CCNA640-802 V13题库试题分析题库讲解：吴老师（艾迪飞CCIE实验室首发网站：1. What are two reasons that a network administrator would use access lists? (Choose two.)A. to control vty access into a routerB. to control broadcast traffic through a routerC. to filter traffic as it passes through a routerD. to filter traffic that originates from the routerE. to replace passwords as a line of defense against security incursionsAnswer: 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-pointB. broadcast multi-accessC. nonbroadcast multi-accessD. nonbroadcast multipointE. broadcast point-to-multipointAnswer: 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. oneB. twoC. threeD. fourE. fiveF. sixAnswer: 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 encryptionB. null SSIDC. cordless phonesD. mismatched SSIDE. metal file cabinetsF. antenna type or directionAnswer: CEF6. 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。
8．Which of the following are associated with the application layer of the OSI model? (Choose two.)A. pingB. TelnetC. FTPD. TCPE. IPAnswer: BC解释一下：在OSI 7层模型中位于应用层的应用有telnet 和ftp 这两种应用。
9. For security reasons, the network administrator needs to prevent pings into the corporate networks from hosts outside the internetwork. Which protocol should be blocked with access control lists?A. IPB. ICMPC. TCPD. UDPAnswer: B解释一下：PING命令利用ICMP协议的echo,和echo-replay两个报文来检测链路是否连通的。
所以如果要阻止PING的流量到网络，就只要过滤掉ICMP的应用就可以了。
10．Refer to the exhibit. The network administrator has created a new VLAN on Switch1 and added host C and host D. The administrator has properly configured switch interfaces FastEthernet0/13 through FastEthernet0/24 to be members of the new VLAN. However, after the network administrator completed the configuration, host A could communicate with host B, but host A could not communicate with host C or host D. Which commands are required to resolve this problem?A. Router(config)# interface fastethernet 0/1.3Router(config-if)# encapsulation dot1q 3Router(config-if)# ip address 192.168.3.1 255.255.255.0B. Router(config)# router ripRouter(config-router)# network 192.168.1.0Router(config-router)# network 192.168.2.0Router(config-router)# network 192.168.3.0C. Switch1# vlan databaseSwitch1(vlan)# vtp v2-modeSwitch1(vlan)# vtp domain ciscoSwitch1(vlan)# vtp serverD. Switch1(config)# interface fastethernet 0/1Switch1(config-if)# switchport mode trunkSwitch1(config-if)# switchport trunk encapsulation islAnswer: A解释一下：这是一个多VLAN间通讯的问题，虽然都同在一台交换机上，但是由于处在不同的VLAN中，而导致了不同VLAN中的主机是不能通讯的。
这时我们就需要借助与trunk和三层的路由功能了，在交换机和路由器之间封装TRUNK，这样可以允许交换机间的二层的通讯，但是由于两个VLAN是划分到不同的网段中的，因此需要借助路由器的路由功能来实现三层的可达，可以将VLAN中的主机的网关指定为路由器与该VLAN相连的子接口的地址，这样VLAN中的数据包就都会发往网关，而由网关来进行进一步的转发。
在这个题中，题目给出了路由器的的子接口的网段，而又给出了VLAN 2与路由器相连的接口的IP地址，所以剩下的一个网段就是给VLAN 3的了，所以要在路由器上将与一个子接口划分到VLAN 3，并给其分配另一个网段中的IP地址。
这样就可以了。
11．What are two recommended ways of protecting network device configuration files from outside network security threats? (Choose two.)A. Allow unrestricted access to the console or VTY ports.B. Use a firewall to restrict access from the outside to the network devices.C. Always use Telnet to access the device command line because its data is automatically encrypted.D. Use SSH or another encrypted and authenticated transport to access device configurations.E. Prevent the loss of passwords by disabling password encryption.Answer: BD解释一下：要确保外部的安全的站点才可以访问我的网络，这就涉及到了安全的问题了，我们可以使用防火墙来限制外网中来的设备；也可以通过SSH或加密和认证来控制。