CCNA第二学期第三章考试答案

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计算机网络第三章课后答案

第三章数据链路层3-01 数据链路(即逻辑链路)与链路(即物理链路)有何区别? “电路接通了”与”数据链路接通了”的区别何在?答：数据链路与链路的区别在于数据链路出链路外，还必须有一些必要的规程来控制数据的传输，因此，数据链路比链路多了实现通信规程所需要的硬件和软件。

“电路接通了”表示链路两端的结点交换机已经开机，物理连接已经能够传送比特流了，但是，数据传输并不可靠，在物理连接基础上，再建立数据链路连接，才是“数据链路接通了”，此后，由于数据链路连接具有检测、确认和重传功能，才使不太可靠的物理链路变成可靠的数据链路，进行可靠的数据传输当数据链路断开连接时，物理电路连接不一定跟着断开连接。

3-02 数据链路层中的链路控制包括哪些功能?试讨论数据链路层做成可靠的链路层有哪些优点和缺点.答：链路管理帧定界流量控制差错控制将数据和控制信息区分开透明传输寻址可靠的链路层的优点和缺点取决于所应用的环境：对于干扰严重的信道，可靠的链路层可以将重传范围约束在局部链路，防止全网络的传输效率受损；对于优质信道，采用可靠的链路层会增大资源开销，影响传输效率。

3-03 网络适配器的作用是什么?网络适配器工作在哪一层?答：适配器（即网卡）来实现数据链路层和物理层这两层的协议的硬件和软件网络适配器工作在TCP/IP协议中的网络接口层（OSI中的数据链里层和物理层）3-04 数据链路层的三个基本问题(帧定界、透明传输和差错检测)为什么都必须加以解决？答：帧定界是分组交换的必然要求透明传输避免消息符号与帧定界符号相混淆差错检测防止合差错的无效数据帧浪费后续路由上的传输和处理资源3-05 如果在数据链路层不进行帧定界，会发生什么问题？答：无法区分分组与分组无法确定分组的控制域和数据域无法将差错更正的范围限定在确切的局部3-06 PPP协议的主要特点是什么？为什么PPP不使用帧的编号？PPP适用于什么情况？为什么PPP协议不能使数据链路层实现可靠传输？答：简单，提供不可靠的数据报服务，检错，无纠错不使用序号和确认机制地址字段A 只置为0xFF。

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第二学期练习答案chapter3

1Which two statements correctly describe the concepts of administrative distanc metric? (Choose two.)Administrative distance refers to the trustworthiness of a particular route.A router first installs routes with higher administrative distances.The value of the administarive distance can not be altered by the networkRoutes with the smallest metric to a destination indicate the best path.The metric is always determined based on hop count.The metric varies depending which Layer 3 protocol is being routed, such as2Refer to the exhibit. Which statement correctly describes how R1 will determinepath to R2?R1 will install a RIP route using network A in its routing table because theadministrative distance of RIP is higher than EIGRP.R1 will install a RIP route using network A in its routing table because the pafrom RIP is lower than EIGRP.R1 will install an EIGRP route using network B in its routing table because th administrative distance of EIGRP is lower than RIP.R1 will install an EIGRP route using network B in its routing table because th cost from EIGRP is lower than RIP.R1 will install an EIGRP route and a RIP route in its routing table and load b between them.3 Which two statements are true regarding classless routing protocols? (Choosesends subnet mask information in routing updatessends complete routing table update to all neighborsis supported by RIP version 1allows for use of both 192.168.1.0/30 and 192.168.1.16/28 subnets in the sareduces the amount of address space available in an organization4 Which command would the network administrator issue to determine if load balin effect on a router?s how ip protocolss how ip routes how ip interface briefs how ip interface5 Which two conditions would create a setting where the use of a distance-vectorprotocol would be efficient? (Choose two.)the network requires a special hierarchical designfast convergence of the network is crucialthe network is using a hub and spoke topologythe network is using a flat designthere are more than 15 hops between the most distant routers6 What is the purpose of a routing protocol?It is used to build and maintain ARP tables.It provides a method for segmenting and reassembling data packets.It allows an administrator to devise an addressing scheme for the network.It allows a router to share information about known networks with other route It provides a procedure for encoding and decoding data into bits for packet forwarding.7 Which of the following best describes the operation of distance vector routing pThey use hop count as their only metric.They only send out updates when a new network is added.They send their routing tables to directly connected neighbors.They flood the entire network with routing updates.8 What attribute is associated with link-state routing protocols?split horizonpoison reverselow processor overheadshortest-path first calculations9 Why is fast convergence desirable in networks that use dynamic routing protocRouters will not allow packets to be forwarded until the network has converg Hosts are unable to access their gateway until the network has converged.Routers may make incorrect forwarding decisions until the network has conv Routers will not allow configuration changes to be made until the network ha converged.10 Which of the following conditions must be met in order for a network to have conThe routers in the network are operating with dynamic routing protocols.The routers in the network are operating with compatible versions of IOS.The routers in the network are operating with the same routing tables.The routers in the network are operating with consistent routing knowledge.11 Which two statements are true regarding metrics? (Choose two.)RIP uses bandwidth as a metric.OSPF uses delay as a metric.EIGRP uses bandwidth as a metric.OSPF uses cost based on bandwidth as a metric.RIP uses delay as a metric.EIGRP uses hop count only as a metric.12 Which two statements are true regarding the advantages of the use of static routes? (Choosincreased securityreduced effort in configuring routesthe administrator maintains control over routingeasier to implement in a growing networkreduces the chance of routing errorsincreased router resource usage13 The following line of code is displayed in a routing table:R 209.165.201.0/24 [120/2] via 192.168.252.2, 00:00:16, S0/0/0What can be concluded from this output?A packet destined for host 192.168.252.2 will be forwarded out the interface connected t209.165.201.0/24.The value, 120, is used to determine the best path when a router has more than one rou protocol configured for the same destination network.This route was manually configured using the ip route command.192.168.252.2 is an interface on the router that produced this output.14 What will be the result of the following commands?ORL(config)# interface fastethernet 0/0ORL(config-if)# ip address 172.16.3.1 255.255.255.0ORL(config-if)# no shutdownThe 172.16.3.0 network will be routed by any dynamic routing protocol automatically.A routing table entry is made to the 172.16.3.0 network with a code of "C".A static route is required to route traffic to the 172.16.3.0 network.The commands will be saved to the startup-configuration automatically.15 An engineer creates a static route by entering the Router(config)# ip route 10.0.0.0 255.255192.168.1.2 command. What can be concluded about this route?The administrative distance of this route is 1.192.168.1.2 is the address of an interface on this router.This route will display as a directly connected network in the routing table.Packets with a destination IP address of 192.168.1.2 will be forwarded to the 10.0.0.0/24 first.16Refer to the exhibit. Router1 and Router2 are running EIGRP. All interfaces are operational a packets can be forwarded between all networks. What information will be found in the routing Router1?Router1 will have 6 directly connected networks.The administrative distance of the route to network 172.16.0.0 will be 90.The metric for routes to 172.16.0.0 will be 1.The interface that is used to forward packets to 172.16.0.0 will always be the S0/1 interfa 17 The following line of code is present in the routing table:O 10.16.1.0/27 [110/129] via 192.168.1.5, 00:00:05, Serial0/0/1What does the number 129 indicate in this output?The cost for this link has a value of 129.The clock rate on this serial interface is set to 129,000.The next-hop router is 129 hops away from this router.This route has been updated 129 times in this routing table.18 A growing medium-sized manufacturing company recently began to have routing instability iscompany uses static routes and has a mixture of over 30 Cisco and non-Cisco routers. The n administrator has decided to convert the network to dynamic routing. What characteristics of should be considered in this selection process?Distance vector routing protocols, such as RIP, converge more quickly than do link-state protocols.EIGRP can be used on all of the routers in the company.OSPF can be used between the routers.An exterior routing protocol, such as BGP, is recommended for growing companies.19Refer to the exhibit. If RIP is the routing protocol, what is the value metric from router A to network 192.168.5.0/24?345662472420 A router learns two paths with equal metrics to a destination network via the RIP routing protwill the router handle packets to the destination network?The router will install the first route it learned into the routing table.The router will install both routes in the routing table and load balance between the two.The router will put the first route in the routing table, and denote the second route as a ba route.The router will pick the path with the higher bandwidth and will place it in the routing tabl。

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。

CCNA2第3章答案

CCNA2第3章答案1. 第3章简介本章讨论了局域网的部署和故障排除。

局域网是一个小范围内的计算机网络，通常被用于连接办公室或住宅中的设备。

本章重点介绍了局域网的构建和故障排除的一些基本概念和技术。

2. 局域网构建局域网的构建需要考虑以下几个关键因素：2.1 路由器和交换机•路由器是一个网络设备，用于将数据包在不同网络之间转发。

它可以连接不同的局域网，并在它们之间进行通信。

路由器通常具有多个接口，每个接口都可以连接到一个局域网。

•交换机是一个网络设备，用于在局域网内转发数据帧。

它可以将数据帧从一个端口转发到另一个端口，以便设备可以进行通信。

交换机根据MAC地址来转发数据帧，这使得局域网中的设备可以直接通信，而不需要经过路由器。

2.2 VLAN•VLAN（Virtual Local Area Network）是一种将局域网分割为多个虚拟网络的技术。

每个VLAN都有自己的逻辑分组，并且设备只能与同一VLAN中的设备进行通信。

VLAN可以提高网络的性能和安全性。

•VLAN可以通过交换机进行配置。

管理员可以将不同的端口分配给不同的VLAN，从而实现不同设备之间的逻辑隔离。

2.3 IP地址规划•IP地址是互联网上的设备进行通信的唯一标识符。

在构建局域网时，我们需要使用IP地址来唯一标识每个计算机或设备。

•IP地址可以手动配置，也可以通过DHCP服务器进行自动分配。

3. 局域网故障排除在网络运行过程中，可能会出现一些故障。

在这种情况下，我们需要进行故障排除来找出问题所在，并采取相应的措施进行修复。

以下是一些常见的局域网故障排除步骤：3.1 确定问题范围首先，我们需要确定问题的范围。

问题可能只影响特定的设备或特定的网络部分。

通过确定问题的范围，我们可以更方便地定位故障的根源。

3.2 确认基本连接检查设备之间的物理连接是否正确。

确保电缆连接可靠，并且没有松动或损坏。

3.3 使用ping工具测试连接使用ping工具测试设备之间的连通性。

CCNA第章考试答案

••试题反馈报告IntroductiontoNetworks(版本-ITN第3章考试以下是针对您未获得满分的试题给出的反馈。

某些交互式试题可能不显示您的答案。

分项分数：1两台计算机可以使用什么方法来确保数据包不会因为过多数据发送过快而被丢弃？正确响应您的响应封装访问方法流量控制响应超时为使两台计算机能够有效通信，必须具有让源和目标设置数据传输和接收时间的机制。

为了正确接收数据，流量控制可以确保数据不会发送的太快。

此试题参考以下领域的内容：IntroductiontoNetworks•规则2哪种类型的通信会向局域网上的所有设备发送消息？正确响应您的响应广播单播组播全播广播通信是一对所有的通信。

单播通信是一对一的通信。

组播是一对多的通信，其中消息会发送给一组特定主机。

全播不是一个描述消息传输的标准术语。

此试题参考以下领域的内容：IntroductiontoNetworks•规则3哪个过程用于将一个消息放入另一消息内以从源传输到目的地？正确响应您的响应流量控制封装访问控制解码封装是将一种消息格式放入另一种消息格式的过程。

例如，一个数据包在封装成帧时如何将其完整放入数据字段中。

此试题参考以下领域的内容：IntroductiontoNetworks•规则4Web客户端向Web服务器发送一个网页请求。

从客户端的角度来讲，用于准备传输请求的协议栈正确顺序是什么？正确响应您的响应HTTP、TCP、IP、以太网HTTP、IP、TCP、以太网以太网、TCP、IP、HTTP以太网、IP、TCP、HTTP用于控制Web服务器和客户端进行交互的方式。

用于管理Web服务器与客户端之间的每次会话。

负责通过最佳路径传输到目标。

4.以太网从IP获取数据包，并将其格式化以供传输。

此试题参考以下领域的内容：IntroductiontoNetworks•协议5下列有关网络协议的陈述哪项是正确的？正确响应您的响应只有在远程网络中的设备之间交换消息时才需要使用网络协议。

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。

计算机网络第三章课后答案

计算机网络第三章课后答案(总4页)--本页仅作为文档封面，使用时请直接删除即可----内页可以根据需求调整合适字体及大小--第三章3-01 数据链路( 即逻辑链路) 与链路( 即物理链路) 有何区别“电路接通了”与”数据链路接通了”的区别何在答：数据链路与链路的区别在于数据链路出链路外，还必须有一些必要的规程来控制数据的传输，因此，数据链路比链路多了实现通信规程所需要的硬件和软件。

3-02 数据链路层中的链路控制包括哪些功能试讨论数据链路层做成可靠的链路层有哪些优点和缺点.答：链路管理帧定界流量控制差错控制将数据和控制信息区分开透明传输寻址可靠的链路层的优点和缺点取决于所应用的环境：对于干扰严重的信道，可靠的链路层可以将重传范围约束在局部链路，防止全网络的传输效率受损；对于优质信道，采用可靠的链路层会增大资源开销，影响传输效率。

3-03 网络适配器的作用是什么网络适配器工作在哪一层答：适配器（即网卡）来实现数据链路层和物理层这两层的协议的硬件和软件网络适配器工作在TCP/IP协议中的网络接口层（OSI 中的数据链里层和物理层）3-04 数据链路层的三个基本问题(帧定界、透明传输和差错检测)为什么都必须加以解决答：帧定界是分组交换的必然要求，透明传输避免消息符号与帧定界符号相混淆，差错检测防止合差错的无效数据帧浪费后续路由上的传输和处理资源3-05 如果在数据链路层不进行帧定界，会发生什么问题答：无法区分分组与分组，无法确定分组的控制域和数据域，无法将差错更正的范围限定在确切的局部3-06 PPP协议的主要特点是什么为什么PPP 不使用帧的编号PPP 适用于什么情况为什么PPP 协议不能使数据链路层实现可靠传输答：简单，提供不可靠的数据报服务，检错，无纠错不使用序号和确认机制地址字段A 只置为 0xFF。

ccna第二学期练习答案

c c n a第二学期练习答案(总45页)--本页仅作为文档封面，使用时请直接删除即可----内页可以根据需求调整合适字体及大小--ERouting Chapter 1 - CCNA Exploration: 路由协议和概念(版本1口令可用于限制对 Cisco IOS 所有或部分内容的访问。

请选择可以用口令保护的模式和接口。

（选择三项。

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

网络管理员已经为路由器连接到直连网络的接口配置了如图所示的 IP 地址。

从路由器 ping 相连网络路由器接口之间相互 ping 都会遭到失败。

此问题最可能的原因是什么必须使用no shutdown命令启用接口。

4请参见图示。

主机 A ping 主机 B。

当 R 网接口的 ping 时，哪两块报头信息包括在内（选择两项。

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

要将配置更改保存到 NVRAM，应该执行哪一条命令Router1# copy running-config startup-config6您需要配置图中所示的串行连接，必须在 Sydney 路由下哪条配置命令才能与 Melbourne 站点建立连接（选择三项）Sydney(config-if)# ip addressSydney(config-if)# no shutdownSydney(config-if)# clock rate 560007请参见图示。

从路由器的运行配置输出可得出什么结论显示的命令决定了路由器的当前运行情况。

8请参见图示。

在主机 2 连接到 LAN 上的交换机后，主主机 1 通信。

导致此问题的原因是什么主机 1 和主机 2 位于不同的网络中。

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

ccna考试题及答案

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

CCNA第二学期考试答案

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？正确响应您的响应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。

CCNA2思科第二学期v20ERoutingFinalExam3答案

1关于数据包通过路由器传输时的封装和解封的叙述，下列哪三项是正确的？(选择三项。

)路由器修改 TTL 字段，将其值减 1。

路由器将源 IP 更改为送出接口的 IP。

路由器保持相同的源IP和目的IP。

路由器将源物理地址更改为送出接口的物理地址。

路由器将目的IP更改为送出接口的IP。

路由器会从所有接口将数据包转发出去，包括路由器接收数据包时使用的那个接口。

Option1,Option3,andOption4arecorrect.2请参见图示。

当数据包发往哪两个网络时需要路由器执行递归查找？(选择两项。

)10.0.0.0/864.100.0.0/16128.107.0.0/16172.16.40.0/24192.168.1.0/24192.168.2.0/24Option 1 and Option 6 arecorrect.3对于为防止路由环路而通过毒性反转实现的水平分割方法，哪两项叙述正确？(选择两项。

)所有CiscoIOS都会默认启用此方法。

会将一个表示无穷大度量的值分配给路由以将其毒化。

将毒化路由更新发回该更新的发送接口。

指示路由器将可能会影响路由的更改保持一段特定的时间。

限制数据包在被丢弃之前能够在网络中传输的跳数。

Option2andOption3arecorrect.4网络管理员在所示网络图中的路由器B和C上启用了 RIP。

什么命令可防止向路由器 A发送RIP更新? A(config)#routerripA(config-router)#passive-interfaceS0/0B(config)#routerripB(config-router)#network192.168.25.48B(config-router)#network192.168.25.64A(config)#routerripA(config-router)#nonetwork192.168.25.32B(config)#routerripB（config-router）#passive-interfaceS0/0A（config）#norouterrip2pointsforOption45请参见图示。

CCNA第3章测验答案

此试题参考以下领域的内容：
Introduction to Networks
3.1.1规则
哪个过程用于将一个消息放入另一消息内以从源传输到目
的地？
正确您的
响应响应
流量控制
封装
访问控制
解码
封装是将一种消息格式放入另一种消息格式的过程。例如，一个数据包在封装成帧时如何将其完整放入数据字段中。
此试题参考以下领域的内容：
网络协议在硬件或软件或两者中实施。它们在协议栈的不同层中交互。协议与网络设备的安装情况无关。本地和远程网络中的源设备和目的设备之间交换信息时需要使用网络协议。
此试题参考以下领域的内容：
Introduction to Networks
3.2.1协议
列有关
正确您的
响应响应
前三个OSI层描述TCP/IP网络层提供的相同常规服务。
4.以太网从IP获取数据包，并将其格式化以供传输。
此试题参考以下领域的内容：
Introduction to Networks
3.2.1协议
只有在远程网络中的设备之间交换消息时才需要使用网络协议。
网络协议定义了所用硬件类型及其如何在机架中安装。
网络协议都是在TCP/IP的网络接入层发挥作用。
网络协议定义了消息在源地址和目的地址之间如何交换。
TCP/IP网络接入层与OSI网络层具有类似的功能。
TCP/IP传输层与OSI第4层提供类似的服务和功能。
OSI第7层和TCP/IP应用层提供相同的功能。
TCP/IP网络层的功能与OSI网络层相同。TCP/IP模型和OSI模型的传输层具有相同的功能。TCP/IP应用层包括OSI第5、6和7层的相同功能。
此试题参考以下领域的内容：

CCNA 2 Final Exam Answers V3.1

1. What are two possible reasons a router would not load a valid IOS from flash? (Choose two.)The configuration register is set to 0×2142.The first boot system command executed in the startup configuration file is boot system rom.The configuration register is set to 0×2100.The boot field is set to the hexadecimal number 2.The startup configuration file is missing or corrupt.2. What are two recommended uses of login banners? (Choose two.)to display security warning messagesto welcome any user to the routerto warn people about misusing privileged EXEC modeto identify circuits and other devices connected to the routerto announce a scheduled system shutdown3.Router A and Router B have been correctly configured to use RIP as a dynamic routing protocol and all intefaces on Router A and Router B are reporting "interface is up, line protocol is up" status. RIP is then configured onRouter C using the following commands:RouterC(config)# router ripRouterC(config-router)# network 192.168.4.0RouterC(config-router)# network 172.16.0.0If no additional routing is configured on Router A, Router B, and Router C, what will be the result?Networks 192.168.12.0/24, 192.168.4.0/24, and 172.16.0.0/16 will be unreachable from Router A.Router A will have no knowledge of network 192.168.12.0/24, but will have routes to networks 192.168.4.0/24 and 172.16.0.0/16.All networks shown in the graphic will be reachable by Router A, Router B, and Router C.Networks 192.168.4.0/24 and 172.16.0.0/16 will be unreachable from Router A and Router B.4. What are the primary functions of a router? (Choose two.) determine the best path for packetsprevent collisions on the network LANregulate flow control between sender and receiverprovide domain name resolutionforward packets to the appropriate interface5. What are some reasons to change the configuration register setting? (Choose two.)to force the system to ignore the configuration file stored in NVRAM to monitor password changesto change the POST sequenceto force the router to boot the IOS from NVRAMto force the system into ROM monitor mode6. A network administrator issues the erase startup-config command on a configured router with the configuration register set to 0×2102 and observes the following output:Erasing the nvram filesystem will remove all files! Continue? [Confirm] [OK]Erase of nvram: completeIf the router unexpectedly loses power after this sequence, what will occur when power is restored?The router will enter ROM monitor mode upon completion of the power-on self test (POST).The router will load the last known valid configuration file.The router will enter Rx-boot mode.The router will prompt the user to enter setup mode or to continue without entering setup mode.7. Why are routed protocols important to networking? (Choose two.) Routed protocols detect collisions and fragments.Routers use routed protocols to calculate the best path to a destination. Routed protocols transport data across the network.The fields and formats used within a packet are defined by routed protocols.Routed protocols are used to configure the metrics used by routing protocols.8. The main router of XYZ company has enough flash and RAM to store multiple IOS images. An administrator wants to upload a second IOS image from a TFTP server to the flash of the router. Which method will accomplish this task?Paste the IOS filename to the command line of the router while in global configuration mode. Press enter. Then issue the copy tftp flash command.Use the setup utility to load the new image to flash.Copy the IOS image file from a TFTP server using the command copy filenameip address flash .Copy the IOS image file from a TFTP server using the command copy tftp flash. When prompted, provide the IP address or name of the TFTP server and the IOS image filename.9.A network administrator has a console connection to the Fremantle router. Pings to Melville are successful, but pings to Cottesloe and Nedlands fail. What could be a first step in troubleshooting the problem?Use an extended ping from Fremantle to each router in the network.Use the show interfaces command from a Telnet session on Melville to check the connection to Cottesloe.Use the traceroute command to discover exactly which link in the network is down.Use the show cdp neighbors detail command from Fremantle to gather information about all Cisco routers in the network.10.Refer to the exhibit. The new security policy for the company allows all IP traffic from the Engineering LAN to the Internet while only web traffic from the Marketing LAN is allowed to the Internet. Which ACL can be applied in the outbound direction of Serial 0/1 on the Marketing router to implement the new security policy?access-list 197 permit ip 192.0.2.0 0.0.0.255 anyaccess-list 197 permit ip 198.18.112.0 0.0.0.255 any eq wwwaccess-list 165 permit ip 192.0.2.0 0.0.0.255 anyaccess-list 165 permit tcp 198.18.112.0 0.0.0.255 any eq wwwaccess-list 165 permit ip any anyaccess-list 137 permit ip 192.0.2.0 0.0.0.255 anyaccess-list 137 permit tcp 198.18.112.0 0.0.0.255 any eq wwwaccess-list 89 permit 192.0.2.0 0.0.0.255 anyaccess-list 89 permit tcp 198.18.112.0 0.0.0.255 any eq www11.Hosts from the Limerick LAN are not allowed access to the Shannon LAN but should be able to access the Internet. Which set of commands will create a standard ACL that will apply to traffic on the Shannon router interface Fa0/0 implementing this security?access-list 42 deny 172.19.123.0 0.0.0.255 192.0.2.0 0.0.0.255 access-list 42 permit anyaccess-list 56 deny 172.19.123.0 0.0.0.255access-list 56 permit anyaccess-list 61 deny 172.19.123.0 0.0.0.0access-list 61 permit anyaccess-list 87 deny ip any 192.0.2.0 0.0.0.255access-list 87 permit ip any12. Which of the following commands will correctly configure an extended ACL? (Choose two).Router(config)# access-list 18 permit tcp host 192.168.73.3 eq 25Router(config)# access-list 102 permit tcp 10.43.0.0 0.0.255.255 any eq 80Router(config)# access-list 187 permit tcp host 192.168.42.34 172.29.0.0 0.0.255.255 eq 23Router(config)# access-list 99 permit host 10.217.32.3Router(config)# access-list 128 permit tcp host 192.168.100.31 eq 2313. What are the results of setting the boot field bits in the configuration register to "0000"? (Choose two.)The startup-config file will be ignored at bootup.The router will load the IOS from Flash.The router will enter ROM monitor mode upon reload.The router will enter boot ROM mode and have limited capabilities. The administrator can enter the b command to manually boot the IOS.14.Refer to the exhibit. Router D interface S0 on has gone down. What is the maximum time that will elapse before Router A learns that network 168.58.14.0 is down?5 seconds13 seconds17 seconds25 seconds30 seconds77 seconds15. During initial router bootup the following line appears: "NVRAM invalid, possibly due to write erase."What are two possible reasons for this result? (Choose two.)The startup-config file was not saved to RAM before reboot.The IOS has been erased.The router has not been configured.The startup-config file cannot be located.The router will not enter initial configuration dialog.16.The Suffolk router is directly connected to the networks shown in the graphic and has a default route that points to the Richmond router. All interfaces are active and properly addressed. However, when the workstation on network 172.29.5.0/24 sends a packet to destination address 172.29.198.5, it is discarded by the Suffolk router. What can be a reason for this result?The ip classless command is not enabled on the Richmond router.The route was ignored if the Richmond router did not include the 172.29.198.0/24 network in its routing updates.The Richmond router is in a different autonomous system than the Suffolk router.The ip subnet-zero command was not configured on the Suffolk router.The ip classless command is not enabled on the Suffolk router.17. access-list 199 deny tcp 178.15.0.0 0.0.255.255 any eq 23 access-list 199 permit ip any anyAssuming this ACL is correctly applied to a router interface, which statements describe traffic on the network? (Choose two.)All FTP traffic from network 178.15.0.0 will be permitted.All Telnet traffic destined for network 178.15.0.0 will be denied.Telnet and FTP will be permitted from all hosts on network 178.15.0.0 to any destination.Telnet will not be permitted from any hosts on network 178.15.0.0 to any destination.Telnet will not be permitted to any host on network 178.15.0.0 from any destination.18.What facts can be determined from the highlighted text shown in the exhibit? (Choose two.)A weak encryption was applied to all unencrypted passwords.The enable password is now more secure than the enable secret password.An MD5 hashing algorithm was used on all encrypted passwords.Any configured user EXEC mode or Telnet passwords will be encrypted in this configuration.The service password-encryption command was used to encrypt all passwords on the router including enable secret.19. What are three features of CDP? (Choose three.)provides information on directly connected devices that have CDP enabled tests Layer 2 connectivityenabled by default on each interfaceprovides a layer of securityused for debugging Layer 4 connectivity issues20. What information can be learned during the initial router bootup? (Choose two.)the configuration register valuethe number and types of interfaces installedthe router model and the amount of memory that is availablethe amount of memory required to load the IOS and configurationthe number of interfaces with connected cables21.What can be concluded from the output shown in the exhibit? (Choose three.)This is a standard IP access list.This is an extended IP access list.The keyword host is implied in the command line access-list 99 deny 10.213.177.76.The wildcard mask must be configured for this access list to function properly.Host 10.213.177.100 will be allowed access to the Serial0/1 interface.22. Which statements are true regarding setup mode? (Choose three.)Press Ctrl-z to terminate setup mode.Enter a question mark (?) for help at any point.Press Spacebar to accept the default settings.Use setup mode to enter complex protocol features.Press Enter to accept the default settings.Press Ctrl-c to abort configuration dialog.23.Refer to the graphic. Which series of commands will create static routes that will allow Router A and Router B to deliver packets destined for LAN A and LAN B, and direct all other traffic to the Internet?RouterA(config)# ip route 10.90.3.0 255.255.255.0 192.168.3.2RouterB(config)# ip route 192.168.2.0 255.255.255.0 192.168.3.1 RouterB(config)# ip route 0.0.0.0 0.0.0.0 s0/0RouterA(config)# ip route 10.90.3.0 255.255.255.0 192.168.3.2RouterA(config)# ip route 0.0.0.0 0.0.0.0 192.168.3.2RouterB(config)# ip route 192.168.2.0 255.255.255.0 192.168.3.1RouterA(config)# ip route 0.0.0.0 0.0.0.0 192.168.3.2RouterB(config)# ip route 192.168.2.0 255.255.255.0 192.168.3.1 RouterB(config)# ip route 172.20.20.4 255.255.255.252 s0/0RouterA(config)# ip route 0.0.0.0 0.0.0.0 192.168.3.2RouterB(config)# ip route 192.168.2.0 255.255.255.0 192.168.3.1 RouterB(config)# ip route 0.0.0.0 0.0.0.0 s0/024.Which devices can be used to convert the data from a WAN router at the customer site into a form acceptable for use by the WAN service provider? (Choose three.)Ethernet switchDTEmodemhubDCE deviceCSU/DSU25.What will occur when the following ACL is applied inbound to both FastEthernet interfaces of Router A in the graphic?access-list 125 permit tcp 192.168.2.0 0.0.0.255 10.90.3.0 0.0.0.255 eq 23access-list 125 permit tcp 10.90.3.0 0.0.0.255 192.168.2.0 0.0.0.255 eq 23access-list 125 permit tcp 192.168.2.0 0.0.0.255 any eq wwwWorkstations A and B will be able to Telnet to each other. WorkstationA will be allowed to access Web servers on the Internet, while WorkstationB will be denied Internet Web access.Workstations A and B will be able to Telnet to each other. All other traffic will be denied.The ACL will have no effect because it should be applied in the outbound direction on the FastEthernet interfaces.The ACL will deny all traffic because of the implied deny ip any any statement at the end of the ACL.26. Based on this partial output of the show ip route command, which routing protocol is configured on the router?R 172.16.3.0/24 [120/3] via 172.16.2.2, 00:00:27, Serial0/0RIPEIGRPOSPFIGPBGP27.Which of the following are correct statements verified by the router output shown in the graphic? (Choose two.)Layer 3 connectivity exists between BigCity and the devices in the Device ID column.Layer 2 connectivity exists between BigCity and the devices in the Device ID column.All devices shown in the Device ID column use the TCP/IP protocol suite.All devices shown in the Device ID column can be pinged from BigCity.All devices listed in the Device ID column are directly connected to BigCity.28. A network administrator must configure a FastEthernet interface with an IP address. The configuration must also identify the remote site to which the interface is connected. Which set of commands will meet these requirements?StPetersburg(config)# banner San Jose T1StPetersburg(config)# interface fa0/0StPetersburg(config-if)# ip address 172.26.155.5 255.255.255.252StPetersburg(config)# interface fa0/0StPetersburg(config-if)# ip address 172.26.155.5 netmask255.255.255.252StPetersburg(config-if)# description San Jose T1StPetersburg(config)# interface fa0/0StPetersburg(config-if)# ip address 172.26.155.5 255.255.255.252 StPetersburg(config-if)# banner remote site San Jose T1StPetersburg(config)# interface fa0/0StPetersburg(config-if)# ip address 172.26.155.5 255.255.255.252 StPetersburg(config-if)# description San Jose T129. What are the features of a serial interface on a router? (Choose two.) enabled by defaultassigned a unique MAC addressmust be configured as a DCE in lab and production environmentsmust be configured with the default clock rate of 56000may be administratively enabled by using the no shutdown commandmust be configured with a valid IP address and subnet mask in order to forward packets30. Assuming the following ACL is correctly applied to a router interface, what can be concluded about this set of commands? (Choose two.) Router(config)# access-list 165 deny tcp 192.28.115.0 0.0.0.255 172.20.0.0 0.0.255.255 eq 23Router(config)# access-list 165 permit ip any anyThis is a standard IP access list that denies network 192.28.115.0 Telnet access to the 172.20.0.0 network.All Telnet traffic destined for 172.20.0.0 from any network will be denied access.Network 192.28.115.0 is denied Telnet access to the 172.20.0.0 network. Network 172.20.0.0 is denied Telnet access to the 192.28.115.0 network.All FTP and HTTP traffic destined for 172.20.0.0 will be permitted access.31. Which two steps describe how to create a functional physical connection between a router console and a terminal? (Choose two.)Use a crossover cable to connect the terminal serial port to the router console port.Use a rollover cable to connect the terminal NIC to the router console port.Use an RJ-45 to DB-9 adapter on the terminal serial port to connect to the cable going to the router console.Use a transceiver to connect a straight-through cable to the router console port.Use a straight-through cable to connect the router console port to the terminal NIC.Use a rollover cable to connect from a terminal serial port to the router console port.32. What critical information about the status of the router can be found in the outputs of both the show interfaces and show protocols commands? (Choose two.)the Layer 3 address of each configured interfacethe routing protocol configured to forward updates out of each interface the operational status of each interfacetraffic statistics for each interfacewhether the interface is configured as a DTE or DCE33.The following access list has been created to prevent traffic from the 192.0.2.63 host on the Sales LAN from accessing servers and hosts on the Payroll LAN.access-list 26 deny host 192.0.2.63access-list 26 permit anyRefer to the exhibit. Which group of commands will properly place the access list so that only the host on the Sales LAN is denied access to the 172.29.7.0 network but all other traffic is permitted?Payroll(config)# interface fa0/0Payroll(config-if)# ip access-group 26 outPayroll(config)# interface fa0/1Payroll(config-if)# ip access-group 26 outSales(config)# interface fa0/1Sales(config-if)# ip access-group 26 inSales(config)# interface fa0/0Sales(config-if)# ip access-group 26 out34.Refer to the exhibit. Assuming default metrics are used and the networkis fully converged, which path will RIP use to send a packet from Router A to Router F?A, D, E, FA, B, D, E, FA, C, D, E, G, FA, B, D, E, G, F35.Refer to the graphic. Communication is needed between the LAN connected to the fa0/0 interface of the Kansas router and the fa0/0 interface of the Maine router. All hosts on those LANs also need connectivity to the Internet. Which commands will allow this communication? (Choose three).Kansas(config)# ip route 192.168.6.0 255.255.255.0 172.18.64.2Kansas(config)# ip route 192.168.6.0 255.255.255.0 s0/1Kansas(config)# ip route 0.0.0.0 0.0.0.0 s0/1Maine(config)# ip route 192.168.6.0 255.255.255.0 172.18.64.1Maine(config)# ip route 0.0.0.0 0.0.0.0 s0/1Maine(config)# ip route 172.16.32.0 255.255.255.0 172.18.64.236. Why are interface descriptions used in router configurations? (Choose three).to enable support personnel to easily identify networks and customers that may be affected by a possible interface issueto provide comments on the interface without affecting the router functionalityto display access warning messages before users enter the interface configuration modeto eliminate the need to use IP addresses when using the ping and telnet commandsto identify the purpose and location of the interface37.A network administrator has enabled RIP on routersB andC in the network diagram. Which of the following commands will prevent RIP updates from being sent to Router A?A(config)# router ripA(config-router)# passive-interface S0/0B(config)# router ripB(config-router)# network 192.168.25.48B(config-router)# network 192.168.25.64A(config)# router ripA(config-router)# no network 192.168.25.32B(config)# router ripB(config-router)# passive-interface S0/0A(config)# no router rip38. What could a Cisco support technician learn from the IOS filename c2600-d-mz.121-3? (Choose three.)the format of the filethe RAM memory requirements of the filethe version number of the filethe size of the filethe device platform of the file39.While planning an IOS upgrade, the administrator issues the show version command. Based on the output in the graphic, what is the current IOS boot location?RAMNVRAMFlashROM40. A new technician must add boot system commands to one of the department routers. Which available commands will the router return as output when the command shown below is entered? (Choose two.)Router(config)# boot system ?RAMNVRAMIOSIP AddressTFTPFLASH41. From the running-config, the following configuration entries are displayed:Router(config)# line vty 0 2Router(config-line)# password g8k33prRouter(config-line)# loginWhat can be interpreted from the exhibited configuration? (Choose two.)Three Telnet lines are available for remote access.Two Telnet lines are available for remote access.Future configuration of the remaining Telnet lines will require the password to be set to g8k33pr.To login to the remote device, g8k33pr will be used as the Telnet and secret password.Remote access to this local router will require a Telnet password of g8k33pr.42. Which router component stores the information that is displayed by the show running-config command?flashNVRAMRAMROM43. What are two characteristics of the support for Telnet within Cisco IOS software? (Choose two.)Up to five separate Telnet lines are supported by default in standard edition IOS files.For security purposes, Telnet sessions are required to be established from the privileged mode.A router can host simultaneous Telnet sessions.Once established, a Telnet session can remain operational regardless of network status.Telnet tests wireless connectivity and does not require a physical connection between devices to gain remote access.44. Which router components and operations are correctly described? (Choose two.)RAM – stores the ARP cacheNVRAM – store the operating systemROM – stores the backup IOSPOST – verifies the validity of the running-configFlash – executes diagnostics at bootupDRAM – loads the bootstrap45.Given the output shown in the exhibit, in what order and location will the router search for the IOS if no boot system commands are found in the startup-config file?ROM, Flash, TFTP serverFlash, NVRAM, RAMROM, TFTP server, FlashRAM, Flash, NVRAMFlash, TFTP server, ROM46. What can a network administrator do to recover from a lost router password?perform a reload or resettelnet from another router and issue the show running-config command to view the passwordboot the router to ROM monitor mode and configure the router to ignore NVRAM when it initializesboot the router to bootROM mode and enter the b command to load the IOS manually47.Neither router in the exhibit has a host table or DNS available. The interfaces and passwords have been correctly configured. Which of the following commands will initiate a Telnet session? (Choose two.)Tottenham# telnet OxfordTottenham> telnet 198.18.139.1Oxford# connect 198.18.139.0Oxford> connect TottenhamOxford# telnet TottenhamOxford# 198.18.139.248. If a PC does not have network connectivity to a router, which router port can be used to establish communication?consoleEthernetserialVTY。

计算机网络课后习题答案(第三章)

计算机网络课后习题答案（第三章）(2009-12-14 18:16:22)转载▼标签：课程-计算机教育第三章数据链路层3-01 数据链路(即逻辑链路)与链路(即物理链路)有何区别? “电路接通了”与”数据链路接通了”的区别何在?答：数据链路与链路的区别在于数据链路出链路外，还必须有一些必要的规程来控制数据的传输，因此，数据链路比链路多了实现通信规程所需要的硬件和软件。

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