SOA record
also: Start of Authority record
An SOA (Start of Authority) record is a DNS resource record that defines the primary nameserver, administrator contact, and important timing parameters for a DNS zone.
An SOA record is a mandatory DNS record that appears at the apex (root) of every DNS zone. It specifies which nameserver is authoritative for the zone, who administers it, and critical values that control how other nameservers handle zone data and caching.
The SOA record contains several key fields: the primary nameserver hostname, the administrator's email address (with the @ replaced by a dot), a serial number that tracks zone changes, and four timing intervals: refresh (how often secondary nameservers check for updates), retry (how long to wait before retrying a failed refresh), expire (when to stop answering queries if primary is unreachable), and TTL (time-to-live, how long other systems cache this record).
Example SOA record for example.com:
example.com. IN SOA ns1.example.com. admin.example.com. (
2024010101 ; serial
3600 ; refresh (1 hour)
1800 ; retry (30 minutes)
604800 ; expire (7 days)
86400 ) ; TTL (1 day)