nslookup / dig
Command-line tools that query DNS servers to diagnose name-resolution problems.
Both nslookup and dig query DNS servers and display the returned records — A, AAAA, MX, CNAME, PTR, and others — along with which resolver answered. This makes them indispensable when a hostname resolves incorrectly or fails despite connectivity being intact. The key exam distinction is that nslookup ships on Windows and supports an interactive mode, while dig is the Linux/macOS standard and gives more detailed output, including query flags and TTL values. Watch for scenarios where aiming the lookup at a specific server — nslookup hostname <server-IP> — reveals a misconfigured forwarder rather than a bad record.
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