CN001计算机网络

1、.Fill in blank: (27%)1. What is the name of each layer of OSI reference model? (List from layer 1 to 7)_physical_, _ data link_, _network_, _transport_,_session_, _presentation_, _application_.2. What are the steps of the data encapsulation process? _data_, _segment_, _packct_, _frame_, _ bits_.3. W

2、hich layer of the OSI model provides connectivity and path selection between two end systems where routing occurs? _layer 3 (network)_4. Which layer of the OSI model is responsible for the form in which data is communicated to the next layer of the OSI model? _presentation_5. Which layer of the OSI

3、model contains a protocol that provides a reliable delivery of data between hosts on different networks? _transport_6. Where do the following items of the router save? (RAM, NVRAM, Flash, ROM)l power-on diagnostics _ROM_l operating system image_Flash_l routing tables_RAM_l startup configuration file

4、_NVRAM_l running configuration file_RAM_7. How many bits are in the network and subnet portion of a class B network with a subnet mask of 92? _16 _10_8. How many usable host addresses are available on the network with a subnet mask of ? _213=8190_9. How many usable subnets

5、are created if 4 bits are borrowed from the host field? _24-2 =14_10. Are these two IP addresses 3 and 3 with subnet mask on the same subnetwork? (yes or no) _YES_11. What type of address is 3 92? (host, network, broadcast, or subnet)A

6、_subnet_ address.12. What is the minimum and maximum number of bits that can be borrowed to create a subnet with the IP address 2 (Class C)? Minimum = _1_, Maximum = _6_.Multiple choices: (57%)1. What is exchanged to provide communication between two hosts' source and destination OSI

7、peer layers?A). Packet datagramsB). Packet data unitsC). Protocol datagramsD). Protocol data units2. Which is a characteristic of a collision domain?A). all computers on a single shared access mediaB). all computers sharing a single IP addressC). all computers sharing a single MAC addressD). all com

8、puters within a WAN3. Which of the following is a benefit of network segmentation?A). reduced congestionB). reduced equipment requirementsC). creation of more IP addressesD). creation of more MAC addresses4. What is the function of ARP?A). It is used to map a known MAC address to an unknown IP addre

9、ss.B). It is used to develop a cached Layer 4 address resource table.C). It is used to map a known IP address to an unknown MAC address.D). It sends a broadcast message looking for the router IP address.5. What happens if a data packet reaches a router that is destined for a network with which that

10、router is not directly connected?A). The router forwards the packet to all other routers.B). The router returns the packet to the source device with no explanation.C). The router forwards the packet to another router that most likely contains information about the destination.D). The router returns

11、the packet to the source device with the explanation that the destination was unreachable.6. Which of the following describes the effect of subnetting on the amount of broadcast traffic?A). decreases it, because broadcasts are not forwarded outside a subnetB). decreases it, because it will take less

12、 time for a host to get broadcasts from the routers.C). increases it, because the packets must be forwarded to all subnetsD). increases it, because router's duplicate broadcasts7. What protocol is used to allow redundant paths in a switched/bridged network?A). RIP B). Spanning Tree C). IGRP D).

13、OSPF8. What does a bridge use to build its address table?A). Destination IP address B). Destination MAC address C). Source IP address D). Source MAC address 9. What happens to the Layer 2 and Layer 3 addressing of data as it is routed from LAN to WAN?A). The Layer 2 and Layer 3 addressing remain con

14、stant throughout the process.B). The Layer 2 addressing will remain constant, while the Layer 3 addressing will change.C). The Layer 2 addressing will change, while the Layer 3 addressing will remain constant.D). The Layer 2 and Layer 3 addressing will both change at each router encountered.10. When

15、 a host receives a data segment, what allows the host to determine which application should receive the segment?A). IP source addressB). IP destination addressC). PARD). sliding windowE). port numberF). SYN packet11. Which of the following protocols uses UDP for transport layer services?A). SMTPB).

16、HTTPC). DNSD). FTP12. How are originating source port numbers assigned during the data encapsulation process?A). assigned manually by the user when starting the applicationB). assigned dynamically by the source hostC). assigned by the routing protocol during the lookup processD). assigned by the des

17、tination host during session negotiation13. What is the purpose of Positive Acknowledgment and Retransmission (PAR)?A). PAR allows the presentation layer to request that data be resent in a format the destination host can process.B). PAR provides a mechanism for the receiving device to request that

18、all segments be retransmitted if one segment is corrupt.C). PAR helps ensure that a number of data segments sent by one host are received by another host before additional data segments are sent.D). PAR is used to renegotiate the window size during the synchronization process.14. Which of the follow

19、ing determines the amount of data that can be sent without an acknowledgment when sending a TCP segment?A). segment numberB). priority numberC). window sizeD). value in the length fieldE). value in the port fieldF). acknowledgment number15. Connection-oriented services involve which three phases?A).

20、 Connection establishment, Data transfer, Connection termination B). Connection establishment, Data transfer, Flow control C). Connection establishment, Flow control, Connection termination D). Data transfer, Flow control, Connection termination 16. Which command sequence will permit access to all f

21、ive router virtual terminal lines with a password of cisco?A). Router(config-line)#config telnetRouter(config-line)# line vty 0 5Router(config-line)# password ciscoB). Router(config)# line vty 0 4Router(config)# password ciscoC). Router(config)# line vty 0 4Router(config-line)# password ciscoRouter(

22、config-line)# loginD). Router(config-line)# config telnetRouter(config-line)# password cisco Router(config-line)# sessions 0 417. What is the correct sequence of initialization for a router that has a configuration file?A). Loads bootstrap, loads configuration file, loads operating systemB). Loads b

23、ootstrap, loads operating system, loads configuration file C). Loads bootstrap, loads RAM, loads operating system D). Loads operating system, loads configuration file, loads RAM18. If a router cannot find a valid configuration file during the startup sequence, what will occur?A). The startup sequenc

24、e will reset.B). The router will enter setup mode.C). The startup sequence will halt until a valid configuration file is acquired.D). The router will generate a default configuration file based on the last valid configuration.E). The router will monitor local traffic to determine routing protocol co

25、nfiguration requirements.19. What can be learned by issuing the show version command? (Choose three.)A). the router hostnameB). the current config-register setting C). the location from which the IOS was loaded D). the boot system commands configured in NVRAM E). the amount of RAM, NVRAM, and Flash

26、memory in the router20. Where does a router look for boot system statements?A). ROMB). RAMC). NVRAMD). Flash21. What does a configuration register setting of 0x2102 indicate on a router?A). It tells the router to locate and load the IOS from NVRAM.B). It tells the router to locate and load the IOS f

27、rom FLASH.C). It tells the router to bypass the configuration in NVRAM.D). It tells the router to look in the startup configuration for boot system commands.22. What do routers use to select the best path for outgoing data packets?A). ARP tablesB). bridging tablesC). routing tablesD). switching tabl

28、es23. Why do we need to specify a list of networks when configuring an interior routing protocol?A). To tell the router how to reach those networks. B). To tell the router which attached networks to listen to for routing updates. C). To tell the router which set of metrics to use for those networks.

29、 D). To tell the router which routing protocol to use. 24. Which of the following methods does split horizon use to reduce incorrect routing information?A). Routing updates are split in half to reduce the update time.B). Information learned from one source is not distributed back to that source.C).

30、New route information must be learned from multiple sources to be accepted.D). The time between updates is split in half to speed convergence.E). New route information is suppressed until the system has converged.25. What does a router do if it is unable to deliver a packet to its destination? (Choo

31、se two.)A). The router sends the original packet back to the source.B). The router keeps the packet in its buffer until the next routing table update.C). The router sends an ICMP "Destination Unreachable" message back to the source.D). The router sends out a broadcast message in search of

32、the destination.E). The router discards the original packet.26. When troubleshooting a network, it is important to interpret the output of various router commands. Using the graphic, identify which of the following statements are true. (Choose three.)A). The missing information for Blank 1 is the co

33、mmand show ip route.B). The missing information for Blank 1 is the command debug ip route.C). The missing information for Blank 2 is the number 100.D). The missing information for Blank 3 is the letter R.E). The missing information for Blank 3 is the letter I.F). The missing information for Blank 4

34、is the letter C.27. According to the router output from the show ip route command shown above, which of the following statements are true? (Choose two.)A). The metric to network is 24.B). The hop count to a device on network is 2.C). The total path cost to network

35、 is the default value of 16.D). The logical address of the next router for network is .E). The devices on network cannot be reached as indicated by the 'C' label.28. Which of the following are valid static IP routes? (Choose three.)A). RouterB(config)# ip r

36、oute S1B). RouterC(config)# ip route S1C). RouterA(config)# ip route D). RouterB(config)# ip route E). RouterC(config)# ip route F). Rout

37、erA(config)# ip route 29. Consider the RIP network shown in the diagram. Which entries would be listed in the routing table of Router A?A). R 120/1 via , 00:00:09, Serial0B). R 120/1 via , 00:00:13, Serial1C). R 192.1

38、68.15.0120/1 via , 00:00:13, Serial0D). R 120/1 via 00:00:29, Serial1R 120/1 via , 00:00:29, Serial1E). R 120/1 via 00:00:18, Serial0R 120/1 via , 00:00:18, Serial030. A router has learned abou

39、t a network through static and dynamic routing processes. Which of the following routes will be used to reach network ?A). I /24 100/8947 via , 00:00:09, Ethernet0B). O /24 110/1012 via , 00:00:22, Ethernet0C). R /24 120/1

40、 via , 00:00:17, Ethernet0D). S /24 1/0 via , 00:00:10, Ethernet031. Refer to the network and routing table entries shown in the graphic. What will happen when a packet destined for network is received by Router A?A). It will be forwarded through int

41、erface S1.B). It will be forwarded to the default route.C). It will be directed toward the Internet.D). It will be discarded.32. Which of the following commands can be used to statically configure default routes? (Choose two.)A). ip static-routeB). ip routeC). ip network-routeD). ip default-networkE

42、). ip default-static33. Which type of message is generated by a host when the ping command is entered?A). ICMP echo requestB). ICMP echo replyC). UDP echo requestD). UDP error message34. What happens when an ICMP packet is not deliverable? (Choose two.)A). The packet is dropped.B). An ICMP error mes

43、sage is returned to the original sender.C). An ICMP error message is returned to the original destination.D). An ICMP packet is returned to the nearest router in the path.E). No further ICMP packets are generated as a result of the transaction.35. ACL statements operate in sequential, logical order.

44、 If a condition match is true, the rest of the ACL statements are not checked. If all of the ACL statements are unmatched, what happens to the packet?A). The packets will be placed in a buffer and forwarded when the ACL is removed.B). The packets will be sent to the source with an error notification

45、 message.C). The implicit permit any statement placed at the end of the list will allow the packets to flow through uninhibited.D). The implicit deny any statement placed at the end of the list will cause the packets to be dropped.36. Which wildcard mask would match the host range for the subnet 192

46、.168.1.32 /26?A). 2 B). 3 C). 55 D). 1 37. Assuming the ACL in the graphic is correctly applied to an interface, what effect will this ACL have on network traffic?A). Host will be denied ftp access to any destination, but will be permitted all other access.B

47、). All ftp traffic to host will be denied.C). All traffic from that interface will be denied.D). No traffic will be denied because a "permit" statement does not exist in this ACL.38. A router that has two Ethernet interfaces and one serial interface is configured to route both

48、 IP and IPX. What is the maximum number of IP ACLs that can be configured to filter packets on this router?A). 1B). 2C). 3D). 6E). 1239. Which items would be displayed when the show ip protocol command is executed? (Choose three.)A). sources of routing updatesB). networks being advertisedC). routing

49、 protocol up or downD). configured routed protocolsE). Layer 2 status of the interfaceF). update timer values40. The show cdp neighbors command is a very useful network troubleshooting tool. Using the output in the graphic, select the statements that are true. (Choose two.)A). CDP operates at the ne

50、twork layer of the OSI model.B). The output of this command displays information about directly connected Cisco devices only.C). The switch is attached to the SanJose1 FastEthernet0/21 interface.D). SanJose1 is running CDP version 12.0. E). SanJose1 has two fully operational, cdp-enabled Cisco switc

51、hes directly connected to it.F). SanJose2 is a 2600 series router running several routed protocols.41. The output of the show ip interface brief command displays Serial0 is up, line protocol is down. Which of the following are possible causes for the line protocol being in the down state? (Choose tw

52、o.)A). The clock rate is not set on the DTE.B). An incorrect default gateway is set on the router.C). A network is missing from the routing protocol configuration.D). The encapsulation on the Serial0 interface is incorrect.E). Keepalives are not being sent.42. The network administrator shown in the

53、graphic is unable to access the TFTP server attached to the Miami router. Consider only the IP addressing scheme to identify the causes of this problem. (Choose two.)A). The default gateway configured on the network administrator's workstation is not a valid host address.B). The IP address confi

54、gured on interface E1 of the Miami router is not a valid host address.C). The IP address of the TFTP server is a subnetwork address.D) The IP address of the S0 interface of the Detroit router is a broadcast address.E). The IP addresses for the Miami S1 interface and the Detroit S0 are not in the same subnet.Question and Answer: (16%)1. (1). Describe the differences between routed and routing protocols. And give some examples of them. Routed protocol: any network protocol that provides enough information in its network layer a