单项选择题
A. The client does not support 802.11n
B. Incorrect frequency on the client is being used
C. Incorrect encryption on the AP
D. The client distance from the AP
单项选择题 At which of the following layers does the ICMP protocol operate?（）
单项选择题 Which of the following security devices would MOST likely be used on a network to screen and prevent malicious traffic?（）
单项选择题 Which of the following is an intelligent repeater that is aware of the MAC addresses of the nodeson either side of the data link?（）