Monitoring objects and services
When it comes to Networked device monitoring with Nagios one should know, what they want to monitor
below is a simple table which defines Monitoring categories.
If a System is reachable (Ping) or a server is available (HTTP tcp port 80)
In this category, you monitor Temperature, Humidity, Camera (Office, Machine room), etc
HTTP tcp port is responding doesn't mean that the server is also delivering pages, hence you should also do content checks
CPU, Memory, Disk or Network usage are some examples
Nagios flexibility allows one to integrate different methods to do active and passiv checks