单项选择题 When troubleshooting ATM, which command would allow you to test reachability from one side of an ATM cloud to the other?（）

单项选择题 Which command would you type to see a concise display of which interfaces are up and which are down?（）

单项选择题 In Ethernet networks, duplex mismatches will lower performance. Which error statistics can be seen if a duplex mismatch is present?（）