passive vs active agents... or both?

[Heinrich]

Dear Zabbix community,
I am wondering what are the different use cases of the agents. When should I use active, when passive agents? I know how they work in general - active sends on its own, passive is waiting for a request from server - but is there a difference within the agents? Are there any items I could only use with active or passive? Couldnt I just say "ok, use active and send whenever there is new data and create a firewallrule for 10051 both ways"? I do not differentiate between active and passive within the installation, so how do I choose between both which one I want to use? Is it just communication between the template and the agent conf file?
And does the green availability icon only show up by using passive agents?

Sorry, I coudnt find any "when to use which" comparison in the helpfiles.
Could you please give me a hint?
Thanks in advance
Heinrich

[cyber]

There are some items, that work only with active agent, like log(), logrt(). Agentless checks are performed by server/proxy (http agent, SNMP/ssh/telnet etc)
When using passive agent, it puts a load on server/proxy to poll those values. Using active one leaves agent to deal with stuff and server/proxy can just listen for incoming data. With a lot of hosts it can make a difference.

The point of FW rules is also to be considered... depending on your security demands, it can be one way or two ways... and not "10051 both ways", agent listens on 10050, so its "server/proxy -> host:10050 and host->server/proxy:10051". If your security guys say "no incoming connections" then you need to use passive .. Rules out log items usage. Or put a passive proxy among those active agents and poll data from proxy regularly. Nothing will be sent to server, only if server polls from proxy... Useful in DMZ-s for example, where you might not want FW holes towards inside...

From agent installation point of view, you have a difference ... either you define Server and ServerActive or just Server.. https://www.zabbix.com/documentation.../zabbix_agentd

Green icon will light up with only active items also, if version is at least 6.2... https://www.zabbix.com/documentation...l=Availability
Older agents will not do that, even if it is possible to use them.

[Heinrich]

Hello cyber, thank you for your detailed explanation. I allways thought the ports are for 10050 passive and 10051 active agents. --> still a lot to learn for me ... Regarding the green icon, I use an older Version of zabbix right now (5.0.28) but plan to update to the new LTS (6.0). Thanks a lot for your help!
Best regards
Heinrich