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Example: Configuring Storm Control

Using storm control can prevent problems caused by broadcast storms. You can configure storm control to rate-limit broadcast traffic and unknown unicast traffic at a specified level and to drop packets when the specified traffic level is exceeded, which prevents packets from proliferating and degrading service or causing a security issue. You can also configure the switch to shut down or temporarily disable an interface when the storm control limit is exceeded.

This example shows how to configure storm control:

Requirements

This example uses the following hardware and software components:

A switch
Junos OS Release 11.1 or later

Overview and Topology

A traffic storm occurs when broadcast packets prompt receiving devices to broadcast packets in response. This prompts further responses, creating a snowball effect. The switch is flooded with packets, and the resulting unnecessary traffic leads to poor performance or even a complete loss of service by some clients. Storm control causes a device to monitor traffic levels and take a specified action when a specified traffic level—called the storm control level—is exceeded, thus preventing packets from proliferating and degrading service.

Storm control monitors the incoming broadcast traffic and unknown unicast traffic and compares it with the level that you specify. If broadcast traffic and unknown unicast traffic exceed the specified level, the switch drops packets for the controlled traffic types. Storm control is disabled by default. If you enable storm control, the default level is 80 percent of the available bandwidth for ingress traffic on all interfaces. You can change the storm control level by configuring it as a specific bandwidth value.

This example shows how to configure the storm control level on interface xe-0/0/0 by setting the level to a traffic rate of 5000000 Kbps, based on the total of the combined broadcast and unknown unicast streams. If broadcast traffic and unknown unicast traffic exceed these levels, the switch drops packets for the controlled traffic types.

Configuration

Step-by-Step Procedure

To configure storm control for a 10-Gigabit Ethernet interface to the equivalent of 50 percent of the available bandwidth:

Specify the level of allowed broadcast traffic and unknown unicast traffic on a specific interface:
[edit ethernet-switching-options] user@switch# set storm-control interface xe-0/0/0 bandwidth 5000000

Results

Display the results of the configuration:

[edit ethernet-switching-options]user@switch# show storm-control

interface xe-0/0/0 {bandwidth 5000000;}