What command can be used to determine if a serial interface is DCE or DTE?

The command that can be used to determine if a serial interface is DCE (Data Communications Equipment) or DTE (Data Terminal Equipment) is "show controllers interface-id."

When executed, this command provides specific information about the hardware and signal characteristics of the specified interface. Among the details displayed, it tells you whether the interface is configured as DCE or DTE. This distinction is significant because it affects how the interface operates, especially concerning clocking; DCE devices typically provide the clocking signal for synchronous connections, while DTE devices rely on an external clock signal.

Other commands, such as "show interfaces," "show ip interface," and "show protocol," provide various types of information regarding an interface's status, configuration, and IP-related details but do not explicitly indicate whether the interface is configured as DCE or DTE. Therefore, they are not suitable for determining the interface type in this context.