1. [单选题]OSPF在同一区域内(intra-region)，下列说法正确的是（）
A. 每台路由器生成的LSA都是相同的
B. 每台路由器的LSDB(链路状态数据库)都是相同的
C. 每台路由器根据该LSDB计算出的最短路径树都是相同的
D. 每台路由器根据该最短路径树计算出的路由都是相同的
2. [单选题]At which layer of the OSI model does the protocol that provides the information displayed by the "show cdp neighbors" command operate?
A. Transport
B. Physical
C. Application
D. Data link
E. Network
3. [多选题]When you compare the differences between half-duplex and full-duplex Ethernet, which of the following characteristics are exclusive to half-duplex? (Select two answer choices)
A. Half-duplex Ethernet operates in a shared collision domain.
B. Half-duplex Ethernet operates in an exclusive broadcast domain.
C. Half-duplex Ethernet has efficient throughput.
D. Half-duplex Ethernet has lower effective throughput.
E. Half-duplex Ethernet operates in an exclusive collision domain.
4. [单选题]命令“ping127.0.0.1”的功能是（）
A. 测试网卡是否正常
B. 测试网关是否正常
C. 测试TCP/IP协议是否正常
D. 测试介质是否正常
5. [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
