CCNA640-802題庫(kù)解析.doc

CCNA640-802題庫(kù)解析訪問(wèn)控制列表(ACL) 本文主要結(jié)合例題描述ACLs的作用和類型，基于網(wǎng)絡(luò)過(guò)濾要求配置和應(yīng)用ACLs。 What are two reasons that a network administrator would use access lists? (Choose two.) A:to control vty access into a router B:to control broadcast traffic through a router C:to filter traffic as it passes through a router D:to filter traffic that originates from the router E:to replace passwords as a line of defense against security incursions Correct Answers: A, C 在路由器上設(shè)置訪問(wèn)控制列表的目的是：控制用戶的訪問(wèn)和過(guò)濾通過(guò)路由器的流量. What is the effect of the following access list condition? access-list 101 permit ip 55 any A: permit all packets matching the first three octets of the source address to all destinations B: permit all packets matching the last octet of the destination address and accept all source addresses C: permit all packets from the third subnet of the network address to all destinations D: permit all packets matching the host bits in the source address to all destinations E: permit all packets to destinations matching the first three octets in the destination address Correct Answers: A 這是一個(gè)擴(kuò)展的訪問(wèn)控制列表，他可以基于源和目的進(jìn)行匹配， 55匹配的是源地址凡是在這個(gè)范圍的都被匹配了，而目的用的是any，表示任何。意思是從/24的地址范圍內(nèi)的任何IP都可以訪問(wèn)任何的網(wǎng)段。 What three pieces of information can be used in an extended access list to filter traffic? (Choose three.) A:protocol B:VLAN number C:TCP or UDP port numbers D:source switch port number E:source IP address and destination IP address F:source MAC address and destination MAC address Correct Answers: A, C, E 1.標(biāo)準(zhǔn)訪問(wèn)控制列表,針對(duì)源地址對(duì)流量進(jìn)行過(guò)濾 2.擴(kuò)展訪問(wèn)控制列表,針對(duì)源或者目標(biāo)地址、協(xié)議、TCP或者UDP端口號(hào)對(duì)流量進(jìn)行過(guò)濾 Refer to the exhibit. The FMJ manufacturing company is concerned about unauthorized access to the Payroll Server. The Accounting1, CEO, Mgr1, and Mgr2 workstations should be the only computers with access to the Payroll Server. What two technologies should be implemented to help prevent unauthorized access to the server? (Choose two.) A:access lists B:encrypted router passwords C:STP D:VLANs E:VTP F:wireless LANs Correct Answers: A, D 首先根據(jù)不同的部門劃分3個(gè)VLAN,office1 shipping production.由于CEO Mgr1 mgr2屬于不同的VLAN,因此需要配置訪問(wèn)列表access lists控制其它主機(jī)對(duì)Payroll Server的訪問(wèn). An access list was written with the four statements shown in the graphic. Which single access list statement will combine all four of these statements into a single statement that will have exactly the same effect? A: access-list 10 permit 55 B: access-list 10 permit 55 C: access-list 10 permit 55 D: access-list 10 permit 55 E: access-list 10 permit 55 Correct Answers: C 用一個(gè)單獨(dú)的語(yǔ)句來(lái)匹配上面寫出的四條ACL，也就一一個(gè)匯總的問(wèn)題，將/24，/24, /24, /24進(jìn)行匯總，將他們的第3個(gè)八字節(jié)以二進(jìn)制展開(kāi)，相同的位作為他們的匯總的條目，然后計(jì)算他們的掩碼位數(shù)為多少，所以這四個(gè)條目匯總到一個(gè)條目為/22,掩碼用通配符來(lái)寫應(yīng)該是55。 Refer to the exhibit. The access list has been configured on the S0/0 interface of router RTB in the outbound direction. Which two packets, if routed to the interface, will be denied? (Choose two.) access-list 101 deny tcp 2 5 any eq telnet access-list 101 permit ip any any A:source ip address: ; destination port: 21 B:source ip address:, 7 destination port: 21 C:source ip address:, 1 destination port: 21 D:source ip address:, 6 destination port: 23 E:source ip address: 6; destination port: 23 F:source ip address:, 9 destination port: 23 Correct Answers: D, E 通過(guò)訪問(wèn)控制列表的配置信息,可以推算出被拒絕的網(wǎng)絡(luò)范圍是: 2 5 即:2/28 27 只要是位于該網(wǎng)段內(nèi)的主機(jī)對(duì)外發(fā)出的telnet請(qǐng)求都將被拒絕，telnet的端口號(hào)為23. Refer to the exhibit. Why would the network administrator configure RA in this manner A: to give students access to the Internet B: to prevent students from accessing the command prompt of RA C: to prevent administrators from accessing the console of RA D: to give administrators access to the Internet E: to prevent students from accessing the Internet F: to prevent students from accessing the Admin network Correct Answers: B 在這兒，將應(yīng)用到線路下，而且是的方向，表示凡是被我的允許的才能telnet到我在上配置的是permit 55根據(jù)隱式的deny any允許dmin的網(wǎng)段中的用戶可以telnet到他，所以tudent的網(wǎng)段中的用戶是被拒絕的. An access list has been designed to prevent HTTP traffic from the Accounting Department from reaching the HR server attached to the Holyoke router. Which of the following access lists will accomplish this task when grouped with the e0 interface on the Chicopee router? A: permit ip any any deny tcp 55 52 eq 80 B: permit ip any any deny tcp 52 55 eq 80 C: deny tcp 52 55 eq 80 permit ip any any D: deny tcp 55 52 eq 80 permit ip any any Correct Answers: D 因?yàn)镠TTP服務(wù)是通過(guò)TCP建立連接,所以拒絕掉accounting部門子網(wǎng)所有通過(guò)80接口的TCP請(qǐng)求,并且拒絕掉HR服務(wù)器對(duì)accounting部門的TCP連接請(qǐng)求. CCNA640-802題庫(kù)解析EIGRP協(xié)議分類：CCNA, Cisco | 點(diǎn)擊量240次 | 給我留言 本文主要結(jié)合例題講解EIGRP協(xié)議的定義，配置和檢錯(cuò)。 Which routing protocol by default uses bandwidth and delay as metrics? A: RIP B: BGP C: OSPF D: EIGRP Correct Answers: D RIP使用跳數(shù)做為度量值;BGP使用復(fù)雜的路徑屬性來(lái)做為度量值;OSPF使用帶寬做為度量值;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，他們?cè)谀J(rèn)的情況下是使用帶寬和延時(shí)來(lái)計(jì)算度量的。 Which tables of EIGRP route information are held in RAM and maintained through the use of hello and update packets? (Choose two.) A:neighbor table B:SPF table C:RTP table D:topology table E:query table F:DUAL table Correct Answers: A, D 在EIGRP路由中，只有鄰居表與拓?fù)浔砟艽鎯?chǔ)在RAM中，并且通過(guò)使用hello包與報(bào)文更新進(jìn)行互連. What can be determined from the router output shown in the graphic? A: 4 is a default route. B: The output shows that there are three default routes. C: The output came from router R2. D: The output came from a router that has four physical interfaces. E: EIGRP is in use in this network. Correct Answers: E 簡(jiǎn)單點(diǎn)就是，因?yàn)樵诼酚蓸?biāo)記上有一個(gè)D，表示這條路由是從EIGRP學(xué)到的，所以肯定是有EIGRP運(yùn)行在網(wǎng)絡(luò)中的。接下來(lái)我們來(lái)仔細(xì)看每一條的輸出:從92/26 是直連lo0口的，可以推斷出這個(gè)信息是R1上的信息。D /24 is a summary ,NUllo：表示這是一條匯總的EIGRP 的路由。S* /0 is directly connected, serial1：表示這是一條缺省的路由，出接口為serial。這樣應(yīng)該就很明白了。 Which statements are true about EIGRP successor routes? (Choose two.) A:A successor route is used by EIGRP to forward traffic to a destination. B:Successor routes are saved in the topology table to be used if the primary route fails. C:Successor routes are flagged as “active” in the routing table. D:A successor route may be backed up by a feasible successor route. E:Successor routes are stored in the neighbor table following the discovery process. Correct Answers: A, D EIGRP的successor路徑是他選出的最優(yōu)的路徑，路由器將選擇這條路徑到達(dá)目的地。而feasible successor 則是successor的備份的路徑，如果successor路徑出了問(wèn)題，就立即將feasible successor路徑轉(zhuǎn)為successor路徑轉(zhuǎn)發(fā)數(shù)據(jù)。EIGRP 學(xué)習(xí)到的路由是由鄰居發(fā)送的，一條正確的路由可能被失效的路由器所終止,而無(wú)法正確被其它路由器學(xué)習(xí)到。 Refer to the exhibit. How will router A choose a path to the /24 network when different routing protocols are configured? (Choose three.) A:If RIPv2 is the routing protocol, only the path AD will be installed in the routing table by default. B:If RIPv2 is the routing protocol, the equal cost paths ABD and ACD will be installed in the routing table by default. C:If EIGRP is the routing protocol, only the path AD will be installed in the routing table by default. D:If EIGRP is the routing protocol, the equal cost paths ABD and ACD will be installed in the routing table by default. E:If EIGRP and OSPF are both running on the network, the EIGRP paths will be installed in the routing table. F:If EIGRP and OSPF are both running on the network, the OSPF paths will be installed in the routing table. Correct Answers: A, D, E RIP是通過(guò)跳數(shù)來(lái)選擇路徑的,雖然abd,acd的帶寬比ad高很多,但是ad的跳數(shù)只有2跳所以只有AD將被放在路由表表里面 EIGRP是通過(guò)成本來(lái)選擇路徑而帶寬包括在里面,所以它會(huì)選擇abd和acd走并且負(fù)載均衡 因?yàn)镋IGRP的度量值比OSPF的要低 所以路由器會(huì)優(yōu)先選擇度量值低的路由協(xié)議通告來(lái)的條目,所以通過(guò)EIGRP學(xué)習(xí)到的條目會(huì)被放在路由表中,而通過(guò)OSPF學(xué)習(xí)來(lái)的條目不會(huì)放入路由表. Refer to the exhibit. Why does RouterA show multiple unequal cost paths to network /24? A: A variance was configured for EIGRP autonomous system 109. B: The EIGRP topology table displays all routes to a destination. C: The EIGRP topology table shows only backup routes to a destination. D: Multiple floating static routes were configured to network via interface Serial0. Correct Answers: B EIGRP不能顯示所有的路由信息,它會(huì)根據(jù)成本不停的調(diào)整刷新. IP addresses and routing for the network are configured as shown in the exhibit. The network administrator issues the show ip eigrp neighbors command from Router1 and receives the output shown below the topology. Which statement is true? A: It is normal for Router1 to show one active neighbor at a time to prevent routing loops. B: Routing is not completely configured on Router3. C: The IP addresses are not configured properly on the Router1 and Router3 interfaces. D: The no auto-summary command configured on the routers prevents Router1 and Router2 from forming a neighbor relationship. Correct Answers: B 在R3上只公告了和的網(wǎng)段，也只激活了接口S1和的接口，而接口s0沒(méi)有激活，因此R3與R1之間是無(wú)法建立鄰居的。雖然R1會(huì)向R3的S0口發(fā)EIGRP的Hello包，但是R3是無(wú)法回復(fù)的。所以在R1上看到的EIGRP的鄰居只有。 CCNA640-802題庫(kù)解析OSPF中的選舉分類：CCNA, Cisco | 點(diǎn)擊量141次 | 給我留言 本文主要講解OSPF協(xié)議中的DR/BDR,RID選舉過(guò)程。 On which types of network will OSPF elect a backup designated router? A: point-to-point and multiaccess B: point-to-multipoint and multiaccess C: point-to-point and point-to-multipoint D: nonbroadcast and broadcast multipoint E: nonbroadcast and broadcast multiaccess Correct Answers: E DR,BDR的選舉是在一個(gè)共享介質(zhì)下才需要進(jìn)行的，我們的廣播和非廣播都是需要選舉DR和BDR的。 Refer to the exhibit. Router1 was just successfully rebooted. Identify the current OSPF router ID for Router1. A: 0 B: 62 C: 94 D: 0 Correct Answers: C Router1剛剛完成重啟，此時(shí)OSPF進(jìn)程開(kāi)始決定Router1的Router-ID.Router-ID的選舉規(guī)則如下： 1.在所有激活的接口中選擇 2.比較loopback接口的IP數(shù)值大小 3.如果沒(méi)有l(wèi)oopback接口,那么就比較所有物理接口的IP數(shù)值大小. A network administrator is configuring the routers in the graphic for OSPF. The OSPF process has been started and the networks have been configured for Area 0 as shown in the diagram. The network administrator has several options for configuring RouterB to ensure that it will be preferred as the designated router (DR) for the /24 LAN segment. What configuration tasks could be used to establish this preference? (Choose three.) A:Configure the priority value of the Fa0/0 interface of RouterB to a higher value than any other interface on the Ethernet network. B:Change the router id of Router B by assigning the IP address 30/24 to the Fa0/0 interface of RouterB. C:Configure a loopback interface on RouterB with an IP address higher than any IP address on the other routers. D:Change the priority value of the Fa0/0 interface of RouterB to zero. E:Change the priority values of the Fa0/0 interfaces of RouterA and RouterC to zero. F:No further configuration is necessary. Correct Answers: A, C, E OSPF中的共享介質(zhì)下是需要選舉DR和BDR的，而這個(gè)選舉的過(guò)程是通過(guò)比較優(yōu)先級(jí)和RID來(lái)實(shí)現(xiàn)的。優(yōu)先級(jí)越高的越優(yōu)先選舉成為DR，優(yōu)先級(jí)為0的接口是不參加DR的選舉的，如果優(yōu)先級(jí)相同就比較他們的RID,RID越大的越優(yōu)先。RID的選舉過(guò)程是：手工指定的最為優(yōu)先，如果沒(méi)有手工指定RID，則比較路由器上活動(dòng)接口的IP地址，如果有回環(huán)口就選用回環(huán)口IP地址最大的地址作為RID,如果沒(méi)有回環(huán)口，就選用物理接口地址中最大的IP地址為RID這個(gè)題中需要確保Router B成為網(wǎng)絡(luò)/24的DR，根據(jù)上面的解釋可以看出，讓他成為DR的方式有：改Router B的f0/0的優(yōu)先級(jí)為最大的；改/24網(wǎng)段上的其他接口的優(yōu)先級(jí)為0;設(shè)置Router B的RID最大。 Refer to the exhibit. Router1 was just successfully rebooted. Identify the current OSPF router ID for Router1. A. 0 B. 62 C. 94 D. 0Answer: C 這是個(gè)關(guān)于OSPF的RID的選舉的問(wèn)題。在OSPF中，RID的選舉過(guò)程是這樣的：如果通過(guò)命令router-id 來(lái)指定一個(gè)RID，那么就采用手工指定的這個(gè)RID；如果沒(méi)有手工指定，則在可以使用的接口中來(lái)選舉，他是優(yōu)先采用回環(huán)口的，如果只有一個(gè)回環(huán)口，就采用這個(gè)回環(huán)口的IP作為RID，如果有多個(gè)回環(huán)口，就采用這多個(gè)回環(huán)口中IP地址最大的作為RID；如果沒(méi)有回環(huán)口，就采用物理接口中IP地址最大的接口IP作為RID。在上面的圖中可以看到有兩個(gè)回環(huán)口，而Loopback1的IP更大，所以94就做為RID了。 CCNA640-802題庫(kù)解析OSPF協(xié)議分類：CCNA, Cisco | 點(diǎn)擊量176次 | 給我留言 本文主要結(jié)合例題講解OSPF協(xié)議的概念，定義以及配置，檢錯(cuò)。 The OSPF Hello protocol performs which of the following tasks? (Choose two.) A:It provides dynamic neighbor discovery. B:It detects unreachable neighbors in 90 second intervals. C:It maintains neighbor relationships. D:It negotiates correctness parameters between neighboring interfaces. E:It uses timers to elect the router with the fastest links as the designated router. F:It broadcasts hello packets throughout the internetwork to discover all routers that are running OSPF. Correct Answers: A, C HELLO協(xié)議在OSPF網(wǎng)絡(luò)中的功能： 1.鄰居動(dòng)態(tài)發(fā)現(xiàn)(neighbor discovery) 2.鄰居關(guān)系維持(neighbor keepalive) A routing protocol is required that supports: 1) routing update authentication 2) an addressing scheme that conserves IP addresses 3) multiple vendors 4) a network with over 50 routers Which routing protocol fulfills these requirements? A: RIPv1 B: RIPv2 C: EIGRP D: OSPF Correct Answers: D 首先RIPv1是不支持認(rèn)證的，因此答案A我們可以排除。是支持多廠商的，因此是一個(gè)開(kāi)放的標(biāo)準(zhǔn)的協(xié)議，可以排除EIGPR，因?yàn)檫@是個(gè)CISCO私有的協(xié)議。網(wǎng)絡(luò)的大小可以超過(guò)50臺(tái)路由器，那RIPv2就不滿足了，因?yàn)镽IP最大支持16跳。那么答案就是OSPF了。 On point-to-point networks, OSPF hello packets are addressed to which address? A: B: C: D: E: F: 55 Correct Answers: E 在OSPF中Hello包發(fā)向的是和這兩個(gè)地址的。大家在做OSPF實(shí)驗(yàn)的時(shí)候，用debug命令是可以看到這兩個(gè)個(gè)地址的。 Which of the following describe the process identifier that is used to run OSPF on a router? (Choose two.) A:It is locally significant. B:It is globally significant. C:It is needed to identify a unique instance of an OSPF database. D:It is an optional parameter required only if multiple OSPF processes are running on the router. E:All routers in the same OSPF area must have the same process ID if they are to exchange routing information. Correct Answers: A, C OSPF的進(jìn)程號(hào)只在本地有效。在一臺(tái)路由器上需要為每個(gè)進(jìn)程維護(hù)各自的OSPF數(shù)據(jù)庫(kù)。 Refer to the exhibit. Why are two OSPF designated routers identified on Core_Router? A: Core_Router is connected to more than one multiaccess network. B: The router at 30 is a secondary DR in case the primary fails. C: Two router IDs have the same OSPF priority and are therefore tied for DR election. D: The DR election is still underway and there are two contenders for the role. Correct Answers: A 我們看上圖顯示Core_Router有多個(gè)鄰居，進(jìn)行了DR/BDR選舉，它連接的是多路訪問(wèn)網(wǎng)絡(luò)。 A network administrator is troubleshooting the OSPF configuration of routers R1 and R2. The routers cannot establish an adjacency relationship on their common Ethernet link. The graphic shows the output of the show ip ospf interface e0 command for routers R1 and R2. Based on the information in the graphic, what is the cause of this problem? A: The OSPF area is not configured properly. B: The priority on R1 should be set higher. C: The cost on R1 should be set higher. D: The hello and dead timers are not configured properly. E: A backup designated router needs to be added to the network. F: The OSPF process ID numbers must match. Correct Answers: D OSPF鄰居建立過(guò)程中有幾個(gè)參數(shù)是需要嚴(yán)格匹配的：Hello time和dead time，Area id, MTU,特殊區(qū)域標(biāo)識(shí)符。然后比較圖中的R1和R2的內(nèi)容可以看到他們的Hello time 和dead time是不同的，因此他們的鄰居關(guān)系是無(wú)法建立的。 Refer to the exhibit. Assume that all router interfaces are operational and correctly configured. In addition, assume that OSPF has been correctly configured on router R2. How will the default route configured on R1 affect the 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 communicate with the , 28, and 4 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. Correct Answers: E 在R1上產(chǎn)生了一個(gè)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 Serial0/0的路由。所以R2收到任何路由表中沒(méi)有的目的網(wǎng)段時(shí)，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(gè)路由的環(huán)路。 Refer to the exhibit. A network associate has configured OSPF with the command: City(config-router)# network 4 3 area 0 After completing the configuration, the associate discovers that not all the interfaces are participating in OSPF. Which three of the interfaces shown in the exhibit will participate in OSPF according to this configuration statement? (Choose three.) A:FastEthernet0 /0 B:FastEthernet0 /1 C:Serial0/0 D:Serial0/1.102 E:Serial0/1.103 F:Serial0/1.104 Correct Answers: B, C, D 根據(jù)City(config-router)# network 4 3 area 0,可以得知： Ospf進(jìn)程只advertisement了 4-27的接口地址,f0/1、s0/0、s0/1.102的IP地址都在此范圍內(nèi)。 CCNA640-802題庫(kù)解析RIPv1和RIPv2的區(qū)別分類：CCNA, Cisco | 點(diǎn)擊量223次 | 給我留言 本文主要是結(jié)合例題講解RIPv1和RIPv2的區(qū)別。 Which three statements are correct about RIP version 2? (Choose three.) A:It has the same maximum hop count as version 1. B:It uses broadcasts for its routing updates. C:It is a classless routing protocol. D:It has a lower default administrative distance than RIP version 1. E:It supports authentication. F:It does not send the subnet mask in updates. Correct Answers: A, C, E 關(guān)于RIPv2，首先要了解他是一個(gè)無(wú)類的路由協(xié)議，在發(fā)送路由更新的