Why is sshd logging the internal IP and not the external one?

Question

linux

stands ubuntu 12.04.1
in the file /var/log/auth.log I observe the entry:

Sep 19 23:05:55 qwerty-desktop sshd[16851]: Accepted password for [user_name] from 10.82.14.37 port 57837 ssh2

question: why is the local IP fixed? The connection was made remotely. The user sits at home behind NAT. As I understand it, just the address of the computer in its LAN is fixed

Answer 1

You're probably peering with his home network.
It's exactly the same with me :) Sometimes it's useful, you don't have to pay for the Internet at home, you can sit through your proxy ...

Answer 2

Make a simple .php on a typewriter with text like:
echo "IP: ".$_SERVER["REMOTE_ADDR"];
and see what it produces when you open it in a browser from that machine. If the address is 10.*, then it's not about SSH, but, as they said above, about direct routing. Well, as an option, you can ping the client's address from this server - if it is definitely NAT'ed - pings will not work.