3Com 2500 manual generates an alarm only under the following conditions

13-8 CHAPTER 13: REMOTE MONITORING (RMON) TECHNOLOGY

RMON Hysteresis The RMON hysteresis mechanism provides a way to prevent small Mechanism fluctuations in counter values from causing alarms. This mechanism

generates an alarm only under the following conditions:

■The counter value exceeds the high threshold after previously exceeding the low threshold. (An alarm does not occur if the value has not fallen below the low threshold before rising above the high threshold.)

■The counter value exceeds the low threshold after previously exceeding the high threshold. (An alarm does not occur if the value has not risen above the high threshold before falling below the low threshold.

In Figure 13-3, for example, an alarm occurs the first time the counter exceeds the high threshold , but not at the second time. At the first instance, the counter is rising from the low threshold, while in the second instance, it is not.