Start of Authority (SOA) Record


Definition of Start of Authority (SOA) Record in the Network Encyclopedia.

What is Start of Authority (SOA) Record?

SOA Record stands for Start of Authority Record, is the first record in a zone file which defines the general properties of the zone for a name server.

SOA Record or Start of Authority Record
SOA Record or Start of Authority Record





Here is an example of a start of authority (SOA) record:

@   IN  SOA     nameserver.place.dom.  postmaster.place.dom. (
1 ; serial number
3600 ; refresh [1h]
600 ; retry [10m]
86400 ; expire [1d]
3600 ) ; min TTL [1h]

This SOA record contains the following information:

  • The name of the subdomain over which a particular name server has authority (nameserver.place.dom)
  • The name of the host on which this zone file resides
  • The e-mail address of the person responsible for administering the subdomain (postmaster@nameserver.place.dom)
  • A serial number, which increases when the zone data is updated and which is used in zone transfers to determine whether the secondary name server needs a new version of the zone file
  • A refresh interval, in seconds, that informs the secondary name server how frequently it should check with the master name server to see whether its zone information is current
  • A retry interval, in seconds, that tells the secondary name server how often to contact the master name server if the initial contact is unsuccessful
  • An expiry interval, in seconds, that informs the secondary name server how long to keep trying to contact the master name server for a refresh of the zone data before the data expires and the secondary name server no longer responds to name queries
  • The Time to Live (TTL), which is a value returned by the name server to resolvers when a name is resolved, informing the resolver how long it can cache the resolved name and IP address




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