Eventually I've removed all references to real_ip, added those lines: proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; and defined a new log format for my apache server with %{X-Forwarded-For}i

And it works like a charm.

I don't know if changing the log format is the cleanest solution, but for my simple setup mod_rpaf is a bit overkill and the log change just works (kiss).