1. Start of Authority (SOA) Records
The Start of Authority (SOA) record in a DNS
database indicates which server is authoritative for that particular
zone. The server referenced by the SOA records is subsequently the
server that is assumed to be the authoritative source of information
about a particular zone and is in charge of processing zone updates.
The SOA record contains information such as the Time-to-Live (TTL)
interval, the contact person responsible for DNS, and other critical
information, as illustrated in Figure 1.
Figure 1. A sample SOA record.
An SOA record is automatically
created when DNS is installed for AD DS in Windows Server 2012 and is
populated with the default TTL, primary server, and other pertinent
information for the zone. After installation, however, these values can
be modified to fit the specific needs of an organization.
2. Host (A) Records
The most common type of RR in DNS is the host
record, also known as an A record. This type of RR simply contains the
name of the host and its corresponding IP address, as illustrated in Figure 2.
Figure 2. Sample host record.
The vast majority of RRs
in DNS are A records because they are used to identify the IP addresses
of most resources within a domain.
Note
Most resource records also contain advanced
information about the record, which includes the TTL and, optionally,
the record time stamp. To view or update this information, select
Advanced from the View menu of the DNS Management console.
3. Name Server (NS) Records
Name Server (NS) records identify which
computers in a DNS database are the name servers, essentially the DNS
servers for a particular zone. Although there can be only one SOA
record for a zone, there can be multiple NS records for the zone, which
indicate to clients which machines are available to run DNS queries
against for that zone.
Note
Name Server records, or NS records, do not
actually contain the IP information of a particular resource. In fact,
in most cases, only A records contain this information. NS records and
other similar records simply point to a server’s A record. For example,
an NS record will simply point to dc1.companyabc.com, which will then
direct the query to the dc1 A record in the companyabc.com zone.
