100-150 Question 229
Single answerYou are troubleshooting a network connectivity issue between your local workstation and a web server. You attempt to use the 'ping' command to check connectivity, but the request times out. You then use 'tracert' (or 'traceroute') to trace the route to the server, and it successfully displays multiple hops until it stops at a firewall before the server. What is the most likely reason for the ping failure?
- A
The firewall is blocking ICMP packets.
- B
The server is offline and unreachable.
- C
The tracert/traceroute command is incorrectly configured.
- D
The DNS server is not resolving the server's domain name.
Show answer and explanation
Correct answer: A
Explanation
The 'ping' command uses ICMP packets to test connectivity, but many firewalls block ICMP traffic by default for security reasons. This results in a 'request timed out' response when using 'ping'. However, 'tracert' or 'traceroute' uses UDP or ICMP packets (depending on the protocol) and can often bypass such restrictions to trace the network path. The successful traceroute result indicates that the server is reachable, and the issue lies with the firewall blocking ICMP traffic.
- A. Correct.
Firewalls commonly block ICMP packets used by the 'ping' command for security reasons, but other traffic such as traceroute may still pass through.
- B. Incorrect.
If the server were offline, both the 'ping' and 'traceroute' commands would fail, not just 'ping'.
- C. Incorrect.
The tracert/traceroute command does not need special configuration in this scenario, and it successfully displayed hops, proving it worked properly.
- D. Incorrect.
If the DNS server failed to resolve the domain name, neither 'ping' nor 'traceroute' would work unless the server was accessed directly by its IP address.