nslook Utility

A common and useful network utility, nslookup, is present on most Unix, Windows NT and Windows 2000 systems, but sadly lacking on Windows 95, Windows 98 and Windows ME systems. To fill this void, PC Pitstop has developed a simple command-line utility, nslook, that performs two of nslookup's most useful functions: It determines an IP address from a DNS name, and a DNS name from an IP address (DNS address www.pcpitstop.com, for example, corresponds to IP address 64.29.193.182).

How to use it

What are the uses for this utility? Here are some examples of when to use nslook:

• SPAMMED? If you're getting spam directing you to a Web site given by a number (IP address), look up the IP address with nslook and find out the domain of the Web site. Then look up the owner of the domain in Whois.Net and file your complaint with the Web hosting provider. To do that, you might have to dig for the SOA (start of authority), which nslookup can do but PC Pitstop's nslook currently can't, or go to Whois.Net and see who provides the DNS services for the site--almost always the provider.

• SECURITY VIOLATION? Similarly, you notice an attempted penetration of your network on your firewall logs. Use nslook to determine the domain of the IP address, then visit Whois.Net to find the service provider and report the hack attempt.

Note: This utility is copyrighted, but free to all PC Pitstop users.

How it works

DNS, the Domain Name System, maintains a distributed database of host names (domain names) and their associated IP addresses. The nslook utility sends its name resolution and address-lookup requests to whatever DNS server is currently configured for your Internet connection.

Installing the nslook utility

To install nslook, download the utility from one of the links to the right and save it to any directory, such as C:\WINDOWS, on the path on your system (i.e., any of the directories Windows automatically checks when trying to run a program--type PATH at a DOS prompt to see which directories are defined for your PC's path). This way, you can run the utility from any directory in DOS. There is no further installation.

Using the nslook utility

To use nslook, first open a DOS box, MS-DOS Prompt or Command Prompt window (click here for instructions on opening these windows).

From the command line, type nslook followed by the DNS names and/or IP addresses you wish to look up, separated only by spaces. (<address> below stands for one or more DNS or IP addresses)

nslook <address>

The nslook utility will send each argument (address) to your computer's DNS server for resolution and display the result.

Here's an example of its usage and typical results. In this case, we are looking up four addresses: