单项选择题 How many bits are contained in each field of an IPv6 address?（）

单项选择题 For which type of connection should a straight-through cable be used?（）

单项选择题 A system administrator installed a new switch using a script to configure it. IP connectivity was tested using pings to SwitchB. Later attempts to access NewSwitch using Telnet from SwitchA failed. Which statement is true?（）