Send message before connection close on idle timeout

I know this thread is very (very) old. I have some questions about behavior of the TCP idle timeout.

If the TCP connection is idle beyond the setting (default 300 seconds), the connection is dropped from the F5, right?

When this is dropped is there any iRule triggered? In Particular is the CLIENT_CLOSED triggered?

I'm trying to understand if connections are being dropped due to being idle and I've set a couple iRule monitors. Interesting as sometimes the counter goes just above the 300 and then the CLIENT_CLOSED seems to have triggered.. yet other times it does not and it continues to clock.

thanks.