Simple Network Monitoring Protocol (SNMP) may not be as simple as the name suggests; it's a de facto standard for many appliances and applications. It's not just ubiquitous—it's often the only sensible way in which one can extract the monitoring information from a network switch, disk array enclosure, UPS battery, and so on.

The basic architecture layout for SNMP monitoring is actually straightforward. Every monitored host or appliance runs an SNMP agent. This agent can be queried by any probe (whether it's just a command-line program to do manual queries or a monitoring server such as Zabbix) and will send back information on any metric it has made available or even change certain predefined settings on the host itself as a response to a set command from the probe. Furthermore, the agent is not just a passive entity that responds to the get and set commands but can also send warnings and alarms as SNMP traps to a predefined host when some specific conditions arise...