Extreme Networks EPICenter 4.1, Руководство по установке программного обеспечения

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Threshold Configuration
EPICenter Software Installation and User Guide 145
NOTE
To configure an alarm using an RMON threshold event, select RMON Rising or RMON Falling as the
Event Type.
The following diagram, shown in Figure 60, shows how alarms are generated for an RMON rule using
Delta values, where the startup alarm condition is set to “Rising” or “RisingOrFalling.”
Figure 60: 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 B the 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.
Note that in order to have any of these trap events cause an alarm in the EPICenter Alarm System, you
need to define an alarm that responds to a RMON Rising Threshold or RMON 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 to respond to RMON
Rising Threshold events, the falling threshold trap events that occur at points A and D do not trigger
an EPICenter alarm.
• If you also define an alarm based on an RMON Falling Threshold event, then EPICenter alarms
would also be generated at points A and D.
For a more detailed discussion of Remote Network Monitoring alarm behavior, refer to a book such as
SNMP, SNMPv2, SNMPv3, and RMON 1 and 2, Third Edition, by William Stallings (Addison-Wesley,
1999).
XM_022
Rising
threshold
Falling
threshold
Initial
sample
value
Time (sample intervals)
Sampled
variable
value
A
B C
= alarm event generated
D
E