Which command is used on a Cisco router to display detailed interface statistics, including error counters?
Correct Answer: A
Detailed Explanation: Monitoring interface performance is critical for ensuring network reliability and for troubleshooting issues. Cisco IOS provides several commands to display interface statistics, but the most comprehensive among these is the "show interfaces" command. What "show interfaces" Displays: When you issue the "show interfaces" command, the router provides detailed information about each interface. This includes the interface’s physical status (up or down), the line protocol state, input/output statistics, and various error counters. Error counters might include data on input errors, CRC errors, collisions, late collisions, runts, and giants. These counters are essential for diagnosing physical layer issues (such as cabling problems or duplex mismatches) and determining whether an interface is experiencing performance degradation or data loss. Why Interface Counters Are Important: Interface error counters help network administrators identify problems that may not be immediately obvious from connectivity alone. For example: CRC Errors: Often indicate issues with cabling or interference. Input Errors: Could suggest problems with the physical medium or faulty hardware. Collisions: In half-duplex environments, collisions indicate that the network is congested or that duplex settings are mismatched. By analyzing these statistics, administrators can pinpoint issues, plan for maintenance, or adjust configurations to improve overall performance. How to Use the Command: The command is typically entered from the privileged EXEC mode (often after entering the router’s CLI): Router# show interfaces GigabitEthernet0/1 This command will display detailed statistics for the specified interface. To view all interfaces, you can simply use: Router# show interfaces This provides a summary for all interfaces and their respective error counters. Comparing with Other Options: show ip interface (Option B): This command provides information about IP-related parameters, such as IP addresses and status, but does not include the detailed physical and error statistics provided by "show interfaces". show counters (Option C): Although this command might exist in some platforms or operating systems, it is not the standard command in Cisco IOS for retrieving interface error statistics. show log (Option D): This command displays the system log, which contains event messages and error logs, but not real-time interface performance statistics. Conclusion: For network monitoring and troubleshooting, the "show interfaces" command is essential. It gives network administrators a comprehensive view of interface statistics, including error counters that are crucial for diagnosing and resolving physical or performance issues. This makes Option A the correct answer.
This CCNA practice question helps students prepare for Cisco networking certification exams by testing knowledge of network fundamentals, routing, switching, and network security concepts.