Managing Mission - Critical Domains and DNS

Start of Authority (SOA)

The SOA record is the "start-of-authority record." There must be one SOA RR present in every zone at the apex. It signals basic information about the zone to other name servers, such as (ostensibly) who the responsible party for the zone is, at what intervals secondaries should refresh their zones, and how long resolvers should cache negative lookups.

Here is the SOA RR Syntax:

<OWNER-NAME> IN SOA <MNAME> <RNAME> <SERIAL> <REFRESH> <RETRY> <EXPIRE> <MINIMUM>

It can also be written as:

<OWNER-NAME IN SOA <MNAME> <RNAME> (<SERIAL><REFRESH><RETRY><EXPIRE><MINIMUM>)

The Right-Hand Side (RHS) or "rdata" of an SOA record consists of seven fields:

• Originating nameserver (MNAME)
• The responsible person (RNAME)
• Serial
• Refresh ...