Monitoring a Device with System Logging
You can use other techniques to remotely manage the Junos OS. Gaining access to the device is essential for remote management, and it allows you to issue diagnostic commands to monitor the health and state of the device. However, monitoring even a single box in real time using interactive commands is impossible. For example, to monitor a router — and by extension, your network — you must be able to generate router messages that you can either act on or use for historical data, without having to be actively on the router.
The Junos OS software supports extensive system logging capabilities, as well as tracing functionality, which makes watching over your network easier.
The Junos OS software generates system messages (known as syslog messages) when system events occur. A system event can be anything from a user logging on to the device, to a particular command being issued, to a process on the device failing and restarting. As we mention in Chapter 6, these syslog messages are constantly being generated and are either saved or processed by the device, providing you with the real-time and historical data you need to remotely monitor your network.
Now, take a look at these syslog messages in more detail.
Digging into syslog messages
The most important aspect of logging is understanding what and when something is logged. Events across the entire system, covering both hardware and software conditions, are included in the Junos OS software syslog ...