单项选择题 What command verifies connectivity between two hosts by sending and receiving ICMP echo messages?（）

单项选择题 A new Catalyst switch is connected to an existing switch using a crossover cable. As a result of this, what would the switch port link lights display?（）

多项选择题 Which of the following IOS commands could you use to troubleshoot a router connectivity problem on an IP network?（）