Cisco Catalyst 2000 Configuration Handbook page 190

current count of broadcasts within the 1-second interval, and when a threshold is
reached, filters out subsequent broadcast packets.
Because hardware broadcast suppression uses a bandwidth-based method to meas-
ure broadcast activity, the most significant implementation factor is setting the per-
centage of total available bandwidth that can be used by broadcast traffic. Because
packets do not arrive at uniform intervals, the 1-second interval during which broad-
cast activity is measured can affect the behavior of broadcast suppression. The
threshold% specifies the percentage of bandwidth limit that would have to be
reached by broadcast traffic before action would be taken.
Specify action to be taken:
2.
(interface) storm-control {broadcast level high level [lower level]} |
action {shutdown | trap}}
When broadcast suppression occurs, the default action is to suppress or filter the
packets. This means that packets are dropped and do not make it onto the backplane
of the switch. You can, on some of the platforms, configure the switch to take
another action. For the IOS devices, you can change the device from the default
action of trap to the shutdown option. When the port is placed in shutdown mode,
it remains there until an administrator has reenabled the port with the no shutdown
command. Each time the threshold is crossed, the administrator must reenable the
port. For the 2960 broadcast, frames are dropped unless the action has changed to
shutdown. The 2960 default is to filter out the traffic and not to send traps. To
revert to filtering the frames, the administrator must issue the command no port
storm-control broadcast action shutdown. Another option that can be configured
on the 2960 is for the switch to generate an SNMP trap. The action trap is not con-
figurable for the Catalyst 6500 running Supervisor IOS.
Note Because the action trap is not a configuration option for the Catalyst 6500 running
Supervisor IOS 12.2.33SXH, one solution would be to have the Embedded Event Manager
(EEM) to monitor for the syslog, and if it is seen then, the interface could be shut down
and a syslog or trap generated to inform the network admin.
(Optional) Control unicast or multicast:
3.
(interface)storm-control unicast | multicast level level[.level]
In addition to configuring the switch to control broadcast floods, you can also con-
figure a port to drop frames or become disabled when it encounters a large number
of unicast or multicast packets. To configure this option, use the multicast and
unicast keywords in the commands to enable the control of the frames.
Chapter 11: Controlling Traffic and Switch Access 169