ccna1答案第七章
计算机网络-课后答案第七章
问题7-1：用一个例子说明置换密码的加密和解密过程。
假定密钥为CIPHER，而明文为attack begins at four，加密时明文中的空格去除。
答：在英文26个字母中，密钥CIPHER这6个字母在26个英文字母中出现的位置用红色a b然后按行问题7-2答：(1)向一个特定服务器非常快地发送大量任意的分组，使得该服务器过负荷因而无法正常工作。
(2)向一个特定服务器发送大量的TCP SYN报文段（即建立TCP连接的三次握手中的第一个报文段）。
服务器还误以为是正常的因特网用户的请求，于是就响应这个请求，并分配了数据结构和状态。
但攻击者不再发送后面的报文段，因而永远不能够完成TCP连接的建立。
这样可以浪费和耗尽服务器的大量资源。
这种攻击方式又称为SYN flooding（意思是使用同步标志进行洪泛）。
(3)重复地和一个特定服务器建立TCP连接，然后发送大量无用的报文段。
(4)将IP数据报分片后向特定服务器发送，但留一些数据报片不发送。
这就使得目的主机永远无法组装成完整的数据报，一直等待着，浪费了资源。
(5)向许多网络发送ICMP回送请求报文（就是使用应用层的PING程序），结果使许多主机都向攻击者返回ICMP回送回答报文。
无用的、过量的ICMP报文使网络的通信量急剧增加，甚至使网络瘫痪。
这种攻击方式被称为smurf攻击。
Smurf就是能够对网络自动发送这种ICMP报文攻击的程序名字。
分布式拒绝服务DDOS的特点就是攻击者先设法得到因特网上的大量主机的用户账号。
然后攻击者设法秘密地在这些主机上安装从属程序(slave program)，如图所示。
一时刻在拒绝服务和分布式拒绝服务都是很难防止的。
使用分组过滤器并不能阻止这种攻击，因为攻击者的IP地址是事先不知道的。
当主机收到许多攻击的数据报时，很难区分开哪些是好的数据报，而哪些是坏的数据报。
例如，当服务器收到请求建立TCP连接的SYN报文时，很难区分这是真的请求建立TCP连接，还是恶意消耗服务器资源的连接请求。
CCN认证试题中文答案
C C N A认证试题一（附答案和解析）中文版(一)1、目前，我国应用最为广泛的LAN标准是基于（）的以太网标准.(A) IEEE 802.1(B) IEEE 802.2(C) IEEE 802.3(D) IEEE 802.5答案：C参考知识点：现有标准：IEEE 802.1 局域网协议高层IEEE 802.2 逻辑链路控制IEEE 802.3 以太网IEEE 802.4 令牌总线IEEE 802.5 令牌环IEEE 802.8 FDDIIEEE 802.11 无线局域网记住IEEE802.1-------IEEE802.5的定义以太网是一种计算机局域网组网技术。
IEEE制定的IEEE 802.3标准给出了以太网的技术标准。
它规定了包括物理层的连线、电信号和介质访问层协议的内容。
以太网是当前应用最普遍的局域网技术。
它很大程度上取代了其他局域网标准，如令牌环、FDDI和ARCNET。
以太网的标准拓扑结构为总线型拓扑，但目前的快速以太网（100BASE-T、1000BASE-T标准）为了最大程度的减少冲突，最大程度的提高网络速度和使用效率，使用交换机（Switch）来进行网络连接和组织，这样，以太网的拓扑结构就成了星型，但在逻辑上，以太网仍然使用总线型拓扑的C***A/CD介质访问控制方法。
电气电子工程师协会或IEEE（Institute of Electrical and Electronics Engineers）是一个国际性的电子技术与信息科学工程师的协会。
建会于1963年1月1日。
总部在美国纽约市。
在150多个国家中它拥有300多个地方分会。
目前会员数是36万。
专业上它有35个专业学会和两个联合会。
IEEE发表多种杂志，学报，书籍和每年组织300多次专业会议。
IEEE定义的标准在工业界有极大的影响。
下面列出：IEEE802．3以太网标准802.3--------- 10Base以太网标准802.3u-------- 100Base-T（快速以太网）802.3z-------- 1000Base-X（光纤吉比特以太网）802.3ab-------- 1000Base-T（双绞线吉比特以太网）答案：CE注：IP地址中关键是看她的主机位，将子网掩码划为二进制，1对应上3、Quidway系列路由器在执行数据包转发时，下列哪些项没有发生变化（假定没有使用地址转换技术）？（）(A) 源端口号(B) 目的端口号(C) 源网络地址(D) 目的网络地址(E) 源MAC地址(F) 目的MAC地址答案：ABCD参考知识点：路由功能就是指选择一条从源网络到目的网络的路径，并进行数据包的转发。
思科网院-网络工程-CCNA1-2017计算机科学与技术-一到十一章-题库及答案
某公司正在考虑是使用客户端/服务器还是对等网络。
下列哪三项是对等网络的特征？（选择三项。
）哪种设备的功能是确定消息在网际网络中传输的路径？哪两个条件有助于您从各种网络介质当中选择一种网络介质？（请选择两项。
）下列哪两项描述了中间设备？（选择两项。
）网络上的终端设备有哪两项功能？（选择两项。
）由于许多学生带着自己的平板电脑和智能手机去学校访问学校资源，大学里的IT 人员最有可能需要重新设计的网络区域是什么？家庭用户必须要有哪种网络类型访问才能进行网上购物？一位分支机构办公室的员工正在为客户创建报价。
为此，该员工需要访问位于总部办公室的内部服务器上的机密定价信息。
该员工将要访问哪种类型的网络？下列哪两种连接选项可以为家庭办公室中的计算机提供始终在线的高带宽Internet 连接？（选择两项。
）下列哪两个Internet 连接选项不需要建筑物铺设物理电缆？（请选择两项。
）以下哪种术语描述了当对网络资源的请求超出可用容量时网络的状态？哪种类型的网络流量需要QoS？以下哪项表述准确定义了术语“带宽”？网络管理员正在实施一种要求复杂强密码的策略。
该策略支持哪种数据保护目标？下列哪种说法正确描述了云计算的特征？什么是Internet？下列哪种说法描述了电力线网络技术的用途？哪种安全侵犯会对家庭用户的生活造成最大损害？一位用户正在一个小型办公室网络上实施安全策略。
以下哪两种操作将为此网络提供求？（选择两项。
）A网络能够通过相同的通信通道传输语音、视频、文本和图形。
填空题。
缩写词是指允许员工在公司办公室中使用其个人设备访问网络和其他资源的策略。
正确答案：byod将每个描述与网络通信形式配对请将每个特征对应的internet连接类型进行匹配将每个定义与安全目标配对操作软件内核的作用是什么？网络管理员与交换机建立远程CLI 连接对其实施管理时，需要确保用户ID、密码和会话内容的保密性。
应当选择哪种访问方法？当在安全环境下执行初始配置时，下列哪个程序可用来访问Cisco 2960 交换机？哪个命令或组合键让用户返回命令层级中的上一级？某台路由器具有有效的操作系统，且NVRAM 中存储有配置文件。
CCNA认证基础课程-课后作业.习题答案
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。
ccna章节与期末答案
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。
2016CCNA1各章及期末考试答案分析
ITN 第7 章考试1什么是套接字？正确响应您的响应源和目的IP 地址以及源和目的以太网地址的组合源IP 地址与端口号的组合或目的IP 地址与端口号的组合源和目的序列号和确认号的组合源和目的序列号和端口号的组合此试题参考以下领域的内容：Introduction to Networks7.1.2 TCP 和UDP 简介2主机设备需要通过网络发送大型视频文件，同时为其他用户提供数据通信。
下列哪种功能可以让不同通信流同时发生，而不会让一个数据流使用所有可用带宽？正确响应您的响应窗口大小多路复用端口号确认多路复用对交替发送多个通信流很有用。
窗口大小用于降低数据通信速率。
端口号用于将数据流传送到正确的应用程序。
确认用于通知发送设备数据包流已收到或未收到。
此试题参考以下领域的内容：Introduction to Networks7.1.1 数据传输3主机设备通过HTTP 协议向Web 服务器发送数据包。
传输层使用下列哪项来将数据流传送到服务器上的正确应用程序？正确响应您的响应序列号确认源端口号目的端口号目的端口号用于将数据流传输到正确的应用程序，而源端口号由源设备随机生成并进行跟踪。
序列号用于指示如何重组和重新排序收到的数据段。
确认用于通知发送设备数据包流已收到或未收到。
此试题参考以下领域的内容：Introduction to Networks∙7.1.1 数据传输4UDP 传输协议有什么有利功能？正确响应您的响应确认已接收的数据减少传输延迟使用序列号跟踪数据段能够重新传输丢失的数据此试题参考以下领域的内容：Introduction to Networks∙7.1.1 数据传输5下列哪种场景描述了传输层提供的功能？正确响应您的响应学生使用教室里的VoIP 电话给家里打电话。
刻录到电话中的唯一标识符是一种传输层地址，用于联系同一网络中的其他网络设备。
学生使用Web 浏览器播放一小段有声电影。
电影和声音在传输层报头内编码。
思科第一学期期末考试最新答案CCNA1
要将数据包发送到远程网络，应使用哪种设备？访问交换机DHCP 服务器集线器路由器OSI 哪一层使用面向连接的协议来确保数据的可靠传输？应用层表示层会话层传输层请参见图示。
根据显示的IP 配置回答，主机 A 和主机 B 无法在本地网络外通信的原因是什么？对主机 A 分配了网络地址。
对主机 B 分配了组播地址。
主机 A 和主机 B 属于不同的网络。
对网关地址分配了广播地址。
请参见图示。
包含路由器 B 的网络遇到问题。
助理网络工程师已确定此网络的问题出在路由行什么操作可以纠正该网络问题？在接口Serial 0/0/0 上发出clock rate命令在接口Serial 0/0/1 上发出description命令在接口FastEthernet 0/0 上发出ip address命令在接口FastEthernet 0/1 上发出no shutdown命令请参见图示。
对于从主机 A 向Web 服务器发出的网页请求，正确的目的套接字数字是什么00-08-a3-b6-ce-46198.133.219.25:80C 172.18.0.0/24 is directly connected, FastEthernet0/0在Cisco IOS 设备中，启动配置文件存储于何处？闪存NVRAMRAMROM在配置路由器时，网络技术人员想要命名路由器。
输入hostname命令后，技术人员会看到下列示？Router>Router#Router(config)#Router(config-line)#下列哪三个IPv4 地址代表子网的广播？（选择三项）172.16.4.63 /26172.16.4.129 /26172.16.4.191 /26172.16.4.51 /27172.16.4.95 /27172.16.4.221 /27网络管理员想要限制访问路由器的特权执行模式。
管理员应该使用哪一种口令？使能aux控制台VTY请参见图示。
计算机组织与系统结构第七章习题答案
习题1．给出以下概念的解释说明。
指令流水线（Instruction pipelining）流水线深度（Pipeline Depth）指令吞吐量（Instruction throughput）流水线冒险（Hazard）结构冒险（Structural hazard）控制冒险（Control hazard）数据冒险（Data hazard）流水线阻塞（Pipeline stall）气泡（Bubble）空操作（nop）分支条件满足（Branch taken）分支预测（Branch predict）静态分支预测（Static predict）动态分支预测（Dynamic predict）延迟分支（Delayed branch）分支延迟槽（Delayed branch slot）转发（Forwarding）旁路（Bypassing）流水段寄存器（Pipeline register）IPC（Instructions Per Cycle）静态多发射（Static multiple issue）动态多发射（Dynamic multiple issue）超流水线（Superpipelining）超长指令字VLIW超标量流水线（Superscalar）动态流水线（Dynamic pipelining）指令预取（Instruction prefetch）指令分发（Instruction dispatch）按序发射（in-order issue）无序发射（out-of-order issue）存储站（Reservation station）重排序缓冲（Reorder buffer）指令提交单元（Instruction commit unit）乱序执行（out-of-order execution）按序完成（in-order completion）无序完成（out-of-order completion）2. 简单回答下列问题。
第七章课后习题参考答案
2. 试简单说明下列协议的作用：IP、ARP、RARP和ICMP。
答：IP协议：实现网络互连。
使参与互连的性能各异的网络从用户看起来好像是一个统一的网络。
ARP协议：完成IP地址到MAC地址的映射。
RARP：使只知道自己硬件地址的主机能够知道其IP地址。
ICMP：允许主机或路由器报告差错情况和提供有关异常情况的报告。
5. 试说明IP 地址与硬件地址的区别。
为什么要使用这两种不同的地址？答：IP地址在IP数据报的首部，而硬件地址则放在MAC帧的首部。
在网络层以上使用的是IP地址，而链路层及以下使用的是硬件地址。
在IP层抽象的互连网上，我们看到的只是IP数据报，路由器根据目的站的IP地址进行选路。
在具体的物理网络的链路层，我们看到的只是 MAC 帧，IP 数据报被封装在 MAC 帧里面。
MAC帧在不同的网络上传送时，其MAC帧的首部是不同的。
这种变化，在上面的IP层上是看不到的。
每个路由器都有IP 地址和硬件地址。
使用IP地址与硬件地址，尽管连接在一起的网络的硬件地址体系各不相同，但IP层抽象的互连网却屏蔽了下层这些很复杂的细节，并使我们能够使用统一的、抽象的IP地址进行通信。
6.（1）子网掩码为255.255.255.0代表什么意思？（2）一网络的子网掩码为255.255.255.248，问该网络能够连接多少台主机？（1）一A类网络和一B类网络的子网号subnet-id分别为16bit的8bit，问这两个网络的子网掩码有何不同？（2）一个B类地址的子网掩码是255.255.240.0。
试问在其中每一个子网上的主机数最多是多少？（3）一个A类地址的子网掩码为255.255.0.255。
它是否为一个有效的子网掩码？（4）某个IP地址的十六进制表示是C22F1481，试将其转换为点分十进制的形式.这个地址是哪一类IP 地址?（5）C类网络使用子网掩码有无实际意义?为什么?答：（1）C类地址对应的子网掩码值。
CCNA第一学期各章习题及答案
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002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006请参见图示。
所示网络属于哪一类型WANMANLANWLAN007 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009 请参见图示。
下列哪组设备仅包含终端设备A、C、DB、E、G、HC、D、G、H、I、JD、E、F、H、I、JE、F、H、I、J010 选择关于网络协议的正确陈述。
CCNA第一学期第7章章节考试题答案100%
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。
思科CCNA考试答案(全)
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。
计算机网络谢希仁第七版课后答案完整版
计算机网络谢希仁第七版课后答案完整版在学习计算机网络这门课程时，谢希仁教授所著的第七版教材是众多学子的重要参考资料。
而课后答案则对于我们理解和掌握知识点起着关键的作用。
以下将为您呈现一份完整的计算机网络谢希仁第七版课后答案。
第一章主要介绍了计算机网络的基本概念、组成和分类等。
课后习题中，对于网络的定义和功能的理解，答案强调网络是将地理位置不同的具有独立功能的多台计算机及其外部设备，通过通信线路连接起来，在网络操作系统、网络管理软件及网络通信协议的管理和协调下，实现资源共享和信息传递的计算机系统。
其功能包括数据通信、资源共享、分布式处理、提高可靠性和负载均衡等。
第二章探讨了物理层的相关知识。
对于信号的传输方式，答案解释了基带传输、宽带传输以及频带传输的特点和适用场景。
在涉及到信道复用技术的问题时，答案详细阐述了频分复用、时分复用、波分复用和码分复用的工作原理和优缺点。
第三章聚焦于数据链路层。
关于数据链路层的三个基本问题，即封装成帧、透明传输和差错检测，答案给出了清晰的解释和示例。
在滑动窗口协议方面，详细分析了停止等待协议、后退 N 帧协议和选择重传协议的工作流程和性能特点。
第四章讲述了网络层。
对于网络层提供的两种服务，即虚电路服务和数据报服务，答案对比了它们的差异和适用情况。
在路由算法的问题上，分别介绍了距离向量路由算法和链路状态路由算法的原理和计算过程。
关于 IP 地址的分类和子网掩码的使用，答案通过实例进行了详细的说明。
第五章涉及运输层。
在运输层的端口号相关问题上，答案解释了端口号的作用和分类，并说明了如何通过端口号来识别不同的应用进程。
对于 TCP 和 UDP 协议的特点和应用场景，答案进行了深入的比较和分析。
在 TCP 的拥塞控制算法方面，详细阐述了慢开始、拥塞避免、快重传和快恢复等算法的工作机制。
第六章阐述了应用层。
对于 DNS 系统的工作原理，答案说明了域名解析的过程以及各级域名服务器的作用。
CCNA第一学期各章习题和参考答案.doc
CCNA第一学期各章习题和参考答案第二章网络通信1、TCP/IP网络接入层有何作用？A路径确定和数据包交换B数据表示、编码和控制C可靠性、流量控制和错误检测E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）B发起数据通信D发送数据流F数据流最后的终止点3、下列哪三项陈述是对局域网(LAN) 最准确的描述？（选择三项）C LAN 中的不同网段之间一般通过租用连接的方式连接。
D此类网络的安全和访问控制由服务提供商控制。
F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？A传输期间的帧损坏B在目的设备上重组的数据C因通信丢失而重新传输的数据包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）018哪个应用层协议通常用于支持客户端与服务器之间的文件传输？A HTMLB HTTP D Telnet019哪个应用层协议中规定了Microsoft 网络中用于文件共享的服务？A DHCPB DNS D SMTP E Telnet020服务器上的应用层通常如何处理多客户端服务请求？A终止与服务的所有连接B拒绝与单一守护程序的多个连接C暂停当前连接，建立新连接第四章OSI传输层001下列哪两项是用户数据报协议(UDP) 的功能？（选择两项）A流量控制 D 面向连接E 序列和确认002请参见图示。
此Wireshark 捕获输出的第7 行中执行的是哪一项TCP 操作？A会话创建B 数据段重传C 数据传输D 会话断开003数据段的TCP 报头中为什么包含端口号？A指示转发数据段时应使用的正确路由器接口B 标识接收或转发数据段时应使用的交换机端口C确定封装数据时应使用的第3 层协议让接收主机转发数据到适当的应用程序E让接收主机以正确的顺序组装数据包004OSI 模型哪一层负责规范信息从源设备到目的设备准确可靠地流动？A应用层 B 表示层 C 会话层传输层 E 网络层005请参见图示。
CCNA第一学期各章知识题及答案解析
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002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006请参见图示。
所示网络属于哪一类型？WANMANLANWLAN007 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009 请参见图示。
思科CCNA1第七章试题及答案英文版
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第一章练习答案
1．Several computers in the company require new NICs. A technician has located a good price on the Internet for the purchase of these NICs. Before these NICs are purchased and installed, what details must be verified? (Choose three.)the MAC address on the NICthe size of the RAM on the NICthe bandwidth supported by the NICthe type of media supported by the NICthe type of network architecture supported by the NIC2. What are three conditions that would require a network administrator to install a new NIC? (Choose three.)whenever a NIC is damagedwhen there is a need to provide a secondary or backup NICwhen there is a change from copper media to wirelesswhenever operating system security patches are appliedwhenever the PC has been moved to a different location3. What is the hexadecimal equivalent for the binary number 10001110?2267142AE8E4. Represented as a decimal number, what is the result of the logical ANDing of binary numbers 00100011 and 11111100?332352202555. What is the binary equivalent for the decimal number 248?111000001111000011110100111110006. Convert the binary number 01011011 into its hexadecimal equivalent. Select the correct answer from the list below.5A5B5C5D6B7A7. What is the binary equivalent for decimal number 149?1001011110010101100110011001011110101011101011018. What is the binary equivalent for the decimal number 162?10100010101001001010110110110000101011009. Which device connects a computer with a telephone line by providing modulation and demodulation of incoming and outgoing data?NICCSU/DSUroutermodemtelco switch10. Convert the Base 10 number 116 into its eight bit binary equivalent. Choose the correct answer from the following list:01111010011100100111010001110110011101110101011011. Which specialized equipment is used to make a physical connection from a PC to a network?routerRAMnetwork interface card12. Which phrases describe a byte? (Choose two.)a single binary digit+5 volts of electricitythe value range 0 to 127a grouping of eight binary digitsa single addressable data storage location13. What is the hexadecimal equivalent for the binary number 00100101?15202530374014. In an 8 bit binary number, what is the total number of combinations of the eight bits?128254255256512102415. Which of the following are popular web browsers? (Choose two.)AcrobatInternet ExplorerMacromedia FlashNetscape NavigatorQuicktimeWorld Wide Web16. Convert the decimal number 231 into its binary equivalent. Select the correct answer from the list below.111100101101101111110110111001111110010111101110。
计算机网络自顶向下第七版第七章答案
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.。
ccna刘之七张
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。
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第七章OSI 数据链路层
1.
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
2.
请参见图示。
假设图示中的网络已收敛，即路由表和
的以太网帧目的地址字段中放入以下哪个MAC地址？
ARP表均完整，主机 A 将在发往www.server
0 0-1c-41-ab-c0-00
00-0c-85-cf-65-c0
00-0c-85-cf-65-c1
00-12-3f-32-05-af
3.
下列哪些选项是共享介质以竞争为原则的介质访问属性？（选择三项）
非确定性
开销较低
每次只有一个站点能够传输
存在冲突
设备必须等待轮到自己
令牌传递
4.
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。
5.
决定介质访问控制方法的因素是什么？（选择两项）
网络层编址
介质共享
应用进程
逻辑拓扑
中间设备的功能
6.
下列哪些有关介质访问控制的陈述是正确的？（选择三项）
以太网采用CSMA/CD
定义为帧在介质中的放置方法
以竞争为原则的访问亦称确定性访问
802.11采用CSMA/CD
数据链路层协议定义了访问不同介质的规则
受控访问存在数据冲突
7、
下列哪些陈述描述的是令牌传递逻辑拓扑？（选择两项）
按照先到先得原则使用网络。
只有当计算机拥有令牌时才能传输数据。
所有主机都将接收其它主机发送的数据。
相互之间依次传递电子令牌。
令牌传递网络存在冲突率高的问题。
8、
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
9、
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。
10 、
下列哪些关于OSI 模型各层地址的陈述是正确的？（选择两项）
第 2 层通过烧录到网卡的物理地址来标识设备
第 2 层地址标识正在通信的应用程序
第 3 层地址代表分层编址方案
第 4 层地址将通信转发到正确的目的网络
第 4 层地址由中间设备用于转发数据
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 。
所有网络都不需要介质访问控制。
网络 1 采用CSMA/CD而网络 3 采用CSMA/CA 。
网络 1 采用CSMA/CA而网络 2 采用 CSMA/CD 。
网络 2 采用CSMA/CA而网络 3 采用 CSMA/CD 。
12 、
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？
1
2
4
6
8
1 6
13 、
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IP 地址分别是什么？（选择两项）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 Fa0/1
14、
数据链路层的哪个子层负责准备供物理层传输的信号？
LLC
MAC
HDLC
网卡
15、
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。
16、
数据链路层有何功能？
提供数据格式化
在两台主机之间提供端到端数据传送
在两个应用程序之间提供数据传送
通过公共本地介质提供数据交换
17、
逻辑点对点拓扑的特征是什么？
对节点进行物理连接。
节点的物理布局受到限制。
介质访问控制协议可以非常简单。
链路上使用的数据链路层协议需要较大的帧头。
18、
将数据包封装成帧的主要作用是什么？
提供网间路由
格式化数据以便向用户显示
有助于数据进出介质
标识与传输的数据相关联的服务
19 、
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
20 、
有效的以太网第 2 层地址有哪三项特征？（选择三项）
其长度为48 个二进制位。
被视为物理地址。
通常以十六进制格式表示。
由四个二进制八位数组成。
用于确定数据的网络通路。
当网络中添加或删除以太网设备时必须更改。