The zone’s header: primary server, contact, serial and timers.
Every zone has exactly one SOA record at its apex. It names the primary nameserver and a contact mailbox (with the @ written as a dot), and carries a serial number that secondary servers compare to know when to copy the zone.
- Type
- SOA
- Code
- 6
- Defined in
- RFC 1035
- IANA description
- marks the start of a zone of authority
- Field: MNAME
- Primary nameserver
- Field: RNAME
- Contact mailbox, @ written as .
- Field: SERIAL
- Zone version
- Field: REFRESH / RETRY / EXPIRE
- Secondary server timers, seconds
- Field: MINIMUM
- Negative-caching TTL (RFC 2308)
How it works
Its last field, the minimum, is used today as the TTL for negative answers (RFC 2308): how long a resolver may remember that a name or record does not exist. That is why a record you just added can stay “missing” for a while if someone looked it up moments earlier.
Example
example.com. 3600 IN SOA ns1.dns-host.example. hostmaster.example.com. 2026100501 7200 3600 1209600 300
Example uses reserved documentation names and addresses (RFC 2606, RFC 5737, RFC 3849).
Common mistakes
- Forgetting to raise the serial on hand-edited zones, so secondaries keep the old copy.
- A very long negative TTL, which delays new records appearing.
How to check yours
You rarely edit an SOA record on a managed DNS host; the host maintains it. It is still useful when debugging: the serial tells you whether a secondary server has the latest copy, and the negative TTL tells you how long a ‘record not found’ answer can stick after you add something.
Related record types
Sources
Sources
- IANA: Resource Record (RR) TYPEs registry · checked 5 Oct 2026
- RFC 1035 · checked 5 Oct 2026