Information Technology Reference
In-Depth Information
Exam Essentials
Understand the purpose of DNS.
DNS is a standard set of protocols that defines a
mechanism for querying and updating address information in the database, a mechanism
for replicating the information in the database among servers, and a schema of the
database.
Understand the different parts of the DNS database.
The SOA record defines the general
parameters for the DNS zone, including who is the authoritative server. NS records list
the name servers for a domain; they allow other name servers to look up names in your
domain. A host record (also called an address record or an A record) statically associates a
host's name with its IP addresses. Pointer records (PTRs) map an IP address to a hostname,
making it possible to do reverse lookups. Alias records allow you to use more than one
name to point to a single host. The MX record tells you which servers can accept mail
bound for a domain. SRV records tie together the location of a service (like a domain
controller) with information about how to contact the service.
Know how DNS resolves names.
With iterative queries, a client asks the DNS server for
an answer, and the client, or resolver, returns the best kind of answer it has available. In a
recursive query, the client sends a query to one name server, asking it to respond either with
the requested answer or with an error. The error states either that the server can't come up
with the right answer or that the domain name doesn't exist. With inverse queries, instead
of supplying a name and then asking for an IP address, the client first provides the IP
address and then asks for the name.
Understand the differences among DNS servers, clients, and resolvers.
Any computer
providing domain name services is a DNS server. A DNS client is any machine issuing
queries to a DNS server. A resolver handles the process of mapping a symbolic name to an
actual network address.
Know how to install and configure DNS.
DNS can be installed before, during, or after
installing the Active Directory service. When you install the DNS server, the DNS snap-in
is installed too. Configuring a DNS server ranges from easy to difficult, depending on what
you're trying to make it do. In the simplest configuration, for a caching-only server, you
don't have to do anything except to make sure the server's root hints are set correctly. You
can also configure a root server, a normal forward lookup server, and a reverse lookup
server.
Know how to create new forward and reverse lookup zones.
You can use the New Zone
Wizard to create a new forward or reverse lookup zone. The process is basically the same
for both types, but the specific steps and wizard pages differ somewhat. The wizard walks
you through the steps, such as specifying a name for the zone (in the case of forward
lookup zones) or the network ID portion of the network that the zone covers (in the case
of reverse lookup zones).
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