Online DNS record lookup

DNS maps names to addresses and service settings. A and AAAA: IPv4 and IPv6. CNAME: alias. MX: mail server and priority (lower is preferred). NS: authoritative servers. SOA: zone parameters. TXT: text data. CAA: permitted certificate authorities. SRV: service host, port, priority and weight. PTR: reverse IP lookup.

TTL is the cache lifetime in seconds. Resolvers refresh independently, so changes do not appear everywhere at once. TTL differences are excluded from record comparison. GeoDNS and load balancing can also return different addresses. Queries originate from the Runstack server, not from multiple countries.

SPF usually lives in the root domain TXT records; DMARC at _dmarc.example.com. DKIM requires a known selector: selector._domainkey.example.com; selectors are not guessed. SRV requires an exact hostname, such as _sip._tcp.example.com. ALL queries nine types for the supplied name, excluding PTR, without discovering subdomains.

OK: records returned. NODATA: name exists but the requested record type is absent. NXDOMAIN: name does not exist. SERVFAIL: server failed to process the query. REFUSED: query rejected. TIMEOUT: deadline exceeded. ERROR: transport failure or invalid response. Incomplete: some servers failed or only one was selected. System uses the first DNS IP in the OS configuration. Custom DNS accepts public IPs only, on port 53. Limit: 6 checks per minute per IP.