[计算机类试卷]思科认证640-802模拟试卷5及答案与解析.doc

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1、思科认证 640-802模拟试卷 5及答案与解析 1 Assuming you build networks to exact specifications, what is the recommended maximum length a 10BaseT cable can be before it has to be segmented or repeated? （ A） 100 meters （ B） 100 feet （ C） 100 yards （ D） 200 meters （ E） None of the above 2 Ezonexam has implemented the

2、use of the Virtual Trunking Protocol (VTP). Which statement below accurately describes a benefit of doing this? （ A） VTP will allow physically redundant links while preventing switching loops （ B） VTP will allow switches to share VLAN configuration information （ C） VTP will allow a single port to ca

3、rry information to more than one VLAN （ D） VTP will allow for routing between VLANs （ E） None of the above 3 A Ezonexam PC has the IP address 172.16.209.10 /22. What is the subnet of this address? （ A） 172.16.42.0 （ B） 172.16.107.0 （ C） 172.16.208.0 （ D） 172.16.252.0 （ E） 172.16.254.0 4 What kind of

4、 cable should be used to establish a trunked line between two Catalyst switches? （ A） A straight-through cable （ B） An EIA/TIA-232 serial cable （ C） An auxiliary cable （ D） A modem cable （ E） A cross-over cable 5 Split horizon has been enabled within the Ezonexam routed network. Which one of the fol

5、lowing statements best explains the split horizon rule? （ A） Only routers can split boundaries (horizons) between networks in separate AS numbers. （ B） Each AS must keep routing tables converged to prevent dead routes from being advertised across boundaries. （ C） Once a route is received on an inter

6、face, advertise that route as unreachable back out the same interface. （ D） Information about a route should never be sent back in the direction from which the original update came. （ E） None of the above 6 Which protocol below uses TCP port 443 at layer 4? A. HTML B. HTTPS C. TFTP D. Telnet E. SMTP

7、 F. None of the above 7 Which IOS user EXEC command will allow a network technician to determine which router in the path to an unreachable network host should be examined more closely for the cause of the network failure? A. EzonexamB telnet B. EzonexamB ping C. EzonexamB trace D. EzonexamB show ip

8、 route E. EzonexamB show interface F. EzonexamB show cdp neighbors 8 In a switched LAN network, what is the Spanning-Tree algorithm used for? A. It is used to provide a mechanism for routing updates in switched environments. B. It is used to prevent routing loops in networks with redundant routes. C

9、. It is used to prevent switching loops in networks with redundant switched routes. D. It is used to manage, the addition, deletion, and naming of VLANs across multiple switches. E. It is used to segment a network into multiple collision domains. F. None of the above. G. All of the above are functio

10、ns of STP. 9 What is the subnet for the host IP address 172.16.210.0/22? A. 172.16.42.0 B. 172.16.107.0 C. 172.16.208.0 D. 172.16.252.0 E. 172.16.254.0 F. None of the above 10 Which one of the following commands would you enter to terminate a VTY line session? A. close B. disable C. disconnect D. su

11、spend E. exit F. None of the above 11 Ezonexam is migrating to a private IP addressing scheme. Which of the following describe the use of private IP addresses? (Choose two) （ A） Addresses chosen by E to communicate with the Internet. （ B） Addresses that cannot be routed through the public Internet.

12、（ C） Addresses that can be routed through the public Internet. （ D） A scheme to conserve public addresses. （ E） Addresses licensed to enterprise or ISPs by an Internet registry organization. 12 Which fields are included in the TCP header? (Choose three). A. Source Port B. Acknowledgement Number C. R

13、equest Number D. Destination Address E. Window F. Data 13 You are the administrator of the Ezonexam LAN and you have been reviewing error logs of networking devices and notice a large number of errors associated with several MAC addresses. You suspect that some of the errors are being generated by t

14、he routers. Which router commands will allow you to find the ip address associated with each MAC address? (Choose two) A. show arp B. show version C. show address D. show hosts E. show interface F. show protocols 14 Which of the following a true statements regarding the use of VLANs to segment a net

15、work? (Select three) A. They increase the size of collision domains B. They allow logical grouping of users by function. C. They can enhance network security. D. They increase the size of the broadcast domain while decreasing the number of collision domains. E. They increase the number of broadcast

16、domains while decreasing the size of the broadcast domains. F. They simplify switch administration. 15 Which of following VLAN frame encapsulation types are configurable on a Cisco switch? (Select two answer choices.) A. VTP B. 802.1Q C. LLC D. ISL E. CDP F. PAP 16 Which two of the following values

17、does STP take into consideration when it elects the root bridge? (Select two answer choices) A. The BPDU version number B. The access layer bridge setting C. The Bridge ID D. The spanning-tree update number E. The bridge priority F. The VLAN number 17 What are some of the characteristics of a typica

18、l VLAN arrangement, found throughout the Ezonexam switched LAN? (Select all that apply) A. VLANs logically divide a switch into multiple, independent switches at Layer 2. B. Trunk links can carry traffic for multiple VLANs. C. VLAN implementation significantly increases traffic due to added trunking

19、 information. D. A VLAN can span multiple switches. E. VLANs typically increase the number of switches needed F. VLANs typically decrease the number of switches needed 18 You need to create a new VLAN on your Catalyst switch. This VLAN is to be named EZONEXAM. Which of the following need to be compl

20、eted for the creation of this new VLAN? (Select all that apply) A. The EZONEXAM VLAN must be created. B. The desired ports must be added to the new EZONEXAM VLAN. C. The EZONEXAM VLAN must be added to all of the domains. D. The EZONEXAM VLAN must be named. E. An IP address must be configured for the

21、 EZONEXAM VLAN. F. None of the above. VLAN creations are automatic. 19 Your ISP has assigned you the following IP address and subnet mask: IP address: 199.141.27.0 Subnet mask: 255.255.255.240 Which of the following addresses can be allocated to hosts on the resulting subnet? (Select all that apply)

22、 A. 199.141.27.2 B. 199.141.27.175 C. 199.141.27.13 D. 199.141.27.11 E. 199.141.27.208 F. 199.141.27.112 20 Which of the following devices can the Ezonexam network administrator use to segment the LAN? (Choose all that apply) A. Hubs B. Repeaters C. Switches D. Bridges E. Routers F. Media Converters

23、 G. All of the above 21 You are working as a network technician at Ezonexam University, when you get a call from the Engineering Faculty. Theyre complaining that theyre receiving obsolete information from the Business Facultys network traffic broadcasts. What can you do to contain the Business Facul

24、tys broadcast while still keeping it connected to the internet and the enterprise services of the University? (Select all valid answer choices) A. Use half and full-duplex Ethernet on the Engineering Department LAN B. Establish a VTP domain to minimize the obsolete traffic C. Change the switch IP ad

25、dress of the switch D. Create separate VLANs and subnets for the two departments and route between the two E. Provide greater bandwidth to the Engineering Department LAN F. Place the business department on a separate subnet and route between networks 思科认证 640-802模拟试卷 5答案与解析 1 【正确答案】 A 【试题解析】 Explana

26、tion: The distance standards are in meters and 10BaseT has a distance restriction of 100 meters. If you go further then that, you compromise data integrity. 10BastT is the predominant cable type used in Ethernet networks. 2 【正确答案】 B 3 【正确答案】 C 【试题解析】 Explanation: 172.16.209.10/22 translates to 10101

27、100.00010000.11010001.00001010 in binary form. The network portion is 22 bits, so after the logical AND comparison the network address translates to 10101100.00010000.110100001.00001010. Converting the network portion to decimal results in the address 172.16.208.0/22 4 【正确答案】 E 【试题解析】 Explanation: A

28、 crossover cable is used to connect two of the same device types, or devices from the same OSI layer. 5 【正确答案】 D 【试题解析】 Explanation:The split horizon rule states:* Never advertise a route out of the interface through which you learned it.For instance, in Figure 4a below, if Router One is connected t

29、o Routers Two and Three through a single multipoint interface (such as Frame Relay), and Router One learned about Network A from Router Two, it will not advertise the route to Network A back out the same interface to Router Three. Router one assumes that Router Three would learn about Network A dire

30、ctly from Router Two. Incorrect Answers:A: There is no such requirementB: Distance vector protocols updates routing table at regular intervals instead of Topology changesC: This is the definition of the poison reverse rule, not the split horizon rule. 6 【正确答案】 B 【试题解析】 Explanation: HTTPS is the secu

31、red version of the HTTP application, which normally uses 128 bit SSL encryption to secure the information sent and received on a web page. An example is a banking web site, or a trustworthy shopping web site that takes credit card information. It is an application layer protocol which uses TCP port

32、443. Incorrect Answers: A. HTML is not a protocol. C. TFTP uses UDP port 69. D. Telnet uses TCP port 23. E. SMTP uses TCP port 25. 7 【正确答案】 C 【试题解析】 Explanation: This can perform the trace command. It sends the ping packets to each of the routers on the way to the receiver. The router which doesnt r

33、espond will be a potential failure place in this network. 8 【正确答案】 C 【试题解析】 Explanation: To avoid loops, all bridging devices, including switches, use STP. STP causes each interface on a bridging device to settle into a blocking state or a forwarding state. Blocking means that the interface cannot f

34、orward or receive data frames. Forwarding means that the interface can send and receive data frames. By having a correct subset of the interfaces blocked, a single currently active logical path will exist between each pair of LANs. STP resides at the data link layer, so it is used to prevent loops w

35、ithin a switched network. It is not used to prevent routing loops; that is the function of the mechanisms within a routing protocol. 9 【正确答案】 C 【试题解析】 Explanation: This question is much easier then it appears when you convert it to binary and do the Boolean operation as shown below: IP address 172.1

36、6.210.0 = 10101100.00010000.11010010.00000000 /22 mask = 11111111.11111111.11111100.00000000 AND result = 11111111.11111111.11010000.00000000 AND in decimal= 172. 16. 208. 0 10 【正确答案】 E 【试题解析】 Explanation: A VTY line is a telnet session. To end a telnet session from a remote device, enter the exit o

37、r logout command. Incorrect Answers: A, B, C, D. These are all invalid commands. 11 【正确答案】 B,D 【试题解析】 Explanation: Private IP address space has been allocated via RFC 1918. This means the addresses are available for any use by anyone and therefore the same private IP addresses can be reused. However

38、 they are defined as not routable on the public Internet. They are used extensively in private networks due to the shortage of publicly registered IP address space and therefore network address translation is required to connect those networks to the Internet. 12 【正确答案】 A,B,E 【试题解析】 Explanation:TCP

39、header:Source Port: 16 bits.Destination Port: 16 bits.Sequence Number: 32 bits.The sequence number of the first data byte in this segment. If the SYN bit is set, the sequence number is the initial sequence number and the first data byte is initial sequence number + 1.Acknowledgment Number: 32 bits.I

40、f the ACK bit is set, this field contains the value of the next sequence number the sender of the segment is expecting to receive. Once a connection is established this is always sent.Data Offset: 4 bits.The number of 32-bit words in the TCP header. This indicates where the data begins. The length o

41、f the TCP header is always a multiple of 32 bits.Reserved: 3 bits.Must be cleared to zero.ECN, Explicit Congestion Notification: 3 bits.Added in RFC 3168.Control Bits: 6 bits.Window: 16 bits, unsigned.The number of data bytes beginning with the one indicated in the acknowledgment field which the sen

42、der of this segment is willing to accept.Checksum: 16 bits.This is computed as the 16-bit ones complement of the ones complement sum of a pseudo header of information from the IP header, the TCP header, and the data, padded as needed with zero bytes at the end to make a multiple of two bytes.Urgent

43、Pointer: 16 bits, unsigned.If the URG bit is set, this field points to the sequence number of the last byte in a sequence of urgent data.Options: 0 to 44 bytes.Options occupy space at the end of the TCP header. All options are included in the checksum. An option may begin on any byte boundary. The T

44、CP header must be padded with zeros to make the header length a multiple of 32 bits.Data: Variable length. 13 【正确答案】 A,E 【试题解析】 Explanation: The “show arp“ command Displays the entries in the ARP table, including their layer 2 MAC address and layer 3 IP address. Example: The following is the output

45、for the show arp command on Router 1: VE1 # show arp Protocol Address Age (min) Hardware Addr Type Interface Internet 10.0.0.3 0 0004.dd0c.ffcb ARPA Ethernet01 Internet 10.0.0.1 - 0004.dd0c.ff86 ARPA Ethernet0 To see the MAC (hardware) address of the router interfaces as well as their IP addresses,

46、use the “show interfaces“ command as shown in the example below: VE1# show interfaces Ethernet 0 is up, line protocol is up Hardware is MCI Ethernet, address is 0000.0c00.750c (bia 0000.0c00.750c) Internet address is 10.108.28.8, subnet mask is 255.255.255.0 MTU 1500 bytes, BW 10000 Kbit, DLY 100000

47、 usec, rely 255/255, load 1/255 14 【正确答案】 B,C,E 【试题解析】 Explanation: VLANs are used to segment a LAN into multiple, smaller LANs. This can be used to enhance security as local traffic from one VLAN will not be passed to users in other VLANS. Incorrect Answers: A. VLANs are used to decrease the size o

48、f a collision domain, not increase it. D. The opposite is true. F. The default operation of a switch is to allow all traffic and to enable all ports in VLAN1. The use of VLANs will increase the complexity of the switch environment, making for more difficult administration. 15 【正确答案】 B,D 【试题解析】 Expla

49、nation: ISL and 802.1Q are the two trunking encapsulations that can be configured on a Cisco switch. ISL is Cisco proprietary and 802.1Q is the IEEE standard method. Incorrect Answers: A. VTP is the VLAN Trunking Protocol, which is used to carry VLAN information across the trunks. The question is asking for the encapsulation options for the trunk, which will be used by VTP. C. LLC is the Logical Link Control, which is a sub-layer of the data link layer. E. CDP is the Cisco Discovery Protocol, which is used by Cisco devices to discover information on neighboring Cisco devices.