nslookup

By Joshua Erdman
Digital Foundation, inc.

If you have read our DNS primer, you already know that when computers communicate, they do not care about the hostname, all communication occurs via numerical addresses.  This is where DNS servers and name resolution comes in play.

You may not notice it, but name resolution is happening all the time on the back-end of your PC.  You type in www.google.com in your web browser, but for it to work properly, your PC must resolve an IP address.  So at least one DNS server must be specified in your network TCP/IP configurations.  You can see what TCP/IP configurations you currently have by running ipconfig:

ipconfig /all

If you ever find the need to manually resolve a domain name, you use this nslookup tool.  Typically you would do this if you were changing where your website was hosted and wanted to verify DNS settings.

To run nslookup, just type this command in a command prompt or in the run window.  Immediately you can type in a hostname and get a response.

When you first start using nslookup, this tool queries your primary DNS server.  But if you wanted to test a different DNS server you must use the server command:

server ns1.isp.com

Finally, you can also change the type of records to resolve.  If you wanted to get a list of handled SMTP servers for a particular domain you would type:

nslookup
set type=MX
domain.com.

CLUE:  Notice the extra period after the domain name. This prevents your computer from appending its local domain name.

References:

Microsoft Knowledge Base - 200525

Article last reviewed: 11/13/2006

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