5.1.6 SNMPv3 traps and informs
When NNMi uses SNMPv3 to communicate with a device, it uses a discovery process to identify the device's engine ID, boot count, and engine time. NNMi then uses this information, together with the configured user and protocol details, to start sending messages to the device.
A device might not have the NNMi information when it needs to send a trap to NNMi, and because a trap is a single-packet transaction, it has no way to obtain the necessary information. In such a case, the device uses its own engine ID, boot count, and engine time in the trap, together with the user name and protocol details. These device details must be the same as those configured for the device in NNMi. You cannot configure multiple SNMPv3 users for a single device in NNMi.
An inform is an acknowledged packet, so this is more like an SNMP request that NNMi would make to the device except, this time, it is the device initiating the first packet and NNMi responding with an acknowledgment. The device, therefore, performs the discovery to NNMi to learn NNMi's engine ID, boot count, and engine time. The user name and protocol configuration that the device uses must match what is configured in the NNMi trap forwarding configuration; this is, in effect, NNMi's SNMPv3 agent configuration.