DNS Lookup   «Prev  Next»
Lesson 1

DNS and the Program NSLookup

Introduction to DNS Lookup

This module will explore DNS and use the program nslookup to probe the DNS database. The nslookup program is free software, available under all UNIX versions as well as Windows. It generates name server queries on command, and is useful for debugging DNS.
  1. DNS: Domain Name Service (DNS) is an Internet-wide service for converting numeric IP addresses to host names and back.
  2. name server: A name server is a process that accepts queries into the DNS database. It is also fairly common usage to refer to the computer on which this process is running as a name server.
By the end of this module, you will be able to:
  1. Domain Name Service (DNS)
  2. name server:
  3. DNS Database
  4. nslookup program
  1. Explain the basic use of the nslookup program
  2. Use nslookup to read other types of Resource Records
  3. Use nslookup to use a different name server and to list an entire zone
  4. Describe the components of the BIND package
  5. Define the elements of the name server configuration file

Domain Name System (DNS)

Domain Name System (DNS) translates between domain names and IP addresses, and is supported by nearly every operating system. All Internet based name resolution utilizes DNS. DNS is organized as a hierarchy. Consider the following translation: 

www.google.com = 209.85.225.104

The above domain name represents a Fully Qualified Domain Name (FQDN)
  1. .com represents a top level domain.
  2. .google represents a secondary level domain
  3. www represents a host computer in the .google.com domain.

Other top level domains include .org, .net, and .gov. Top level domains can also include country codes, such as .ca, .nl, and .de