Icinga2 / Check Host in Network on remote Site

Hello,

I have Icinga2 incl. Icinga Director in use and we have various sites. Now at one site we have a network that is only accessible within the site. However, I would like to take the hosts contained there also under the monitoring.

The question is, what is the easiest way to monitor the hosts? I would probably have to install an agent on a reachable system, which can talk to the Icinga2 master and also has access to the network of the site.

Does anyone have a small HowTo on what I need to do for this?

An Icinga satellite is want you most likely need.
All checks will be performed on the satellite (or on the clients themself if your are using agent based Monitoring)
You only need one connection (usually TCP 5665) between the master and satellite, and you can decide which one initiates the connection. This can be useful if your are using a NAT connection.

More information is available here:
https://icinga.com/docs/icinga-2/latest/doc/06-distributed-monitoring/