While digging through the Linux iptables firewall documentation I stumbled upon the clusterip extension. In short this extension of the firewall allows you to setup a number of servers on the same IP and MAC address working as a load balancing cluster. The difference with normal load balancing clusters is that no dedicated hardware load balancer is necessary to route the packets to one of the servers. The servers themselves decide which traffic to respond to. To do this the clusterip module in the firewall of each of the servers decides if it will respond to incomming traffic based on the source IP and/or the source Port number.
This seems to be a very cheap way to implement load balancing. No external hardware is needed, only a software configuration.
Has anyone used clusterip load balancing in practice? It would be good to hear some experiences about quality of balancing, etc.