DNS SOA records

  • Last updated on: 2016-06-17
  • Authored by: Rose Contreras

A Start of Authority (SOA) resource record indicates which domain name server (DNS) is the best source of information for the specified domain. Every domain must have an SOA record.

When you add a domain to DNS, the email address that you indicate is added to the SOA record for the domain. This publicly associates the email with the domain.

For example, the email address associated with the rackspace.com domain is hostmaster@rackspace.com. You can see the SOA record for rackspace.com by running the following command:

$ dig rackspace.com +nssearch

Note: dig is used for Linux systems. If you have a Windows server, use nslookup instead.

The following information is returned:

SOA ns.rackspace.com. hostmaster.rackspace.com. 1392389079 300 300 1814400 300 from server 69.20.95.4 in 12 ms.

The SOA record includes the following details:

  • The primary name server for the domain, ns.rackspace.com
  • The email for the domain, hostmaster@rackspace.com
  • Revision number that changes whenever you update the domain
  • Refresh time, which is the number of seconds before the zone should be refreshed
  • Retry time, which is the number of seconds before a failed refresh should be retried
  • Expiration time, which is the time, in seconds, before the data is considered unreliable
  • Minimum TTL, which is the default that applies to all resource records in the zone

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