The Simple Network Management Protocol is a network protocol for the central monitoring of network components.
In this process, a central SNMP manager queries certain values from the monitored components at regular intervals (polling procedure). For this purpose, agents are installed on the systems concerned, which answer the corresponding queries. For their part, the agents can proactively transmit values to the SNMP manager via SNMP traps, for example in the case of critical temperatures.
Which data points a component provides is defined in the MIB, the management information base of the device. This is a tree-like description of the information provided by the device. The leaves within this tree are the SNMP Object Identifiers (SNMP OIDs). The temperature sensor of an IP thermometer can be assigned one SNMP OID, the humidity sensor another. The SNMP manager can query the corresponding values via the SNMP OIDs.
SNMPv1 and SNMPv2c are still widely used today, but offer hardly any security mechanisms. SNMPv3 offers up-to-date encryption, but also brings with it greater complexity.