Most network devices and host computers have a variety of triggers already set or programmed into them to generate events. Before you start configuring events, you should understand what is already set up on the devices you are interested in.
Built-in events are reported using a variety of techniques, including the following:
Devices write messages to their console. Some of these messages may be the result of thresholds being crossed, for example,when the temperature of the device exceeds a set point.
Many systems log messages to files. Windows NT has an event log that records system events. Many UNIX systems use the syslog protocol to log system events. Network devices such as routers and switches can record system events ...