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发表于 2009-7-29 16:35:25
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CCNA640-802 V12题库试题分析5(艾迪飞吴老师讲解)
1． Refer to the exhibit. Which switch provides the spanning-tree designated port role for the network segment that services the printers?
1.jpg (39.29 KB)
2007-11-14 13:19
A. Switch1
B. Switch2
C. Switch3
D. Switch4
Answer: C
解释一下：这是个关于生成树选举的问题，我们首先需要找到根桥，而根桥的选举是通过比较桥ID的,而且是越小越优先，桥ID的组成为桥优先级和MAC地址。所以我们通过上图可以找到根桥为switch 1。
然后在非根桥上选出根端口，通过比较到根桥的花费来选举的，花费最小的就是根端口。因为上图中没有表示出链路的带宽，所以无法比较他们的花费。
下一步我们来选举指派端口。每条链路都需要有一个DP，先是比较花费，如果花费相同则比较BID（桥优先级），仍是越小越优先，根据上图的表识，我们可以找到每条链路上的DP，而连Printers的链路上的DP就为Switch 3，因为他有更小的MAC地址。
以下内容需要回复才能看到
2． Refer to the exhibit. Switch-1 needs to send data to a host with a MAC address of 00b0.d056.efa4. What will Switch-1 do with this data?
2.jpg (36.33 KB)
2007-11-14 13:19
A. 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 originated.
C. Switch-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.
Answer: B
解释一下：首先Switch 1需要发送一个数据到MAC地址为00b0.d056.efa4的主机，了解到目的地后，就查看他的MAC 地址表，然后发现在MAC地址表中没有这个MAC地址的条目存在。交换机在收到未知的单播，组播和广播时，都采用的是泛洪的方式，往除收到数据的这个接口外的所有接口都发送。所以在这儿，Switch 1也采取的上泛洪的方式。
3．In the implementation of VLSM techniques on a network using a single Class C IP address, which subnet mask is the most efficient for point-to-point serial links?
A. 255.255.255.0
B. 255.255.255.240
C. 255.255.255.248
D. 255.255.255.252
E. 255.255.255.254
Answer: D
解释一下：在点到点的链路上因为只需要分配两个地址给两端就可以了，所以加上网络地址和广播地址，这个网段也就只需要有4个地址了，所以网络位需要匹配30位,掩码就为255.255.255.252．
4． Refer to the exhibit. Why would the network administrator configure RA in this manner?
4.jpg (35.43 KB)
2007-11-14 13:19
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
Answer: B
解释一下：在这儿，将ＡＣＬ应用到ＶＴＹ线路下，而且是ＩＮ的方向，表示凡是被我的ＡＣＬ允许的才能telnet到我．在ＲＡ上配置的是permit 10.1.1.0 0.0.0.255根据隐式的deny any
允许Ａdmin的网段中的用户可以telnet到他，所以Ｓtudent的网段中的用户是被拒绝的．
5．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
解释一下：生成树的选举的问题，根桥的选举是通过比较ＢＩＤ的，而ＢＩＤ由桥优先级和ＭＡＣ地址组成的．所以在选根桥的时候需要比较的是桥优先级和ＭＡＣ address.．
6．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 255.255.255.252. Given the output that is shown, what three statements are true of these devices? (Choose three.)
6.jpg (29.44 KB)
2007-11-14 13:19
A. The Manchester serial address is 10.1.1.1.
B. The Manchester serial address is 10.1.1.2.
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
解释一下：ＣＤＰ是ＣＩＳＣＯ私有的一个二层的协议，但是他却可以发现三层的ＩＰ信息的．通过ＣＤＰ可以发现的邻居的信息有：设备的名称，ＩＰ地址，端口，能力，平台，对端的holddown time．在上图的show cdp entry *命令的显示可以看到的信息有：设备名称：Ｌondon；ＩＰ地址：10.1.1.2；平台：cisco 2610；能力：Router；端口：s0/１；holdtime：１２５Ｓ．Ｍanchesteter收到这个ＣＤＰ信息的接口为S0/0．
综合一下，这个题目的答案就出来了．4 |
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