Cisco Certified Network Associate (CCNA) Practice Exam

What would you use to troubleshoot issues on a serial interface after a failed ping?

1. show interfaces

2. show ip route

3. show running-config

4. show ip interface brief

The correct answer is: show ip interface brief

Using "show ip interface brief" is a effective command for troubleshooting issues on a serial interface following a failed ping. This command provides a concise overview of the interface status and IP address assignments. It will display whether the interface is up or down, which is crucial information when diagnosing connectivity problems. If the serial interface is down, that would directly explain the failed ping. Additionally, the command gives insight into the status of all interfaces on the device, allowing for a quick assessment of whether other interfaces might also be experiencing issues. This command also indicates if an interface has been administratively shut down or if there are any other configuration problems that could affect connectivity. The other commands, while useful in their own right, do not deliver the same level of immediate clarity regarding the operational status of serial interfaces. For instance, "show interfaces" provides a more detailed output, but it can be overwhelming in terms of the volume of data presented. "Show ip route" focuses on the routing table, which might not directly help address interface-specific issues. "Show running-config" displays the current configuration but requires careful examination to ascertain interface statuses or potential misconfigurations. Thus, for a quick and straightforward diagnostic assessment, "show ip interface brief" is the most efficient choice