Tài liệu Answer Key pdf

1 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Answer Key 12 1. a, d 2. b 3. b, c 4. b 5. b 6. e 7. b 8. b 9. d 10. c 11. b 12. b 13. d 14. a 15. c 16. c 17. b 18. c, d 19. a 20. a, b, c 21. d 22. b 23. d 24. b 25. b 26. e 27. d 28. c 29. d 30. c 31. c 32. d 33. e 34. b, c, d 35. c 36. b 37. a 38. d 39. a 40. d 41. d 42. c 43. a 44. c 45. b 46. d 47. c 48. b 49. b 50. a, d 51. a, b 52. c 53. c 54. c 55. b, c, d, f 56. e 57. b 58. a 59. c 60. e 61. b 62. a, b, c 63. f 64. c, d 65. e 66. a, b, d 67. e 68. c 69. a 70. a, c, e 71. d 72. d 73. c 74. d 75. c 76. d 77. d 78. c 79. a 80. e 81. a, b, c, d, f, h, j 82. b 83. b, d 84. a 85. b, d, e 86. d 87. a 88. a 89. e 90. d 91. c 92. a 93. a 94. b, c 95. a, c, d 96. a, c, d 97. b, d 98. a 99. b 100. d 2 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Chapter 12 Question 1 The correct answers are a and d. Layer 2 (Data Link layer) handles frames across the physical medium. Answer b is incorrect, because bits are transferred at layer 1 (Physical layer) of the OSI model. Answer c is incorrect, because layer 3 (Net- work layer) is commonly known as packets. Question 2 The correct answer is b. To enable RIP routing, you issue the router rip global command. By default, a Cisco router will send only RIP version I packets but will listen for RIP I and RIP II. Therefore, if you only configure RIP I, then RIP II packets will also be received and placed in the routing table, but they will not be advertised by RIP. If you enable RIP II with the version 2 command, then you’ll only send and receive RIP II packets. Answer a is incorrect, because router-rip is an invalid IOS command. Answer c is incorrect, because the version 2 command is only applicable to the interface and does not satisfy the question. Answer d is incorrect, because ip rip version 2 is an invalid IOS command. Answer e is incor- rect, because answer a is an invalid IOS command. Question 3 The correct answers are b and c. The unique bridge identifier is made up of the bridge’s MAC address and the priority, which is either set by the administrator or is a default value. Answer a is incorrect, because the IP address (layer 3 or the Network layer) is not part of the spanning tree protocol or the bridge identifier. Answer d is incorrect, because the cost is used between switches and is not part of the unique bridge identifier. Question 4 The correct answer is b. The Simple Server Redundancy Protocol (SSRP) creates fault tolerance using standard LANE protocols and mechanisms. Typically, SSRP is implemented in large ATM LANE environments. Answer a is incorrect, be- cause Ethernet is defined in 802.3 and not by LANE. Answer c is incorrect, because Token Ring is defined in 802.5 and not by LANE. Answer d is incorrect, because answers a and c are incorrect. Question 5 The correct answer is b. When a SNAP header is found (DSAP [Destination Service Access Point] and SSAP [Source Service Access Point] fields in the frame are set to AA AA, respectively) this tells the device to look further into the data for the type of payload being sent. SSAP/DSAP is used to the destination, plus 3 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Answer Key they define the recipient of a packet. Answer a is incorrect, because the routing information field is indicated by the first bit in the source address. Answer c is incorrect, because the DSAP/SSAP fields are not used to detect collisions. An- swer d is incorrect, because the address copied and the recognized fields are part of the frame status field in a Token Ring data frame, which are found further down the frame, after the SNAP header. Question 6 The correct answer is e. The address recognized (A) bit and the address copied (C) bit are duplicated to ensure the integrity of the two fields. The A and C bits are not checked by the frame check sequence fields because only the FC, DA, SA, and data fields are checked. Answer a is incorrect, because the A/C bits are present in a Token Ring data frame. Answer b is incorrect, because the A/C fields are not always 1, except when the address was recognized and the frame was copied. Answer c is incorrect, because the A/C fields are duplicated to ensure frame integrity. Answer d is incorrect, because the A/C fields are present in To- ken Ring data frames. Question 7 The correct answer is b. When a user tries to authenticate to a RADIUS server, there are three valid responses. They are Accept (user has an authorized account), Reject (user is not authorized), and Challenge (additional information is required). Answer b is not a valid response, because ARP (Address Resolution Protocol) is not part of the RADIUS authentication protocol. Question 8 The correct answer is b. The default update interval is 90 seconds, and the maxi- mum hop count for IGRP is 255 (although the default is 100 hops). Answers a, c, and d are incorrect, because as they represent wrong update intervals and hop counts. Hop count is not used as a metric; it is used to determine route integrity. Question 9 The correct answer is d. Any single IGRP update can advertise a total of 104 networks. Answers a, b, c, and e are incorrect, because 104 is the correct answer. Question 10 The correct answer is c. OSPF requires a valid IP address to be allocated to the router id. The router id is sent in all updates and in the discovery of new routers. 4 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Chapter 12 Answer a is incorrect, because, without a router id, OSPF will not start on a Cisco router. Answer b is incorrect, because the error message is not related to memory requirements. Answer d is incorrect, because answers a and b are incorrect. Question 11 The correct answer is b. When RSRB is configured on Cisco routers, the RIF is not terminated at the local router. The RIF will be composed of every device that needs to be traversed. The virtual ring on Device A is 10, or 0x00A in hex. On Device B, the virtual ring is 0x010. Hence, the RIF will be, 0A10.0011.00A1.0101.0020 (that is, through ring 001, bridge 1, ring 00A, bridge 1, ring 010, bridge 1, and finally to the destination ring 002, bridge 0). A RIF always ends with 0 to identify the destination ring. Therefore, answers a and c are immediately discounted. Answer d is incorrect because in a RSRB environment the RIF is used to determine the path to remote SRB devices. Question 12 The correct answer is b. The 0.0.0.0 255.255.255.255 parameter is shorthand for the any keyword. This means we are not concerned about hosts or which net- works are to be passed to the IP routing software. Answer a is incorrect, because the dash is missing between the access and list keywords. Answer c is incorrect, because the IOS will display the wildcard address 0.0.0.0 255.255.255.255 as any. Answer d is incorrect, because the question provides enough IOS code to determine that answer b is the correct answer. Question 13 The correct answer is d. The IOS syntax is ip policy route-map <name>. The route-map name is case sensitive. Answer a is incorrect, because the question contains enough data to determine the correct answer. Answer b is incorrect, because the IOS syntax is missing route-. Answer c is incorrect, because the command uses the wrong case—cisco is incorrectly used in place of Cisco. Question 14 The correct answer is a. RTMP, a distance-vector protocol, sends full broadcasts every 10 seconds. Answers b, c, and d are incorrect, because the answers state the wrong broadcast intervals. 5 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Answer Key Question 15 The correct answer is c. In a BGP table, any network displayed with a next hop address of 0.0.0.0 indicates that the network is a local interface. The next hop address of 131.108.1.2 describes the remote 10.1.2.0/24. Answers a and b are incorrect, because BGP networks are indicated by a valid next hop address and not the address 0.0.0.0. Answer d is incorrect, because the question provides enough data to deduce that answer c is correct. Question 16 The correct answer is c. To start AppleTalk EIGRP, the correct syntax is appletalk routing eigrp <router-id>. The router-id must be unique to each router. Answer a is incorrect, because the appletalk routing command starts RTMP, not EIGRP. Answer b is incorrect, because the syntax is wrong—no dash is required between eigrp and the process ID. Answer d is incorrect, because the no appletalk proto- col RTMP command is used to stop RTMP updates after AppleTalk EIGRP is enabled. Question 17 The correct answer is b. In a DECnet environment, such as Ethernet, the DR helps end nodes find other devices. The priority is used by default, but if two or more routers have the same priority, the node with the highest node address becomes the DR. In this case, 1.2 is higher than 1.1, so the router with address 1.2 will become the DR. Answer a is incorrect, because 1.1 is lower than 1.2. Answer c is incorrect, because a DR is required on a DECnet broadcast network. Answer d is incorrect, because the question provides enough data to deduce that answer b is correct. Question 18 The correct answers are c and d. IP and AppleTalk (AARP) use ARP. Answers a and b are incorrect, because DECnet and IPX do not use ARP. IPX and DECnet both use their own MAC address as part of the network address. Question 19 The correct answer is a. PC-A resides on a Token Ring network and PC-C re- sides on a Ethernet network. Ethernet devices do not use RIFs, so PC-C cannot see the RIF frame. Therefore, answers b, c and d are incorrect because they are examples of RIFs. 6 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Chapter 12 Question 20 The correct answers are a, b, and c. RIP uses split horizon, hold downs, and poison reverse to help speed up RIP convergence. Answer d is incorrect, because IP RIP does not deploy the hello protocol. Instead, because RIP is a distance- vector protocol, it sends the full contents of its routing table to all neighboring routers. Question 21 The correct answer is d. CHAP and PAP are authentication protocols used in Point-To-Point (PPP) networks. CHAP and PAP ensure that the correct devices gain access to a network. Answers a, b, c, and e are incorrect, because frame relay, HDLC, ATM, and LANE do not use CHAP or PAP authentication techniques. Question 22 The correct answer is b. When redistributing from one IP routing protocol to another, the network administrator must convert metrics used from one domain to the other. For example cost in OSPF to hop count in RIP, and vice versa. Answer a, is incorrect, because RIP must be advised about the metric to be ap- plied when redistributing OSPF to RIP. Answer c is incorrect, because the OSPF process id is only locally significant to a Cisco router. Answer d is incorrect, because OSPF or BGP can be used to route information from a RIP domain. Question 23 The correct answer is d. The router named Simon has two IP addresses in Area 100 and, therefore, requires the network statements for the two IP addresses only. To place the directly attached networks into Area 6, two network statements are required: network 131.108.1.0 0.0.0.255 area 6 network 131.108.2.0 0.0.0.255 area 6 Answer a is incorrect, because the network 131.108.3.0/24 is not directly at- tached to the Simon router. Answer b is incorrect, because the network statement 131.108.0.0 0.0.255.255 will place the whole class B range 131.108.0.0 to 131.108.255.255 in area 6. Answer c is incorrect, because the network statements configured are using the subnet address and not the interface address. The com- mand 131.108.1.0 0.0.0.0 (subnet address is reserved) will not identify what in- terface to place under the OSPF process. 7 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Answer Key Question 24 The correct answer is b. The access list 100 has not been defined, although the configuration displays the ip access-group 100 in interface command. When an access list is not defined, the router will not perform any IP-based filtering. An- swer a is incorrect, because access list 100 is not defined. Answer c is incorrect, because serial0 is configured for IP. Answer d is incorrect, because access 100 is not defined in the global configuration. Question 25 The correct answer is b. IEEE 802.2 defines the Logical Link Control. Answer a is incorrect, because Ethernet is defined in IEEE 802.3. Answer c is incorrect, because Token Ring bus is defined in IEEE 802.4. Answer d is incorrect, because Token Ring star is defined in IEEE 802.5. Question 26 The correct answer is e. To copy files from the startup (or NVRAM) configura- tion to a TFTP server, use the copy startup-config tftp command. Answer a is incorrect, because the copy tftp running-config command copies a configuration from a TFTP server to the running configuration. Answers b and c are incorrect, because the commands are invalid IOS commands. Answer d is incorrect, be- cause config is not a valid IOS command. Question 27 The correct answer is d. Ethernet II specifies a type field, and Ethernet 802.3 specifies a length field. Answer a is incorrect, because Ethernet II was released and Ethernet 802.3 was released in the 1980s. Answer b is incorrect, because Ethernet 802.3I does not specify the protocol field but the length field following the source MAC address field. Answer c is incorrect, because Ethernet II speci- fies a type field, not a length field. Answer e is incorrect, because there is a small difference between Ethernet II and Ethernet 802.3, even though both versions of Ethernet transmit in non-canonical order (least significant bit first). Question 28 The correct answer is c. Bootlfash is used to store IOS images. When an IOS image is deleted from bootflash (such as a pcmcia flash card) the command squeeze devicename must be issued to delete the file from the bootflash. Answers a is incorrect, because reloading the router will have no effect on the bootflash. An- swer b is incorrect, because you cannot shutdown the bootflash device. Answer d is incorrect, because this is not a known bug. 8 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Chapter 12 Question 29 The correct answer is d. When a change is made on a Cisco router’s interface to change an IP address, the effect is immediate. Answer a is incorrect, because the command goes into effect immediately—not after exiting the global configura- tion mode. Answer b is incorrect, because changing the IP address does not re- quire a router reload. Answer c is incorrect, because you do not need to shut down the interface when changing the IP address. Question 30 The correct answer is c. When you intercept a router reload by hitting control break, you cause the router to enter ROM mode. ROM mode allows you to determine hardware or software issues. Answer a is incorrect, because, after 60 seconds, the break command has no effect unless specifically configured on the boot register. Answer b is incorrect, because a break sequence will not cause a router to enter global configuration mode. Answer d is incorrect, because there is no engineering mode available to end users. Answer e is incorrect, because the router will boot into ROM mode when a break key is issued before 60 seconds when a router reloads. Question 31 The correct answer is c. Class C addresses, which have only 8 bits, provide the least number of host devices (254). Answer a is incorrect, because there are more than 16 million host addresses available with a class A address. Answer b is in- correct, because a class B address allows more than 16,000 host addresses. An- swers d and e are incorrect, because class D and class E addresses are reserved. Question 32 The correct answer is d. The IP checksum only checks for errors in the IP header. Answers a and b are in incorrect, because the checksum does not involve a packet’s data portion. Higher layers, such as TCP, check a packet’s data portion. Answer c is incorrect, because the IP header checksum is not calculated on the whole IP packet. Answer e is incorrect, because only answer b provides the correct re- sponse to the question. Question 33 The correct answer is e. The mask 255.255.255.0 allows for 8 bits to be used by end devices. Two host addresses (00000000 and 11111111) are reserved for broad- casts, so you can have up to 2 8 -2=256-2=254 host addresses. Answers a, b, c, and d are incorrect, because the correct answer is 254 hosts. 9 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Answer Key Question 34 The correct answers are b, c, and d. Manual configuration or static routing can route IP. IP can also be routed using the IS-IS and OSPF routing protocols. Answer a is incorrect, because IPX RIP is used to route the desktop protocol IPX and not IP. Answer e is incorrect because RTMP is used for AppleTalk. Question 35 The correct answer is c. The line that indicates the bandwidth of the interface in the question is: MTU 4464 bytes, BW 4000 Kbit, . The BW represents the bandwidth in Kbit—4000Kbit in this example. Answers a, b, d, e, and f are incorrect, because 4 is the correct response. Question 36 The correct answer is b. An IP routing table or routing information base never lists layer 2 MAC address information, because a routing table is based on layer 3 information. Answers a, c, and d are incorrect, because IP routing tables list char- acteristics such as next hop addresses, routing metrics, and outbound interfaces. Question 37 The correct answer is a. ATM LANE is used to allow protocols such as Ethernet and Token Ring the high bandwidth that ATM can offer. ATM LANE consists of the following devices: ➤ LAN Emulation Client (LEC)—Implements the LANE standard including data forwarding, address resolution (LE-ARP). Each LEC is made up of a unique ATM address. ➤ LAN Emulation Server (LES)—Manages stations that make up the emulated LAN ➤ Broadcast and Unknown Server (BUS)—Handles all broadcast frames to un- known destinations ➤ LAN Emulation Configuration Server (LECS)—Contains information about all emulated LANs Therefore, answers b, c, d, and e are incorrect. The HEC (Header Error Control) is an algorithm used in ATM to check and correct cells that may be corrupted. The HEC field is part of the ATM cell header. HEC is not part of ATM LANE. 10 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Chapter 12 Question 38 The correct answer is d. A TCP session requires a device to request a session to terminate, which requires one TCP segment. Then, an acknowledgment is sent and the second device requests termination, which also requires an acknowledg- ment. Therefore, four TCP segments are involved. Answers a, b, c, e, and f are incorrect, because four is the correct number of segments required to close a TCP session. Question 39 The correct answer is a. To copy files from the running configuration (or RAM) to the NVRAM (or startup) configuration, you use the copy running-config startup-config command. Answers b and c are incorrect, because they are invalid IOS commands. Answer d is incorrect, because the copy running-config tftp command copies the configuration to a TFTP server. Question 40 The correct answer is d. The last line of the display indicates that the ring speed is 16MB: Ring speed: 16 Mbps Answers a, b, c, and e are incorrect, because 16Mbps is the correct answer. Question 41 The correct answer is d. The show interface command displays vital statistics about the state of a LAN or WAN interface. The described state—serial line is down, line protocol is up—is not a possible condition. The four possible states are: ➤ serial 0 line is down, line protocol is down—No cable or modem is connected. ➤ serial 0 line is up, line protocol is up—The WAN service is working fine and keepalives from the remote site are being sent and received. ➤ serial 0 line is up, line protocol is down—A cable is plugged into the router, but no keepalives are being received from the remote router. ➤ serial 0 is administratively down, line protocol is down—The interface has not been enabled by the administrator. Answer a is incorrect, because, when keepalives are received, the line protocol is typically up or active. Answer b is incorrect, because, if the remote modem is down, the condition would be serial 0 line is up, line protocol is down. Answer c [...]... destination address as 00-00-0b-ba-da-aa Layer 3 IP addressing is not altered Answers a, c, and d are incorrect, because they present incorrect source addresses Answer e is incorrect, because the correct answer is provided Answer Key 13 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Question 49 The correct answer is b When IP routing is enabled on a device, the local PC named... correct answer is e Route maps can be used for a number of purposes, including setting the next hop, setting the IP precedence, administering policy routing, and setting outbound interfaces Answers a, b, c, and d are incorrect, because, while each option specifies a route map, answer e provides the most comprehensive answer Answer f is incorrect, because a router map can be used as described in answers... addressing is not altered Answers a, c, and d are incorrect, because they present incorrect destination addresses Answer e is incorrect, because there is enough layer 2 information to deduce the correct answer Question 50 The correct answers are a and d To set a designated router in an OSPF network, you can set the priority or use the router with the highest loopback address Answer b is incorrect, because... ineligible to become the DR Answer c is incorrect, because, in an OSPF broadcast environment, the election of the DR does not depend on the router that boots first Answer e is incorrect, because answers a and d satisfy the question Question 51 The correct answers are a and b Token Ring 802.5 supports two broadcast destination addresses, namely all Fs or C0-00-FF-FF-FF-FF Answer c is incorrect, because... VLSM Answer a is incorrect, because RIP version 1 does not support VLSM Answer e is incorrect, because IGRP does not support VLSM Both RIP I and IGRP only support fixed-length masks, which means that all IP networks in the administrative domain must have the same subnet mask Answer Key 15 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Question 56 The correct answer. .. correct answer is f EIGRP is not a WAN service—it’s a routing protocol supported on Cisco routers EIGRP can handle IP, IPX, and AppleTalk routing Answers a, b, c, d, and e are incorrect, because Cisco routers support many WAN services, including ISDN, frame relay, PPP, HDLC, and SDLC Answer Key 17 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Question 64 The correct answers... IOS, the command was write terminal Answer a is incorrect, because it will display the configuration stored in NVRAM or the startup configuration Answer b is incorrect, because write config is an invalid IOS command Answer e, is not a valid IOS command also Question 65 The correct answer is e The syntax for a static router is: ip route Answer a is incorrect, because the... routing table Answer b is incorrect, because the command contains the wrong next hop address Answer c is incorrect, because the next hop address cannot be the subnet address Answer d is incorrect, because it is an invalid IOS command Question 66 The correct answers are a, b, and d TCP, FTP, and Logical Link Control type 2 are connection-orientated protocols, so they guarantee data delivery Answers c and... CPU queue Answer c is incorrect, because you do not need to reboot a router to view debug information Answer d is incorrect, because there is an exhaustive debug command set Answer e is incorrect, because the auxiliary port is used for remote management via a modem, for example Answer f is incorrect, because you can view debug information via a console or VTY session Question 46 The correct answer is... or show ha Answers a, b, and d are incorrect, because show components, display hardware, and list hardware are invalid IOS commands Answer Key 21 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Question 79 The correct answer is a The IOS command to copy the NVRAM configuration (startup-config) to the RAM (running-config) is copy startup-config runningconfig Answers b, . any. Answer d is incorrect, because the question provides enough IOS code to determine that answer b is the correct answer. Question 13 The correct answer. seconds. Answers b, c, and d are incorrect, because the answers state the wrong broadcast intervals. 5 ○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○ Answer Key