7.2. Threshold values and types

Every threshold has a current value, which is displayed by the threshold indicator . The value ranges from 0 - 100%, and the position of the bar in the indicator shows this value. In addition, as the threshold value exceeds predefined levels, the color of the indicator will change. If the threshold value is below the normal level, then the indicator is shown in green. As the threshold value reaches 70%, the threshold becomes marginal, and is shown in yellow. At 90%, the threshold is critical, which is indicated by red.

The value of the threshold is defined by two factors: the trigger, and how long the threshold must have triggered for. For example, for the errors threshold, you might consider that the trigger is 5 errors per second. The duration might be 4 out of the previous 10 minutes. If the number of errors per second was 5 or more, in at least 4 out of the previous 10 minutes, then the threshold value would be 100%. The percent value is a combination of how long the trigger was exceeded for, relative to the configured setting, and how close the parameter being monitored was to the trigger.

To make it easier to find interfaces which have exceeded thresholds, the value of the threshold propagates up from a switch interface to the overall threshold value for the switch, and from there to the overall threshold value for the network as a whole. The maximum threshold value propagates up, so that the overall value for a switch is the largest of the values for each of its interfaces.

Thresholds can be set on six different parameters:

The percent utilization of an interface.
The number of unicast frames per second.
The number of broadcast frames per second.
The number of layer 2 multicasts per second.
The number of errored frames per second.
The number of discarded frames per second.

When viewing the threshold table, you can click with the left mouse button on any threshold indicator to investigate the root cause of the threshold value (see Section 7.4, “Root cause analysis”).

Clicking with the left mouse button on a switch in the threshold table, the table will change to display the thresholds for all interfaces of the selected switch.