Submitting passive checks in response to SNMP traps

In this recipe, we'll learn how to configure Nagios Core to process Simple Network Management Protocol (SNMP) traps, information sent by monitored network devices to a central monitoring server.

Because SNMP traps often contain useful or urgent information about how a host is working, processing them in at least some way can be very helpful, particularly for firmware network devices that can't use send_nsca to submit a passive check result in a standard form, as explained in the Submitting passive checks from a remote host with NSCA recipe.

As an example, most SNMP-capable hosts can be configured to send SNMP traps when one of their network interfaces changes state, perhaps due to a pulled network cable. These are known as linkUp and linkDown traps. Monitoring this particular kind of trap is especially useful for devices with a large number of interfaces, such as switches or routers.

Keeping track of these events in Nagios Core is valuable...