Information Technology Reference
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queries about that domain. At the root of the domain namespace are the root servers. More
on these later.
Domain names and hostnames must contain only characters a to z , A to Z ,
0 to 9 , and - (hyphen). Other common and useful characters, such as the
& (ampersand), / (slash), . (period), and _ (underscore), are not allowed.
This is in conflict with NetBIOS's naming restrictions. However, you'll find
that Windows Server 2012 R2 is smart enough to take a NetBIOS name, like
Server_1 , and turn it into a legal DNS name, like server1.example.com .
DNS servers work together to resolve hierarchical names. If a server already has
information about a name, it simply fulfills the query for the client. Otherwise, it queries
other DNS servers for the appropriate information. The system works well because it
distributes the authority over separate parts of the DNS structure to specific servers.
A DNS zone is a portion of the DNS namespace over which a specific DNS server has
authority (DNS zone types are discussed in detail later in this chapter).
There is an important distinction to make between DNS zones and Active
Directory (AD) domains. Although both use hierarchical names and require
name resolution, DNS zones do not map directly to AD domains.
Within a given DNS zone, resource records (RRs) contain the hosts and other database
information that make up the data for the zone. For example, an RR might contain the
host entry for www.example.com , pointing it to the IP address 192.168.1.10.
Understanding Servers, Clients, and Resolvers
You will need to know a few terms and concepts in order to manage a DNS server.
Understanding these terms will make it easier to understand how the Windows Server 2012
R2 DNS server works.
DNS Server Any computer providing domain name services is a DNS name server . No
matter where the server resides in the DNS namespace, it's still a DNS name server. For
example, 13 root name servers at the top of the DNS tree are responsible for delegating
the TLDs. The root servers provide referrals to name servers for the TLDs, which in turn
provide referrals to an authoritative name server for a given domain.
The Berkeley Internet Name Domain (BIND) was originally the only soft-
ware available for running the root servers on the Internet. However, a few
years ago the organizations responsible for the root servers undertook
an effort to diversify the software running on these important machines.
Today, root servers run multiple types of name server software. BIND is
still primarily on Unix-based machines, and it is also the most popular for
Internet providers. No root servers run Windows DNS.
 
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