DNS Servers provide core name resolution functionality for your Windows 2000
and other TCP/IP based networks. These servers are tasked with the duty to
resolve host names to IP addresses, so that when a request from an
application that includes a Fully Qualified Domain Name is passed to lower
layers of the TCP/IP protocol stack, they will have an IP address to which
to connect.
In a recent article in the Win2k News, we covered the variety
of roles a Windows 2000 DNS Server can play on your network. These roles
included those of the:
Standard Primary DNS Server
Secondary DNS Server
Caching-only DNS Server
Active Directory Integrated DNS Server
Dynamic DNS Server
In this article we'll cover three
other important roles a DNS Server can play on your network. This
include:
The DNS Forwarder
The Slave Server
Before getting into the specifics of
these types of DNS Servers, let's do a quick review of how DNS queries are
answered.
Formulating a DNS Query
When a DNS client
sends a query to a DNS Server for resolution, it includes in the request the
entire Fully Qualified Domain Name (FQDN) of the host it needs to resolve.
For example, if you type in your browser's address bar: www.brainbuzz.com, a
request is sent to the DNS Server to resolve that name to an IP
address.
A FQDN consists of two parts: a host name and a domain name. In
the example of www.brainbuzz.com, the host name portion is "www" and the
domain name portion is "brainbuzz.com". The host name portion is always the
leftmost entry to the leftmost period in the name.
What if you just
typed "www" in the address bar instead of the entire FQDN? As we said
earlier, the DNS client must send an entire FQDN to the DNS Server for
resolution. In this case, where you make a request for an "unqualified"
name, the DNS resolver (DNS client service) will append to the request a
domain name that you've configured in your TCP/IP settings. If you did not
configure a particular domain name in the TCP/IP settings, the resolver
will append the domain name of the domain to which the computer sending the
request belongs.
For example, if the computer sending the request belongs
to "fooey.net", the resolver on the computer would formulate a query for
www.fooey.net and then send a request to have that FQDN resolved by the DNS
Server.
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