[dns-operations] service showing (last) resolver's IP ?

[Frank Habicht]

Hi,

I don't understand why I don't find / remember / know ....

There MUST be somewhere one (or more) service(s) that can tell me from
what source IP the resolver (or the last one in a chain) queries the
authorities. I guess answering a query for TXT.

I can't find it. Maybe a personal Google-foo outage. (I tried)
Can anyone help?

Thanks,
Frank