when i add new members to pool (unknown enabled node address does not have service checking enabled)

That message is just telling you that you don't have a monitor enabled on that pool. The ltm is unaware of the status of the pool member. Objects that have squares are unmonitored, circles are monitored and up, diamonds are monitored and in a failed status. As a quick test, add an icmp monitor to your pool, you should see your pool member become circles; green if enabled, black if disabled.

 

 

Hope this helps.