The keepalive directive sets the interval between heartbeat packets. It is specified according to the HeartbeatTimeSyntax[1].
Two sample keepalive directives are shown below:
keepalive 100ms
keepalive 2 # 2 seconds
| [1] | http://www.linux-ha.org/HeartbeatTimeSyntax |
This information provided courtesy of the Linux-HA project at http://linux-ha.org/