These messages are generated by the Syslog Daemon every 20 minutes of inactivity within the Kemp LoadMaster to highlight that the logging daemon is still running on the Loadmaster.
Mar 21 11:24:03 kmplb01 -- MARK -- Mar 21 11:44:04 kmplb01 -- MARK -- Mar 21 12:04:04 kmplb01 -- MARK -- Mar 21 12:24:04 kmplb01 -- MARK --