1. [单选题]What is the purpose of the spanning-tree algorithm in a switched LAN?
A. To provide a monitoring mechanism for networks in switched environments.
B. To manage VLANs across multiple switches.
C. To prevent switching loops in networks with redundant switched paths.
D. To segment a network into multiple collision domains.
E. To prevent routing loops in networks.
2. [单选题]PPP工作在OSI的哪一层（）
A. 物理层
B. 数据链路层
C. 网络层
D. 传输层
3. [单选题]OSPF的度量值是什么()
A. 跳数
B. 接口开销
C. 矢量距离
D. 链路状态
4. [单选题]A Ezonexam technician is troubleshooting connectivity problems between two routers that are directly connected through the serial line. The technician notices that the serial line is up but cannot see any neighbors displayed in the output of the show cdp neighbors command.In which OSI layer is the problem most likely occurring?
A. Physical
B. Data link
C. Network layer
D. Transport layer
E. Application layer
5. [多选题]Which of the following are types of flow control? (Choose three)
A. Buffering
B. Cut-through
C. Windowing
D. Congestion avoidance
E. Load balancing
