Configuring the Domain Name Service

DNS resolution

When a DNS client requests hostname and address data from a DNS server, the process is called resolution. In standard DNS installations, basic DNS configuration results in a server that performs default resolution, possibly including one of the following examples:

A primary server queries itself for data. Client software on the system requests information about another machine in the current zone, and the server answers out of its authoritative data file.
A remote server queries another server (for example, a primary server) for data on a machine in the current zone. Client software on the remote server queries the resolver, which answers the request from its database files.
A caching-only server queries its own cache for data on a computer outside its zone. Not finding it, it queries the primary server for its zone, then others outside the zone, until it finds the requested data.

The preceding represent three common resolution scenarios. The presence of resolvers, forwarders, and the file /etc/resolv.conf alter this default behavior.