[计算机类试卷]思科认证640-802模拟试卷2及答案与解析.doc

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1、思科认证 640-802模拟试卷 2及答案与解析 1 A new Ezonexam switch is installed into an existing LAN and a new VTP trunk is set up with an existing switch. Which VLANs will be allowed on this new trunk? （ A） All defined VLANs are allowed on the trunk by default. （ B） Each VLAN, or VLAN range, that is specified with t

2、he switchport mode command. （ C） Each VLAN, or VLAN range, that is specified with the vtp domain command. （ D） Each VLAN, or VLAN range, that is specified with the vlan database command. （ E） None of the above 2 While troubleshooting a connectivity issue from a PC you obtain the following informatio

3、n: Local PC IP address: 190.0.3.35/24 Default Gateway: 190.0.3.1 Remote Server: 190.0.5.250/24 You then conduct the following tests from the local PC: Ping 127.0.0.1 - Unsuccessful Ping 190.0.3.35 - Successful Ping 190.0.3.1 - Unsuccessful Ping 190.0.5.250 Unsuccessful What is the underlying cause o

4、f this problem? （ A） TCP/IP not correctly installed （ B） Local physical layer problem （ C） NIC not functioning （ D） Remote physical layer problem （ E） None of the above 3 You want to upgrade the Ezonexam LAN so that all ports operate in full duplex mode. Which statement is true about full-duplex Eth

5、ernet when comparing to half-duplex Ethernet? （ A） Full-duplex Ethernet consists of a shared cable segment. Half-duplex provides a point-to-point link （ B） Full-duplex Ethernet uses two wires to send and receive. Half-duplex Ethernet uses one wire to send and receive （ C） Full-duplex Ethernet can pr

6、ovide higher throughput than can half-duplex Ethernet of the same bandwidth （ D） Full-duplex Ethernet uses a loopback circuit to detect collisions. Half-duplex Ethernet uses a jam signal （ E） None of the above 4 The Ezonexam LAN is upgrading all devices to operate in full duplex. Which statement is

7、true about full-duplex Ethernet in comparison to half-duplex Ethernet? （ A） Full-duplex Ethernet uses two wires to send and receive. Half-duplex Ethernet uses one wire to send and receive （ B） Full-duplex Ethernet consists of a shared cable segment. Half-duplex Ethernet provides a point-to-point lin

8、k （ C） Full-duplex Ethernet can provide higher throughout than can half-duplex Ethernet of the same bandwidth （ D） Full-duplex Ethernet uses a loopback circuit to detect collisions. Half-duplex ethernet uses a jam signal （ E） None of the above 5 From where does a small network typically get its IP n

9、etwork addresses or IP block? （ A） From the Internet Domain Name Registry (IDNR) （ B） From the Internet Assigned Numbers Authority (IANA) （ C） From the Internet Service Provider (ISP) （ D） From the Internet Architecture Board (IAB) （ E） None of the above 6 After working all night and successfully co

10、nfiguring a Cisco router for the Ezonexam network you save your changes on the startup config, reboot the router, and go out for a cigarette. When you return, none of your changes are active and the router boots to the initial configuration mode! Which of the choices below indicates the source of yo

11、ur problem? （ A） Hardware failure in NVRAM prevents the router from loading the config （ B） Startup-config in flash is corrupt and cannot be analyzed （ C） Router configuration-register set to bypass startup configuration （ D） Startup-config in NVRAM is corrupt and cannot be analyzed （ E） None of the

12、 above 7 You need to decide on which trunking method to implement in the Ezonexam network. What is a characteristic of ISL and 802.1q frame tagging in a switched LAN environment? （ A） They are used to find the best path through a network. （ B） They allow the exchange of filtering tables. （ C） They s

13、pecify different implementations of the Spanning-Tree Protocol. （ D） They allow the exchange of routing tables （ E） They provide inter-switch VLAN communication. 8 Ezonexam users have noticed extremely slow network performance, intermittent connectivity, and connection losses. After entering the “sh

14、ow interfaces“ command, you notice that the Ethernet interface is configured as 100 Mbps full-duplex and that there is evidence of late collisions. What could be the cause of this problem? A. Duplex mismatch B. A routing loop C. Trunking mode mismatch D. Improperly configured root bridge E. Improper

15、ly configured static VLAN F. None of the above 9 Acknowledgements, sequencing, and flow control are functions that are handled by which layer of the OSI model? A. Layer 5 B. Layer 4 C. Layer 7 D. Layer 6 E. Layer 3 F. Layer 2 G. Layer 1 10 In a Ezonexam network that supports VLSM, which network mask

16、 should be used for point-to-point WAN links in order to reduce waste of IP addresses? A. /24 B. /30 C. /27 D. /26 E. /32 F. None of the above 11 At which OSI layer is a logical path created between two host systems named VE1 and VE2 on the Ezonexam LAN? A. Physical B. Session C. Data link D. Transp

17、ort E. Network F. Application G. Presentation 12 Which layer of the OSI reference model is responsible for ensuring reliable end-to-end delivery of data? A. Application B. Presentation C. Session D. Transport E. Network F. Data-Link 13 VE1 is a switch in the Ezonexam network. Why will VE1 never lear

18、n the broadcast address? A. Broadcast frames are never sent to switches B. A broadcast frame is never forwarded by a switch C. Broadcasts only use network layer addressing D. A broadcast address will never be the source address of a frame E. Broadcast addresses use an incorrect format for the switch

19、ing table F. None of the above 14 After making some network changes you power off and then power on your Cisco router named VE1. What sequence of events occurs when VE1 is powered up? A. Perform POST, locate configuration statements, apply configuration statements, locate Cisco IOS software, and loa

20、d Cisco IOS software. B. Locate Cisco IOS software, load Cisco IOS software, locate configuration statements, apply configuration statements, and perform POST. C. Test software routines, POST, load configuration files, load Cisco IOS software, test Cisco IOS software. D. Perrform POST, locate Cisco

21、IOS software, load the Cisco IOS software, locate configuration statements, and apply configuration statements. E. Load and test IOS, load configuration files, test software routines, POST. F. None of the above 15 What are two characteristics of “store and forward“ switching? (Select two answer choi

22、ces) （ A） Latency fluctuates regardless of frame size. （ B） The switch receives the complete frame before beginning to forward it. （ C） Latency through the switch varies with frame length. （ D） The switch checks the destination address upon receipt of headers. 16 Which three statements are true abou

23、t the operation of a full-duplex Ethernet network, which is being used in the Ezonexam LAN? (Choose three) （ A） Ethernet hub ports are preconfigured for full-duplex mode. （ B） The host network card and the switch port must be capable of operating in full-duplex mode. （ C） There are no collisions in

24、full-duplex mode. （ D） In a full-duplex environment, the host network card must check for the availability of the network media before transmitting. （ E） A dedicated switch port is required for each full-duplex node. 17 As a CCNA candidate, you must know the various layers of the OSI model. At which

25、 layers of the OSI Model do Wide Area Networks operate in? (Choose two) A. Physical Layer B. Datalink Layer C. Network Layer D. Session Layer E. Transport Layer F. Presentation Layer G. Application Layer 18 As a network administrator, you will need to decide on the appropriate network devices to use

26、. Which of the following correctly describes the roles of devices in a WAN? (Choose three) A. A CSU/DSU terminates a digital local loop. B. A router is commonly considered a DCE device. C. A modem terminates an analog local loop. D. A router is commonly considered a DTE device. E. A modem terminates

27、 a digital local loop. F. A CSU/DSU terminates an analog local loop. G. A modem is used to terminate a T1 19 Ezonexam is installing IP phones in a new office. The phones and office computers connect to the same device. To ensure maximum throughout for the phone data sessions, the company needs to ma

28、ke sure that the phone traffic is on a different network from that of the office computer data traffic. What is the best network device to which to directly connect the phones and computers and what technology should be implemented on this device? (Choose two) A. VLAN B. Subinterface C. STP D. Hub E

29、. Switch F. Router G. Wireless Access Point H. VTP 20 Router VE1 has just received a packet and needs to route it. What two actions must this router take in order to route incoming packets? (Choose two) A. Inspect the routing table to select the best path to the destination network addresses. B. Val

30、idate sources of routing information. C. Inspect the ARP table to verify a legitimate source MAC address for each packet. D. Identify the destination network address of each packet. E. Verify the receipt of routed packets by the next hop router. F. Identify the source network address of each packet.

31、 21 RIP version 2 is being used as the routing protocol within the Ezonexam network. What does RIP version 2 use to prevent routing loops? (Choose two) A. CIDR B. Split horizon C. Authentication D. Classless masking E. Hold-down timers F. Multicast routing updates G. Path Vectoring 22 Which of the p

32、rotocols below use TCP at the transport layer? (Select four) A. TFTP B. SMTP C. SNMP D. FTP E. HTTP F. HTTPS 23 ICMP is often used in troubleshooting and verifying network. What statements are true regarding ICMP packets? (Choose two) A. They acknowledge receipt of TCP segments. B. They guarantee da

33、tagram delivery. C. They can provide hosts with information about network problems. D. They are encapsulated within IP datagrams. E. They are encapsulated within UDP datagrams. F. They are encapsulated within TCP datagrams. 24 There are 2 switches in the Ezonexam LAN, with no routers. Ports 1, 2 TCP

34、, that includes reliability and flow control features, and a second, UDP, that doesnt. 13 【正确答案】 D 14 【正确答案】 D 【试题解析】 Explanation: Upon initial start up, Cisco routers perform the following steps in order: 1. The router performs a power-on self-test (POST) to discover and verify the hardware. 2. The

35、 router loads and runs bootstrap code from ROM. 3. The router finds the IOS or other software and loads it. 4. The router finds the configuration file and loads it into running config. 15 【正确答案】 B,C 【试题解析】 Explanation: With store-and-forward, the entire frame is received by the switch before the fir

36、st bit of the frame is forwarded. As soon as the incoming switch port receives enough of the frame to see the destination MAC address, the forwarding decision is made and the frame is transmitted out the appropriate outgoing port to the destination device. So, each frame might experience slightly le

37、ss latency. Store and forward switching may add latency when compared to other switching methods such as cut through, but it can reduce the amount of errors that become forwarded through a network. Incorrect Answers: A. The amount of latency that is introduced with this method of switching is depend

38、ent on the size of the frame, as the switch must wait to receive the entire frame before sending it. D. The switch must wait for the entire frame before forwarding it on, and not just the headers. 16 【正确答案】 B,C,E 【试题解析】 Explanation: Half-duplex Ethernet is defined in the original 802.3 Ethernet and

39、Cisco says you only use one wire pair with a digital signal running in both directions on the wire. It also uses the CSMA/CD protocol to help prevent collisions and to permit retransmitting if a collision does occur. If a hub is attached to a switch, it must operate in half-duplex mode because the e

40、nd stations must be able to detect collisions. Half-duplex Ethernet-typically 10BaseT-is only about 30 to 40 percent efficient as Cisco sees it, because a large 10BaseT network will usually only give you 3- to 4Mbps-at most. Full-duplex Ethernet uses two pairs of wires, instead of one wire pair like

41、 half duplex. Also, full duplex uses a point-to-point connection between the transmitter of the transmitting device and the receiver of the receiving device, which means that with full-duplex data transfer, you get a faster data transfer compared to half duplex. And because the transmitted data is s

42、ent on a different set of wires than the received data, no collisions occur. The reason you dont need to worry about collisions is because now Full-duplex Ethernet is like a freeway with multiple lanes instead of the single-lane road provided by half duplex. Full-duplex Ethernet is supposed to offer

43、 100 percent efficiency in both directions; this means you can get 20Mbps with a 10Mbps Ethernet running full duplex, or 200Mbps for FastEthernet. 17 【正确答案】 A,B 【试题解析】 Explanation:A WAN is a data communications network that covers a relatively broad geographic area and that often uses transmission f

44、acilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower two layers of the OSI reference model: the physical layer and the data link layer as shown below. Note: Occasionally WANs would also be considered to operate at layer 3, but since thi

45、s question asked for only 2 chopices layers 1 and 2 are better choices. 18 【正确答案】 A,C,D 19 【正确答案】 A,E 20 【正确答案】 A,D 【试题解析】 Explanation: The router decides how to forward an incoming packet by finding the routes that “match“ the destination address of the packet, and then forwarding it according to t

46、he most narrowly applicable one. A packet matches a route in the following way: a packet has (among other things) a destination address in its header, a route contains either a network or a host address, a network mask (netmask), and instructions on how to forward a packet using the route. The packe

47、t matches the route if its destination address is part of the address subspace defined by the network address or exactly matches the host address of the route. A route is more narrowly applicable than another if the address subspace defined by its network address contains fewer actual addresses than

48、 the other, which is indicated by the netmask. An entry with a host address, rather than a network address, is the narrowest kind. 21 【正确答案】 B,E 【试题解析】 Explanation: Distance Vector routing protocols employ the split horizon mechanism to reduce the possibility of routing loops. Split horizon blocks i

49、nformation about routes from being advertised by a router out of any interface from which that information originated. RIP versions 1 and 2 also use the concept of hold timers. When a destination has become unreachable (or the metric has increased enough to cause poisoning), the destination goes into “holddown“. During this state, no new path will be accepted for the same destination for this amount of time. The hold time indicates how long this state should last. Incorrect Answers: A, C, D, F. Although these are all features and functions of RIP version 2, they are not mechanisms used to