#> set tcp active=on

Once this is done, tcp will see how long a connection has been idle (no traffic at all). This value is controlled by the 'idle' setting. The default value for this is 2 hours.

#> set tcp keepalive_idle=hr:min:sec

Once a connection has been idle for the specified time, tcp will try to communicate with the other end, by sending it probes. The number of probes is controlled by the 'probe_cnt' setting. If a response to a probe is not received, within the 'interval' time, another probe is sent. Once number of probes has been sent without any response, the connection is timed out.