Alarms - 3Com LANPLEX 2500 EXTENDEDPLEX®2500 EXTENDED User Manual

13-6 C 13: R M (RMON) T
HAPTER EMOTE ONITORING ECHNOLOGY

Alarms

The LANplex system supports the following syntax for alarms: counters,
gauges, integers and timeticks. These mechanisms report information about
the network to the network administrator. Counters, for example, hold and
update the number of occurrences of a particular event through a port,
module, or switch on the network. Alarms monitor the counters and report
instances of when counters exceed their set threshold.
Counters are useful when you compare their values at specific time intervals
to determine rates of change. The time intervals can be short or long,
depending on what you measure. Occasionally, reading counters can give
you misleading results.
Counters are not infinite, which makes rate comparisons an efficient way to
use them. When counters reach a predetermined limit, they return to 0 (roll
over). A single low counter value might accurately represent a condition on
the network. It might simply indicate that a roll over has occurred.
When you disable a port, the application might not update some of the
statistics counters associated with it.
An alarm calculates the difference in counter values over a set time interval
and remembers the high and low values. When the value of a counter
exceeds a preset threshold, the alarm reports this occurrence.
You can assign alarms with Transcend Enterprise Manager or any other
SNMP network management application to monitor any counter, gauge,
time tick, or integer. Consult the documentation for your management
application for details on setting up alarms.