how about this iRule ?

That is a lot of possible evalutions if there aren't any matches or the match for a particular connection is late in the list. You might try combining a few of the checks together to reduce the number of IP checks you're doing.

For example, you could replace this:

 
 if {[IP::addr [LB::server addr] equals 222.35.42.126] and [IP::addr [IP::client_addr] equals 172.16.1.11] } {  
    snatpool snat_crt_test2 
 } elseif {[IP::addr [LB::server addr] equals 221.218.248.155] and [IP::addr [IP::client_addr] equals 172.16.1.11] } {  
    snatpool snat_uni_test2 
 } 
 

with this:

 
 if {[IP::addr [IP::client_addr] equals 172.16.1.11] }{ 
  
    if {[IP::addr [LB::server addr] equals 222.35.42.126] }{  
       snatpool snat_crt_test2  
    } elseif {[IP::addr [LB::server addr] equals 221.218.248.155]} {  
       snatpool snat_uni_test2  
    } 
 } 
 

Aaron