1. [多选题]网络中经常使用DDN服务，请选出DDN的优点（）
A. 传输质量高
B. 接入方式灵活
C. 偷占带宽
D. 使用虚电路
E. 专用线路
2. [单选题]Given that you have a class B IP address network range, which of the subnet masks below will allow for 100 subnets with 500 usable host addresses per subnet?
A. 255.255.0.0
B. 255.255.224.0
C. 255.255.254.0
D. 255.255.255.0
E. 255.255.255.224
3. [单选题]What is the purpose of the Spanning Tree Protocol (STP)?
A. To prevent routing loops
B. To create a default route
C. To provide multiple gateways for hosts
D. To maintain a loop-free Layer 2 network topology
E. To enhance the functions of SNMP
4. [单选题]某网络中，拟设计10子网，每个子网中放有14台设备，用IP地址段为199.41.10.X，请问符合此种规划的子网掩码是()
A. 255.255.255.0
B. 255.255.240.0
C. 255.255.255.240
D. 255.248.0.0
5. [单选题]NAT可以被用于完成多种功能，以下不属于其功能的是：（）
A. 转换内部局部地址
B. 内部全局地址复用
C. TCP负载均衡
D. 内部网络流量控制
6. [单选题]路由器当前的模式为“端口模式”，要退回到“特权模式”，应该使用的快捷键(shortcut key)为（）
A. ctrl+b
B. ctrl+z
C. ctrl+c
D. ctrl+p
7. [单选题]路由器“全局模式”的提示符为（）
A. >
C. (config)
D. (config-router)
8. [多选题]在路由器上，可以使用的命令有：()
A. ping
B. show interfaces
C. show ip route
D. ipconfig
E. wincfg
9. [多选题]The LAN needs are expanding at the Ezonexam corporate office, which is quickly growing. You are instructed to enlarge the area covered by a single LAN segment on the Ezonexam network.Which of the following are layer 1 devices that you can use? (Choose all that apply.)
A. A switch
B. A router
C. A network adapter card
D. A hub
E. A repeater
10. [单选题]On a half-duplex Ethernet LAN, two hosts attempt to send data simultaneously, resulting in a collision. Following this collision, what will the hosts do? (Select all valid answers)
A. The destination host sends a request to the source for retransmission.
B. The jam signal indicates that the collision has been cleared.
C. The hosts will attempt to resume transmission after a time delay has expired.
D. An electrical pulse indicates that the collision has cleared.
E. The router on the segment will signal that the collision has cleared.
F. F. The hosts will do nothing, as the higher layers are responsible for data error correction and re-transmission.
