Using Network Address Translation (NAT) Dispatcher capability removes the limitation for the backend servers to be on a locally attached network. With the NAT forwarding method, Dispatcher load balances the incoming request to the server. The server returns the response to Dispatcher. The Dispatcher machine then returns the response to the client.
You need three IP addresses for the Dispatcher machine – NFA, cluster, and return address. The return address is a unique address or host name that you configure on the Dispatcher machine. Dispatcher uses the return address as its source address when load balancing the client's request to the server. Using the return address ensures that the server returns the packet to the Dispatcher machine, rather than sending the packet directly to the client (Dispatcher then forwards the IP packet to the client).
You must specify the return address value when you add the server. You cannot modify the return address unless you remove the server and then add it again. The return address cannot be the same as the cluster, server, or NFA address. When you use the NAT forwarding method, you must define a return address for communication between Load Balancer and the backend servers. The number of connections that Load Balancer can keep active with the backend server is limited by the return addresses and the server combination.
In addition, you must configure a client-gateway, which is the router to send the response back to the client. Specify the router address to reach the backend server. If the backend server is in same subnet as the dispatcher machine, then the router IP address must be same as the backend server.