How to select a server based on client ip ?

[wsq003]

Hi,

If we have 5 servers within a back-end, how can we specify some request to 
certain server based on client ip?

For example:

backend
        server s01
        server s02
        server s03
        server s04
        server s05

How can we make all requests comes from 217.192.7.* goes to server s01 ? 

Thanks.