20.1.6 Inform

(1) Overview of Inform

SNMP agent has a function called inform (Inform) event notification (mainly fault information and logging information). Inform is a function that sends an inform request and notifies SNMP manager of critical events from SNMP agent. The SNMP manager can detect changes to the switch status by receiving inform requests. Based on such notification, the SNMP manager can extract the MIBs on switches to obtain more detailed information.

Informs are supported only for SNMPv2C. In addition, informs must be supported by the SNMP manager.

An inform is an event notification function using UDP like a trap, but it requests a response from the SNMP manager. Therefore, you can verify whether an inform request has arrived by checking for a response. This allows you to deal with a problem such as network congestion by resending an inform. The following figure shows an example of an inform.

Figure 20-26: Example of an inform

(2) Inform request format

An inform request frame contains information about what has occurred in the switch and when it occurred. The following figure shows the inform request format.

Figure 20-27: Inform request format