When Apache is behind a load balancer, frequently the load balancer IP will be recorded in the access/error logs instead of the actual client IP. This module modifies the inbound requests to show the actual client IP instead of the load balancer IP. This does not work for every load balancer.
This guide assumes you built Apache from source using my guide.
1. Download the mod_rpaf source from http://stderr.net/apache/rpaf/download/
2. Untar the source tarball
3. As root run
/usr/local/apache/bin/apxs -ci mod_rpaf-2.0.c
4. The module will be installed correctly in /usr/local/apache/modules
5. Create a new folder called custom under /usr/local/apache/conf
6. Create a file called httpd-modrpaf.conf in /usr/local/apache/conf/custom with the following content
LoadModule rpaf_module modules/mod_rpaf-2.0.so
7. Replace 188.8.131.52 with the IP address of the load balancer.
8. Update the RPAFheader with the correct value if your load balancer does not pass “X-Forwarded-For”.
9. Make sure you include the new “custom” folder in your main httpd.conf
10. Restart Apache web server