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Example: Configuring Fast Failover on Uplink Module VCPs to Reroute Traffic When an EX4200 Virtual Chassis Switch or Intermember Link Fails

The Virtual Chassis fast failover feature is a hardware-assisted failover mechanism that automatically reroutes traffic and reduces traffic loss in the event of a link or switch failure. If a link between two members fails, traffic flow between those members must be rerouted quickly so that there is minimal traffic loss.

Fast failover is enabled by default on all dedicated EX4200 Virtual Chassis ports (VCPs).

This example describes how to configure fast failover on uplink module VCPs in an EX4200 Virtual Chassis configuration:

Requirements

This example uses the following hardware and software components:

  • Junos OS Release 9.3 or later for EX Series switches

  • Six EX4200-24T switches

  • Four SFP uplink modules

Before you begin configuring fast failover, be sure you have:

  1. Mounted the switches. See Mounting an EX4200 Switch.

  2. Cabled the switches in a multiple-ring topology to create the Virtual Chassis configuration. See Connecting a Virtual Chassis Cable to an EX4200 Switch.

Overview and Topology

In a Virtual Chassis configuration, fast failover automatically reroutes traffic and reduces traffic loss in the event of a link failure or a member switch failure. By default, fast failover is enabled on all dedicated VCPs. If you configure uplink module ports as VCPs, you must manually configure fast failover on these ports.

For fast failover to be effective, the Virtual Chassis members must be configured in a ring topology. The ring topology can be formed by using either dedicated VCPs or user-configured uplink module VCPs. Fast failover is supported only in a ring topology that uses identical port types, for example, either a topology that uses all dedicated VCPs or one that uses all uplink module VCPs. Fast failover is not supported in a ring topology that includes both dedicated VCPs and uplink module VCPs. Fast failover is supported, however, in a Virtual Chassis configuration that consists of multiple rings.

This example shows how to enable fast failover on uplink module VCPs.

Figure 1 shows an example of a multiple-ring topology.

Figure 1: Traffic Redirected by Fast Failover After VCP Link Failures in a Topology with Multiple RingsTraffic Redirected by Fast Failover After VCP Link Failures in a Topology with Multiple Rings

Topology

The topology for this example consists of six switches:

  • Six EX4200-24T switches, four of which have an SFP uplink module installed (switches 1, 3, 4, and 6)

Configuration

To configure the fast failover feature on uplink module VCPs:

CLI Quick Configuration

To configure fast failover on all SFP uplink module VCPs, copy the following command and paste it into the terminal window on switch 1:

Procedure

Step-by-Step Procedure

To configure fast failover on SFP uplink module VCPs:

  1. Enable fast failover on all SFP uplink module VCPs in the Virtual Chassis configuration:

    Note:

    We recommend that you use the commit synchronize command to save any configuration changes that you make to a multimember Virtual Chassis.

Results

Check the results of the configuration:

Verification

To confirm that fast failover is enabled on SFP uplink module VCPs in the Virtual Chassis configuration, perform this task:

Verifying That Fast Failover Is Enabled

Purpose

Verify that fast failover has been enabled in a Virtual Chassis configuration.

Action

Issue the show virtual-chassis fast-failover command.

user@switch1> show virtual-chassis fast-failover

Meaning

Fast failover is enabled on all dedicated VCPs and SFP uplink module VCPs in the Virtual Chassis configuration.