单项选择题 What value is primarily used to determine which port becomes the root port on each nonroot switch in a spanning-treetopology?（）

单项选择题 A network administrator wants to add a line to an access list that will block only Telnet access by the hosts on subnet 192.168.1.128/28 to the server at 192.168.1.5.What command should be issued to accomplish this task？（）

单项选择题 一个网络管理员配置了两台交换机London和Madrid，让它们使用VTP。但是，两台交换机之间没有共享VTP信息，根据下图，回答交换机之间没有分享VTP信息的原因是（）。