User's Manual

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Users Manual of CS-6306R
43.2.3.4 Providing TCP Load Balance
Another fashion of using NAT is unrelated to the Internet address. Your organization may have multiple hosts
to communicate with a frequently used host. In this case, you can use NAT technology to create a virtual host
in the inside network, helping the load balance among actual hosts. You need to replace the destination
address of the access list with the address in the cycle address pool. The distribution is complete in a cycle
when a new connection from the outside to the inside is opened. The non-TCP communication need not be
translated (unless other translations are effective). The following figure illustrates the attribute.
Figure 43-4 NAT TCP load balance
When translating the cycle address, the routing switch performs the following steps:
(1) The user of host B (9.6.7.3) sends instructions for connecting the virtual host 1.1.1.127 in the inside
network.
(2) The routing switch receives the connection request and creates a new translation item to allocate the
next host 1.1.1.1 for the inside local IP address.
(3) The routing switch replaces the destination address with the selected actual address of the host, and
forwards the message.
(4) Host 1.1.1.1 receives the message and makes response.
(5) The routing switch receives the message and uses the inside local addresses and their port numbers,
the outside address and port number as keywords to check the NAT table. The routing switch then
transfers the source address to the address of the virtual host, and forwards the message.
(6) Next connection request invokes the routing switch to distribute address 1.1.1.2 for the inside local
address. To configure the destination address transfer, run the following commands in global
configuration mode. These commands permit to map one virtual host to multiple real hosts. Each TCP
session with the virtual host will be transferred to the sessions with different real hosts.