1. [单选题]路由器上的命令“show version”的功能是（）
A. 显示版本信息
B. 显示端口配置信息
C. 显示路由表
D. 显示路由协议信息
2. [单选题]After connecting a PC to an available port on a switch, you find that the PC can not access any of the resources on the LAN. No other PC's connected to the switch appear to be having any issues. What is the most likely cause for this problem?
A. The router lacks a routing table entry for the new host
B. The host switch port is assigned to the incorrect VLAN
C. The host MAC address is incorrectly configured
D. A STP instance for the new host has not been initialized
E. The switch does not have the MAC address hard coded in the CAM table.
3. [多选题]交换机的三大功能为（）
A. 地址学习
B. 转发过滤
C. 消除回路
D. 发送数据包(packet)
4. [单选题]OSI第二层(the second layer)数据封装完成后的名称是：()
A. 比特
B. 包
C. 帧
D. 段
5. [单选题]在OSPF的DR/BDR选举过程中，在路由器有相同的接口优先级情况下，什么用于确定DR或BDR（）
A. 最高的OSPF进程ID
B. 最低的接口IP地址
C. 最低的接口开销
D. 路由器ID
