单项选择题 A natural disaster has occurred and the administrator must return the network to a healthy status.Which of the following should the administrator do in this case?（）

单项选择题 Which of the following network devices would MOST likely be installed on a network to helpreduce broadcast traffic and to allow individual virtual networks?（）

单项选择题 Users report an intermittent degradation of sound on their IP phones. Which of the following woulda network administrator do to alleviate the problem?（）