DNS problems explained: NXDOMAIN, NODATA, propagation and drift
The difference between a name that does not exist, a record type that is missing, a stale cache and a change you did not intend.
By the UptimeMonitor360 team · updated
NXDOMAIN
The authoritative servers say the name does not exist. Typos, a zone that was not published, or the wrong zone.
NODATA
The name exists but has no record of the requested type. A hostname that is only a CNAME has no A record of its own; the resolver follows the CNAME for you.
Propagation
Resolvers cache answers up to the TTL. Lower the TTL before a planned change and expect caches to lag afterwards. Comparing two public resolvers shows whether a difference is propagation or a real split.
Drift
Record sets change for good reasons (new mail provider) and bad ones (hijacked registrar account, forgotten CDN). Monitoring normalizes answers so ordering and TTL differences are ignored, and alerts on actual changes to the set.
Lookup failure is not missing records
When the resolver itself fails (SERVFAIL, timeout) the honest result is unknown, not down.
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