This is the documentation page for an unsupported version of Zabbix.
Is this not what you were looking for? Switch to the current version or choose one from the drop-down menu.

7 Data flow

7.1 Child to Master

Each Child Node periodically sends configuration changes, historical data and events to its Master Node.

Data Frequency
Configuration changes Every 120 seconds.
Events Every 10 seconds.
History Every 10 seconds.

Child Node will resend data in case of communication problems.

Trends are calculated locally based on received historical data.

Zabbix does not send operational data across the nodes. For example, item-related information (last check, last value, etc) exists only locally.

Sending of Events and History can be controlled by configuration parameters NodeNoEvents and NodeNoHistory.

7.2 Master to Child

Each Master Node (a node with at least one child) periodically sends configuration changes to Child Nodes either directly or via other Child Nodes directly connected to the Master Node.

Data Frequency
Configuration changes Every 120 seconds.

Zabbix does not send configuration of a Master Node to Childs.

7.3 Firewall settings

Inter-node communications use TCP protocol only.

Data flow Source port Destination port
Child to Master Any 10051

This is default port used by Zabbix trapper process.