irule based on source ip not working..plz help!

Can you try this and reply back with the specific error messages you see when trying to save the iRule?

when CLIENT_ACCEPTED {
   if { [class match [IP::client_addr] equals ip_subnets_class] }{
    pool VDI_TEST_pool
  } else {
    pool VDI_TEST_POOL_INT
  }
}