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DNS Zone Overview
A DNS zone is a contiguous portion of the domain namespace for which a
particular DNS server has authority to resolve DNS queries.
DNS namespaces are almost always divided into zones that
store name information about one or more DNS domains or
portions of a DNS domains.
In the Windows 2000 Active Directory domain structure there are three different zone types.
The
Standard Primary zone contains a read/write version of
the zone file that is stored in a standard
text file. Any changes to the zone are recorded in that file
and that file only. Any other copies of that zone are
Secondary zone copies and are read only
The Standard Secondary zone contains a read-only version of a Primary zone file, and it is stored in a standard text
file. Any changes to the zone are performed on the Primary
zone file and are replicated to the Secondary zone file. You
would create a Standard Secondary zone to create a copy of
an existing Primary zone and its zone file, which allows the
DNS name resolution workload to be distributed among
multiple DNS servers.
Active
Directory integrated zones
store the DNS zone information in the Active Directory
database rather than in a text file. Updates to the Active
Directory integrated zone occur automatically during Active
Directory replication. You do not need to manually configure
DNS servers to specify update intervals as Active Directory
maintains the zone information and replicates the
information based on its own replication schedule.
The Active
Directory integrated option is not available in the Change
Zone Type dialog box until you implement Active Directory.
If Active Directory is not present in your environment the
option will be grayed out in the New Zone Wizard and the
Change Zone Type dialog box from the DNS MMC.
DNS zone
files contain the name resolution data for a zone and they
also include resource records that contain database entries
that contain various attributes of network systems. Below is
a list of the most common resource records.
(A)
records, sometimes called host records or address
record, contain the name-to-IP address mapping information
used to map DNS domain names to a host IP address on the
network.
Alias
records, normally referred to as CNAME (canonical name)
records allow you to provide additional names to a server
that already has a name in an A (host) resource record. This
is how a Web server with a name of Server1 in a domain of
Zandri.net “becomes”
www.zandri.net as far as DNS resolution is concerned.
There is an Alias record referencing
www.zandri.net to Server1.zandri.net.
MX (Mail Exchanger)
records specify the server where e-mail can be delivered in a given
domain. When you have a Mail server named Mailbox.zandri.net
and you want all mail for all_users@zandri.net to be
delivered to this mail server (named Mailbox in this
example), the Mail Exchanger resource record must exist in
the zone for Zandri.net and must point to Mailbox.
NS (Name
Server)
records designate the DNS domain names for the servers that
are authoritative for a given DNS zone.
PTR
(Pointer) records are
used for reverse look up queries. A reverse lookup query
resolves an IP address to a name. Reverse lookup zones are
created in the in-addr.arpa domain to designate a reverse
mapping of a host IP address to a host DNS domain name.
SOA
(Start of Authority)
records indicate the starting point of authority for a given
DNS zone on a specific DNS server. The SOA resource record
is the first resource record created when you add a new
zone.
SRV
(Service)
records, sometimes referred to as Service Location
records, contain registered services within the zone so
that clients can locate these available services by using
DNS. SRV records are mainly used to identify services in
Active Directory.
Well, that wraps up this section
of “Learn Active Directory Design and Administration in 15
Minutes a Week.” I hope
you found it informative and will return for the next
installment.
If you have any questions, comments or
even constructive criticism, please feel free to drop me a
note.
I want to write solid technical
articles that appeal to a large range of readers and skill
levels and I can only be sure of that through your feedback.
Until next time, best of luck in your
studies and remember:
I remember how my mother taught me RELIGION – “You better pray that will
come out of the carpet.”
