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terminal to monitor the system operation status. However information outputted from these channels are of
low traffic capacity and can not be recorded for later view. The other two channels---the log buffer zone and
log host channel are two important channels
SDRAM (Synchronous Dynamic Random Access Memory) and NVRAM (Non Vulnerable Random Access
Memory) is provided inside the switch as two part of the log buffer zone, The two buffer zone record the log
information in a circuit working pattern, namely when log information need to be recorded exceeds the buffer
size, the oldest log information will be erased and replaced by the new log information, information saved in
NVRAM will stay permanently while those in SDRAM will lost when the system restarts or encounter an power
failure. Information in the log buffer zone is critical for monitoring the system operation and detecting
abnormal states.
the NVRAM log buffer may not exist on some switches, which only have the
SDRAM log buffer zone.
It is recommended to use the system log server. By configuring the log host
on the switch, the log can be sent to the log server for future examination.
35.7.1.2 Format and Severity of the Log Information
The log information format is compatible with the BSD syslog protocol, so we can record and analyze the log
by the systlog (system log protect session) on the UNIX/LINUX, as well as syslog similar applications on PC.
The log information is classified into eight classes by severity or emergency procedure. One level per value
and the higher the emergency level the log information has, the smaller its value will be. For example, the
level of critical is 2, and warning is 4, debugging is leveled at 7, so the critical is higher than warnings which no
doubt is high than debugging. The rule applied in filtering the log information by severity level is that: only the
log information with level equal to or higher than the threshold will be outputted. So when the severity
threshold is set to debugging, all information will be outputted and if set to critical, only critical, alerts and
emergencies will be outputted.
Follow table summarized the log information severity level and brief description.
these severity levels are in accordance with the standard UNIX/LINUX syslog.
Table 36-1 Severity of the log information
Severity Value Description
emergencies 0 System is unusable
alerts 1 Action must be taken immediately
critical 2 Critical conditions
errors 3 Error conditions
warnings 4 Warning conditions
notifications 5 Normal but significant condition