SOA Record Lookup
Find Start of Authority records for DNS zones
This page provides original, human-reviewed information about SOA record lookups, explaining serial numbers, refresh and retry timers, negative caching TTL, and how SOA serials drive zone transfers.
SOA (Start of Authority) records define the authoritative information about a DNS zone. Every DNS zone must have exactly one SOA record that specifies the primary nameserver and various timing parameters for the zone.
SOA Record Components:
- Primary Nameserver:The authoritative nameserver for the zone
- Admin Email:Email address of the zone administrator (with @ replaced by .)
- Serial Number:Version number of the zone data (usually YYYYMMDDNN format)
- Refresh:How often secondary nameservers check for updates
- Retry:How long to wait before retrying failed zone transfers
- Expire:When secondary nameservers stop answering queries
- Minimum TTL:Default TTL for records in the zone
Purpose of SOA Records:
- Define zone authority and ownership
- Control zone transfer timing between nameservers
- Specify contact information for zone administration
- Set default caching behavior for zone records
Basic SOA Record Format:
Recommended Values:
Serial Number
Use YYYYMMDDNN format (e.g., 2024010101)
Increment whenever you make changes
Refresh (7200 seconds / 2 hours)
How often secondary nameservers check for updates
Retry (3600 seconds / 1 hour)
Retry interval if zone transfer fails
Expire (604800 seconds / 1 week)
When secondary nameservers stop serving the zone
Minimum TTL (86400 seconds / 1 day)
Default TTL for records without explicit TTL
Missing SOA Record
Zone has no SOA record
Solution: Every zone must have exactly one SOA record
Outdated Serial Number
Serial number not incremented after changes
Solution: Always increment serial when making zone changes
Incorrect Email Format
Admin email uses @ instead of . separator
Solution: Use admin.example.com instead of admin@example.com
Poor Timing Values
Refresh/retry/expire values too aggressive or too conservative
Solution: Use recommended values based on your update frequency
How often should I update the serial number?
Update the serial number every time you make any change to the zone. Secondary nameservers use this to detect updates.
What happens if I don't increment the serial?
Secondary nameservers won't detect your changes and will continue serving old data until therefresh interval expires.
Can I have multiple SOA records?
No, each DNS zone must have exactly one SOA record. Multiple SOA records will cause DNS resolution issues.
What's a good refresh interval?
2-6 hours is typical. Use shorter intervals if you make frequent changes, longer for stable zones.
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