20.1.5 Trap

(1) Trap overview

SNMP Agents have an event notification, called a trap (Trap), which is primarily fault information and logging information. Traps are used to report important events asynchronously to an SNMP manager from an SNMP agent. The SNMP manager can detect changes to the switch status by receiving traps. Based on such notification, the SNMP manager can extract the MIBs on switches to obtain more detailed information.

Note, however, that the SNMP manager cannot verify whether a trap has arrived from a switch because traps use UDP. Accordingly, some traps might not arrive at the SNMP manager due to network congestion. The following figure shows an example of a trap.

Figure 20-23: Trap example

(2) Trap-format (SNMPv1)

A trap frame contains the IP address of a switch, and information about what has occurred in the switch and when it occurred. The following figure shows the trap format (SNMPv1).

Figure 20-24: Trap format (SNMPv1)

(3) Trap-format (SNMPv2C,SNMPv3)

A trap frame contains information about what has occurred in the switch and when it occurred. The following figure shows the trap format (SNMPv2C and SNMPv3).

Figure 20-25: Trap format (SNMPv2C,SNMPv3)