Hi,
in clustering environment Heart beat signal is passing through VIA 'private ip', at the time of configuring clustering we set the 'timeout property' like 30 sec.
in clustering Ping the one server to another server, if it is giving response, it means Heart beat signal is passing.
if u want to change the timeout property, open the clustering properties & set the timeout property.
i hope this will help u.
Regards
Subha