Andrew Pennebaker
https://github.com/mcandre/cheatsheets/blob/master/stun.md
Stun is a protocol for robustly querying network information such as IP addresses, even through NAT and proxies.
Wikipedia: STUN Public STUN server list
$ apt-get install stun
$ brew install stuntman
$ stunclient <stun-server>
Example:
$ stunclient stun.ekiga.net
stunclient stun.ekiga.net
Binding test: success
Local address: 192.168.100.121:56531
Mapped address: 107.48.201.7:56531
In other words, stunclient returns the internal IP address, as well as the external (global) IP address, of the host computer.