About SNMP I am taking note about this iteresting Paessler article that well explain some SNMP basics and tool useful to be used with PRTG monitoring tools.
Have a nice reading time:
https://blog.paessler.com/snmp-monitoring-via-oids-mibs
Explore some standard MIB files with a tool that allows you to, like the Paessler MIB Importer (free). Pro tip: If you are a PRTG Network Monitor user, the MIB folder under the installation path of your PRTG instance is a little treasure chest.
Check the capabilities of your own devices. Pro tip: To easily get an overview, you can run an SNMP walk over the main branch OID with a suitable tool, like the Paessler SNMP Tester (free).
