Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2Network AssuranceHard
A network technician is troubleshooting a client's inability to connect to a specific internal server. The technician suspects a potential firewall issue blocking the traffic. Which troubleshooting step is generally the LEAST effective for quickly diagnosing a firewall blocking issue in this scenario?
- APerforming a traceroute from the client to the server.
- BRunning a packet capture on the client and server interfaces.
- CPinging the server's IP address from the client.
- DChecking the firewall logs for denied connections.
Show answer & explanationAnswer & explanation
Correct answer: C. Pinging the server's IP address from the client.
Pinging the server's IP address only tests ICMP reachability. While useful for basic connectivity, a firewall might block only specific application ports (e.g., TCP 80, 443) while allowing ICMP. Thus, a successful ping does not rule out a firewall blocking the application traffic, making it the least effective for *quickly diagnosing a firewall blocking issue* for a specific application.
Why the other options are wrong
- A. Traceroute can show where traffic stops or if it takes an unexpected path, potentially pointing to a firewall as the last reachable hop before failure.
- B. Packet captures on client and server interfaces can show if traffic leaves the client, if it arrives at the server, and if the server responds, providing definitive proof of where the traffic is being dropped or blocked.
- D. Firewall logs are the most direct source of information for denied connections, explicitly stating if and why traffic was blocked.
Troubleshooting Firewall Blocks
The process of identifying if and why a firewall is preventing specific network traffic from reaching its destination.
- Firewalls block based on IP, port, protocol, state.
- Logs are critical for 'denied' messages.
- Packet captures show traffic flow and drops.
Memory trick: Logs are truths, captures show path, traceroute finds hop, but ping's a narrow wrath.