System Log (mainly called Syslog) is very important in Juniper devices as well as on any other brand. You have to think of syslog like in case someone broke his leg while doing skiing, then he goes to the doctor and the doctor sends him to the scan or MRI. Once the result of the scan is given, the doctor can know the severity of the injury and whether the patient needs a surgery or not to be recovered.
Same on juniper, whenever something goes wrong on the juniper router, the router will give us a syslog message saying what has happened, so you can check it you as an administrator and if it is something so serious you can take an action.
So, in another term, the syslog is used to record what is happening in the system such as interface up/down, users login/logout, and so on…
All log files of the Juniper router are stored in /var/log/ directory. The messages files are found in /var/log/messages.
Please note that each syslog message belongs to a facility, which is a group of messages that have similar activity – for example all security messages belong to the same facility responsible for security, all command line message belong to the same facility responsible for the command line, and so on.
Just be aware that the messages have severity levels from 0 to 7 where 0 is the least severity and 7 and the highest severity. This is handy because we don’t care too much for low severity such as a user login/logout to the Juniper router, we need to be notified by the highest one so we can take an immediate action.
This is all what I wanted to explain in this lesson, see you in the upcoming one 😊