【正文】 erfaces 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 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(biāo)記為O*E2 。所以不管怎么樣都有一句是能被匹配的。10．Refer to the exhibit. The network administrator has created a new VLAN on Switch1 and added host C and host D. The administrator has properly configured switch interfaces FastEthernet0/13 through FastEthernet0/24 to be members of the new VLAN. However, after the network administrator pleted the configuration, host A could municate with host B, but host A could not municate with host C or host D. Which mands are required to resolve this problem? A. Router(config) interface fastethernet 0/ Router(configif) encapsulation dot1q 3 Router(configif) ip address B. Router(config) router rip Router(configrouter) network Router(configrouter) network Router(configrouter) network C. Switch1 vlan database Switch1(vlan) vtp v2mode Switch1(vlan) vtp domain cisco Switch1(vlan) vtp server D. Switch1(config) interface fastethernet 0/1 Switch1(configif) switchport mode trunk Switch1(configif) switchport trunk encapsulation isl Answer: 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。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?A. one B. two C. three D. four E. five F. six Answer: 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。這時我們就需要借助與trunk和三層的路由功能了，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)。在上題中， 的流量，然后第二句定義的就是允許所有的IP流量。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。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176183，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。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。然后我們檢查圖題目給出的信息，可以看到兩臺交換機的VTP domain是不一致的，所以這個就是問題的所在了。40. Refer to the exhibit. The network shown in the exhibit is running the RIPv2 routing protocol. The network has converged, and the routers in this network are functioning properly. The FastEthernet0/0 interface on R1 goes down. In which two ways will the routers in this network respond to this change? (Choose two.) A. All routers will reference their topology database to determine if any backup routes to the network are known. B. Routers R2 and R3 mark the route as inaccessible and will not accept any further routing updates from R1 until their holddown timers expire. C. Because of the splithorizon rule, router R2 will be prevented from sending erroneous information to R1 about connectivity to the network. D. When router R2 learns from R1 that the link to the network has been lost, R2 will respond by sending a route back to R1 with an infinite metric to the network.E. R1 will send LSAs to R2 and R3 informing them of this change, and then all routers will send periodic updates at an increased rate until the network again converges. Answer: CD解釋一下：這涉及到RIP關(guān)于環(huán)路避免的幾種機制了。所以需要在交換機上指定一個處于VLAN 2的接口，并將SVI地址配置為和路由器POP的f0/。在OSPF中，RID的選舉過程是這樣的：如果通過命令routerid 來指定一個RID，那么就采用手工指定的這個RID；如果沒有手工指定，則在可以使用的接口中來選舉，他是優(yōu)先采用回環(huán)口的，如果只有一個回環(huán)口，就采用這個回環(huán)口的IP作為RID，如果有多個回環(huán)口，就采用這多個回環(huán)口中IP地址最大的作為RID；如果沒有回環(huán)口，就采用物理接口中IP地址最大的接口IP作為RID。53. What is the function of the Cisco IOS mand ip nat inside source static ? A. It creates a global address pool for all outside NAT transactions. B. It establishes a dynamic address pool for an inside static address. C. It creates dynamic source translations for all inside local PAT transactions. D. It creates a onetoone mapping between an inside local address and an inside global address. E. It maps one inside source address to a range of outside global addresses. Answer: D解釋一下：ip nat inside source static 這條命令是靜態(tài)創(chuàng)建一個一對一的地址轉(zhuǎn)換。同樣內(nèi)網(wǎng)要訪問外部，也只能通過路由器InternetRouter才能到達，所以也可以在CentralRouter上配置一條缺省路由到外部。2．在NVRAM的配置文件中查看boot system命令，這個命令告訴引導(dǎo)程序在哪里尋找IOS。在一般來說我們的每個單播幀都是只有一個目的地，從而從一個相關(guān)接口發(fā)送出去就可。因為只有相同vlan中數(shù)據(jù)才可以通訊，所以我們應(yīng)該將host A的地址和f0/，而將host B的地址和f0/。所以，host （）的地址。因為我到一個目的地從一條路走就可以了，如果出現(xiàn)了多條路，那么就應(yīng)該是做冗余的，可是不正確的配置可能導(dǎo)致我的LAN中產(chǎn)生環(huán)路，從而形成在LAN中有同一個幀的多個拷貝。所以這步跳過。路由器是工作在三層的設(shè)備，因此我們可以基于三層的信息來實現(xiàn)過濾；而且大家知道路由器是可以過濾廣播的。當(dāng)ARP報文傳到switch 2，交換機對廣播的流量是以泛洪的形式處理的，報文就從除了連接PC1的接口外的所有接口都發(fā)出去了。51. What can a network administrator utilize by using PPP Layer 2 encapsulation? (Choose three.) A. VLAN support B. pression C. authentication D. sliding windows E. multilink support F. quality of service Answer: BCE解釋一下：PPP協(xié)議是能支持認證的，包括PAP和CHAP；PPP還支持壓縮功能和差錯校驗，還可實現(xiàn)多鏈路捆綁。46. 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. Answer: ACE解釋一下：關(guān)于RIPv2，首先要了解他是一個無類的路由協(xié)議，在發(fā)送路由更新的時候是攜帶掩碼的。42. Which of the following describe the process identifier that is used to run OSPF on a