CompTIA Network+ (N10-009)Network TroubleshootingMedium
A network technician is troubleshooting a client's workstation that cannot access a specific web server by its hostname (e.g., 'webserver.internal.com') but can successfully access it using its IP address (e.g., '192.168.1.100'). Other workstations on the same subnet do not experience this issue. Which of the following is the MOST likely cause?
- AIncorrect DNS server configuration on the client workstation.
- BThe web server is offline.
- CA firewall blocking HTTP traffic from the client.
- DThe client workstation has a duplicate IP address.
Show answer & explanationAnswer & explanation
Correct answer: A. Incorrect DNS server configuration on the client workstation.
The ability to reach the web server by IP address but not by hostname is a classic symptom of a DNS resolution problem. Since other workstations on the same subnet can resolve the hostname, the issue is specific to this client, making an incorrect DNS server configuration on the client the most likely cause.
Why the other options are wrong
- B. If the web server were offline, it wouldn't be reachable by either hostname or IP address.
- C. A firewall blocking HTTP traffic would prevent access by both hostname and IP address, as it operates at a higher layer than DNS.
- D. A duplicate IP address would cause intermittent or complete network connectivity issues for that client, not specifically a hostname resolution failure while IP access works.
DNS Resolution Failure
Occurs when a device cannot translate a human-readable hostname into a numerical IP address.
- Symptoms: cannot access resources by name, but can by IP.
- Common causes: incorrect DNS server settings, DNS server offline, or invalid DNS records.
- Tools: `nslookup`, `dig`, `ping hostname`.
Memory trick: Name doesn't work, but number does? It's a 'phone book' problem.