snat irule not working as expected

Give this a shot.

when CLIENT_ACCEPTED { 
  if {[class match [IP::remote_addr] equals app_servers]}{ 
    if {(not [IP::addr [IP::local_addr] equals 10.0.0.0/16]) or (not [IP::addr [IP::local_addr] equals 10.128.0.0/24])}{ 
      snat 10.0.255.1 } 
    } 
  }