Example: Configuring Storm Control to Prevent Network Outages on EX Series Switches

Storm control enables you to prevent network outages caused by broadcast storms on the LAN. You can configure storm control on the EX Series switch to rate limit broadcast traffic, multicast traffic, and unknown unicast traffic at a specified level and to drop packets when the specified traffic level is exceeded, thus preventing packets from proliferating and degrading the LAN.

Note: Storm control does not apply to multicast traffic by default on EX2200, EX3200, EX3300, EX4200, and EX6200 switches.

This example shows how to configure storm control on a single EX Series switch:

Requirements

• One EX Series switch
• Junos OS Release 9.5 or later for EX Series switches

Overview and Topology

A storm is generated when messages are broadcast on a network and each message prompts a receiving node to respond by broadcasting its own messages on the network. This, in turn, prompts further responses, creating a snowball effect and resulting in a broadcast storm that can cause network outages.

You can use storm control to prevent broadcast storms by specifying the amount, also known as the storm control level, of broadcast traffic, multicast traffic, and unknown unicast traffic to be allowed on an interface. You specify the storm control level as the traffic rate in kilobits per second of the combined applicable traffic streams.

On EX2200, EX3200, EX3300, and EX4200 switches—The factory default configuration enables storm control on all interfaces at 80 percent of the combined unknown unicast, unregistered multicast, and broadcast traffic. On EX4500 and EX8200 switches—The factory default configuration enables storm control on all interfaces at 80 percent of the combined broadcast, multicast, and unknown unicast streams. On EX6200 switches—The factory default configuration enables storm control on all interfaces at 80 percent of the combined unknown unicast and broadcast traffic. Storm-control can be disabled for each type of traffic individually.

Storm control monitors the level of applicable incoming traffic and compares it with the level that you specify. If the combined level of the applicable traffic exceeds the specified level, the switch drops packets for the controlled traffic types. As an alternative to having the switch drop packets, you can configure it to shut down interfaces or temporarily disable interfaces (see the action-shutdown statement or the port-error-disable statement) when the storm control level is exceeded.

The topology used in this example consists of one switch with 24 ports. The switch is connected to various network devices. This example shows how to configure the storm control level on interface ge-0/0/0 by setting the level to a traffic rate of 15,000 Kbps, based on the traffic rate of the combined applicable traffic streams. If the combined traffic exceeds this level, the switch drops packets for the controlled traffic types to prevent a network outage.

Configuration

CLI Quick Configuration

To quickly configure storm control based on the traffic rate in kilobits per second of the combined traffic streams, copy the following command and paste it into the switch terminal window:

Step-by-Step Procedure

1. Specify the traffic rate in kilobits per second of the combined traffic streams on a specific interface:
   [edit ethernet-switching-options]
user@switch# set storm-control interface ge-0/0/0 bandwidth 15000

Results

Display the results of the configuration: