wget -q -O – http://www.atomicorp.com/installers/atomic | sh
yum install mod_rpaf

vi /etc/httpd/conf.d/mod_rpaf.conf
LoadModule rpaf_module modules/mod_rpaf.so

RPAF_Enable On
RPAF_ProxyIPs 127.0.0.1 your_proxy_server_ip
RPAF_Header X-Forwarded-For
RPAF_SetHostName On
RPAF_SetHTTPS On
RPAF_SetPort On