Loadbalancer.org glossary
Layer 4 DR mode
What is the Layer 4 DR mode load balancing method?
This mode offers the best performance and requires limited physical Real Server changes. The load balanced application must be able to bind to the Real Server’s own IP address and the VIP at the same time.
This mode requires the “ARP Problem” to be solved. Layer 4 DR mode is transparent i.e. the Real Servers will see the source IP address of the client.