多项选择题 Which two values are used by Spanning Tree Protocol to elect a root bridge?（）

多项选择题 What are two advantages of Layer 2 Ethernet switches over hubs?（）

多项选择题 The network security policy requires that only one host be permitted to attach dynamically to each switch interface. If that policy is violated, the interface should shut down. Which two commands must the network administrator configure on the 2950 Catalyst switch to meet this policy (Choose two.)（）。