最新CCNA题库,Word版

1.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 Answer: AC

解释一下：在VTY线路下应用ACL，可以控制从VTY线路进来的telnet的流量。

也可以过滤穿越一台路由器的流量。

2.A default Frame Relay WAN is classified as what type of physical network?

A. point-to-point

B. broadcast multi-access

C. nonbroadcast multi-access

D. nonbroadcast multipoint

E. broadcast point-to-multipoint

Answer: C

解释一下：在默认的情况下，帧中继为非广播多路访问链路。但是也可以通过子接口来修改他的网络的类型。

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

解释一下：广播域的问题，在默认的情况下，每个交换机是不能隔离广播域的，所以在同一个区域的所有交换机都在同一个广播域中，但是为了减少广播的危害，将广播限制在一个更小的范围，有了VLAN的概念，VLAN表示的是一个虚拟的局域网，而他的作用就是隔离广播。所以被VLAN隔离了的每个区域都表示一个单独的广播域，这样一个VLAN中的广播的流量是不能传到其他的区域的，所以在上题中就有3个广播域了。

4.A single 802.11g access point has been configured and installed in the center of

a square office. A few wireless users are experiencing slow performance and drops while most users are operating at peak efficiency. What are three likely causes of this problem? (Choose three.)

A. mismatched TKIP encryption

B. null SSID

C. cordless phones

D. mismatched SSID

E. metal file cabinets

F. antenna type or direction

Answer: CEF

解释一下:cordless phones：无线电话。

metal file cabinets：金属文件柜。

antenna type or direction：天线类型及方向。

TKIP：Temporal Key Integrity Protocol（暂时密钥集成协议）负责处理无线安全问题的加密部分。如果加密出了问题，那么就根本连接不上，而不会出现性能下降的问题。

SSID（Service Set Identifier）也可以写为ESSID，用来区分不同的网络。如果是空的ssid，那么也会出现不能联网的情况

5.Refer to the exhibit. What two facts can be determined from the WLAN diagram? (Choose two.)

A. The area of overlap of the two cells represents a basic service set (BSS).

B. The network diagram represents an extended service set (ESS).

C. Access points in each cell must be configured to use channel 1.

D. The area of overlap must be less than 10% of the area to ensure connectivity.

E. The two APs should be configured to operate on different channels.

Answer: BE

解释一下：一个ap提供的覆盖范围称为一个microcell，微单元.或者是基本服务区域，basic service area，当有多个微单元连接到lan，就称为扩展服务级。往往可以通过增加ap来连接，如果一个ap不能满足覆盖范围，可以增加ap，建议两个ap重叠区域为10－15％。

6.The command frame-relay map ip 10.121.16.8 102 broadcast was entered on the router. Which of the following statements is true concerning this command?

A. This command should be executed from the global configuration mode.

B. The IP address 10.121.16.8 is the local router port used to forward data.

C. 102 is the remote DLCI that will receive the information.

D. This command is required for all Frame Relay configurations.

E. The broadcast option allows packets, such as RIP updates, to be forwarded across the PVC.

Answer: E

解释一下：关于命令 frame-relay map ip 10.121.16.8 102 broadcast ,这个命令用于手工静态添加一条映射，到达10.121.16.8的流量封装一个DLCI号为102，而且这条PVC是支持广播的流量的，比如RIP的更新包。因为在默认的情况下，帧中继的网络为非广播的，而RIP 在其上是无法发包的。

7.Which type of attack is characterized by a flood of packets that are requesting

a TCP connection to a server?

A. denial of service

B. brute force

C. reconnaissance

D. Trojan horse

Answer: A

解释一下:请求tcp连接到服务器的攻击其是就是syn-flooding攻击，利用tcp三次握手的天生缺陷，向对方主机发送大量的syn位置1的请求包，造成对方服务器正常服务的中断正常的服务这是一种典型的dos攻击，就是拒绝服务攻击：denial of service。

8.Which of the following are associated with the application layer of the OSI model?