【正文】 operation of R2? A. Any packet destined for a network that is not directly connected to router R1 will be dropped. B. Any packet destined for a network that is not directly connected to router R2 will be dropped immediately. C. Any packet destined for a network that is not directly connected to router R2 will be dropped immediately because of the lack of a gateway on R1. D. The networks directly connected to router R2 will not be able to municate with the , , and subnetworks. E. Any packet destined for a network that is not referenced in the routing table of router R2 will be directed to R1. R1 will then send that packet back to R2 and a routing loop will occur. Answer: E解釋一下：在R1上產(chǎn)生了一個OSPF的缺省路由，出接口指定為S0/0，這條缺省路由以5類LSA的形式通告給了R2，于是R2上也有了一條標記為O*E2 。17. A network interface port has collision detection and carrier sensing enabled on a shared twisted pair network. From this statement, what is known about the network interface port? A. This is a 10 Mb/s switch port. B. This is a 100 Mb/s switch port. C. This is an Ethernet port operating at half duplex. D. This is an Ethernet port operating at full duplex. E. This is a port on a network interface card in a PC. Answer: C解釋一下：一個接口有沖突檢測和載波偵聽，而且是使用雙絞線的網(wǎng)絡(luò)，那么對于這個接口我們可以推測出他是以太接口，而且是工作在半雙工的模式下。21. A pany is installing IP phones. The phones and office puters connect to the same device. To ensure maximum throughput for the phone data, the pany needs to make sure that the phone traffic is on a different network from that of the office puter data traffic. What is the best network device to which to directly connect the phones and puters, and what technology should be implemented on this device? (Choose two.) A. hub B. router C. switch D. STP E. subinterfaces F. VLAN Answer: CF解釋一下：公司的語音設(shè)備和辦公的設(shè)備都連在相同的設(shè)備上，還要確保語音的數(shù)據(jù)流在不同與公司的辦公的數(shù)據(jù)流量，最好的網(wǎng)絡(luò)設(shè)備當(dāng)然是交換機了，然后利用VLAN的技術(shù)就完全可以滿足所有的要求了。我們以R2上的DLCI 17來看，DLCI 17描述的是：從這個接口出去的目的地為R3的接口的這條PVC的二層的地址為17。25. In the implementation of VLSM techniques on a network using a single Class C IP address, which subnet mask is the most efficient for pointtopoint serial links? A. B. C. D. E. Answer: D解釋一下：在點到點的鏈路上因為只需要分配兩個地址給兩端就可以了，所以加上網(wǎng)絡(luò)地址和廣播地址，這個網(wǎng)段也就只需要有4個地址了，所以網(wǎng)絡(luò)位需要匹配30位,．26. Refer to the exhibit. The networks connected to router R2 have been summarized as a (Choose two.) A. B. C. D. E. F. Answer: BE解釋一下：這個題其實就是考察的匯總的問題，哪兩個包文的目的地R1仍將轉(zhuǎn)發(fā)給R2。27. Refer to the exhibit. Switch1 needs to send data to a host with a MAC address of . What will Switch1 do with this data? A. Switch1 will drop the data because it does not have an entry for that MAC address. B. Switch1 will flood the data out all of its ports except the port from which the data originated. C. Switch1 will send an ARP request out all its ports except the port from which the data originated. D. Switch1 will forward the data to its default gateway. Answer: B解釋一下：首先Switch ，了解到目的地后，就查看他的MAC 地址表，然后發(fā)現(xiàn)在MAC地址表中沒有這個MAC地址的條目存在。所以在這兒，Switch 1也采取的上泛洪的方式。29. Which two values are used by Spanning Tree Protocol to elect a root bridge? (Choose two.) A. amount of RAM B. bridge priority C. IOS version D. IP address E. MAC address F. speed of the links Answer: BE解釋一下：生成樹的選舉的問題，根橋的選舉是通過比較ＢＩＤ的，而ＢＩＤ由橋優(yōu)先級和ＭＡＣ地址組成的．所以在選根橋的時候需要比較的是橋優(yōu)先級和ＭＡＣ　address。所以我們通過上圖可以找到根橋為switch 1。因為上圖中沒有表示出鏈路的帶寬，所以無法比較他們的花費。每條鏈路都需要有一個DP，先是比較花費，如果花費相同則比較BID（橋優(yōu)先級），仍是越小越優(yōu)先，根據(jù)上圖的表識，我們可以找到每條鏈路上的DP，而連Printers的鏈路上的DP就為Switch 3，因為他有更小的MAC地址。而在VTY線路下設(shè)置密碼的命令為 passwork string ,而VTY線路下的另一個命令login則是默認的，可寫也可不寫。34. Refer to the exhibit. The two exhibited devices are the only Cisco devices on the network. The serial network between the two devices has a mask of . Given the output that is shown, what three statements are true of these devices? (Choose three.) A. The Manchester serial address is . B. The Manchester serial address is . C. The London router is a Cisco 2610. D. The Manchester router is a Cisco 2610. E. The CDP information was received on port Serial0/0 of the Manchester router. F. The CDP information was sent by port Serial0/0 of the London router. Answer: ACE解釋一下：ＣＤＰ是ＣＩＳＣＯ私有的一個二層的協(xié)議，但是他卻可以發(fā)現(xiàn)三層的ＩＰ信息的．通過ＣＤＰ可以發(fā)現(xiàn)的鄰居的信息有：設(shè)備的名稱，ＩＰ地址，端口，能力，平臺，對端的holddown time．在上圖的show cdp entry *命令的顯示可以看到的信息有：設(shè)備名稱：Ｌondon；ＩＰ地址：；平臺：cisco 2610；能力：Router；端口：s0/１；holdtime：１２５Ｓ．Ｍanchesteter收到這個ＣＤＰ信息的接口為S0/0．綜合一下，這個題目的答案就出來了．35. A network administrator has configured two switches, named London and Madrid, to use VTP. However, the switches are not sharing VTP messages. Given the mand output shown in the graphic, why are these switches not sharing VTP messages? A. The VTP version is not correctly configured. B. The VTP operating mode is not correctly configured. C. The VTP domain name is not correctly configured. D. VTP pruning mode is disabled. E. VTP V2 mode is disabled. F. VTP traps generation is disabled. Answer: C解釋一下：交換機間不能共享VTP的信息，我們就需要檢查VTP的狀態(tài)，首先需要檢查的是VTP的域名，只有同一個域中的才可能相互學(xué)習(xí)，再來檢查VTP的模式，必須有一個server模式才能有VTP學(xué)習(xí)的過程的，默認的情況下VTP的模式為Server的。36. Host 1 is trying to municate with Host 2. The e0 interface on Router C is down. Which of the following are true? (Choose two.) A. Router C will use ICMP to inform Host 1 that Host 2 cannot be reached. B. Router C will use ICMP to inform Router B that Host 2 cannot be reached. C. Router C will use ICMP to inform Host 1, Router A, and Router B that Host 2 cannot be reached. D. Router C will send a Destination Unreachable message type. E. Router C will send a Router Selection message type. F. Router C will send a Source Quench message type. Answer: AD解釋一下：連Host 2的接口E0/0 down了，那么最直接的反映就發(fā)生在路由器C上，C的路由表中的這個條目就消失了，因此當(dāng)Host 1 想要跟Host 2建立連接的時候，Router C就發(fā)送一個目的網(wǎng)段不可達的消息；如果是使用ping命令，那么Router C就使用ICMP 的包文告訴Host 1，Host 2是不可打的?？梢钥吹浇涌诘腗AC地址，表示這個接口肯定不是串行接口，所以可以排除D和E的選項。38. On pointtopoint networks, OSPF hello packets are addressed to which address? A. B. C. D. E. F. Answer: E解釋一下：。 troubleshooting a connectivity problem, a