User`s guide

Alarms and Traps

Setting Alarms

5967–9446 437

The threshold’s sample type works in conjunction with the value you

specify to determine when the threshold is crossed:

● Choose delta to set an alarm based on the change in value for the mon-

itored object over a speciﬁed period of time. For example, you could set

an alarm that triggers when more than 5,000 packets are seen in a ten-

second interval.

● Choose units per second to set an alarm based on the value of the

monitored object over a time interval. For example, you could set an

alarm that triggers when the rate of packets exceeds 500 packets per

second for a period of ten seconds.

When conﬁguring the threshold, NetMetrix converts the units per sec-

ond value that you specify to a delta alarm. For example, a threshold of

500 packets per second for ten seconds is converted to a delta alarm of

5,000 packets for ten seconds; this conversion is reﬂected in the alarm

log, as discussed on page 452.

● Choose absolute to set an alarm based on the absolute value for the

monitored object. For example, you could set an alarm that triggers

when the total packet count seen by the agent exceeds 5,000,000.

With an absolute threshold, the “seconds” ﬁeld determines how often

the agent checks whether the object has crossed the threshold.

An absolute threshold can be useful when the monitored object is a

Protocol Analyzer packet capture. You can conﬁgure the packet capture

with a particular ﬁlter, then trigger an alarm when the speciﬁed num-

ber of packets is captured. (Alarms and packet captures are discussed

on page 444.)

● Choose percent when conﬁguring an alarm based on Utilization %.

For example, you could set an alarm that triggers when utilization

reaches 50% for ten seconds.

When conﬁguring the threshold, NetMetrix converts the percent value

that you specify to an absolute alarm expressed as hundreths of a per-

cent (because that’s how SNMP expresses percentages). For example, a

threshold of 15% utilization is converted to an absolute alarm of 1500;

this conversion is reﬂected in the alarm log, as discussed on page 452.