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An additional question is, can I find out what zones example.com is delegating to?

This all assumes I am not an Admin for any of the sites/zones in question -- I'm just on the public internet, these are public-facing servers/zones, etc.

If i know that foo.example.com exists, and it has an SOA record, does that mean that it is being delegated to, by definition? (assuming it's not configured incorrectly)

so if I query a domain for NS records, and they show up, then, by definition, those are the authoritative name servers for that domain?

me@WIN-0G109DMKIEK:~$ dig NS example.com +short b.iana-servers.net. a.iana-servers.net.

Peter Smith
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1 Answers1

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By definition, a delegation means NS records.

So check if foo.example.com has NS records on authoritative nameservers for example.com.

The NS records will show, if there, the authoritative nameservers for the subdomain.

This works the same way at all level of the DNS tree, here showing the delegation from com to example.com:

$ dig NS @$(dig NS com +short | head -1) example.com +noall +auth
example.com.        2d IN NS a.iana-servers.net.
example.com.        2d IN NS b.iana-servers.net.

If i know that foo.example.com exists, and it has an SOA record, does that mean that it is being delegated to, by definition? (assuming it's not configured incorrectly)

The SOA in the child is technically also a proof of delegation, normally. To be 100% correct you need more than that to check the delegation point or cut zone case, at the parent, and if it has NS records.

Patrick Mevzek
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  • so if I query a domain for NS records, and they show up, then, by definition, those are the authoritative name servers for that domain? `me@WIN-0G109DMKIEK:~$ dig NS example.com +short b.iana-servers.net. a.iana-servers.net.` – Peter Smith Mar 30 '22 at 19:46
  • You need to ask the authoritative servers where you think the delegation happens, so you need the `@` option, see my example. But the `NS` records are designing who are the authoritative nameservers for that delegation, yes. – Patrick Mevzek Mar 30 '22 at 20:16