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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 an EX Series switch to rate-limit broadcast traffic, multicast traffic, and unknown unicast traffic at a specified level so that the switch drops 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 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 (Kbps) of the combined applicable traffic streams.

Note
  • On EX2200, EX3200, EX3300, and EX4200 switches—Storm control is not enabled for multicast traffic by default. The factory default configuration enables storm control on all interfaces at 80 percent of the available bandwidth used by the combined unknown unicast and broadcast traffic streams.

  • On EX4500 and EX8200 switches—The factory default configuration enables storm control on all interfaces at 80 percent of the available bandwidth used by the combined broadcast, multicast, and unknown unicast traffic streams.

  • On EX6200 switches—Storm control is not enabled for multicast traffic by default. The factory default configuration enables storm control on all interfaces at 80 percent of the available bandwidth used by the combined unknown unicast and broadcast traffic streams. 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 Kbps per second of the combined traffic 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 Kbps 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:

Verification

Verifying That the Storm Control Configuration Is in Effect

Purpose

Confirm that storm control is limiting the rate of traffic on the interface.

Action

Use the show interfaces ge-0/0/0 detail or show interfaces ge-0/0/0 extensive operational mode command to view traffic statistics on the storm controlled interface. The input rate (bps) must not exceed the storm control limit.

user@switch> show interfaces ge-0/0/0 extensive

Meaning

The traffic statistics input bytes field shows the ingress traffic rate at 512 bits per second (bps). This rate is within the storm control limit of 15,000 Kbps.