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S9700 Core Routing Switch
Configuration Guide - SPU
destination IP address of service request packets, namely, the IP address of a real server, and
forwards them to real servers through routes. In MAC mode, when allocating service requests,
the SPU replaces the destination MAC address of the service request packets with the MAC
address of a real server without changing the destination IP address. Then the SPU forwards the
packets to the real server.
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Issue 01 (2012-03-15)
Server load balancing in DNAT mode
The networking of DNAT mode is flexible. The backup servers can be located in different
physical positions and on different LANs.
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
characteristics 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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Figure 6-2
Switch
VIP
shows the typical networking.
6 Load Balancing Configuration
shows the typical networking.
ServerA
IPA
ServerB
IPB
ServerC
IPC
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