Hello,

On both the CSM and ACE, destination NAT (a.k.a. server nat) is enabled by default in a serverfarm. Source NAT needs to be manually configured on both devices, as it is not a default configuration.

In server load balancing, destination NAT is very common. When clients connect to a VIP on the load balancer, the load balancer will then choose a real server the send the connection to. The destination IP address of the client-to-server traffic will be NAT'd from the virtual IP address (VIP) to the real server's IP address. The server's reply will be sourced with the real server's IP address, initially. The load balancer will again perform NAT to change the source IP address from the real server's IP address back to the VIP address prior to forwarding the response back to the client. This way, the client only knows about the VIP address, and not the real server's IP address.

Best regards,

Sean