutdownC. disableD. no enable答案：B12. 在配置静态路由时，以下哪个命令用于指定下一跳地址？B. ip static-routeC. route ipD. static-route ip答案：A13. 以下哪个命令用于在Cisco设备上清除ARP表？A. clear arp-cacheB. clear arpC. clear arp tableD. clear ip arp答案：D14. 在配置动态路由协议时，以下哪个命令用于在接口上启用RIP？A. ip rip enableB. ip rip receiveD. network rip答案：C15. 以下哪个命令用于在Cisco设备上查看RIP路由表？A. show ip ripB. show ip route ripC. show ripD. show ip protocols答案：B16. 在配置EIGRP时，以下哪个命令用于指定自动汇总？A. metric weightsB. auto-summaryC. network auto-summaryD. no auto-summary答案：B17. 以下哪个命令用于在Cisco设备上查看EIGRP邻居？A. show ip eigrp neighborsB. show eigrp neighborsC. show ip eigrpD. show eigrp interfaces答案：A18. 在配置OSPF时，以下哪个命令用于指定路由器ID？A. router-idB. router ospfC. networkD. area答案：A19. 以下哪个命令用于在Cisco设备上查看OSPF路由表？A. show ip ospfB. show ip ospf databaseC. show ospfD. show ip route ospf答案：D20. 在配置VLAN时，以下哪个命令用于创建一个新的VLAN？A. vlan databaseB. configure terminalC. vlan [vlan-id]D. new-vlan答案：C21. 以下哪个命令用于将接口分配给VLAN？A. switchport mode accessB. switchport mode trunkC. switchport access vlan [vlan-id]D. switchport trunk vlan [vlan-id]答案：C22. 在配置交换机时，以下哪个命令用于将接口设置为Trunk 模式？A. switchport mode accessB. switchport mode trunkC. switchport access vlan [vlan-id]D. switchport trunk vlan [vlan-id]答案：B23. 以下哪个命令用于在Cisco设备上查看VLAN配置？A. show vlanB. show vlan briefC. show vlan detailD. show vlan all答案：B24. 在配置VTP时，以下哪个命令用于将交换机设置为VTP服务器模式？A. vtp mode serverB. vtp mode clientC. vtp mode transparentD. vtp mode off答案：A25. 以下哪个命令用于在Cisco设备上查看VTP状态？A. show vtp statusB. show vtp statisticsC. show vtp passwordD. show vtp configuration答案：A26. 在配置STP时，以下哪个命令用于设置根桥？A. spanning-tree root primaryB. spanning-tree root secondaryC. spanning-tree root primary [priority]D. spanning-tree root secondary [priority]答案：C27. 以下哪个命令用于在Cisco设备上查看STP状态？A. show spanning-treeB. show spanning-tree detailC. show spanning-tree summaryD. show spanning-tree interface答案：A28. 在配置VLAN Trunking Protocol (VTP) 时，以下哪个命令用于设置VTP域名？A. vtp domain [domain-name]B. vtp password [password]C. vtp mode [mode]D. vtp version [version]答案：A29. 以下哪个命令用于在Cisco设备上查看当前的VTP版本？A. show vtp statusB. show vtp statisticsC. show vtp passwordD. show vtp configuration答案：A30. 在配置端口安全时，以下哪个命令用于限制接口上可以学习到的最大MAC地址数量？A. switchport port-security maximum [mac-count]B. port-security maximum [mac-count]C. switchport port-security violation restrictD. port-security violation shutdown答案：A这些题目和答案仅供学习和参考之用，实际的CCNA考试内容和形式可能会有所不同。

Chapter7 Virtual LANs(VLANs)VLAN Basics如何在1个交换性的网络里,分割广播域呢?答案是创建VLAN.VLAN是连接到定义好了的switch的端口的网络用户和资源的逻辑分组.给不同的子网分配不同的端口,就可以创建更小的广播域.默认情况下,在某个VLAN中的主机是不可以与其他VLAN通信的,除非你使用router来创建VLAN间的通信VLAN的一些特点:1.网络的增加,移动和改变,只需要在适当的VLAN中配置合适的端口2.安全,因为不同VLAN的用户不能互相通信,除非依靠router来做VLAN间的通信3.因为VLAN可以被认为是按功能划分的逻辑分组,所以VLAN和物理位置,地理位置无关4.VLAN增加安全性5.VLAN增加广播域的数量,而减小广播域的大小Broadcast Control每种协议都会有广播的现象发生,至于发生不频率,次数,一般由以下几点决定:1.协议类型2.在网络上运行的应用程序3.这些服务如何的被使用Security安全性是VLAN的1大特点,不同VLAN的用户不能互相通信,除非依靠router来做VLAN 间的通信Flexibility and ScalabilityVLAN的灵活性和可扩展性:1.可以不管物理位置如何,把适当的端口分配到适当的 VLAN中就可以了.可以把VLAN 理解正下面的样子:2.当VLAN增加的太大以后,你可以划分更多的VLAN,来减少广播消耗掉更多带宽的影响,在VLAN中的用户越少,被广播影响的就越少，来比较下下面2个图,明显可以发现,图2,即VLAN的具有更高的灵活性和可扩展性,如下:VLAN Memberships手动由管理员分配端口划分的VLAN叫静态VLAN(static VLAN);使用智能管理软件,动态划分VLAN的叫动态VLAN(dynamic VLAN)Static VLANs静态VLAN:静态VLAN安全性较高,手动划分端口给VLAN,和设备的物理位置没什么关系.而且,每个VLAN中的主机必须拥有正确的IP地址信息,如VLAN2配置为172.16.20.0/24Dynamic VLANs动态VLAN:使用智能管理软件,可以基于MAC地址,协议,甚至应用程序来动态创建VLAN.Cisco设备管理员可以使用VLAN管理策略服务器(VLAN Management Policy Server,VMPS)的服务来建立个MAC地址数据库,来根据这个动态创建VLAN,VMPS数据库把MAC地址映射VLAN上Identifying VLANs当帧在网络中被交换,switches根据类型对其跟踪,加上根据硬件地址来判断如何对它们进行操作.有1点要记住的是:在不同类型的连接中,帧被处理的方式也不一样要交换环境中的2种连接类型:1.access links:指的是只属于一个VLAN,且仅向该VLAN转发数据帧的端口,也叫做native VLAN.switches把帧发送到access-link设备之前,移去任何的VLAN信息.而且access-link设备不能与VLAN外通信,除非数据包被路由。

ERouting Chapter 1 - CCNA Exploration: 路由协议和概念 (版本1口令可用于限制对 Cisco IOS 所有或部分内容的访问。

请选择可以用口令保护的模式和接口。

（选择三项。

）VTY 接口控制台接口特权执行模式2路由器从相连的以太网接口收到消息后，会更改哪项报头地址，再将消息从另一个接口发送出去第 2 层源地址和目的地址3请参见图示。

网络管理员已经为路由器连接到直连网络的接口配置了如图所示的 IP 地址。

从路由器 ping 相连网络上的主机口之间相互 ping 都会遭到失败。

此问题最可能的原因是什么必须使用no shutdown命令启用接口。

4请参见图示。

主机 A ping 主机 B。

当 R4 收到对以太网接口的 ping 时，哪两块报头信息包括在内（选择两项。

）目的 IP 地址：目的 MAC 地址：5网络管理员刚把新配置输入 Router1。

要将配置更改保存到 NVRAM，应该执行哪一条命令Router1# copy running-config startup-config6您需要配置图中所示的串行连接，必须在 Sydney 路由器上发出以下哪条配置命令才能与 Melbourne 站点建立连接（选择三Sydney(config-if)# ip addressSydney no shutdownSydney(config-if)# clock rate 560007请参见图示。

从路由器的运行配置输出可得出什么结论显示的命令决定了路由器的当前运行情况。

8请参见图示。

在主机 2 连接到 LAN 上的交换机后，主机 2 无法与主机 1 通信。

导致此问题的原因是什么主机 1 和主机 2 位于不同的网络中。

9输入以下命令的作用是什么R1(config)# line vty 0 4R1(config-line)# password check123R1(config-line)# login设置通过 Telnet 连接该路由器时使用的口令10以下哪一项正确描述了路由器启动时的顺序加载 bootstrap、加载 IOS、应用配置11加载配置文件时的默认顺序是怎样的NVRAM、TFTP、CONSOLE12请参见图示。

Exam Code: 640-607CCNA7. Layer-2 Switching7.1 Before Layer-2 SwitchingBefore switch is installed, all machines are connected to hubs. They are in the same collision domain and hence share the same bandwidth. If the number of machines are increased, the collision rate will be increased so as the efficiency.After switch is installed, each hub is connected to a port in the switches. Assuming each hub serves the network connection for a floor, each floor is now in the same collision domain and sharing the bandwidth. The efficiency is much better than the all hubs method.A typical switched network design:7.2 Switching ServicesLayer-2 switching is hardware based (ASIC) that fills up its filter table by using the source MAC address of the incoming frames and make switching decision by using the destination MAC address. Hence, Layer-2 switch provide wire speed switching capability with low latency and low cost. Layer-2 switch can be thought as a multiport bridge because it breaks up collision domain (therefore increases bandwidth). You can then create a flatter network design with more network segments than the 10BaseT shared networks.Layer-2 switch and bridge are much faster than routers because they don’t need to read the Network layer header information. Instead, they look at the frame’s MAC address before deciding to either forward the frame or drop it.7.3 Limitations of Layer-2 SwitchingTwo considerations:1)Break up the collision domains correctly(switches and bridges don’t break up broadcast domain)2)80% traffics are in local segment.7.4 Bridging vs LAN SwitchingItem: Bridge SwitchFiltering decision Software based Hardware basedSpanning tree instances One ManyPorts One or two ManyBroadcast frames handling Forward ForwardForwarding decision L2 Address L2 Address7.5 Three Switch Functions at Layer 27.5.1 Address LearningLearn the Source MAC address from the incoming frames received on an interface to a MAC database called a forward/filter tableStep1: Host A send a frame to Host BStep2: The switch add the source MAC address of Host A into its filter tableStep3: Since the filter table does not have any entry of Host B, the frame will be forwarded to all ports.Step4: Host B response the frame. The switch will also add the source MAC address of Host B into its filter table.The filter table now contains two entries. When host A sends another frame to host B, since the entry is found in the filter table, the frame will only be forwarded to E0/1. Host C and D will never see any frames between host A and B.7.5.2 Forward/filter decisionsThe destination MAC address of an incoming frame is compared to the filter table. If an entry is matched, the frame will be forwarded to the corresponding exit port. Otherwise, the frame will be forwarded to all ports.7.5.3 Loop avoidanceRedundant links is used to prevent network failures in the event of one link stops working. However, it creates network loops as below:When there is no loop avoidance scheme, the broadcast frame will reach segment 2 through switch A. The frame goes into Segment2 side of switch B and then goes back into segment 1 again. The process is repeated between segment 1 and segment 2. Switch A and B flood broadcasts endlessly throughout the network. This is called broadcast storm. The MAC address of the sender is updated in the filter table of the switch between Segment 1 and Segment 2. It finally causes the switch to be failed to forward a frame. This is called thrashing the MAC table 7.6 Spanning Tree ProtocolSpanning Tree Protocol is created by Digital Equipment Corporation (DEC) and is standardized by IEEE called 802.1D. All Cisco switch run the IEEE 802.1D version of STP. The aim of the STP is to stop network loops in layer-2 network (bridges or switches). STP uses the spanning-tree algorithm (STA) to create a topology database, then search out and destroy redundant links.7.6.1 Spanning-Tree Operations7.6.1.1 Selecting the Root BridgeA root bridge is the bridge with the lowest (best) bridge ID. The ID is 8 bytes long, and includes both the priority(2 bytes) and the MAC address (6 bytes) of the device. The default priority on all devices running the IEEE STP version is 32,768. If two switches or bridges have the same priority value, then the MAC address becomes the tie breaker for figuring out which one has the lowest (best) ID.BPDU (Bridge Protocol Data Unit) are exchanged between switches to select the root switch. They are sent every 2 seconds out all active ports on a bridge/switch, and the bridge with the lowest (best) bridge ID is elected as the root bridge. You can change the bridge’s ID so that it will become a root bridge automatically.7.6.1.2 Selecting the Designated (選定) PortDesignated Port is either a root port or a port that has been determined as having the best (lower) path cost to the root bridge. If more than one link is connected to the root port, then port cost becomes the factor used to determine which port will be the root port. The STP cost is an accumulated total path cost based on the available bandwidth of each of the links.Typical Cost of Different Ethernet Networks7.6.1.3 Spanning-Tree Port StatesBPDU State Data Frames Rx Tx Transition TimeBlocking Not FWD Y N 20s (Max Age)Listening Not FWD Y Y 15s (Fwd Delay)Learning Rx but not FWD Y Y 15s (Fwd Delay)Forwarding FWD Y Y --Disabled NotFWD N N --Blocking: A blocked port won’t forward frames; it just listens to BPDUs. All ports are in blocking state by default when the switch is powered up.Listening: The port listens to BPDUs to make sure no loops occur on the network before passing data frames. Learning: The switch port listens to BPDUs and learns all the paths in the switched network. It also learns MAC addresses and builds a filter table but does not forward frames.Forwarding: The port sends and receives all data on the bridged port.Disabled: A port in the disabled state does not participate in the frame forwarding or STP. A port in the disabled state is virtually nonoperational.Spanning-tree port state Demonstration:switchhubBoth port 11 and 12 of hub and switch are connected to each other. With both port 11 and 12 are enabled, the spanning-tree will put port 12 into blocking state.To show the state transition from blocking state into forwarding state:Port 11 of the switch will be shutdown administratively.1)Port 12 will remain in the blocking state for 20 seconds (Max age).2)The port will be changed from blocking state into listening state for 15 seconds (Fwd delay).3)The port will be changed from listening state into learning state for 15 seconds (Fwd delay)4)The port will be changed from learning state to forwarding state.To show the state transistion from forwarding state into blocking state:Port 11 of the switch will be brought up administratively.1)Port 12 will be in blocking state at once. Port 11 will be in the listening state immediately for 15 seconds (Fwddelay)2)The port will be changed from listening state into learning state for 15 seconds (Fwd delay)3)The port will be changed from learning state to forwarding state.Command for showing the timer of “max age” and “fwd delay”:1900#show spantreeVLAN1 is executing the IEEE compatible Spanning Tree Protocol Bridge Identifier has priority 32768, address 0010.F628.5940Configured hello time 2, max age 20, forward delay 15Current root has priority 32768, address 0010.F628.5940Root port is N/A, cost of root path is 0Topology change flag not set, detected flag not setTopology changes 7, last topology change occured 0d00h02m46s agoopology ch ge 8960Times: hold 1, t anhello 2, max age 20, forward delay 15Timers: hello 2, topology change 35, notification 2…….Port Ethernet 0/11 of VLAN1 is ForwardingPort path cost 100, Port priority 128Designated root has priority 32768, address 0010.F628.5940Designated bridge has priority 32768, address 0010.F628.5940 Designated port is Ethernet 0/11, path cost 0Timers: message age 20, forward delay 15, hold 1--More--Port Ethernet 0/12 of VLAN1 is BlockingPort path cost 100, Port priority 128Designated root has priority 32768, address 0010.F628.5940Designated bridge has priority 32768, address 0010.F628.5940 Designated port is Ethernet 0/11, path cost 0Timers: message age 20, forward delay 15, hold 17.6.1.4 ConvergenceConvergence occurs when bridges and switches have transitioned to either the forwarding or blocking modes. No data frames is forwarded during this time. It usually takes 50 seconds to go from blocking => listening => learning => forwarding state.7.6.2 Spanning-Tree ExampleAssume that all switches are having priority of 32,768. Since Switch A has the lowest MAC address, it gets to be the root bridge.To determine the root port on Switch B and C, just follow the connection to the root bridge. Each direct connection to the root bridge will be a root port (shortest path to the root bridge), so it will become designated (forwarding mode).On switches D and E, the ports connected to Switches B and C are Switches D and E’s closest ports to the root bridge (lowest cost), so those ports are the root ports and in forwarding mode (designated).To prevent network loop, we need to block port in Switch D or E. Since the connection from Switches D and E to Switches B and C are root ports, they can’t be blocked. Next, the bridge ID is used to determine designated and non-designated ports. Because Switch D has the lowest (best) bridge ID, Switch E’s port to Switch D will become non-designated (blocking), and Switch D’s connection to Switch E will be designated (forwarding).7.7 LAN Switch Types7.7.1 Cut-through (Real Time)Frames are forwarded as soon as it reads the destination address and determines the outgoing interface.7.7.2 FragmentFree (Modified Cut-Through)It is a modified form of cut-through switching, in which the switch waits for the collision window (64 bytes) to pass before forwarding. It provides better error checking than the cut-through mode with nearly no increase in latency. It’s the default mode for 1900 switch.7.7.3 Store-and-ForwardIt is Cisco’s primary LAN switching method. Frames are copied into the onboard buffers and then compute the CRC. Latency varies with the length of the frames. Frames are discarded if it contains a CRC error, or too short ( < 64 bytes including CRC) or too long ( > 1518 bytes including CRC). Frames are forwarded by looking up the filter table in order to find the correct outgoing interface. This is the mode used by Catalyst 5000 series switches, but you can modify it.7.8 Configuration of 1900 SwitchCatalyst 1900 Management ConsoleCopyright (c) Cisco Systems, Inc. 1993-1998All rights reserved.Enterprise Edition SoftwareEthernet Address: 00-10-F6-28-59-40PCA Number: 73-2240-03PCA Serial Number: SAD01470640Model Number: WS-C1912-ENSystem Serial Number: FAA0149W0BTPower Supply S/N:Power Supply P/N:PCB Serial Number:-------------------------------------------------1 user(s) now active on Management Console.User Interface Menu[M] Menus[K] Command Line[I] IP ConfigurationEnter Selection: K Å Change to Command Line Interface modeCLI session with the switch is open.To end the CLI session, enter [Exit].>enable#conf tEnter configuration commands, one per line. End with CNTL/Z(config)#hostname 19001900(config)#enable password level 1 todd Å User mode password1900(config)#enable password level 15 toddl Å Enable mode password1900(config)#exit1900# sh ipÅ Show the IP address of the switch (don’t mix up with interface address of router)IP Address: 0.0.0.0Subnet Mask: 0.0.0.0Default Gateway: 0.0.0.0Management VLAN: 1Domain name:Name server 1: 0.0.0.0Name server 2: 0.0.0.0HTTP server : EnabledHTTP port : 80RIP : Enabled1900#conf tEnter configuration commands, one per line. End with CNTL/Z1900(config)#ip address 172.16.10.16 255.255.255.0 Å IP Address of the Switch1900(config)#ip default-gateway 172.16.10.1 Å Default Gateway1900(config)#int e0/11900(config-if)#description Finance_VLAN Å Give a name to a port1900(config)#int f0/261900(config-if)#description trunk_to_Building_4nvram Å Erase Switch Configuration1900#deleteThis command resets the switch with factory defaults. All systemparameters will revert to their default factory settings. All staticand dynamic addresses will be removed.Reset system with factory defaults, [Y]es or [N]o? Yes7.9 Configuration of 2950 SwitchSwitch(config)#hostname 29502950(config)#enable password todd Å User mode password2950(config)#enable secret todd Å Enable mode passwordThe enable secret you have chosen is the same as your enable password.This is not recommended. Re-enter the enable secret.2950(config)#enable secret toddl2950(config)#int vlan 12950(config-if)#ip address 172.16.10.17 255.255.255.0 Å IP Address of the Switch (in interface vlan 1) 2950(config-if)#no shut2950(config-if)#exit2950(config)#ip default-gateway 172.16.10.1 Å Default Gateway (in global configuration mode) 2950(config)#int f0/12950(config-if)#description Sales Printer Å Give a name to a port2950(config-if)#int f0/122950(config-if)#description Connection to backbone2950(config-if)#endstart Å Erase Switch Configuration2950#eraseErasing the nvram filesystem will remove all configuration files! Continue? [confirm][OK]Erase of nvram: complete2950#。

计算机⽹络⾃顶向下第七版第七章答案Computer Networking: A Top-Down Approach,7th Edition计算机⽹络⾃顶向下第七版Solutions to Review Questions and ProblemsChapter 7 Review Questions1.In infrastructure mode of operation, each wireless host is connected to the largernetwork via a base station (access point). If not operating in infrastructure mode, a network operates in ad-hoc mode. In ad-hoc mode, wireless hosts have noinfrastructure with which to connect. In the absence of such infrastructure, the hosts themselves must provide for services such as routing, address assignment, DNS-like name translation, and more.2.a) Single hop, infrastructure-basedb) Single hop, infrastructure-lessc) Multi-hop, infrastructure-basedd) Multi-hop, infrastructure-less3.Path loss is due to the attenuation of the electromagnetic signal when it travelsthrough matter. Multipath propagation results in blurring of the received signal at the receiver and occurs when portions of the electromagnetic wave reflect off objects and ground, taking paths of different lengths between a sender and receiver. Interference from other sources occurs when the other source is also transmitting in the samefrequency range as the wireless network.4.a) Increasing the transmission powerb) Reducing the transmission rate5.APs transmit beacon frames. An AP’s beacon frames will be transmitted over one ofthe 11 channels. The beacon frames permit nearby wireless stations to discover and identify the AP.6.False7.APs transmit beacon frames. An AP’s beacon frames will be transmitted over one ofthe 11 channels. The beacon frames permit nearby wireless stations to discover and identify the AP.8.False9.Each wireless station can set an RTS threshold such that the RTS/CTS sequence isused only when the data frame to be transmitted is longer than the threshold. This ensures that RTS/CTS mechanism is used only for large frames.10.No, there wouldn’t be any advantage. Suppose there are two stations that want totransmit at the same time, and they both use RTS/CTS. If the RTS frame is as long asa DATA frames, the channel would be wasted for as long as it would have beenwasted for two colliding DATA frames. Thus, the RTS/CTS exchange is only useful when the RTS/CTS frames are significantly smaller than the DATA frames.11.Initially the switch has an entry in its forwarding table which associates the wirelessstation with the earlier AP. When the wireless station associates with the new AP, the new AP creates a frame with the wireless station’s MAC address and broadcasts the frame. The frame is received by the switch. This forces the switch to update itsforwarding table, so that frames destined to the wireless station are sent via the new AP.12.Any ordinary Bluetooth node can be a master node whereas access points in 802.11networks are special devices (normal wireless devices like laptops cannot be used as access points).13.False14.“Opportunistic Scheduling” refers to matching the physical layer protocol to channelconditions between the sender and the receiver, and choosing the receivers to which packets will be sent based on channel condition. This allows the base station to make best use of the wireless medium.15.UMTS to GSM and CDMA-2000 to IS-95.16.The data plane role of eNodeB is to forward datagram between UE (over the LTEradio access network) and the P-GW. Its control plane role is to handle registration and mobility signaling traffic on behalf of the UE.The mobility management entity (MME) performs connection and mobility management on behalf of the UEs resident in the cell it controls. It receives UE subscription information from the HHS.The Packet Data Network Gateway (P-GW) allocates IP addresses to the UEs and performs QoS enforcement. As a tunnel endpoint it also performs datagram encapsulation/decapsulation when forwarding a datagram to/from a UE.The Serving Gateway (S-GW) is the data-plane mobility anchor point as all UE traffic will pass through the S-GW. The S-GW also performs charging/billing functions and lawful traffic interception.17.In 3G architecture, there are separate network components and paths for voice anddata, i.e., voice goes through public telephone network, whereas data goes through public Internet. 4G architecture is a unified, all-IP network architecture, i.e., both voice and data are carried in IP datagrams to/from the wireless device to several gateways and then to the rest of the Internet.The 4G network architecture clearly separates data and control plane, which is different from the 3G architecture.The 4G architecture has an enhanced radio access network (E-UTRAN) that is different from 3G’s radio access network UTRAN.18.No. A node can remain connected to the same access point throughout its connectionto the Internet (hence, not be mobile). A mobile node is the one that changes its point of attachment into the network over time. Since the user is always accessing theInternet through the same access point, she is not mobile.19.A permanent address for a mobile node is its IP address when it is at its homenetwork. A care-of-address is the one its gets when it is visiting a foreign network.The COA is assigned by the foreign agent (which can be the edge router in theforeign network or the mobile node itself).20.False21.The home network in GSM maintains a database called the home location register(HLR), which contains the permanent cell phone number and subscriber profileinformation about each of its subscribers. The HLR also contains information about the current locations of these subscribers. The visited network maintains a database known as the visitor location register (VLR) that contains an entry for each mobile user that is currently in the portion of the network served by the VLR. VLR entries thus come and go as mobile users enter and leave the network.The edge router in home network in mobile IP is similar to the HLR in GSM and the edge router in foreign network is similar to the VLR in GSM.22.Anchor MSC is the MSC visited by the mobile when a call first begins; anchor MSCthus remains unchanged during the call. Throughout the call’s duration and regardless of the number of inter-MSC transfers performed by the mobile, the call is routed from the home MSC to the anchor MSC, and then from the anchor MSC to the visited MSC where the mobile is currently located.23.a) Local recoveryb) TCP sender awareness of wireless linksc) Split-connection approachesChapter 7 ProblemsProblem 1Output corresponding to bit d 1 = [-1,1,-1,1,-1,1,-1,1]Output corresponding to bit d 0 = [1,-1,1,-1,1,-1,1,-1]Problem 2Sender 2 output = [1,-1,1,1,1,-1,1,1]; [ 1,-1,1,1,1,-1,1,1]Problem 3181111)1()1(111111)1()1(1112=?+?+-?-+?+?+?+-?-+?=d 181111)1()1(111111)1()1(1122=?+?+-?-+?+?+?+-?-+?=dProblem 4Sender 1: (1, 1, 1, -1, 1, -1, -1, -1)Sender 2: (1, -1, 1, 1, 1, 1, 1, 1)Problem 5a) The two APs will typically have different SSIDs and MAC addresses. A wirelessstation arriving to the café will associate with one of the SSIDs (that is, one of the APs). After association, there is a virtual link between the new station and the AP. Label the APs AP1 and AP2. Suppose the new station associates with AP1. When the new station sends a frame, it will be addressed to AP1. Although AP2 will alsoreceive the frame, it will not process the frame because the frame is not addressed to it. Thus, the two ISPs can work in parallel over the same channel. However, the two ISPs will be sharing the same wireless bandwidth. If wireless stations in different ISPs transmit at the same time, there will be a collision. For 802.11b, the maximum aggregate transmission rate for the two ISPs is 11 Mbps.b) Now if two wireless stations in different ISPs (and hence different channels) transmitat the same time, there will not be a collision. Thus, the maximum aggregatetransmission rate for the two ISPs is 22 Mbps for 802.11b.Problem 6Suppose that wireless station H1 has 1000 long frames to transmit. (H1 may be an AP that is forwarding an MP3 to some other wireless station.) Suppose initially H1 is the onlystation that wants to transmit, but that while half-way through transmitting its first frame, H2 wants to transmit a frame. For simplicity, also suppose every station can hear every other station’s signal (that is, no hidden terminals). Before transmitting, H2 will sense that the channel is busy, and therefore choose a random backoff value.Now suppose that after sending its first frame, H1 returns to step 1; that is, it waits a short period of times (DIFS) and then starts to transmit the second frame. H1’s second frame will then be transmitted while H2 is stuck in backoff, waiting for an idle channel. Thus, H1 should get to transmit all of its 1000 frames before H2 has a chance to access the channel. On the other hand, if H1 goes to step 2 after transmitting a frame, then it too chooses a random backoff value, thereby giving a fair chance to H2. Thus, fairness was the rationale behind this design choice.Problem 7A frame without data is 32 bytes long. Assuming a transmission rate of 11 Mbps, the time to transmit a control frame (such as an RTS frame, a CTS frame, or an ACK frame) is (256 bits)/(11 Mbps) = 23 usec. The time required to transmit the data frame is (8256 bits)/(11 Mbps) = 751DIFS + RTS + SIFS + CTS + SIFS + FRAME + SIFS + ACK= DIFS + 3SIFS + (3*23 + 751) usec = DIFS + 3SIFS + 820 usecProblem 8a) 1 message/ 2 slotsb) 2 messages/slotc) 1 message/slota)i) 1 message/slotii) 2 messages/slotiii) 2 messages/slotb)i) 1 message/4 slotsii) slot 1: Message A→ B, message D→ Cslot 2: Ack B→ Aslot 3: Ack C→ D= 2 messages/ 3 slotsiii)slot 1: Message C→ Dslot 2: Ack D→C, message A→ BRepeatslot 3: Ack B→ A= 2 messages/3 slotsProblem 10a)10 Mbps if it only transmits to node A. This solution is not fair since only A is gettingserved. By “fair” it m eans that each of the four nodes should be allotted equal number of slots.b)For the fairness requirement such that each node receives an equal amount of dataduring each downstream sub-frame, let n1, n2, n3, and n4 respectively represent the number of slots that A, B, C and D get. Now,data transmitted to A in 1 slot = 10t Mbits(assuming the duration of each slot to be t)Hence,Total amount of data transmitted to A (in n1 slots) = 10t n1Similarly total amounts of data transmitted to B, C, and D equal to 5t n2, 2.5t n3, and t n4 respectively.Now, to fulfill the given fairness requirement, we have the following condition:10t n1 = 5t n2 = 2.5t n3 = t n4Hence,n2 = 2 n1n3 = 4 n1n4 = 10 n1Now, the total number of slots is N. Hence,n1+ n2+ n3+ n4 = Ni.e. n1+ 2 n1 + 4 n1 + 10 n1 = Ni.e. n1 = N/17Hence,n2 = 2N/17n3 = 4N/17n4 = 10N/17The average transmission rate is given by:(10t n1+5t n2+ 2.5t n3+t n4)/tN= (10N/17 + 5 * 2N/17 + 2.5 * 4N/17 + 1 * 10N/17)/N= 40/17 = 2.35 Mbpsc)Let node A receives twice as much data as nodes B, C, and D during the sub-frame.Hence,10tn1 = 2 * 5tn2 = 2 * 2.5tn3 = 2 * tn4i.e. n2 = n1n3 = 2n1n4 = 5n1Again,n1 + n2 + n3 + n4 = Ni.e. n 1+ n1 + 2n1 + 5n1 = Ni.e. n1 = N/9Now, average transmission rate is given by:(10t n1+5t n2+ 2.5t n3+t n4)/tN= 25/9 = 2.78 MbpsSimilarly, considering nodes B, C, or D receive twice as much data as any other nodes, different values for the average transmission rate can be calculated.Problem 11a)No. All the routers might not be able to route the datagram immediately. This isbecause the Distance Vector algorithm (as well as the inter-AS routing protocols like BGP) is decentralized and takes some time to terminate. So, during the time when the algorithm is still running as a result of advertisements from the new foreign network, some of the routers may not be able to route datagrams destined to the mobile node.b)Yes. This might happen when one of the nodes has just left a foreign network andjoined a new foreign network. In this situation, the routing entries from the oldforeign network might not have been completely withdrawn when the entries from the new network are being propagated.c)The time it takes for a router to learn a path to the mobile node depends on thenumber of hops between the router and the edge router of the foreign network for the node.Problem 12If the correspondent is mobile, then any datagrams destined to the correspondent would have to pass through the correspondent’s home agent. The foreign agent in the network being visited would also need to be involved, since it is this foreign agent thatnotifies the correspondent’s home agent of the location of the correspondent. Datagrams received by the correspondent’s home agent would need to be encapsulated/tunneled between the correspondent’s home agent and for eign agent, (as in the case of the encapsulated diagram at the top of Figure 6.23.Problem 13Because datagrams must be first forward to the home agent, and from there to the mobile, the delays will generally be longer than via direct routing. Note that it is possible, however, that the direct delay from the correspondent to the mobile (i.e., if the datagram is not routed through the home agent) could actually be smaller than the sum of the delay from thecorrespondent to the home agent and from there to the mobile. It would depend on the delays on these various path segments. Note that indirect routing also adds a home agent processing (e.g., encapsulation) delay.Problem 14First, we note that chaining was discussed at the end of section 6.5. In the case of chaining using indirect routing through a home agent, the following events would happen: ?The mobile node arrives at A, A notifies the home agent that the mobile is now visiting A and that datagrams to the mobile should now be forwarded to thespecified care-of-address (COA) in A.The mobile node moves to B. The foreign agent at B must notify the foreign agent at A that the mobile is no longer resident in A but in fact is resident in Band has the specified COA in B. From then on, the foreign agent in A willforward datagrams it receives that are addressed to the mobile’s COA in A to t he mobile’s COA in B.The mobile node moves to C. The foreign agent at C must notify the foreign agent at B that the mobile is no longer resident in B but in fact is resident in C and has the specified COA in C. From then on, the foreign agent in B will forwarddatagrams it receives (from the foreign agent in A) that are addressed to themobile’s COA in B to the mobile’s COA in C.Note that when the mobile goes offline (i.e., has no address) or returns to its home network, the datagram-forwarding state maintained by the foreign agents in A, B and C must be removed. This teardown must also be done through signaling messages. Note that the home agent is not aware of the mobile’s mobility beyond A, and that the correspondent is not at all aware of the mobil e’s mobility.In the case that chaining is not used, the following events would happen: ?The mobile node arrives at A, A notifies the home agent that the mobile is now visiting A and that datagrams to the mobile should now be forwarded to thespecified care-of-address (COA) in A.The mobile node moves to B. The foreign agent at B must notify the foreign agent at A and the home agent that the mobile is no longer resident in A but infact is resident in B and has the specified COA in B. The foreign agent in A can remove its state about the mobile, since it is no longer in A. From then on, thehome agent will forward datagrams it receives that are addressed to the mobile’sCOA in B.The mobile node moves to C. The foreign agent at C must notify the foreign agent at B and the home agent that the mobile is no longer resident in B but in fact is resident in C and has the specified COA in C. The foreign agent in B canremove its state about the mobile, since it is no longer in B. From then on, thehome agent will forward datagrams it receives that are addressed to the mobile’sCOA in C.When the mobile goes offline or returns to its home network, the datagram-forwarding state maintained by the foreign agent in C must be removed. This teardown must also bedone through signaling messages. Note that the home agent is always aware of the mobile’s cu rrent foreign network. However, the correspondent is still blissfully unaware of the mobile’s mobility.Problem 15Two mobiles could certainly have the same care-of-address in the same visited network. Indeed, if the care-of-address is the address of the foreign agent, then this address would be the same. Once the foreign agent decapsulates the tunneled datagram and determines the address of the mobile, then separate addresses would need to be used to send the datagrams separately to their different destinations (mobiles) within the visited network.Problem 16If the MSRN is provided to the HLR, then the value of the MSRN must be updated in the HLR whenever the MSRN changes (e.g., when there is a handoff that requires the MSRN to change). The advantage of having the MSRN in the HLR is that the value can be provided quickly, without querying the VLR. By providing the address of the VLR Rather than the MSRN), there is no need to be refreshing the MSRN in the HLR.。

1. Which of the following are specified by IEEE standards as sublayers of the OSI data link layer? (Choose two.)Logical Link ControlLogical Layer ControlMedia Access ControlLogical Link CommunicationMedia Access CommunicationPhysical Access Communication2. Refer to the exhibit. Host A is communicating with host F. What happens to a frame sent from host A to host F as it trave Ethernet segments?The frame format is modified as it passes through each switch.The frame format remains the same across each Ethernet segment.The frame format is modified as the media speed changed at switch B and switch E.The frame format is modified as the media material changes between copper and fiber at switch C and switch D.3. In which two layers of the OSI model does Ethernet function? (Choose two.)applicationsessiontransportnetworkdata linkphysical4. Where does the MAC address originate?DHCP server databaseconfigured by the administratorburned into ROM on the NIC cardnetwork configuration on the computerincluded in the creation of the processor chip5. At what layer of the OSI model does a MAC address reside?123476. A router has an Ethernet, Token Ring, serial, and ISDN interface. Which interfaces will have a MAC address?serial and ISDN interfacesEthernet and Token Ring interfacesEthernet and ISDN interfacesToken Ring and serial interfaces7. Which two devices can provide full-duplex Ethernet connections? (Choose two.)hubmodemrepeaterNICLayer 2 switch8. Refer to the exhibit. The small office network shown in the exhibit consists of four computers connected through a hub. Which configuration would cause collisions and errors on the network?autonegotiationFastEthernetpeer-to-peer shared resourcesadministratively configured full duplex9. Refer to the exhibit. The switch and workstation are administratively configured for full-duplexoperation. Which statement accurately reflects the operation of this link?No collisions will occur on this link.Only one of the devices can transmit at a time.The switch will have priority for transmitting data.The devices will default back to half duplex if excessive collisions occur.10. What are three functions of a NIC in a PC? (Choose three.)A NIC connects the PC to the network media.A NIC detects collisions on the Ethernet segment.A NIC checks the formatting of data before it is transmitted.A NIC passes the contents of selected frames to the upper OSI layers.A NIC acknowledges and retransmits data that was not received properly.A NIC discards frames when the destination IP address does not match the local host.11. In an Ethernet LAN, how does the NIC know when it can transmit data?An Ethernet NIC transmits data as soon as the frame is received.An Ethernet NIC transmits data as soon as the NIC receives a token.An Ethernet NIC transmits data when it senses a collision.An Ethernet NIC transmits data after listening for the absence of a signal on the media.12. Refer to the exhibit. All hosts are in listen mode. Host 1 and Host 4 both transmit data at thesame time. How do the hosts respond on the network? (Choose two.)Hosts 1 and 4 may be operating full duplex so no collision will exist.The hub will block the port connected to Host 4 to prevent a collision.After the end of the jam signal, Hosts 1, 2, 3, and 4 invoke a backoff algorithm.When the four hosts detect the collision, Hosts 1, 2, 3, and 4 generate a jam signal.Hosts 1 and 4 are assigned shorter backoff values to provide them priority to access themedia.If a host has data to transmit after the backoff period of that host, the host checks to determineif the line is idle, before transmitting.13. Which statement describes how CSMA/CD on an Ethernet segment manages the retransmission offrames after a collision occurs?The first device to detect the collision has the priority for retransmission.The device with the lowest MAC address determines the retransmission priority.The devices on the network segment hold an election for priority to retransmit dataThe devices transmitting when the collision occurs DO NOT have priority for retransmission.14. What is the maximum distance that 10BASE-T will transmit data before signal attenuation affects thedata delivery?100 meters185 meters300 meters500 meters15. Which of the following are Fast Ethernet technologies? (Choose two.)100BASE-5100BASE21000BASE-F100BASE-FX100BASE-TX16 . At which OSI layer do the differences between standard Ethernet, Fast Ethernet and Gigabit Ethernet occur?physical layerdata link layernetwork layertransport layer17. How does 1000BASE-T use the UTP wire pairs to accomplish transmission?two pairs are used to transmit and two pairs are used to receiveone pair is used to transmit, one pair is used to receive, one pair is used for clocking, and one pair is used for error correctionall four pairs are used in parallel by both hosts to transmit and receive simultaneouslytwo pairs of wires are used as in 10BASE-T and 100BASE-TX18. Which statements describe Gigabit Ethernet technology? (Choose two.)operates at 100 Mbpstypically used for backbone cablingrequires shielded twisted-pair cablingcan be implemented over copper and fiberprimarily used between workstations option19. Which media types can be used in an implementation of a 10BASE-T network? (Choose three.)Category 5 UTPCategory 5e UTPCategory 3 UTPcoaxial cablemulti-mode fibersingle mode fiber20. Which of the following Ethernet technologies are considered legacy Ethernet? (Choose three.)10BASE210BASE510BASE-T100BASE-T100BASE-FX100BASE-TX。