Which DNS troubleshooting step is commonly performed?

• A. Replace a NIC
• B. Restart the router
• C. Use nslookup to query DNS server
• D. Disable firewall without testing

Answer: (C)

Verifying DNS resolution by querying a DNS server with a dedicated tool is a fundamental step in DNS troubleshooting. Using a tool like nslookup lets you ask a specific DNS server for the IP address of a domain and see exactly what the server replies with, including the returned IP, any error codes, and which servers were consulted. This helps you determine whether the problem is with the local resolver, the DNS server, or the DNS records themselves. If the server returns the expected IP, DNS is functioning for that query; if you encounter errors such as NXDOMAIN, SERVFAIL, or no response, you have actionable clues about where the issue lies. You can also test multiple domains or switch to different DNS servers to isolate the cause. This direct, server-focused check is more precise for DNS issues than broader network steps.

Replacing a NIC is hardware-related and doesn’t diagnose DNS behavior. Restarting the router might clear some caches or transient issues but isn’t a targeted DNS diagnostic. Disabling the firewall without testing offers no reliable insight into DNS functionality and can create security risks.