Extreme Networks EPICenter Guide Manual page 57

If you define an alarm for a CPU Utilization Rising Threshold event, an alarm will be generated each
time the sample value meets the following conditions:
— When the sample value becomes greater than or equal to the Rising Threshold for the first time
(including the initial sample) after the alarm is enabled.
— The first time the sample value becomes greater than or equal to the Rising Threshold, after
having become less than or equal to the Falling Threshold (80% of the Rising threshold).
If you define an alarm for CPU Utilization Falling Threshold events, an event will be generated each
time the sample value meets the following conditions:
— The first time the sample value becomes less than or equal to 80% of the Rising Threshold, after
having become greater than or equal to the Rising Threshold.
It is important to understand that, except for the initial occurrence of a Rising Threshold alarm, a CPU
Utilization alarm will be generated only the when the sample value of the variable crosses the target
threshold for the first time after having crossed the other threshold.
The diagram shown in Figure 23 illustrates how CPU Utilization trap events will occur once you have
configured a CPU Utilization rising threshold. The startup condition for a CPU Utilization event is
always predefined to be Rising.
CPU Utilization Event Generation
Figure 23: CPU Utilization event generation
Sampled
CPU
utilization
value
Rising
threshold
Falling
threshold
(90% of
rising)
= alarm event generated
The first CPU Utilization trap occurs at the initial sample value, since the value is above the CPU
Utilization Rising threshold. If the initial value were below the Rising threshold, no event would occur.
The second event occurs at point X, because the sample value has fallen below the falling threshold,
which is defined as 80% of the rising threshold value. The third event occurs at point A because the
sample value is again above the Rising Threshold after having fallen below the Falling threshold. At
point B the value again passes the Rising Threshold, but no alarm is generated because the value has
not yet become less than the Falling threshold. Another Rising threshold alarm cannot occur until after
a Falling threshold event has occurred, which happens at point Y. The next Rising threshold event
happens at point C.
EPICenter Concepts and Solutions Guide
Initial
sample
value
B
A
X
Time (sample intervals)
C
Z
Y
Using the EPICenter Alarm System
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