Beginners Guide to Using Nslookup

nslookup-iconnslookup is a network administration command-line tool available for many computer operating systems.

It is used for querying the Domain Name System (DNS) to obtain domain name or IP address mapping information .- Wiki

The main use of nslookup is for troubleshooting DNS related problems.

Nslookup can be use in interactive and non-interactive mode.

To use in interactive mode type nslookp at the command line and hit return.

You should get an nslookup command prompt.

nslookup-command-prompt

To use in non-interactive mode type nslookup options at the command prompt.

nslookup-command-prompt-use

Using Nslookup

To illustrate the use of nslookup we are going to use it to:

  • Find the IP address of a host.
  • Find the domain name of an IP address.
  • Find mail servers for a domain.

These are probably the most common usage scenarios.

Finding The IP Address of an Host-

To find the ip address of a host e.g. www.steves-internet-guide.com  type:

nslookup www.steves-internet-guide.com

at a command prompt.

nslookup-host

for an interactive lookup:

nslookup-interactive-host

Reverse Lookup IP address to domain name

Type nslookup IP address

nslookup-reverse

Find Mail Servers for a Domain

Type nslookup  -querytype=mx  domain name

nslookup-mx-records

General Usage Notes:

  1. By default nslookup will use the domain server that is currently configured for your system.

You can switch DNS servers using server name or server IP address option.

To switch to using the open dns server address 208.67.222.222 then go to an interactive prompt and type:

server 208.67.222.222

nslookup-switch-servers

2. You may notice that you get non authoritative answers.

nslookup-non-authoritative

This is nothing to worry about as all it means is that the DNS server has already recently resolved this query.

It can retrieve the results from cache, and doesn’t need to contact the authoritative name server.

You can find out which name servers are responsible (authoritative) for a domain by setting the query type to NS and entering the domain name as shown below:

nslookup-query-name-servers

Summary

Nslookup is a very handy tool for troubleshooting DNS related network problems.

It is available on all of the main Operating systems and can be used in interactive and command line mode.

Resources:

DNS and Bind Book – The definitive guide. This has an entire section on Nslookup.

Related Tutorials:

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