# Troubleshoot heartbeat and synchronization errors

There are several possible causes and solutions when you receive alerts regarding the heartbeat connection between the nodes in a cluster.

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## Steps

1. Apply normal network troubleshooting (for example, check speed and duplex settings and cabling) to make sure that the heartbeat link works reliably.
2. Use a primary and a backup heartbeat connection using separate physical links.
   It is highly recommended that you use a dedicated link for both the primary and the backup heartbeat. The heartbeat and state synchronization are time-critical communications. The heartbeat connection is critical to the operation of a cluster. The cluster cannot work without a reliable heartbeat connection.
3. If you have installed two or more clusters with a single LAN as a shared heartbeat, and you see extra log entries about unauthenticated heartbeat messages, change the Heartbeat IP and the Synchronization IP so that each cluster uses a different address.