DNS Troubleshooting with dig and nslookup
Most “the site is down” reports that turn out to be DNS follow the same short list of checks. Here’s the order to run them in.
1. Confirm what’s actually being returned
dig example.comLook at the ANSWER SECTION — is there a record at all, and does the IP match what you expect? An empty answer section with NOERROR status usually means the record type you queried doesn’t exist for that name (try dig example.com MX or dig example.com TXT if you meant a different record type).
2. Query a specific nameserver directly
If you suspect propagation lag, bypass your resolver and ask the authoritative server directly:
dig @ns1.example.com example.comComparing this against a query through your default resolver tells you whether the authoritative data has updated but your resolver’s cache hasn’t caught up yet.
3. Check the TTL
dig example.com +noall +answerThe number in the answer line is the TTL in seconds — how long resolvers are allowed to cache that record. A TTL of 3600 means a change you just made can take up to an hour to be visible everywhere, which explains a lot of “I changed it but nothing happened” tickets.
4. Trace the full resolution path
dig +trace example.comThis walks the delegation chain from the root servers down, which is invaluable when a domain resolves inconsistently — it’ll show you exactly which nameserver in the chain is returning something unexpected.
5. nslookup as a quick sanity check
dig is more detailed, but nslookup is fine for a fast check, especially on Windows where it’s available without extra tooling:
nslookup example.com
nslookup example.com 8.8.8.8The second form queries Google’s public resolver directly, which is a good way to rule out “is this just my local resolver being weird.”
Quick reference
| Symptom | Command |
|---|---|
| Wrong/missing IP returned | dig example.com |
| Suspected propagation delay | dig @ns1.example.com example.com |
| “Change isn’t showing up” | dig example.com +noall +answer (check TTL) |
| Inconsistent resolution | dig +trace example.com |