Traffic Patterns; How To Configure Storm Control; Configuring Storm Control And Threshold Levels - Cisco Catalyst 2960-X Security Configuration Manual

Configuring Port-Based Traffic Control

Traffic Patterns

This example shows broadcast traffic patterns on an interface over a given period of time.
Figure 29: Broadcast Storm Control Example
Broadcast traffic being forwarded exceeded the configured threshold between time intervals T1 and T2 and
between T4 and T5. When the amount of specified traffic exceeds the threshold, all traffic of that kind is
dropped for the next time period. Therefore, broadcast traffic is blocked during the intervals following T2
and T5. At the next time interval (for example, T3), if broadcast traffic does not exceed the threshold, it is
again forwarded.
The combination of the storm-control suppression level and the 1-second time interval controls the way the
storm control algorithm works. A higher threshold allows more packets to pass through. A threshold value
of 100 percent means that no limit is placed on the traffic. A value of 0.0 means that all broadcast, multicast,
or unicast traffic on that port is blocked.
Because packets do not arrive at uniform intervals, the 1-second time interval during which traffic activity
Note
is measured can affect the behavior of storm control.
You use the storm-control interface configuration commands to set the threshold value for each traffic type.

How to Configure Storm Control

Configuring Storm Control and Threshold Levels

You configure storm control on a port and enter the threshold level that you want to be used for a particular
type of traffic.
However, because of hardware limitations and the way in which packets of different sizes are counted, threshold
percentages are approximations. Depending on the sizes of the packets making up the incoming traffic, the
actual enforced threshold might differ from the configured level by several percentage points.
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Catalyst 2960-X Switch Security Configuration Guide, Cisco IOS Release 15.0(2)EX
How to Configure Storm Control
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