思科認證考試題庫

1、叮叮小文庫CCNA640-802 V13題庫試題分析題庫講解：吳老師（艾迪飛CCIE實驗室首發(fā)網(wǎng)站：.c n1. What are two reas ons that a n etwork admi nistrator would use access lists? (Choose two.)A. to con trol vty access into a routerB. to con trol broadcast traffic through a routerC. to filter traffic as it passes through a routerD. to filter tr

2、affic that origi nates from the routerE. to replace passwords as a line of defe nse aga inst security in curs ionsAn swer: AC解釋一下：在VTY線路下應(yīng)用ACL，可以控制從VTY線路進來的tel net的流量。也可以過濾穿越一臺路由器的流量。2. A default Frame Relay WAN is classified as what type of physical n etwork?A. poin t-to-po intB. broadcast multi-ac

3、cessC. non broadcast multi-accessD. non broadcast multipo intE. broadcast poin t-to-multipo intAn swer: C解釋一下：在默認的情況下，幀中繼為非廣播多路訪問鏈路。但是也可以通過子接口來修改他的網(wǎng)絡(luò)的類型。3. Refer to the exhibit. How many broadcast domains exist in the exhibited topology?fVLAN MVI AN4UVLAM trunkA. oneB. twoC. threeD. fourE. fiveF. si

4、xAn swer: C解釋一下：廣播域的問題，在默認的情況下，每個交換機是不能隔離廣播域的，所以在同一個區(qū)域的所有交換機都在同一個廣播域中，但是為了減少廣播的危害，將廣播限制在一個更小的范圍，有了 VLAN的概念，VLAN表示的是一個虛擬的局域網(wǎng)，而他的作用就是隔離廣 播。所以被VLAN隔離了的每個區(qū)域都表示一個單獨的廣播域，這樣一個VLAN中的廣播的流量是不能傳到其他的區(qū)域的，所以在上題中就有3個廣播域了。4. A sin gle 802.11g access point has bee n con figured and in stalled in the cen ter of a squ

5、are office. A few wireless users are experie ncing slow performa nee and drops while most users are operati ng at peak efficie ncy. What are three likely causes of this problem? (Choose three.)A. mismatched TKIP en crypti onB. n ull SSIDC. cordless phonesD. mismatched SSIDE. metal file cab in etsF.

6、antenna type or direct ionAn swer: CEF6. The comma nd frame-relay map ip 102 broadcast was en tered on the router. Which of the followi ng stateme nts is true concerning this comma nd?A. This comma nd should be executed from the global con figurati on mode.B. The IP address i

7、s the local router port used to forward data.C. 102 is the remote DLCI that will receive the information.D. This comma nd is required for all Frame Relay con figuratio ns.E. The broadcast opti on allows packets, such as RIP updates, to be forwarded across the PVC.An swer: E解釋一下：關(guān)于命令frame-relay map i

8、p 102 broadcast ,這個命令用于手工靜態(tài)添加一條映射，到達的流量封裝一個DLCI號為102，而且這條PVC是支持廣播的流 量的，比如RIP的更新包。因為在默認的情況下，幀中繼的網(wǎng)絡(luò)為非廣播的，而RIP在其上是無法發(fā)包的。8. Which of the following are associated with the application layer of the OSI model? (Choose two.)A. pi ngB. Tel netC. FTPD. TCPE. IPAn swer: BC解釋一下：在OSI 7層模型中

9、位于應(yīng)用層的應(yīng)用有telnet和ftp這兩種應(yīng)用。9. For security reasons, the network administrator needs to prevent pings into the corporate n etworks from hosts outside the in ternetwork. Which protocol should be blocked with access con trol lists?A. IPB. ICMPC. TCPD. UDPAn swer: B解釋一下：PING命令 利用ICMP協(xié)議的echo，和echo-replay兩個

10、報文來檢測鏈路是否連通的。 所以如果要阻止PING的流量到網(wǎng)絡(luò)，就只要過濾掉ICMP的應(yīng)用就可以了。10. Refer to the exhibit. The network administrator has created a new VLAN on Switch1 and added host C and host D. The adm ini strator has properly con figured switch in terfaces FastEther net0/13 through FastEthernet0/24 to be members of the new VLA

11、N. However, after the network adm ini strator completed the con figurati on, host A could com muni cate with host B, but host A could not com muni cate with host C or host D. Which comma nds are required to resolve this problem?25A. Router(c on fig)# in terface fastether net 0/1.3Router(c on fig-if)

12、# en capsulati on dot1q 3Router(config-if)# ip address B. Router(c on fig)# router ripRouter(co nfig-router)# network Router(co nfig-router)# network Router(co nfig-router)# network C. Switch1# vlan databaseSwitch1(vla n)# vtp v2-modeSwitch1(

13、vla n)# vtp domai n ciscoSwitch1(vla n)# vtp serverD. Switch1(co nfig)# in terface fastethernet 0/1Switch1(c on fig-if)# switchport mode trunkSwitch1(config-if)# switchport trunk encapsulation islAn swer: A解釋一下：這是一個多 VLAN間通訊的問題，雖然都同在一臺交換機上，但是由于處在不同 的VLAN中，而導(dǎo)致了不同VLAN中的主機是不能通訊的。這時我們就需要借助與trunk和三層的路由功能

14、了，在交換機和路由器之間封裝TRUNK，這樣可以允許交換機間的二層的通訊，但是由于兩個VLAN是劃分到不同的網(wǎng)段中的，因此需要借助路由器的路由功能來實現(xiàn)三層的可達，可以將 VLAN中的主機的網(wǎng)關(guān)指定為路由器與該VLAN相連的子接口的地址，這樣VLAN中的數(shù)據(jù)包就都會發(fā)往網(wǎng)關(guān)，而由網(wǎng)關(guān)來進行進一步的轉(zhuǎn)發(fā)。在這個題中，題目給出了路由器的的子接口的網(wǎng)段，而又給出了VLAN 2與路由器相連的接口的IP地址，所以剩下的一個網(wǎng)段就是給VLAN 3的了，所以要在路由器上將與一個子接口劃分到VLAN 3，并給其分配另一個網(wǎng)段中的IP地址。這樣就可以了。11. What are two recommended

15、ways of protecting network device configuration files from outside n etwork security threats? (Choose two.)A. Allow un restricted access to the con sole or VTY ports.B. Use a firewall to restrict access from the outside to the n etwork devices.C. Always use Telnet to access the device comma nd line

16、because its data is automatically en crypted.D. Use SSH or ano ther en crypted and authe nticated tran sport to access device con figurati ons.E. Prevent the loss of passwords by disabli ng password en crypti on.An swer: BD解釋一下：要確保外部的安全的站點才可以訪問我的網(wǎng)絡(luò)，這就涉及到了安全的問題了，我們可以使用防火墻來限制外網(wǎng)中來的設(shè)備；也可以通過SSH或加密和認證來控制。

17、12. Refer to the exhibit. The access list has bee n con figured on the S0/0 in terface of router RTB in the outbo und directi on. Which two packets, if routed to the in terface, will be deni ed? (Choose two.) access-list 101 de ny tcp 2 5 any eq tel netaccess-list 101 permit ip an

18、y anyA. source ip address: ; desti nation port: 21B. source ip address:, 7 dest in ation port: 21C. source ip address:, 1 dest in ation port: 21D. source ip address:, 6 dest in ation port: 23E. source ip address: 6; dest in ation port: 23F.

19、 source ip address:, 9 dest in ation port: 23An swer: DE解釋一下：這個訪問列表定義了兩個語句：access-list 101 de ny tcp 2 5 any eq tel netaccess-list 101 permit ip any any在訪問列表中匹配的順序是從上到下，如果匹配了某一句，就退出訪問列表，如果沒有就一直往下匹配，在訪問列表中有一句隱含的拒絕所有。所以不管怎么樣都有一句是能被匹配的。在上題中，他定義的第一句是拒絕到從 2- 192

20、.168.15.47發(fā)出的任何的tel net的流 量，然后第二句定義的就是允許所有的 IP流量。而且要明確teln et的流量使用的是端口 23,所 以這個題的答案就很明確了。13. Refer to the exhibit. Switchl has just been restarted and has passed the POST routine. Host A sends its initial frame to Host C. What is the first thing the switch will do as regards populating the switchi n

21、g table?HostB/wo門Host AMAC*000A.8A47.E612IP-Fa02HostDHosl CMAC - 000BrB95.2EEIP-2A. Switch1 will add to the switching table.B. Switch1 will add 2 to the switching table.C. Switch1 will add 000A.8A47.E612 to the switching table.D. Switch1 will add 000B

22、.DB95.2EE9 to the switching table.An swer: C解釋一下：交換機重新啟動了， 這個時候交換機的MAC地址表是空的，當(dāng)主機A發(fā)送數(shù)據(jù)給 主機C而經(jīng)過交換機時，交換機根據(jù)他的工作的原理他要進行原MAC地址學(xué)習(xí)，而因為對于這個目的MAC地址無記錄，而將這個流量從除收到的這個接口外的所有接口泛洪出去。所 以在最開始的一步中，交換機是記錄下主機A的MAC地址000A.8A47.E612到他的MAC地址表中。14. he user of Host1 wants to ping the DSL modem/router at 54. Based

23、on the Host1 ARP table that is shown in the exhibit, what will Host1 do?A. send a uni cast ARP packet to the DSL modem/routerB. send uni cast ICMP packets to the DSL modem/routerC. send Layer 3 broadcast packets to which the DSL modem/router resp ondsD. send a Layer 2 broadcast that is received by H

24、ost2, the switch, and the DSL modem/routerAn swer: B解釋一下：在下面的表中我們可以看到ARP表中有關(guān)于54的ARP條目，所以在這主機都只需要發(fā)送單播的ICMP包到DSL modem/router即可。15. Refer to the exhibit. What is the most efficient summarization that R1 can use to advertise its networks to R2?A. /22B. /21C. /22D.

25、/24/24172.160/24/24E. /25172.14128/25/24/24/24An swer: C解釋一下：這還是一個關(guān)于匯總的問題。要求R1將所有的網(wǎng)段用匯總的條目發(fā)送給R2,因為這些條目的網(wǎng)絡(luò)位是相同的都為172.1，所以在這需要匯總的只是第3個八位，將4, 4, 5,6，7這些寫成二進制的形式，然后找出相同的位數(shù)，則有相同位數(shù)的字節(jié)就是他們的掩碼 的位數(shù)，而最小的有相同位的最小的數(shù)字就是他們的基數(shù)位，所以R1通告出去 匯總的條目為

26、/22。16. Refer to the exhibit. Assume that all router in terfaces are operatio nal and correctly con figured. In additi on, assume that OSPF has bee n correctly con figured on router R2. How will the default route con figured on R1 affect the operati on of R2?A. Any packet desti ned for a n etwork th

27、at is not directly conn ected to router R1 will be dropped.B. Any packet desti ned for a n etwork that is not directly conn ected to router R2 will be dropped immediately.C. Any packet desti ned for a n etwork that is not directly conn ected to router R2 will be dropped immediately because of the la

28、ck of a gateway on R1.D. The n etworks directly conn ected to router R2 will not be able to com muni cate with the , 28, and 4 sub networks.E. Any packet desti ned for a n etwork that is not referenced in the routi ng table of router R2 will be directed to R1. R1

29、will the n send that packet back to R2 and a routi ng loop will occur.An swer: 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(biāo)記為 O*E2 /0出接口為 SerialO/O的路由。所以R2收到任何路由表中沒有的目的網(wǎng)段時，就將指定給R1，而R1根據(jù)缺省路由的出接口又將數(shù)據(jù)包發(fā)往R2，這樣就形成了一個路由的環(huán)路。17. A n etwork in terface port has collisi on det

30、ect ion and carrier sensing en abled on a shared twisted pair n etwork. From this stateme nt, what is known about the n etwork in terface port?A. This is a 10 Mb/s switch port.B. This is a 100 Mb/s switch port.C. This is an Ether net port operat ing at half duplex.D. This is an Ether net port operat

31、i ng at full duplex.E. This is a port on a n etwork in terface card in a PC.An swer: 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。10 10.0020. Refer to the topology and router configuration shown in the graphic. A host on the LAN is access ing an FTP server across the Intern e

32、t. Which of the follow ing addresses could appear as a source address for the packets forwarded by the router to the desti nati on server?Interfaca- SeriaKip address 200 2 2 IB f66 255 256262 ip natcutaidflSI; 200.12 18/30 laO. 10J 0,0.1/21 side1intarfsce F BsrEtnemetotpMd僧踽 WJO.OJ 255.255J55,0 ip n

33、*t irrndespted autoip 冷H pul199 99 WO 199 99 9 62 “EmK 2S5 26626.221ip nat invld* vouro M ll pool twtip fOutttDC.DOOOOO2002.2.171 0 00.0.255A. B. C. 3D. 7E. 7F. 8An swer: D解釋一下：這是個 NAT地址轉(zhuǎn)換的題目，在這fO/O接口連接下的為私有的地址，這些地址是 不能同外網(wǎng)進行通訊的，這時就借助NAT,將內(nèi)網(wǎng)的私有地

34、址轉(zhuǎn)換為可以在公網(wǎng)上通訊的地址，我們看到NAT POOL中定義的轉(zhuǎn)換后的公有地址為0到2，則表示這段地址是我轉(zhuǎn)換后的內(nèi)網(wǎng)全局地址，所以HOST想要穿過INTERNET訪問FTP服務(wù)器，則需要轉(zhuǎn)換為公有地址0到2之內(nèi)的地址，在上面的答案中只有地址 7滿足條件，所以答案就是D 了。21. A company is installing IP phones. The phones and office computers connect to the same device. To en sure m

35、aximum throughput for the phone data, the compa ny n eeds to make sure that the phone traffic is on a different network from that of the office computer data traffic. What is the best n etwork device to which to directly connect the pho nes and computers, and what tech no logy should be impleme nted

36、 on this device? (Choose two.)A. hubB. routerC. switchD. STPE. sub in terfacesF. VLANAn swer: 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。22. Refer to the exhibit. Which statement describes DLCI 17?A. DLCI 17 describes the ISDN circuit between R2 an

37、d R3.B. DLCI 17 describes a PVC on R2. It cann ot be used on R3 or R1.C. DLCI 17 is the Layer 2 address used by R2 to describe a PVC to R3.D. DLCI 17 describes the dial-up circuit from R2 and R3 to the service provider.An swer: C解釋一下：DLCI是在Frame-relay中的描述二層信息的地址， 他的地位等同于以太網(wǎng)中的 MAC 地址。我們以R2上的DLCI 17來看

38、，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。23. Which routing protocol by default uses bandwidth and delay as metrics?A. RIPB. BGPC. OSPFD. EIGRPAn swer: D解釋一下：在我們的路由協(xié)議中使用復(fù)合度量的協(xié)議只有IGP和EIGPR，而他們在默認的情況下是使用帶寬和延時來計算度量的。25. In the impleme ntati on of VLSM tech niq ues on a n etwork using a sin gle Clas

39、s C IP address, which sub net mask is the most efficie nt for poin t-to-po int serial li nks?A. B. 40C. 48D. 52E. 54An swer: 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,掩碼就為52 .26. Refer to

40、the exhibit. The networks connected to router R2 have been summarized as a/21 route and sent to R1. Which two packet dest in ation addresses will R1 forward to R2? (Choose two.)OtherNetworksA. 60B. 1C. D. 55E. F. 192.168.1

41、84.45An swer: BE解釋一下：這個題其實就是考察的匯總的問題，他說的意思是R2發(fā)送了一個匯總的路由/21給R1，哪兩個包文的目的地 R1仍將轉(zhuǎn)發(fā)給R2。這還是匯總的問題的一個反 向的考察，根據(jù)21位的掩碼位數(shù)可以推斷在第 3個八位字節(jié)的前5位是相同的，不同的是后面 的3位，而將176寫成二進制的形式為1011 0000,所以可以看出來明細的路由可以是176-183，所以在上面的答案中可以很容易看到答案B和E是我們的明細路由。27. Refer to the exhibit. Switch-1 needs to send data to a host wit

42、h a MAC address of 00b0.d056.efa4. What will Switch-1 do with this data?Sitch-1# show mac address-tableDynamic Addresses Count3Secure Addresses (User-defined) Count 0 s怕tic(Jser-defined) Cunt UresdressSystem Self Addresses Count Total MacNon-staticDetiriNDcin AddrE Address Type VLAN Destination Port

43、Fas-tEtherrietC/1FastEthemetC/3FastEthemeO2CI01D DdeO e?89_Dynamic3010 7bD0 1510DynarricDOW 7b00 1545CtynamicA. Switch-1 will drop the data because it does not have an entry for that MAC address.B. Switch-1 will flood the data out all of its ports except the port from which the data origi nated.C. S

44、witch-1 will send an ARP request out all its ports except the port from which the data originated.D. Switch-1 will forward the data to its default gateway.An swer: B解釋一下：首先Switch 1需要發(fā)送一個數(shù)據(jù)到 MAC地址為00b0.d056.efa4的主機，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。 交換機在收到未知的單播，組播和廣播時，都采用的是泛洪的方式，往除收到數(shù)

45、據(jù)的這個接 口外的所有接口都發(fā)送。所以在這兒，Switch 1也采取的上泛洪的方式。28. wo routers n amed Atla nta and Brevard are conn ected by their serial in terfaces as show n in the exhibit, but there is no data connectivity between them. The Atlanta router is known to have a correct configuration. Given the partial configurations show

46、n in the exhibit, what is the problem on the Brevard router that is caus ing the lack of conn ectivity?A. A loopback is not set.B. The IP address is in correct.C. The sub net mask is in correct.D. The serial line en capsulati ons are in compatible.E. The maximum tran smissi on un it (MTU) size is to

47、o large.F. The ban dwidth setti ng is in compatible with the conn ected in terface.An swer: B解釋一下：很明顯的錯誤啊，兩臺路由器的串行接口的地址配置錯誤，不是在相同的網(wǎng)段， 從而導(dǎo)致了不能通訊。29. Which two values are used by Spanning Tree Protocol to elect a root bridge? (Choose two.)A. amou nt of RAMB. bridge priorityC. IOS versionD. IP addressE

48、. MAC addressF. speed of the linksAn swer: 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MACaddresso30. Refer to the exhibit. Which switch provides the spanning-tree designated port role for the n etwork segme nt that services the prin ters?A. SwitchlB. Switch2C. Switch3D. S

49、witch4An swer: C解釋一下：這是個關(guān)于生成樹選舉的問題， 我們首先需要找到根橋， 而根橋的選舉是通過比 較橋ID的，而且是越小越優(yōu)先，橋ID的組成為橋優(yōu)先級和 MAC地址。所以我們通過上圖可以 找到根橋為switch 1。然后在非根橋上選出根端口，通過比較到根橋的花費來選舉的，花費最小的就是根端口。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。下一步我們來選舉指派端口。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

50、有更小的 MAC地址。32. Refer to the exhibit. Why would the n etwork admi nistrator con figure RA in this manner?10*1251(MZ3 10JJJ 10 4.1210.L1JF?A(confiQ)* access list 2 pennit 55RA(gntie# line vty 0 4 RWcanTiGbilneff accessias 2 inA. to give stude nts access to the InternetB. to preve nt st

51、ude nts from access ing the comma nd prompt of RAC. to preve nt adm ini strators from access ing the con sole of RAD. to give adm ini strators access to the InternetE. to preve nt stude nts from access ing the InternetF. to preve nt stude nts from access ing the Adm in n etworkAn swer: B解釋一下：在這兒，將AC

52、L應(yīng)用到VTY線路下，而且是IN的方向，表示凡是被我的ACL允許的才能tel net到我.在RA上配置的是permit 55根據(jù)隱式的de ny any允許A dmin的網(wǎng)段中的用戶可以tel net到他，所以S tude nt的網(wǎng)段中的用戶是被拒絕的.33. In order to allow the establishme nt of a Telnet sessi on with a router, which set of comma nds must be con figured?A. router(c on fig)# line con sole 0r

53、outer(c on fig-li ne)# en able password ciscoB. router(c on fig)# line con sole 0router(c on fig-li ne)# en able secret ciscorouter(c on fig-li ne)# logi nC. router(c on fig)# line con sole 0router(c on fig-li ne)# password ciscorouter(c on fig-li ne)# logi nD. router(c on fig)# line vty 0router(c o

54、n fig-li ne)# en able password ciscoE. router(c on fig)# line vty 0router(c on fig-li ne)# en able secret ciscorouter(c on fig-li ne)# logi nF. router(c on fig)# line vty 0router(c on fig-li ne)# password ciscorouter(c on fig-li ne)# logi nAn swer: F解釋一下：teln et是一個應(yīng)用層的應(yīng)用，他使用的是vty線路，而且在默認的情況下，是需要訪問的線

55、路下設(shè)有密碼的。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。如果想 Telnet時在VTY線路下不設(shè)置密碼 也可以訪問這個線路，可以在該VTY線路下輸入命令no login。34. Refer to the exhibit. The two exhibited devices are the only Cisco devices on the network. The serial n etwork betwee n the two devices has a mask of 52.

56、Give n the output that is show n, what three stateme nts are true of these devices? (Choose three.)A. The Ma nchester serial address is .B. The Man chester serial address is .C. The Lon don router is a Cisco 2610.D. The Ma nchester router is a Cisco 2610.E. The CDP in formati on was

57、received on port SerialO/O of the Man chester router.F. The CDP information was sent by port Serial0/0 of the London router.An swer: 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：L ondon ;IP 地址：;平臺：cisco 2610;能力：Router;端口： s0/1; holdtime : 1 2 5S.M anc