CCNA 第一章课后习题答案

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CCNA第一册2——11章所有答案

第二章1.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）答案：1，确定数据传输路径3，重新定时和重新传输数据信号5，管理数据流2.请选择关于网络协议的正确陈述（选择三项）答案：1，定义特定层PDU的结构3，概述层与层之间通信所需的功能5，需要取决于协议层的封装过程3.封装的两个功能是什么？（选择两项）答案：4，标识属于同一通信的数据片段5，确保数据片段可以转发到正确的接收端设备4.数据链路层封装添加的报尾信息有何主要功能？答案：1，支持差错校验5.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）答案：3，物理层4，数据链路层6.什么是PDU？答案：4，特定层的封装7.以下哪种特征正确代表了网络中的终端设备？答案：2，发送数据流8.请参见图示。

IP地址为10.0.0.34的“手机A”已经与IP地址为172.16.1.103的“IP电话1”建立了IP会话。

请根据图示回答，下列哪个设备类型是对无线设备“手机A”功能的最准确描述？答案：2，终端设备9.请参见图示。

下列哪三个标签正确标识了图示网段的网络类型？（选择三项）答案：2，网络B—WAN 3,网络C—LAN 6，网络A—LAN10.下列哪三项陈述是对局域网（LAN）最准确的描述？（选择三项）答案：1，LAN通常位于一个地域内2，此类网络由一个组织管理5，LAN为同一个组织内的用户提供网络服务和应用程序访问11.请参见图示。

哪个网络术语描述了图中所示的数据交替发送过程？答案：4，多路复用12.第4层端口指定的主要作用是什么？答案：5，标识终端设备内正在通信的进程或服务13.哪种设备被视为中间设备？答案：5，交换机14.请参见图示。

哪个术语正确判断出了包含于区域B中的设备类型？答案：4，中间设备15.请参见图示。

所示网络属于哪一类型？答案：3，LAN16.哪一层负责将数据段封装成数据包？答案：3，网络层17.通过检查网络层头部可以确定什么？答案：2，目的主机地址18.请参见图示。

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。

1.计算机网络原理第一章课后习题及答案

第一章1.(Q1) What is the difference between a host and an end system? List the types ofendsystems. Is a Web server an end system?Answer: There is no difference. Throughout this text, the words “host” and “end system” are used interchangeably. End systems include PCs, workstations, Web servers, mail servers, Internet-connected PDAs, WebTVs, etc.2.(Q2) The word protocol is often used to describe diplomatic relations. Give an example of adiplomatic protocol.Answer: Suppose Alice, an ambassador of country A wants to invite Bob, an ambassador of country B, over for dinner. Alice doesn’t simply just call Bob on the phone and say, come to our dinner table now”. Instead, she calls Bob and sugges ts a date and time. Bob may respond by saying he’s not available that particular date, but he is available another date. Alice and Bob continue to send “messages” back and forth until they agree on a date and time. Bob then shows up at the embassy on the agreed date, hopefully not more than 15 minutes before or after the agreed time. Diplomatic protocols also allow for either Alice or Bob to politely cancel the engagement if they have reasonable excuses.3.(Q3) What is a client program? What is a server program? Does a server programrequestand receive services from a client program?Answer: A networking program usually has two programs, each running on a different host, communicating with each other. The program that initiates the communication is the client.Typically, the client program requests and receives services from the server program.4.(Q4) List six access technologies. Classify each one as residential access, company access, ormobile access.Answer:1. Dial-up modem over telephone line: residential; 2. DSL over telephone line: residential or small office; 3. Cable to HFC: residential; 4. 100 Mbps switched Etherent: company; 5. Wireless LAN: mobile; 6. Cellular mobile access (for example, 3G/4G): mobile5.(Q5) List the available residential access technologies in your city. For each type of access,provide the advertised downstream rate, upstream rate, and monthly price.Answer: Current possibilities include: dial-up (up to 56kbps); DSL (up to 1 Mbps upstream, up to 8 Mbps downstream); cable modem (up to 30Mbps downstream, 2 Mbps upstream.6.(Q7) What are some of the physical media that Ethernet can run over?Answer: Ethernet most commonly runs over twisted-pair copper wire and “thin” coaxial cable.It also can run over fibers optic links and thick coaxial cable.7.(Q8)Dial-up modems, HFC, and DSL are all used for residential access. For each of theseaccess technologies, provide a range of transmission rates and comment on whether the transmission rate is shared or dedicated.Answer:Dial up modems: up to 56 Kbps, bandwidth is dedicated; ISDN: up to 128 kbps, bandwidth is dedicated; ADSL: downstream channel is .5-8 Mbps, upstream channel is up to1 Mbps, bandwidth is dedicated; HFC, downstream channel is 10-30 Mbps and upstreamchannel is usually less than a few Mbps, bandwidth is shared.8.(Q13)Why is it said that packet switching employs statistical multiplexing? Contraststatistical multiplexing with the multiplexing that takes place in TDM.Answer:In a packet switched network, the packets from different sources flowing on a link do not follow any fixed, pre-defined pattern. In TDM circuit switching, each host gets the same slot in a revolving TDM frame.9.(Q14) Suppose users share a 2Mbps link. Also suppose each user requires 1Mbps whentransmitting, but each user transmits only 20 percent of the time. (See the discussion of statistical multiplexing in Section 1.3.)a.When circuit switching is used, how many users can be supported?b.For the remainder of this problem, suppose packet switching is used. Why will there beessentially no queuing delay before the link if two or fewer users transmit at the same time? Why will there be a queuing delay if three users transmit at the same time?c.Find the probability that a given user is transmitting.d.Suppose now there are three users. Find the probability that at any given time, allthree users are transmitting simultaneously. Find the fraction of time during which the queue grows.Answer:a. 2 users can be supported because each user requires half of the link bandwidth.b.Since each user requires 1Mbps when transmitting, if two or fewer users transmitsimultaneously, a maximum of 2Mbps will be required. Since the available bandwidth of the shared link is 2Mbps, there will be no queuing delay before the link. Whereas, if three users transmit simultaneously, the bandwidth required will be 3Mbps which is more than the available bandwidth of the shared link. In this case, there will be queuing delay before the link.c.Probability that a given user is transmitting = 0.2d.Probability that all three users are transmitting simultaneously=33p3(1−p)0=0.23=0.008. Since the queue grows when all the users are transmitting, the fraction oftime during which the queue grows (which is equal to the probability that all three users are transmitting simultaneously) is 0.008.10.(Q16)Consider sending a packet from a source host to a destination host over a fixed route.List the delay components in the end-to-end delay. Which of these delays are constant and which are variable?Answer:The delay components are processing delays, transmission delays, propagation delays, and queuing delays. All of these delays are fixed, except for the queuing delays, which are variable.11.(Q19) Suppose Host A wants to send a large file to Host B. The path from Host A to Host Bhas three links, of rates R1 = 250 kbps, R2 = 500 kbps, and R3 = 1 Mbps.a.Assuming no other traffic in the network, what is the throughput for the file transfer.b.Suppose the file is 2 million bytes. Roughly, how long will it take to transfer the file toHost B?c.Repeat (a) and (b), but now with R2 reduced to 200 kbps.Answer:a.250 kbpsb.64 secondsc.200 kbps; 80 seconds12.(P2)Consider the circuit-switched network in Figure 1.8. Recall that there are n circuits oneach link.a.What is the maximum number of simultaneous connections that can be in progress atany one time in this network?b.Suppose that all connections are between the switch in the upper-left-hand cornerand the switch in the lower-right-hand corner. What is the maximum number ofsimultaneous connections that can be in progress?Answer:a.We can n connections between each of the four pairs of adjacent switches. This gives amaximum of 4n connections.b.We can n connections passing through the switch in the upper-right-hand cornerandanother n connections passing through the switch in the lower-left-hand corner, giving a total of 2n connections.13.(P4) Review the car-caravan analogy in Section 1.4. Assume a propagation speed of 50km/hour.a.Suppose the caravan travels 150 km, beginning in front of one tollbooth, passingthrough a second tollbooth, and finishing just before a third tollbooth. What is theend-to-end delay?b.Repeat (a), now assuming that there are five cars in the caravan instead of ten.Answer: Tollbooths are 150 km apart, and the cars propagate at 50 km/hr, A tollbooth services a car at a rate of one car every 12 seconds.a.There are ten cars. It takes 120 seconds, or two minutes, for the first tollbooth to servicethe 10 cars. Each of these cars has a propagation delay of 180 minutes before arriving at the second tollbooth. Thus, all the cars are lined up before the second tollbooth after 182 minutes. The whole process repeats itself for traveling between the second and third tollbooths. Thus the total delay is 364 minutes.b.Delay between tollbooths is 5*12 seconds plus 180 minutes, i.e., 181minutes. The totaldelay is twice this amount, i.e., 362 minutes.14.(P5) This elementary problem begins to explore propagation delay and transmission delay,two central concepts in data networking. Consider two hosts, A and B, connected by a single link of rate R bps. Suppose that the two hosts are separated by m meters, and suppose the propagation speed along the link is s meters/sec. Host A is to send a packet of size L bits to Host B.a.Express the propagation delay, d prop , in terms of m and s.b.Determine the transmission time of the packet, d trans, in terms of L and R.c.Ignoring processing and queuing delays, obtain an expression for the end-to-enddelay.d.Suppose Host A begins to transmit the packet at time t = 0. At time t = d trans, where isthe last bit of the packet?e.Suppose d prop is greater than d trans. At time t = d trans, where is the first bit of thepacket?f.Suppose d prop is less than d trans.At time t = d trans,where is the first bit of the packet?g.Suppose s = 2.5*108, L = 100bits, and R = 28kbps. Find the distance m so that dprop equals d trans .Answer:a. d prop = m/s seconds.b. d trans = L/R seconds.c. d end-to-end = (m/s + L/R) seconds.d.The bit is just leaving Host A.e.The first bit is in the link and has not reached Host B.f.The first bit has reached Host B.g.Wantm=LRS=10028∗1032.5∗108=893 km.15.(P6) In this problem we consider sending real-time voice from Host A to Host B over apacket-switched network (VoIP). Host A converts analog voice to a digital 64 kbps bit stream on the fly. Host A then groups the bits into 56-Byte packets. There is one link between Host A and B; its transmission rate is 500 kbps and its propagation delay is 2 msec.As soon as Host A gathers a packet, it sends it to Host B. As soon as Host B receives an entire packet, it converts the packet’s bits to an analog signal. How much time elapses from the time a bit is created (from the original analog signal at Host A) until the bit is decoded(as part of the analog signal at Host B)?Answer: Consider the first bit in a packet. Before this bit can be transmitted, all of the bits in thepacket must be generated. This requires56∗8sec=7 msec64∗103The time required to transmit the packet is56∗8sec=896 μsec500∗103Propagation delay = 2 msec.The delay until decoding is7msec +896μsec + 2msec = 9.896msecA similar analysis shows that all bits experience a delay of 9.896 msec.16.(P9) Consider a packet of length L which begins at end system A, travels over one link to apacket switch, and travels from the packet switch over a second link to a destination end system. Let d i, s i, and R i denote the length, propagation speed, and the transmission rate of link i, for i= 1, 2. The packet switch delays each packet by d proc. Assuming no queuing delays, in terms of d i, s i, R i, (i= 1, 2), and L, what is the total end-to-end delay for the packet? Suppose now the packet Length is 1,000 bytes, the propagation speed on both links is 2.5 * 108m/s, the transmission rates of both links is 1 Mbps, the packet switch processing delay is 2 msec, the length of the first link is 6,000 km, and the length of the last link is 3,000 km. For these values, what is the end-to-end delay?Answer: The first end system requires L/R1to transmit the packet onto the first link; the packet propagates over the first link in d1/s1; the packet switch adds a processing delay ofd proc; after receiving the entire packet, the packet switch requires L/R2to transmit the packetonto the second link; the packet propagates over the second link in d2/s2. Adding these five delays givesd end-end = L/R1 + L/R2 + d1/s1 + d2/s2 + d procTo answer the second question, we simply plug the values into the equation to get 8 + 8 +24 + 12 + 2= 54 msec.17.(P10) In the above problem, suppose R1 = R2 = R and d proc= 0. Further suppose the packetswitch does not store-and-forward packets but instead immediately transmits each bit it receivers before waiting for the packet to arrive. What is the end-to-end delay?Answer: Because bits are immediately transmitted, the packet switch does not introduce any delay;in particular, it does not introduce a transmission delay. Thus,d end-end = L/R + d1/s1 + d2/s2For the values in Problem 9, we get 8 + 24 + 12 = 44 msec.18.(P11) Suppose N packets arrive simultaneously to a link at which no packets are currentlybeing transmitted or queued. Each packet is of length L and the link has transmission rate R.What is the average queuing delay for the N packets?Answer:The queuing delay is 0 for the first transmitted packet, L/R for the second transmitted packet, and generally, (n-1)L/R for the nth transmitted packet. Thus, the average delay for the N packets is(L/R + 2L/R + ....... + (N-1)L/R)/N = L/RN(1 + 2 + ..... + (N-1)) = LN(N-1)/(2RN) = (N-1)L/(2R) Note that here we used the well-known fact that1 +2 + ....... + N = N(N+1)/219.(P14) Consider the queuing delay in a router buffer. Let I denote traffic intensity; that is, I =La/R. Suppose that the queuing delay takes the form IL/R (1-I) for I<1.a.Provide a formula for the total delay, that is, the queuing delay plus the transmissiondelay.b.Plot the total delay as a function of L/R.Answer:a.The transmission delay is L / R . The total delay isILR(1−I)+LR=L/R1−Ib.Let x = L / R.Total delay=x 1−αx20.(P16) Perform a Traceroute between source and destination on the same continent at threedifferent hours of the day.a.Find the average and standard deviation of the round-trip delays at each of the threehours.b.Find the number of routers in the path at each of the three hours. Did the pathschange during any of the hours?c.Try to identify the number of ISP networks that the Traceroute packets pass throughfrom source to destination. Routers with similar names and/or similar IP addresses should be considered as part of the same ISP. In your experiments, do the largest delays occur at the peering interfaces between adjacent ISPs?d.Repeat the above for a source and destination on different continents. Compare theintra-continent and inter-continent results.Answer: Experiments.21.(P18) Suppose two hosts, A and B, are separated by 10,000 kilometers and are conn ectedby a direct link of R =2 Mbps. Suppose the propagation speed over the link is 2.5•108 meters/sec.a.Calculate the bandwidth-delay product, R•d prop.b.Consider sending a file of 400,000 bits from Host A to Host B. Suppose the file is sentcontinuously as one large message. What is the maximum number of bits that will be in the link at any given time?c.Provide an interpretation of the bandwidth-delay product.d.What is the width (in meters) of a bit in the link? Is it longer than a football field?e.Derive a general expression for the width of a bit in terms of the propagation speed s,the transmission rate R, and the length of the link m.Answer:a.d prop= 107 / 2.5•108= 0.04 sec; so R •d prop= 80,000bitsb.80,000bitsc.The bandwidth-delay product of a link is the maximum number of bits that can be inthelink.d. 1 bit is 125 meters long, which is longer than a football fielde.m / (R •d prop ) = m / (R * m / s) = s/R22.(P20) Consider problem P18 but now with a link of R = 1 Gbps.a.Calculate the bandwidth-delay product,R·d prop .b.Consider sending a file of 400,000 bits from Host A to Host B. Suppose the file is sentcontinuously as one big message. What is the maximum number of bits that will be inthe link at any given time?c.What is the width (in meters) of a bit in the link?Answer:a.40,000,000 bits.b.400,000 bits.c.0.25 meters.23.(P21) Refer again to problem P18.a.How long does it take to send the file, assuming it is sent continuously?b.Suppose now the file is broken up into 10 packet is acknowledged by the receiver andthe transmission time of an acknowledgment packet is negligible. Finally, assumethat the sender cannot send a packet until the preceding one is acknowledged. Howlong does it take to send the file?pare the results from (a) and (b).Answer:a. d trans + d prop = 200 msec + 40 msec = 240 msecb.10 * (t trans + 2 t prop ) = 10 * (20 msec + 80 msec) = 1.0sec。

CCNAITN第1章考试(供参考)

1第 1 章: 探索网络1 选择网络介质时应遵循哪两个标准？（请选择两项。

）需要优先处理的数据类型网络上使用的终端设备的成本介质可以成功传送信号的距离安装在网络中的中间设备的数量要安装介质的环境选择网络介质的标准包括：介质可以成功传送信号的距离、要安装介质的环境、必须传输的数据量和速度以及介质和安装的成本。

答案说明最高分值correctness of response Option 3 and Option 5 are correct.1 point for each correct option. 0 points if more options are selected than required.22 网络上的中间设备有哪两项功能？（请选择两项。

）2它们是为终端设备提供信息和服务的主要来源和提供者。

它们运行应用程序来支持业务协作。

它们形成了以人为本的网络与底层通信网络之间的界面。

它们在发生链路故障时按照备用路径转发数据。

它们根据安全设置过滤数据流。

中间网络设备上运行的进程可以执行以下功能：重新生成和重新传输数据信号，维护网络和网际网络中的现存路径的相关信息，在发生链路故障时将数据指向备用路径，根据安全设置允许或拒绝数据流。

答案说明最高分值correctness of response Option 4 and Option 5 are correct.1 point for each correct option. 0 points if more options are selected than required.23 哪种设备的功能是确定消息在网际网络中传输的路径？路由器防火墙3Web 服务器DSL 调制解调器路由器用于确定消息在网络中的传输路径。

防火墙用于过滤传入和传出的流量。

DSL 调制解调器用于为家庭或组织提供 Internet 连接。

答案说明最高分值correctness of response 2 points for Option 1 0 points for any other option244请参见图示。

ccna1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。

ccna2答案第一章

第一章路由内部故障CCNA2 Exploration:路由协议和概念(2010-12-15 18:45:19)转载▼标分类： 2010｜ CCNA2 官方试题 --路由签：ccna21杂谈1窗体顶端ERouting Chapter 1 - CCNA Exploration: 路由协议和概念(版本 4.0)在启动过程中，路由器可以从哪些位置加载Cisco IOS ？（选择两项。

）RAMTFTP 服务器NVRAM设置例程闪存终端窗体底端2窗体顶端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 、应用配置加载bootstrap、应用配置、加载IOS加载IOS、加载bootstrap、应用配置、检查硬件检查硬件、应用配置、加载bootstrap、加载IOS窗体底端3窗体顶端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？仅第 2 层源地址仅第 2 层目的地址仅第 3 层源地址仅第 3 层目的地址第 2 层源地址和目的地址第 3 层源地址和目的地址窗体底端4窗体顶端如果路由器在启动时无法找到有效的配置文件，将发生什么情况？启动过程将重置。

路由器将提示用户进行响应，以进入设置模式。

启动过程将停止，直到获得有效的配置文件。

路由器将根据上次的有效配置生成默认配置文件。

路由器将监控本地流量，以确定路由协议配置要求。

窗体底端5窗体顶端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 flashRouter1(config)# copy running-config flashRouter1# copy running-config startup-configRouter1(config)# copy running-config startup-configRouter1# copy startup-config running-configRouter1(config)# copy startup-config running-config窗体底端6窗体顶端下列哪些是路由器的功能？（选择三项。

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。

版本ccna考试第一章期末考试答案b

最新版本C C N A考试第一章期末考试答案bPDU 封装的正确顺序是什么？答案说明最高分值2correctness of response 2 points for Option 10 points for any other option此试题参考以下领域的内容：Introduction to Networks3.3.1 数据封装建立融合网络有何用途？为所有终端设备提供高速连接确保平等对待所有类型的数据包实现数据网络基础架构设备的容错能力和高可用性降低部署和维护通信基础设施的成本随着技术的发展，各个公司现在可以将不同的网络整合到一个平台之上，称为融合网络。

在融合网络中，语音、视频和数据通过同一网络传输，从而使人们不必再创建和维护各个单独的网络。

这也降低了提供和维护通信网络基础设施相关的成本。

答案说明最高分值2 correctness of response 2 points for Option 40 points for any other option此试题参考以下领域的内容：Introduction to Networks• 1.3.1 融合网络请参见图示。

哪个区域最有可能是图中所示的公司网络的外联网？区域 A区域 B区域 C区域 D外联网是外部实体访问其他公司的数据的平台。

其形式可能是产品供应商所使用的库存服务器，也可能是外部实体用来访问当天客户数量的当前信息的 Web 服务器。

Internet 用云和区域 A 表示。

内部网通常仅供内部人员使用。

区域 B 和 D 均是内部网的示例。

答案说明最高分值2 correctness of response 2 points for Option 30 points for any other option此试题参考以下领域的内容：Introduction to Networks• 1.2.3 Internet主机正在访问远程网络的 FTP 服务器。

(完整版)CCNA第一学期第一章答案

CCN/第一学期第一章答案1选择网络介质时应遵循珈两个标准？（请进择两项。

）正确您的响应响应需要优宪处理的埶据樂型网络上使用的终端设毎的成末4仲质可以成功倍送信号的拒葛安装在网络中的中i可设备的敎里/ 要安装介质的环愷2网络上的中间设备有哪两项功能？（请选择两项*）G应G应它们是址终端设备提供:信息和服务的主娶来源和提仪者。

匚它们运行应用程序来支持业务协作。

它们冊咸T以人为本的冋络与底层通信网络之间的界页。

它们在发生議路故障时按照备用路筈转发数摇4V 它们根捋安全设蛊过澹敎据淙。

3哪种设备的功能退确定消息在网麻网络中传输的路径?正确您的“ 路由器防火埴Web服势3!DSL调制晞调器Io IB G请参见图示。

下列哪组设备仅包含中间设备?正确您的响应响应G O A.B、D、GAx B\ E\ FC \D \ G、IG、H、I、J5下列有关LAN和WAN两者关系的说法，哪两项是正确的？（请选择两项。

）正咅您的LAN和W2I均能连接终端设备。

丿匚与LAN连接内部终训i殳旨％比，WAN连擾LAN於注觅速厦较低。

Inta mot 届于WAUWAN必须呈扯牡的・而L AN可囚由公有或私有实休拥有。

“ 匚WAN進常通过多个ISP运营.面LAN通常由一个组狽或个人运昏6曰于许多学生芒者自己的平仮电胞和智能手机去学校访问学校资源，大学里的IT人员最冇可能路要亘新设计的网络区域是什么？EM有线LAN孜LAN7家庭用户必须要有哪种网络类型访问才能进行网上购物?正确您的响应响应c內部网" Internet外联网局域网8下列哪两个Internet连接选项不斋要建筑物铺设物理电缆？（请选择两项。

）正确酗匚DSL'L移动电活丿匚卫星匚抜号专用村斟线洛9哪两个Internet 决方案可以为LAN上的计算机畫供始终在线的高带宽连接？（请选择两顼，）响应G应饲冼话4OD3L电用蝎10下列哪项描述正确定义了融合网络?正确您的响应昭应J单个网络信道能够传输多种通信节纽允许用户通过多个信道直接互动的网络视频和语音胆务使用独立信道的专用网络仅限于交换宇苻信息的网络11下列哪种说法正确摘述了支持QoS的网络?正场您的响应响应❸故障影响尽可能少的设备。

CCNA第二学期路由协议和概念chapter1答案.doc

哪两项说法正确描述了路由器的组件？（选择两项。

）RAM永久存储着在启动过程中使用的配置文件。

ROM含有硬件模块所执行的诊断程序。

NVRAM存储着在启动过程中使用的TOS的备份副本。

重新启动时闪存屮的内容不会丢失。

ROM包含最新而且最完整的10S版本。

闪存包含用于标识I0S位置的启动系统命令。

Option 2 and Option 4 are correct.1 point for each correct option.0 points if more options are sclccted than required.此试题参考以下领域的内容：CCNA Exploration:路由协议和概念* 1. 1.5路由器接口考试试题：图中的哪些接口可用于租用线路WAN连接？（选择两项。

）123456重置评分规贝|J：corrcc tn css of responseOption 1 and Option 4 are correct.1 point for each correct option.0 points if more options are seiected than required.此试题参考以下领域的内容：CCNA Exploration:路由协议和概念* 1. 1.4路由器启动过程考试试题：如果路由器在启动时无法找到有效的配置文件，将发牛什么情况? 启动过程将重置。

路由器将提示用户进行响应，以进入设置模式。

启动过程将停止，直到获得有效的配置文件。

路由器将根据上次的有效配置生成默认配置文件。

路由器将监控本地流量，以确定路由协议配置要求。

重置评分规贝lj：correctness of rcsponsc2 points for Option 20 points for any other option此试题参考以下领域的内容：CCNA Exploration:路由协议和概念* 1.1.4路由器启动过程考试试题：以下哪一项正确描述了路由器启动吋的顺序？加载bootstrap、加载I0S＞应用配置加载bootstrap、应用配置、加载10S加载I0S、加载bootstrap＞应用配置、检查硬件检查硬件、应用配置、加载bootstrap^加载I0S重置评分规贝lj：correctncss of response2 points for Option 10 points for any other option此试题参考以下领域的内容：CCNA Exploration:路由协议和概念* 1.1.4路由器启动过程考试试题:加载配置文件时的默认顺序是怎样的?NVRAM> FLASH、ROMNVRAM. TFTP、CONSOLEFLASH、TFTP、ROMFLASH. TFTP、CONSOLE重曽评分规则：correctness of response2 points for Option 30 points for any other option 最高分值二2此试题参考以下领域的内容：CCNA Exploration:路由协议和概念* 1. 1.4路由器启动过程考试试题：在启动过程中，路由器可以从哪些位置加载Cisco IOS?（选择两项。

2017CCNA第二学期第一章考试答案解析

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 与固定配置的交换机相比，模块化交换机具有哪两个优点？（请选择两项。

）正确响应您的响应每台交换机的成本更低可扩展性更高转发率更低需要的电源插座数目更少带宽聚合可以使用多个端口固定配置交换机价格较低，但是它具有指定数量的端口且不能添加端口。

它们提供的高速端口通常比较少。

为了在包含固定配置交换机的网络上扩展交换，需要购买更多的交换机。

这增加了需要使用的电源插座数量。

模块化交换机只需要购买额外的线卡便可以扩展。

带宽聚合也更容易，因为机箱的背板可以为交换机端口线卡提供所需的带宽。

此试题参考以下领域的内容：Routing and Switching Essentials• 1.1.2 交换网络2 思科无边界架构接入层的基本功能是什么？正确响应您的响应聚合第 2 层广播域聚合第 3 层路由边界为用户提供访问权提供高可用性思科无边界架构接入层的功能是为用户提供网络访问。

第 2 层广播域聚合、第 3 层路由边界聚合和高可用性是分布层的功能。

也有说答案是聚合第 3 层路由边界此试题参考以下领域的内容：Routing and Switching Essentials• 1.1.1 融合网络3 思科无边界架构分布层的基本功能是什么？正您的充当主干聚合所有园区块聚合第 3 层路由边界为用户提供访问权思科无边界架构的分布层的一项基本功能是在不同的 VLAN 之间路由。

充当主干和聚合园区块是核心层的功能。

为用户提供访问是接入层的功能。

此试题参考以下领域的内容：Routing and Switching Essentials• 1.1.1 融合网络4 若将大端口密度、容错和低价作为重要指标，应使用哪个交换机外形因素？正确响应您的响应固定配置交换机模块化交换机可配备机架的 1U 交换机可堆叠式交换机堆叠式交换机可以使用特殊电缆实现互联，从而在交换机之间提供高带宽的吞吐量，并像单个大型交换机一样运行。

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附录A
复习题和问题答案
第1章
复习题
1．D 外部网
D 局域网（LAN）和广域网（WAN）是一种复合技术，用于创建内部网和外部网，进而组成企业网络。

内部网只允许企业内部员工连接到安全的数据库。

外部网扩展了这个服务，允许信任的个人（例如顾客）访问数据库。

2．B 分配层
B 过滤流量发生在分配层。

接入层提供了最终用户到设备的接入点，核心层提供了高速中枢。

3．B 企业边缘
B 预测入侵和入侵检测必须放在边缘设备中，检查从服务提供商网络传输到公司网络的流量。

4．B 建筑分配模型
B 建筑接入模型包括第二层和第三层交换机，提供环境密度的正确端口。

这个模型对应VLAN 的实施和到建筑分配模型的主干链路。

建筑分配模型使用第三层设备，集合了建筑接入。

路由、接入控制和质量服务（QoS）是这个模型实施的。

设备冗余和链路是设计考虑的重点。

园区核心模型提供了建筑分配模型、数据重心服务器群和企业边缘的高速连接。

5．C 聊天
C 聊天允许个人之间实时的交流。

FTP用于在计算机之间传输文件，Telnet允许终端被远程机器打开，电子邮件（E-mail）没有实时的功能。

6．A部门文件共享
B打印
C内部备份
D内部园区声音
所有的答案都是正确的。

一些普通的流量类型保留在本地给LAN的用户，包括文件共享、打印、内部备份、镜像和内部园区声音。

如果这些类型的流量在WAN链路中发现，它们会占用带宽并引发安全问题。

7．当使用虚拟专用网络（VPN）时，将创建一个虚拟的隧道，链接来源和目的端地址。

所有在来源和目的端之间的数据流都会使用一个安全协议加密并封装起来。

这个安全包将在网络中传送。

当这个数据包到达目的地后，将被拆封和解密。

8．声音和视频应用程序需要不间断的数据流，以保证高质量的会话和图像。

TCP的承认过程引入延迟，这将中断这些数据流并降低应用程序的质量。

因此，声音和视频应用程序使用UDP而不是TCP。

因为UDP不会合并转发丢失数据包的机制将延迟降到最低。

9．当不可预知的流量在网络的某个区域被检测出来时，这个流量可以被过滤，而流量的来源可以调查出来。