D-Link DES-3326SR User Manual page 94

DES-3326SR Layer 3 Fast Ethernet Switch User's Guide
The Domain Name System (DNS) is used to map names to IP
addresses throughout the Internet and has been adapted for
use within intranets.
For two DNS servers to communicate across different subnets,
the DNS Relay of the DES-3326SR must be used. The DNS
servers are identified by IP addresses.
Mapping Domain Names to Addresses
Name-to-address translation is performed by a program called
a Name server. The client program is called a Name resolver.
A Name resolver may need to contact several Name servers to
translate a name to an address.
The Domain Name System (DNS) servers are organized in a
somewhat hierarchical fashion. A single server often holds
names for a single network, which is connected to a root DNS
server – usually maintained by an ISP.
Domain Name Resolution
The domain name system can be used by contacting the name
servers one at a time, or by asking the domain name system to
do the complete name translation. The client makes a query
containing the name, the type of answer required, and a code
specifying whether the domain name system should do the
entire name translation, or simply return the address of the
next DNS server if the server receiving the query cannot resolve
the name.
When a DNS server receives a query, it checks to see if the
name is in its subdomain. If it is, the server translates the
name and appends the answer to the query, and sends it back
to the client. If the DNS server cannot translate the name, it
determines what type of name resolution the client requested.
A complete translation is called recursive resolution and
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