问题：

　　The switches in the diagram are each installed on a different floor.Each PC has a dedicated switch port.PCs 1,2,3,4 and 5 each belong to users in the sales department.What would be the most effective solution that will limit the propagation of broadcasts from these hosts and secure their communications.The solution should allow for ease of management,troubleshooting and scalability.

　　A.Create a Sales VLAN on each of the switches and assign the ports connected to PCs 1,2,3,4 and 5 to that VLAN

　　B. Create a Sales VPN and use VTP across the trunk links of the switches to propagate membership to PCs 1,2,3,4 and 5

　　C. Move PCs 1,2,3,4 and 5 to the 3rd floor,and disconnect the 3rd floor switch from the rest of the LAN

　　D. Replace the switches with routers and use ACLs to control traffic between hosts

　　Select the 1 best answer

　　在交换机的图表中，每个交换机都不在同一层，每台PC机都连接在交换机的端口上面，如图PC机1。2。3。4。5都是销售部门的电脑，有什么解决方案可以隔离广播和提高网络通讯安全，这个解决方案要有容易管理，排错和较高的可行性。

　　解答：

　　在如上的四种方法中最好的方法是利用vlan技术。如果在交换机中使用vlan技术，不需要改变网络的拓扑结构和交换设备，也可以达到隔离广播和提高网络通讯安全的要求，同时也有很高的可行性。所以选择A。

　　vlan的介绍：英文Virtual Local Area Network的缩写，中文名为"虚拟局域网".

　　VLAN是一种将局域网(LAN)设备从逻辑上划分(注意，不是从物理上划分)成一个个网段(或者说是更小的局域网LAN)，从而实现虚拟工作组(单元)的数据交换技术。