User guide

5-30 ExtremeWare EPICenter Software Installation and User Guide
The EPICenter Alarm System
Figure 5-13: RMON Alarm event generation
Because the initial sample value of the variable is greater than the value of the Rising
threshold, an RMON rising threshold trap is generated. A second trap occurs at the next
sample interval (point A) because the sample variable value is now less than the Falling
Threshold.At point Bthe value again passes the Rising Threshold, and another trap event
is generated. However, no trap occurs at point C, even though the value of the variable
again becomes greater than the Rising Threshold, because the value has not yet become
less than the Falling threshold. Another Rising threshold trap event cannot occur until
after a Falling threshold alarm has occurred, as happens at point D.
Notethat in order to have any ofthesetrap events cause an alarm in theEPICenter Alarm
System,you needtodefineanalarmthatrespondstoaRMON RisingThresholdorRMON
Falling Threshold event.
• If you define an alarm based on the RMON Rising Threshold event, then EPICenter
alarms will occur at the initial sample, and at points B and E. Because the alarm is
defined torespond toRMONRisingThreshold events, thefalling thresholdtrap events
that occur at points A and D do not trigger an EPICenter alarm.
• IfyoualsodefineanalarmbasedonanRMONFallingThresholdevent, then EPICenter
alarms would also be generated at points A and D.
XM_022
Rising
threshold
Falling
threshold
Initial
sample
value
Time (sample intervals)
Sampled
variable
value
A
B
C
= alarm event generated
D
E