If you are running a reverse proxy, like Varnish or Squid, in front of your webserver, then it will report the proxy’s IP address instead of the visitors’. This is a problem if you, for example, allow anonymous users to vote with VotingAPI.
You configure the settings.php file, which is most likely located in the sites/default directory. It already contains all the documentation you need but I prefer to keep my settings.php lean and strip that out. Instead I add the following lines to the bottom of my file:
$conf['reverse_proxy'] = TRUE; $conf['reverse_proxy_addresses'] = array('188.8.131.52');
If you have more than one webfront, simply add its IP to the array. This tells Drupal which reverse proxies you trust and helps protect against users spoofing their IP with a fake X-Forwarded-For header.