nslookup produces a daft error message because it is badly designed.

You've come to this page because you've asked a question similar to the following:

nslookup does not work correctly. When I run it, it displays the error message

*** Can't find server name for address 10.0.0.1: ...
*** Default servers are not available

What am I doing wrong to produce this error ? How can I get rid of it ?

This is the Frequently Given Answer to that question.

(You can find different approaches to this answer on Dan Bernstein's tinydns FAQ page and on FAQTS.)

The simple answer is: You are using nslookup. Don't.

The root cause of this error is not in the DNS servers, either yours or anyone else's. It is in nslookup itself. If someone tells you to make modifications to your DNS servers to "fix" this problem, they are attempting to cure the symptoms, not the disease.

nslookup is a badly designed and highly flawed tool. The daft design flaw that causes this error message is just one of its many flaws.

Stop using nslookup right now. Start using better, less flawed, tools instead. Almost every DNS server software package comes bundled with tools to manually query the DNS for diagnostic purposes. Use the tools that came with the package that you have.