SOA record

Start of Authority — metadata about the zone, including serial, refresh, retry and minimum TTL.

What is a SOA record?

There is exactly one SOA per zone. It declares the primary name server, the responsible person's email (in DNS notation), and the timers that govern how secondaries refresh and how negative answers are cached.

Example zone-file entry

example.com. 86400 IN SOA ns1.example.com. hostmaster.example.com. (
  2026010101 ; serial
  3600       ; refresh
  600        ; retry
  604800     ; expire
  300        ; minimum TTL )

Common use cases

▸Diagnose stale secondaries by comparing their SOA serial to the master.
▸Set the minimum TTL for negative caching (RFC 2308) — prevents NXDOMAIN storms.
▸Audit zone changes: monotonic serial increments on every edit.
▸Validate ownership when transferring a zone between providers.

Common gotchas

The SOA serial must increase on every change, even after a reset. Many issues stem from forgetting to bump it. Format YYYYMMDDnn is conventional but not mandated.

Look up DNS records →

Related record types

NS record

Lists the authoritative name servers for a zone.

A record

Maps a domain name to an IPv4 address.