SNMP trap processing

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Trap PDUs are defined by RFC 1157 to have the format shown in this table.

Table 1. Trap PDU format
enterprise agent-address generic-trap specific-trap time-stamp variable-bindings
Object ID Integer Integer Integer TimeTicks VarBindList

The fields are used as follows:

Item Description
enterprise The object identifier assigned to the vendor implementing the agent. This is the value of the sysObjectID variable, and it is unique for each implementer of an SNMP agent. The value assigned to this implementation of the agent is 1.3.6.1.4.1.2.3.1.2.1.1.3, or risc6000snmpd.3.
agent-address IP address of the object generating the trap.
generic-trap Integer, as follows:
0
coldStart
1
warmStart
2
linkDown
3
linkUp
4
authenticationFailure
5
egpNeighborLoss
6
enterpriseSpecific
specific-trap Unused, reserved for future development.
time-stamp Elapsed time, in hundredths of a second, from the last reinitialization of the agent to the event generating the trap.
variable-bindings Extra information, dependent on generic-trap type.

The following generic-trap values indicate that certain system events have been detected:

Item Description
coldStart The agent is reinitializing. Configuration data or MIB variable values, or both, might have changed. Restart the measurement epochs.
warmStart The agent is reinitializing but configuration data or MIB variable values have not changed. In this implementation of the SNMP agent, a warmStart trap is generated when the /etc/snmpd.conf file is reread. The configuration information in the /etc/snmpd.conf file is for agent configuration that has no side effects on SNMP manager databases. Measurement epochs should not be restarted.
linkDown The agent has detected that a known communications interface has been disabled.
linkUp The agent has detected that a known communications interface has been enabled.
authenticationFailure A message was received that could not be authenticated.
egpNeighborLoss An Exterior Gateway Protocol (EGP) neighbor was lost. This value is only generated when the agent is running on a host that runs the gated daemon using EGP.
enterpriseSpecific Not implemented; reserved for future use.

The linkDown and linkUp traps contain a single instance ID/value pair in the variable-bindings list. The instance ID identifies the ifIndex of the adapter that was disabled or enabled, and the value is the ifIndex value. The trap for egpNeighborLoss also contains a binding consisting of the instance ID and value of egpNeighAddr for the lost neighbor.