Essential SNMP, 2nd Edition

Chapter 9. Traps

Traps provide a way for an agent to send a monitoring station asynchronous notification about conditions that the monitor should know about. The traps that an agent can generate are defined by the MIBs it supports; the number of traps can range from zero to hundreds. To see what traps are defined in any MIB file, search for the term TRAP-TYPE (SMIv1) or NOTIFICATION-TYPE (SMIv2) in the MIB file. This search will quickly get you a list of possible traps.

Of course, just having asynchronous traps arrive at your NMS isn't terribly useful. You can configure the NMS's response to different traps; the response can be anything from discarding the trap to running a script that sends a message to your pager (or even takes some drastic action, such as shutting down your power supplies). In this chapter, we'll show you how to handle incoming traps using OpenView and other tools such as Perl. Then we'll discuss how to read and configure different aspects of trap events. Finally, we'll show you how to define your own traps to report special conditions of particular interest for your network.

Understanding Traps

Before discussing the tools for receiving and generating traps, it's worth reviewing what a trap is. Traps were introduced in Chapter 2. A trap is basically an asynchronous notification sent from an SNMP agent to a network management station. Like everything else in SNMP, traps are sent using UDP (port 162) and are therefore unreliable. This means that the sender cannot ...