100-150 Question 246
Single answerYou are troubleshooting a connectivity issue in a small network where a switch connects multiple devices. A user reports they cannot reach an external server. You begin by using the 'show ip interface brief' command on the switch. The output shows all interfaces are 'up' and have correct IP addresses. Next, you use the 'show mac address-table' command and notice that the MAC address of the user's device is not listed. Which command should you use next to determine the issue?
- A
show cdp neighbors
- B
show interface x
- C
show ip route
- D
show version
Show answer and explanation
Correct answer: B
Explanation
Since the MAC address of the user's device is not in the MAC address table, the issue is likely at Layer 2. The 'show interface x' command allows you to examine the specific interface connected to the user's device to identify errors, drops, or other issues that might explain why the MAC address is not being learned. Other commands, such as 'show cdp neighbors' or 'show ip route', do not provide the detailed interface-level troubleshooting needed in this scenario.
- A. Incorrect.
The 'show cdp neighbors' command provides information about directly connected Cisco devices. However, this does not help identify issues with a specific host's connectivity.
- B. Correct.
The 'show interface x' command displays detailed information about a specific interface, including its operational status, error counters, and traffic statistics. This is the most appropriate command to check for issues such as errors or drops on the port connected to the user’s device.
- C. Incorrect.
The 'show ip route' command displays the routing table, which is used to troubleshoot Layer 3 routing issues. Since the issue appears to be at Layer 2 (MAC address not in the table), this command is not relevant here.
- D. Incorrect.
The 'show version' command provides information about the switch's software version and hardware details. This is not useful for troubleshooting the user's connectivity issue.