单项选择题
You have been asked to use a 23-bit network mask to segment the network block 209.18.12.0, How many usable host address will there e per subnet?（）
A. 510 B. 1022 C. 2046 D. 8190
单项选择题 You want to log into the router and make a configuration change.After loggin in as the root user, what is the next command you must enter?（）
单项选择题 What is the operating system do Juniper Networks MX Series routers use?（）
单项选择题 What information does the help reference command provide?（）
