The syntax of the ping_group directive is simple:
ping_group group-name ip-address ...
Each IP address listed in a ping_group directive is considered to be related, and connectivity to any one node is considered to be connectivity to the group.
A ping group is considered by Heartbeat to be a single cluster node (group-name). The ability to communicate with any of the group members means that the group-name member is reachable. This is useful when (for example) two different routers may be used to contact the internet, depending on which is up, or when finding an appropriate reliable single ping node is difficult.