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Comment by greyface- | Hacker News Reader

There is one odd case where asking DNS won't work accurately: if a domain is registered but has no nameservers.

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

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

   echo nmu360.se|exec nc -vvn 91.226.37.83 43

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).

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

Very good example. Thanks a lot.

Almost always, you need to provide nameservers when you register a domain. host -t NS example.org should return something, even if the listed nameservers don't exist, don't respond for that domain, or return NXDomain.

Isn't there always an SOA record?

No. If there are no name servers, there isn’t a zone, and if there isn’t a zone, there is no SOA record.

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