SYSLOGs
SYSLOG or system logging is one of many interesting concepts
in Cisco world. Log messages monitoring and audit is one of the main parts of a
network engineer life. Log messages are displayed in real time on the route,
once we make some changes in the network, or if any issue happens to our
network devices. We can also send these log messages from the router to a
centralized NMS for monitoring in a Network Operations Center. IOS can log messages to :
- Console
- Monitor (VTY, AUX) usually enabled via terminal monitor command in global config mode.
- Buffer
- Trap (SYSLOG) to send logs to an NMS
One important thing to understand is the concept of logging
levels. Logging levels simply specify the type of log messages we want to send
to our desired logging buffer/terminal/server. Different logging levels can be set via logging console command:
Let understand severity level concept:
Severity level 3 means 0, 1 , 2, 3 ( severity level 0/1/2/3 enabled), and the router will send
all corresponding severity level log messages to our desired destinations.
If we don’t want to mention the severity level # , we can
specifity the name of the logging severity, for which we want the router to
send all updates, for example if we want to send all Critical Condition logs,
we can enable it via the following command :
R1(config)#logging console critical
The severity level command comes in handy, when we want to
enable different types of logging in one go.
In the second part of this article, i will discuss the practical implementation of SysLog in GNS3.
