SOA Record Reference

This article serves as a reference for the formal structure, components, and key technical details of an SOA (Start of Authority) record .

SOA record format

An SOA record is a mandatory administrative record that must exist in every DNS zone. It is defined in RFC 1035 and has a type code of 6.

The record’s data section (RDATA) is composed of several fields that provide vital administrative information about the zone:

<name> <TTL> IN SOA <mname> <rname> (
  <serial>
  <refresh>
  <retry>
  <expire>
  <minimum-ttl>
)

mname (master name): This is the hostname of the primary name server for the zone. All updates to the zone should originate here.
rname (responsible person): This is the email address of the person responsible for the zone, with the @ replaced by a . (e.g., admin@example.com becomes admin.example.com).
serial: This is a version number for the zone file. It must be updated every time a record in the zone changes. This is used by secondary name servers to determine if they need to request a new copy of the zone data.
refresh: This tells secondary name servers how often (in seconds) to check the primary server’s SOA record for a new serial number.
retry: If a secondary server fails to connect to the primary during a refresh, this value tells it how long (in seconds) to wait before retrying.
expire: This is the upper limit (in seconds) after which a secondary server should stop responding authoritatively for the zone if it cannot refresh the data.
minimum-ttl: This specifies how long (in seconds) a DNS resolver should cache a negative response (e.g., for a non-existent record) before retrying the query.

If you have additional questions or need any assistance with your DNS records, just contact support, and we’ll be happy to help.