The Domain Name System; Mapping Domain Names To Addresses - D-Link DES-3326 User Manual

DES-3326 Layer 3 Fast Ethernet Switch User's Guide
packet. ICMP does not, however use ports because its messages
are processed by the network software.

The Domain Name System

Computer users usually prefer to use text names for computers
they may want to open a connection with. Computers themselves,
require 32 bit IP addresses. Somewhere, a database of network
devices' text names and their corresponding IP addresses must be
maintained.
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-3326 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 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.
92
Switch Management and Operating Concepts