SNAT

So, on the VS don't have an option for Source Address Translation and then an irule like this might do the trick:

when CLIENT_ACCEPTED { 

     Check if client is in same subnet as pool members 
    if {[IP::addr [IP::client_addr] equals x.x.x.x/x]}{ 

        Use snat automap
       snat automap
    } 
 } 

Change x.x.x.x/x to the relevant subnet and any source IP on this range will use SNAT automap. If not then no SNATing will be done.

Hope this helps,

N