Default Storm Control Configuration; Configuring Storm Control And Threshold Levels - Cisco Catalyst 2975 Software Configuration Manual

Chapter 23 Configuring Port-Based Traffic Control
Figure 23-1
Total
number of
broadcast
packets
or bytes
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
Note
activity 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.

Default Storm Control Configuration

By default, unicast, broadcast, and multicast storm control are disabled on the switch interfaces; that is,
the suppression level is 100 percent.

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.
Storm control is supported on physical interfaces. You can also configure storm control on an
Note
EtherChannel. When storm control is configured on an EtherChannel, the storm control settings
propagate to the EtherChannel physical interfaces.
OL-19720-02
Broadcast Storm Control Example
0 T1 T2 T3
Threshold
T4 T5 Time
Catalyst 2975 Switch Software Configuration Guide
Configuring Storm Control
Forwarded traffic
Blocked traffic
23-3