The Zabbix proxy first appeared in Zabbix version 1.6, back in 2008. Since then, it has proven to be a very good solution. When the Zabbix proxy first appeared, it supported connecting to the Zabbix server only, similarly to active agent. Zabbix version 1.8.3 introduced a capability of the server to connect to the proxy, and now, active proxies and passive proxies are available. While the Zabbix agent can communicate with the server in both ways at the same time by having active and passive items on the same host, the Zabbix proxy communicates with the server only in one way at a time; the whole proxy is designated as active or passive.

The proxy mode does not change the direction of connections to or from the monitored devices. If using active items through a proxy, the agent will still be the one making the connections, and if using passive items, the agent will be accepting connections. It's just that instead of the server, the agent will now communicate with the proxy.

In both active and passive mode, server-proxy communication requires a single TCP port, to a single address only, to be open. That is much easier to handle on the firewall level than allowing connections to and from all of the monitored devices. There are more benefits that a proxy may provide—but let's discuss those once we have a proxy running.