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• Each host in the cluster pings other (simple and fragmented package)
• Hosts use a DNS server
• Hosts are synchronized with NTP server (it's necessary for the shared storage)

Composition

An odd number of hosts is recommended. A vote is taken in a quorum for the high avaibility.

RSTP protocol

Rapid Spanning Tree Protocol is a protocol in the link layer. It provides a loop-free network (more details here).