H3C Technologies H3C SecPath F1000-E - Manual (Page 868)

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Figure 2 Work flow of NAT-mode Layer 4 server load balancing
The following describes the work flow of NAT-mode Layer 4 server load balancing.
1. The host sends a request, with the host IP being the source IP and VSIP being the destination IP.
2. Upon receiving the request, the LB device uses an algorithm to calculate to which server it
distributes the request.
3. The LB device uses the Destination NAT (DNAT) technology to distribute the request, with the host
IP being the source IP and Server IP being the destination IP.
4. The server receives and processes the request and then sends a response, with the server IP being
the source IP, and the host IP being the destination IP.
5. The LB device receives the response, translates the source IP, and forwards the response, with VSIP
being the source IP, and the host IP being the destination IP.
The above work flow indicates that NAT is used in server load balancing, and NAT-mode server load
balancing is thus called.