单项选择题 Given an IP address 172.16.28.252 with a subnet mask of 255.255.240.0, what is the correct network addres?（）

单项选择题 You have been asked to come up with a subnet mask that will allow all three web servers to be on the same network while providing the max number of subnets.Which network address and subnet mask meet this requirement?（）

单项选择题 Which command encrypts all plaintext passwords?（）