A managed device sends unsolicited trap messages to notify a network management system (NMS) that an urgent and significant event has occurred on the managed device. For example, the managed device restarts. Figure 1 shows the process of transmitting a trap message.
If the trap triggering conditions defined for the agent's module are met, the agent sends a trap message to notify the NMS that a significant event has occurred. Network administrators can promptly handle the event.
The NMS uses port 162 to receive trap messages from the agent. The trap messages are carried over the User Datagram Protocol (UDP). After the NMS receives trap messages, it does not need to acknowledge the messages.