[anh79]

Can you give some example? I have tried some registrars and if you don't provide some NS information, the default NS information is used.

I have a tool in the past https://gist.github.com/icy/b30893cecc8ec657317ba93831b0fd4a... it works fine as I experience. The tool has option `--all` to check by using both google/open dns. E.g,

  $ whoisvn google-is-good.com --all
      opendns.org:   google-is-good.com   available
        googledns:   google-is-good.com   available
  
  $ whoisvn google-is-bad.com --all
      opendns.org:    google-is-bad.com   available
        googledns:    google-is-bad.com   available

[teddyh]

Look at, for example, "nmu360.se". It is registered, but has no name servers configured.

[marcosdumay]

Whois says it has no name server (what a weird format that of .se), but digg finds an A record with 92.242.140.20 (what seems to be a register IP).

[teddyh]

Let me guess: Your ISP is injecting fake DNS responses.

[feelin_googley]

   echo nmu360.se|exec nc -vvn 91.226.37.83 43

[anh79]

Very good example. Thanks a lot.