Many times on RHEL, haproxy is not reliable it gives an errors while connecting to apache backend, at that time it logs the following errors into /var/log/messages
kernel: ip_conntrack: table full, dropping packet
this is related to ip_conntrack kernel module.
If found this error message into /var/log/messages need to apply following steps
Advanced Policy Firewall (APF) is an iptables(netfilter) based firewall system designed around the essential needs of today’s Internet deployed servers and the unique needs of custom deployed Linux installations. The configuration of APF is designed to be very informative and present the user with an easy to follow process, from top to bottom of the configuration file. The management of APF on a day-to-day basis is conducted from the command line with the ‘apf’ command, which includes detailed usage information and all the features one would expect from a current and forward thinking firewall solution. APF is developed and maintained by R-fx Networks: http://www.rfxnetworks.com/apf.php
