Older agents from Zabbix 1.x and previous versions of Zabbix 2.x can still be used with Zabbix 2.4. It does not require any configuration changes on agent side.
However, to take full advantage of new and improved items, improved performance and reduced memory usage, use the latest 2.4 agent.
Only Zabbix 2.4 proxies may be used with Zabbix server. Zabbix 1.6, 1.8, 2.0 and 2.2 proxies are not supported with Zabbix 2.4 server.
Zabbix 2.4 proxies may only be used with Zabbix 2.4 server. They will not work with 2.2 or older Zabbix server.
XML files, exported with 1.8, 2.0 and 2.2 are supported for import in Zabbix 2.4.