单项选择题 How would you express the binary number: 10101010 in its decimal and hexadecimal forms?（）

单项选择题 You have a network that supports VLSM and you need to reduce IP address waste in your point to point WAN links. Which of the masks below would you use?（）

单项选择题 You have a single Class C IP address and a point-to-point serial link that you want to implement VLSM on. Which subnet mask is the most efficient?（）