10-4
Catalyst 2950 Desktop Switch Software Configuration Guide
78-11380-03
Chapter 10 Configuring the Switch Ports
Configuring Flooding Controls
To disable flow control, use the flowcontrol receive off and flowcontrol send off interface configuration
commands.
Configuring Flooding Controls
You can use these flooding techniques to block the forwarding of unnecessary flooded traffic.
Enabling Storm Control
A packet storm occurs when a large number of broadcast, unicast, or multicast packets are received on
a port. Forwarding these packets can cause the network to slow down or to time out. Storm control is
configured for the switch as a whole but operates on a per-port basis. By default, storm control is
disabled.
Storm control uses rising and falling thresholds to block and then restore the forwarding of broadcast,
unicast, or multicast packets. You can also set the switch to shut down the port when the rising threshold
is reached.
Storm control uses a bandwidth-based method to measure traffic activity. The thresholds are expressed
as a percentage of the total available bandwidth that can be used by the broadcast, multicast, or unicast
traffic.
The rising threshold is the percentage of total available bandwidth associated with multicast, broadcast,
or unicast traffic before forwarding is blocked. The falling threshold is the percentage of total available
bandwidth below which the switch resumes normal forwarding. In general, the higher the level, the less
effective the protection against broadcast storms.
Beginning in privileged EXEC mode, follow these steps to enable storm control:
Step 4
end Return to privileged EXEC mode.
Step 5
show interfaces interface-id Verify the interface flow control settings.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface Enter interface configuration mode, and enter the port to configure.
Step 3
storm-control {broadcast | multicast |
unicast} level level [level-low]
Configure broadcast, multicast, or unicast storm control.
Specify the rising threshold level for either broadcast, multicast, or
unicast traffic. The storm control action occurs when traffic
utilization reaches this level.
(Optional) Specify the falling threshold level. The normal
transmission restarts (if the action is filtering) when traffic drops
below this level.
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