Questions regarding "cluster-zone" check

It looks like “cluster-zone” check is the best way to monitor Icinga agent availability and generate a problem if agent is down (Monitor Icinga agent's availability - #2 by stevie-sy). I have a question regarding “cluster-zone” check and would appreciate some details about it. From the documentation:
cluster-zone - this built-in check provides the possibility to check for connectivity between zones.

What does “check for connectivity between zones” mean? Does Icinga check port availability? Does it wait for a specific response from the agent? In other words: does “cluster-zone” check equal to a simple “5665 agent’s port” check? Or it is more “smart”?

Hello @Heilig!

As the doc you mentioned says: that command checks “whether the master zone is connected and processing messages with the child zone”.

Best,
AK

I would say “… target zone is currently connected or not”.

It still doesn’t answer my initial questions regarding this check. :frowning: Does anyone know how it works?