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Catalyst 3750 Switch Software Configuration Guide
78-16180-02
Chapter 24 Configuring Port-Based Traffic Control
Configuring Storm Control
Note Because packets do not arrive at uniform intervals, the 200-millisecond time interval during which traffic
activity is measured can affect the behavior of storm control.
The switch continues to monitor traffic on the port, and when the utilization level is below the threshold
level, the type of traffic that was dropped is forwarded again.
You use the storm-control interface configuration commands to set the threshold value for each traffic
type.
Note Although visible in the command-line interface (CLI) online help, the switchport broadcast,
switchport multicast, and switchport unicast interface configuration commands for setting
suppression levels are not available. These commands are obsolete, replaced by the storm-control
interface configuration commands.
Default Storm Control Configuration
By default, unicast, broadcast, and multicast storm control is disabled on the switch interfaces; that is,
the suppression level is 100 percent.
Enabling Storm Control
You enable storm control on an interface and enter the percentage of total available bandwidth that you
want to be used by a particular type of traffic; entering 100 percent allows all 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.
Note Storm control is supported only on physical interfaces; it is not supported on EtherChannel port channels
or physical interfaces that are members of port channels even though the command is available in the
CLI. If a physical interface with storm control configured joins an EtherChannel, the storm control
configuration for the physical interface is removed from the running configuration.
Beginning in privileged EXEC mode, follow these steps to enable a particular type of storm control:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and enter the type and number
of the physical interface to configure.
Step 3
storm-control broadcast level level [.level] Specify the broadcast traffic suppression level for an interface as a
percentage of total bandwidth. The level can be from 1 to 100; the
optional fraction of a level can be from 0 to 99. A threshold value
of 100 percent means that no limit is placed on broadcast traffic. A
value of 0.0 means that all broadcast traffic on that port is blocked.
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