Cisco Certified Network Associate (CCNA) Practice Exam

To verify the clockrate and DTE/DCE status of an interface, which command is applicable?

1. #show ip interface brief

2. #show controllers

3. #show interface INTERFACE NUMBER

4. #show running-config

The correct answer is: #show controllers

The command provided is applicable because it displays crucial information about the physical layer of the interfaces on a router or switch, including their DTE (Data Terminal Equipment) or DCE (Data Circuit-terminating Equipment) status. Specifically, when you use the "show controllers" command, it reveals details such as the clock rate assigned to the DCE device, as well as the cable type and the specific role of the interface (whether it’s DTE or DCE). Understanding the DTE/DCE relationship is important as it impacts how data is transmitted over serial connections, particularly in point-to-point configurations. The DCE device provides the clocking for the line, while the DTE device does not. The other commands, while useful for different purposes, do not provide the same level of detail related to DTE/DCE status and clock rate. For example, "show ip interface brief" gives an overview of the interface status and IP information but doesn't touch on physical layer specifics. The "show interface INTERFACE NUMBER" command provides statistics and status for that interface more extensively but still lacks the DTE/DCE designation and clock rate. Lastly, "show running-config" reveals the device configuration but does not address the real-time status of the