Extreme Networks EPICenter 5.0, Manual

Page: 55 / 208

Using the EPICenter Alarm System
EPICenter Concepts and Solutions Guide 55
The following diagram, shown in Figure 22, shows how alarms are generated for an RMON rule using
Delta values, where the startup alarm condition is set to “Rising” or “RisingOrFalling.”
RMON Alarm Event Generation
Figure 22: 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.
Example 3: Create an RMON Rule to Detect Excessive Port Utilization
Example: Create an RMON rule that will cause an RMON Rising Trap when port utilization on a set of
critical ports, members of the port group “CriticalPorts,” exceeds 15%.
1 Bring up the New Configuration dialog. On the Configuration page, do the following:
a Type a name for the rule in the Name field (for example, “WAN Link 15%”).
If you have already created an alarm definition that will use this rule, make sure the name
matches the name you entered in the alarm definition.
XM_022
Rising
threshold
Falling
threshold
Initial
sample
value
Time (sample intervals)
Sampled
variable
value
A
B
C
= alarm event generated
D
E