单项选择题 As a network administrator, you issue the interface auto qos voip cisco-phone command on a port in an edge network. It is possible for a Cisco Catalyst switch to check if a Cisco IP Phone is directly attached to that port by:（）

单项选择题 What is the most likely reason that an IBGP route that has been selected as a best route is not entered into the IP routing table?（）

单项选择题 Which Cisco IOS command is used to troubleshoot a problem in which a BGP session stays in the active state?（）