Difference between a Trap and an Inform
A Trap, applicable to SNMPv1/2/3, is an unacknowledgeable communication of some condition.
An Inform, applicable to SNMPv3, is an acknowledgeable Trap.
A Notification is a generic term covering both Traps and Informs.
With SNMPv3, Traps and Informs are dropped at the destination if a SecurityName/Username and EngineID are not configured there to match what is used at the source. The EngineID value of the source application is used for Traps (so must be configured on the destination device), and the EngineID value of the destination application is used for Informs (so must be configured on the source device).
For details, see the following documentation:
- RFC3410, "Introduction and Applicability Statements for Internet-Standard Management Framework"
- RFC3411, "An Architecture for Describing Simple Network Management Protocol (SNMP) Management Frameworks"
- RFC3412, "Message Processing and Dispatching for the Simple Network Management Protocol (SNMP)"
- RFC3413, "Simple Network Management Protocol (SNMP) Applications"
- RFC3414, "User-based Security Model (USM) for version 3 of the Simple Network Management Protocol (SNMPv3)"
- RFC3415, "View-based Access Control Model (VACM) for the Simple Network Management Protocol (SNMP)"