DNS Server Intro
From Ubuntu Doctors Guild
A server refers to a software program (although some users colloquially refer to the computer hardware that hosts the server software programs as a "server", which is misleading). Multiple software server programs can reside on a single computer.
An organization may have multiple servers operating within its network (LAN). These may or may not be exposed to the Internet, although the most secure networking methods do not expose servers to the Internet directly. Only users "within" the organization are allowed to access them. Remote users access them either through VPN (or similar) connections, or through a Terminal Server.
Each server is given a unique URL. (Denoting a server by an IP address is not sufficient, as multiple servers may be running on a single computer at a single IP address.) There must be a URL name repository that resolves the URL for each server (or other network resource) to the IP address of the computer on which that server (or resource) resides.
This URL name repository is known as a DNS (domain name server). It keeps track of the location of all servers and directs any requests for the URL associated with the server to the IP address of the computer on which the server is located.
The internet has commercial DNS services that keep track of this data for millions of Internet websites. However, since the servers of an organization may not be available to the Internet at large, an organization needs its own DNS server (for internal use only).
The organization's internal DNS server can include the data from an external DNS server (by copying the data), or can merely maintain data related to the organization's network.
Each computer within the organization's network must know to check this internal DNS server (in addition to any external DNS servers used for the Internet). This is usually set in the TCP/IP settings of each computer on the organization's network.
- Also see DNS servers