My IP over DNS
A resolver query that reports the client address it sees.
“What is my IP?” is often a web-page task. DNS services from OpenDNS and Google also made it available through a resolver query.
The answer can differ from the address a device expects because it reports the address visible to the resolver. That makes it a useful diagnostic as well as a neat DNS trick.
Primary source: https://www.cambus.net/interesting-dns-hacks/