SNMP trap (SNMP-trap) is a special signal sent by the device with SNMP. Typically, these signals are sent by devices to notify the network administrator about the occurrence of some critical events. For example, some types of uninterruptible power supply (UPS) can send SNMP trap in the case when the equipment switches to battery power-UPS. As a rule, such situations require the immediate intervention of staff and, therefore, the device itself sends a signal via SNMP. As another example, some models of the sensor opening of the premises and of the equipment racks. These sensors can be connected to the local network and be able to send SNMP trap in critical situations, such as unauthorized opening of a door, for example.