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Example: Using Storm Control to Prevent Network Outages

Using storm control can prevent problems caused by broadcast storms. You can configure storm control to rate-limit broadcast traffic, multicast traffic (on some devices), 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. You can also have the device shut down or temporarily disable an interface when the storm control limit is exceeded.

A traffic storm occurs when broadcast packets prompt receiving devices to broadcast packets in response. This prompts further responses, creating a knock-on effect that results in a broadcast storm that floods the device with packets, and causing poor performance or even a complete loss of service by some clients

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 storm control to shut down interfaces or temporarily disable interfaces (see the action-shutdown statement or the recovery-timeout statement) when the storm control level is exceeded.

  • On ELS systems, storm control is enabled by default on all interfaces at a level of 80 percent of the available bandwidth.

  • On non-ELS systems, storm control is disabled by default on all interfaces. If you enable storm control, the default level is 80 percent of the available bandwidth.

Note:

If you configure storm control on an aggregated Ethernet interface, the storm-control level is applies to each member interface individually. For example, if the aggregated interface has two members and you configure a storm-control level of 20 kbps, Junos will not detect a storm if one or both of the member interfaces receives traffic at 15 kbps because in neither of these cases does an individual member receive traffic at a rate greater than the configured storm-control level. In this example, Junos detects a storm only if at least one member interface receives traffic at greater than 20 Kbps.

  • 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.

Example: Using Storm Control to Prevent Network Outages (ELS)

This example uses a Junos OS release that supports the Enhanced Layer 2 Software (ELS) configuration style.

Requirements

This example uses the following hardware and software components:

  • One QFX Series switch running Junos OS with ELS

  • Junos OS Release 13.2 or later

Overview and Topology

The topology used in this example consists of one switch connected to various network devices. 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 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

Procedure

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

To configure storm control:

  1. Configure a storm control profile, sc-profile, and specify the traffic rate in kilobits per second of the combined traffic streams:

  2. Bind the storm control profile, sc, to a logical interface:

Results

Display the results of the configuration:

Example: Using Storm Control to Prevent Network Outages (non-ELS)

This example uses a Junos OS release that does not support the Enhanced Layer 2 Software (ELS) configuration style on a single EX Series switch. If your switch runs software that supports ELS, see Example: Using Storm Control to Prevent Network Outages (ELS). For information about how to configure the switch to shut down or temporarily disable an interface when the storm control limit is exceeded, see Example: Using Storm Control to Prevent Network Outages

Requirements

This example uses the following hardware and software components:

  • A switch

  • Junos OS Release 11.1 or later

Overview and Topology

Topology

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

Procedure

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:

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.

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 5000000 Kbps.

Example: Using Storm Control to Prevent Network (MX Routers)

This example shows how to configure storm control on an pair of MX Series routers running Junos OS with Enhanced Layer 2 Software (ELS).

Requirements

This example uses the following hardware and software components:

  • Two MX Series routers

  • Junos OS Release 14.1 or later with ELS

  • A traffic generator that can send broadcast and unknown unicast traffic at a rate that exceeds 100 Kbps

  • A second host

Overview and Topology

On MX Series routers, storm control is not enabled by default.

Topology

This example shows how to configure the storm control level on interface ge-0/0/1 by setting the level to a traffic rate of 100 Kbps. The topology used consists of two routers that could be connected to various network devices. If the combined traffic exceeds this level, the router drops packets for the controlled traffic types to prevent a network outage. (Starting in Junos OS release 17.4R1 for MX Series routers, you can also configure storm control on logical systems.)

Figure 9: Example Storm Control to Prevent Network OutagesExample Storm Control to Prevent Network Outages

Configuration

This example excludes multicast traffic from the storm traffic. Many protocols use multicast for control traffic, and for that reason network administrators and operators may want to keep multicast working to avoid obstructing protocol operation.

Procedure

CLI Quick Configuration

To quickly configure storm control based on the traffic rate in Kbps of the combined traffic streams, copy the following commands and paste them into the terminal window. The configurations of routers R1 and R2 are exactly the same:

Step-by-Step Procedure

To configure storm control:

  1. Configure a storm control profile, sc, and specify the traffic rate in Kbps of the combined traffic streams. Exclude multicast traffic from the storm control profile.

  2. Bind the storm control profile sc to a logical interface. Remember to do this for both interfaces between the routers.

  3. Configure interface ge-0/0/1 (the interface between routers). Do this for both interfaces between the routers.

  4. Configure interface ge-0/0/0 (the interface from host to router). Remember to do this for both interfaces between the routers.

  5. Set the bridge domain domain type and VLAN ID.

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
  1. From Host A to Host B, use a traffic generator to send broadcast and unknown unicast traffic at a rate that exceeds 100 Kbps.

  2. Verify on device R1’s ge-0/0/0 interface that traffic is entering at a rate that exceeds 100 Kbps.

    The Input bytes field shows the ingress traffic rate in bytes per second (bps). The input rate is within the storm control limit of 100 Kbps.

  3. Verify that interface ge-0/0/1 on R1 is down (Admin down).

    Because the link remains up, control traffic continues to flow.

  4. After the timeout period of 120 seconds (2 minutes), verify that the interface comes back up.

Release History Table
Release
Description
17.4R1
(Starting in Junos OS release 17.4R1 for MX Series routers, you can also configure storm control on logical systems.)