Server's IP being reported as users' IP

WP: 4.4.1, 4.3.2

I found that what WordPress is reporting my IP (and of other users) is actually the IP of server on which it’s hosted. This is quite problematic – in case of brute force attacks, I end up blocking server IP and making the site inaccessible.

This is not an isolated issue, I found it earlier on a site running WP 4.3.2 and thought that attacker might have somehow used Server’s IP, but just now I found a spam comment on a 4.4.1 site with my server’s IP and moments later found the site inaccessible. After removing IP from blacklist, when I went to whitelist it, I found that even my current reported IP is actually server’s IP.