Heartbeat is a daemon that provides cluster infrastructure (communication and membership) services to its clients. This allow clients to know appearance or disappearance of peer processes on other machines and to easily exchange message with them.(Heartbeat - Linux-HA)

Heartbeat clusters work only one on same network so if we setup different cluster (different authkeys) on same network it will show up as an error in log file. We can still setup more than one cluster in same network by setting different communication port for heartbeat.

The following example show configuration file for two different clusters in same network. ####host configuration 192.168.123.1 host1.cluster1 192.168.123.2 host2.cluster1 192.168.123.3 host1.cluster2 192.168.123.4 host2.cluster2 ####first cluster #####/etc/ha.d/ha.cf debugfile /var/log/ha-debug logfile /var/log/ha-log logfacility local0 keepalive 2 deadtime 20 udpport 694 udp eth0 bcast eth0 node host1.cluster1 host2.cluster1 auto_failback on debug 1 ####second cluster #####/etc/ha.d/ha.cf debugfile /var/log/ha-debug logfile /var/log/ha-log logfacility local0 keepalive 2 deadtime 20 udpport 695 udp eth0 bcast eth0 node host1.cluster2 host2.cluster2 auto_failback on debug 1 Reference: http://www.gossamer-threads.com/lists/linuxha/users/57074