Zabbix agents from previous Zabbix versions are compatible with Zabbix 3.0. However, you may need to review the configuration of older agents as some parameters have changed, for example, parameters related to logging for versions before 3.0.
To take full advantage of new and improved items, improved performance and reduced memory usage, use the latest 3.0 agent.
Note that Zabbix agent newer than 3.0 cannot be used with Zabbix server 3.0.
Both Zabbix 3.0 proxies and Zabbix 3.0 server are supported to work only with Zabbix 3.0 server and Zabbix 3.0 proxies respectively.
XML files, exported with 1.8, 2.0, 2.2 and 2.4 are supported for import in Zabbix 3.0.
In Zabbix 1.8 XML export format, trigger dependencies are stored by name only. If there are several triggers with the same name (for example, having different severities and expressions) that have a dependency defined between them, it is not possible to import them. Such dependencies must be manually removed from the XML file and re-added after import.