Huawei quidway s7700 Configuration Manual page 237

Quidway S7700 Smart Routing Switch
Configuration Guide - SPU
l
Issue 01 (2011-07-15)
Figure 6-2 Typical networking of server load balancing in DNAT mode
Host
IP
Network
As shown in Figure 6-2, multiple servers provide services through the virtual IP address.
Switch functions as the load balancing device and is responsible for allocating user requests
to multiple servers. The process of server load balancing in DNAT mode is as follows:
1. Users send requests to the virtual IP address.
2. Switch classifies packets at Layer 3 or Layer 7 according to service traffic features
and selects a load balancing group. Then Switch selects a real server according to the
configured load balancing algorithm, weights, priorities, inbound/outbound
bandwidth limits, connection quantity limits, and connection rate limits, and uses NAT
to replace the destination IP address of the request packets with the IP address of the
real server. Switch sends the request packets to the real server.
3. The real server sends the response packets to Switch through a route. Before returning
the response packets to users, Switch changes the source IP address of the response
packets to the virtual IP address. Then Switch sends the response packets to users.
The load balancing process is complete.
Server load balancing in DMAC mode
In DMAC mode, only request packets of users pass through the load balancing device. The
response packets of a server does not pass through the load balancing device. This reduces
the burden of the load balancing device and prevents the load balancing device being the
bottleneck. Figure 6-3
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Switch
VIP
shows the typical networking.
6 Load Balancing Configuration
ServerA
IPA
ServerB
IPB
ServerC
IPC
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