无类路由协议路由表表目为三维组，其中不包括（）。

VLAN tag在OSI参考模型的哪一层？（）A.应用层B.表示层C.会话层D.传输层E.网络层F.链路层G....

单项选择题VLAN tag在OSI参考模型的哪一层？（）

RIP协议引入路由保持机制的作用是防止路由形成环路。

判断题RIP协议引入路由保持机制的作用是防止路由形成环路。

While troubleshooting a network connectivity problem, a...

单项选择题While troubleshooting a network connectivity problem, a technician observes steady link lights on both the workstation NIC and the switch port to which the workstation is connected. However, when the ping command is issued from the workstation, the output message "Request timed out." is displayed. At which layer of the OSI model does the problem most likely exist（）。