CompTIA Network+ (N10-009)Network TroubleshootingEasy
A network technician is troubleshooting a client workstation that can access local network resources but cannot reach any external websites. The technician performs a `ping` to a known external IP address, which succeeds. However, a `ping` to a known external website URL fails. Which of the following is the MOST likely cause of this issue?
- AFirewall blocking outbound traffic
- BIncorrect subnet mask configuration
- CDefault gateway is misconfigured
- DDNS resolution failure
Show answer & explanationAnswer & explanation
Correct answer: D. DNS resolution failure
The ability to ping an external IP address confirms basic network connectivity and an operational default gateway. The failure to ping a URL, while the IP works, strongly points to an issue with translating the website's name to its IP address, which is the function of DNS.
Why the other options are wrong
- A. A firewall blocking outbound traffic would prevent both IP and URL pings to external destinations from succeeding.
- B. An incorrect subnet mask would likely prevent access to local resources as well, or at least cause broader connectivity issues.
- C. If the default gateway were misconfigured, the client would not be able to ping the external IP address successfully.
DNS Resolution Failure
An issue where a client cannot translate domain names (like websites) into their corresponding IP addresses, preventing access to resources by name.
- Client can reach resources by IP address.
- Client cannot reach resources by domain name.
- Often caused by incorrect DNS server configuration or unresponsive DNS servers.
Memory trick: If IPs work but names don't, DNS is where the problem haunts.