SNMP traps work in opposite ways to get and set requests. That is, the agent sends a message, as a UDP packet, to the SNMP manager when a problem occurs. For example, a link down or system crash message can be sent out to the manager so that administrators are alerted instantly. Traps differ across versions of the SNMP protocols. For SNMPv1, they are called traps, and are messages that do not require any confirmation by the manager. For SNMPv2, they are called informs and require the manager to acknowledge that it has received the inform message.

In order to receive traps or informs, the SNMP software needs to accept incoming connections on UDP port 162, which is the standard port for sending and receiving SNMP trap/inform packets. In some SNMP management software, trap notifications are handled within separate applications, while in others, they are integrated into an entire SNMP manager back-end.

For a Net-SNMP trap, the daemon is a part of the SNMP daemons, but is a separate...