Cabletron Systems Lancast Media Converter 7000, User Manual

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Alarm Configuration
4-26 How Rising and Falling Thresholds Work
The top portion of the window contains the device information boxes, as well as
the event index number and the event description; the log itself includes the
following Þelds:
Index This index number is not the eventÕs index, but a separate
index that uniquely identiÞes this occurrence of the
event.
Time Indicates the date and time of each event occurrence.
Description Provides a detailed description of the alarm that
triggered the event: whether it was a rising or falling
alarm, the alarm index number, the alarm variable name
and object identiÞer (OID), the alarmSampleType
(1=absolute value; 2=delta value), the value that
triggered the alarm, the conÞgured threshold that was
crossed, and the event description. Use the scroll bar at
the bottom of the log to view all the information
provided.
Each log will hold only a Þnite number of entries, which is determined by the
resources available on the device; when the log is full, the oldest entries will be
replaced by new ones.
How Rising and Falling Thresholds Work
Rising and falling thresholds are intended to be used in pairs, and can be used to
provide notiÞcation of spikes or drops in a monitored value Ñ either of which can
indicate a network problem. To make the best use of this powerful feature,
however, pairs of thresholds should not be set too far apart, or the alarm
notiÞcation process may be defeated: a built-in hysteresis function designed to
limit the generation of events speciÞes that, once a conÞgured threshold is met or
crossed in one direction, no additional events will be generated until the opposite
threshold is met or crossed. Therefore, if your threshold pair spans a wide range
of values, and network performance is unstable around either threshold, you will
only receive one event in response to what may be several dramatic changes in
value. To monitor both ends of a wide range of values, set up two pairs of
thresholds: one set at the top end of the range, and one at the bottom.
Figure 4-8
illustrates such a conÞguration.