This trap is sent when an alarm gets generated at an external alarm input that is configured for critical severity. The source is a 4 or 5 tuple specifying the type, location, shelf, slot ID, and optionally the port number of the source of the event. In the case of the power supply, fan and ext. alarm input, the shelf number is set to 0. Each event has an unique event ID. It also has a preset event severity. The severity or trap type may be: critical, major, minor, or normal. For a given event severity, there is a corresponding system status, not necessarily the same as the event severity. For each reported trap, the IP address of the CP responsible for sending this trap is also included in the trap structure.