SOA Record
DNSSOA Record is a DNS record that defines the authoritative settings for a domain or DNS zone, including the primary nameserver, administrative contact, and timing values that control zone transfers and caching behavior. It contains a serial number for tracking changes and parameters like refresh, retry, expire, and minimum TTL, which help secondary DNS servers synchronize and resolvers cache responses reliably.
How It Works
The Start of Authority (SOA) record sits at the top of a DNS zone and signals which nameserver is the primary source of truth for that zone. It also includes an administrative email address (stored in a DNS-friendly format) and a serial number that increments when zone data changes. Secondary (slave) DNS servers use the SOA record to decide whether they need to pull an updated copy of the zone from the primary server.
Several timing fields in the SOA record control how DNS data propagates and stays consistent. Refresh tells secondaries how often to check for updates, retry defines how soon to try again after a failed check, and expire sets how long a secondary can keep serving the zone without successfully contacting the primary. The minimum TTL value influences negative caching, meaning how long resolvers may cache “no such record” (NXDOMAIN) responses, affecting how quickly fixes to missing records are noticed.
Why It Matters for Web Hosting
When you move a site, change nameservers, or update records for email and subdomains, the SOA record helps determine how reliably and quickly DNS changes synchronize across authoritative servers. Hosting plans that include managed DNS or secondary DNS often handle SOA values for you, but understanding them helps you evaluate propagation expectations, troubleshoot stale records, and avoid outages caused by misconfigured zone transfers or overly aggressive caching.
Common Use Cases
- Verifying which DNS zone is authoritative for a domain during troubleshooting
- Coordinating primary and secondary DNS servers using the SOA serial number
- Tuning refresh and retry behavior for reliable zone transfers
- Controlling how long secondary DNS can serve data if the primary is unreachable (expire)
- Adjusting negative caching behavior to reduce the impact of missing or recently added records
SOA Record vs NS Record
NS records list the authoritative nameservers for a domain or zone, telling resolvers where to ask for answers. The SOA record provides the zone’s control metadata: which server is the primary source, who administers it, the change-tracking serial, and synchronization and caching timers used mainly by secondary DNS and resolvers. In practice, NS records point to the servers, while the SOA record governs how the zone is managed and kept consistent.