Why query authoritatively?
Most DNS tools ask a public resolver such as 1.1.1.1 or 8.8.8.8. It answers from its cache, and that cache can be minutes to hours old. After a change you still see the old state there or, depending on location, sometimes the old and sometimes the new one. This checker determines the zone's name servers and queries one of them directly. The result is the state the zone has right now.
The record types
What the individual entries mean:
- A and AAAA: IPv4 and IPv6 addresses the name points to. Without AAAA the domain is not reachable over IPv6.
- CNAME: alias to another name. A CNAME must not coexist with other records on the same name.
- MX: mail servers with priority. Without MX no mail arrives.
- TXT: free text, used for SPF, DMARC, DKIM selectors and verifications (Google, Microsoft, Facebook).
- NS: the zone's authoritative name servers. An unnoticed change is the clearest sign of a provider switch or a takeover.
- CAA: defines which certificate authorities may issue certificates. Optional but recommended.
Typical problems
The checker points out the following situations:
- NXDOMAIN: the domain does not exist or has expired.
- SERVFAIL: the name servers answer with an error, often because of broken DNSSEC signatures.
- No A, AAAA, CNAME or MX records: the zone is empty.
- CNAME next to other records: violates the standard and leads to unpredictable behaviour.
- No CAA record: every certificate authority may issue certificates.
Detect changes instead of just looking
A DNS check shows one moment. What agencies actually need is a message when something changes: an MX that disappears, name servers that switch, an SPF record the client edited themselves. DomainWarn stores the zone as a snapshot, compares it on every check and reports typed changes with before and after.
Frequently asked questions
- Why do I see different values here than in my DNS tool?
- Because this checker asks the authoritative name server and not a caching resolver. After a change this result is the current one.
- How long does a DNS change take?
- On the authoritative server it is immediate. Resolvers worldwide pick it up once their cached copy expires, i.e. after the TTL of the old record.
- Does the tool check subdomains too?
- Yes, enter the full host name, for example shop.example.com.