Technical Documentation

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 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.

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

Requirements

This example uses the following hardware and software components:

  • One EX Series switch
  • JUNOS 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 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 broadcast and unknown unicast streams.

Note: The factory default configuration enables storm control on all interfaces at 80 percent of the combined broadcast and unknown unicast streams.

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. As an alternative to having the switch drop packets, you can configure it to shut down interfaces or temporarily disable interfaces (see theaction-shutdown statement or the port-error-disable statement) when the storm control level is exceeded.

The topology used in this example consists of one EX Series 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 15000 Kbps, based on the traffic rate of the combined broadcast and unknown unicast streams. If broadcast traffic and unknown unicast 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 broadcast and unknown unicast streams, copy the following command and paste it into the switch terminal window:


[edit]
set ethernet-switching-options storm-control interface ge-0/0/0 bandwidth 15000

Step-by-Step Procedure

To configure storm control:

  1. Specify the traffic rate in kilobits per second of the combined broadcast and unknown unicast 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:

[edit ethernet-switching-options]user@switch# show storm-controlinterface ge-0/0/0.0 {bandwidth 15000;}

Published: 2010-08-19

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