http://www.haproxy.org/

# yum install haproxy

# apt-get install haproxy

appsession PHPSESSID len 64 timeout 30m request-learn

cookie HAPROXY insert nocache indirect preserve httponly secure maxidle 30m maxlife 8h
server web01 192.168.100.101:80 check cookie web01
server web02 192.168.100.102:80 check cookie web02