Asking DNS Directly
When a name will not resolve, you want to query the Domain Name System by hand instead of guessing. The dig and nslookup tools do exactly that, asking a resolver for specific records.
What You Can Ask
You can target the exact record type you care about.
- An A record maps a name to an IPv4 address, and an AAAA record to an IPv6 one.
- An MX record lists mail servers, while a CNAME points one name at another.
- You can also pick which server to ask, bypassing the system default.
This lets you compare what one resolver returns against another to isolate a problem.
Reading An Answer
Dig output shows the question, the answer section with records and their time to live, and which server replied. If a record is missing or stale, you can ask the authoritative server directly to see the true value. Comparing a local resolver answer with the authoritative one often reveals a caching issue.
Key idea
Dig and nslookup query DNS directly for specific record types and even specific servers, letting you compare a resolver answer with the authoritative one to pinpoint stale or missing records.