单项选择题 Which command is used to display the collection of OSPF link states?（）

单项选择题 When you are troubleshooting an ACL issue on a router,which command can help you to verify which interfaces are affected by the ACL?（）

单项选择题 Three switches are connected to one anther via trunk ports.Assuming the default switch configuration,which switch is elected as the root bridge for the spanning-tree instance of vlan 1?（）