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Example: Configuring a Preprovisioned Mixed EX4200 and EX4500 Virtual Chassis

You can deterministically control both the role and the member ID assigned to each member switch in a mixed EX4200 and EX4500 Virtual Chassis configuration by creating a preprovisioned configuration.


When you use a preprovisioned configuration, you cannot modify the primary-role priority or member ID of member switches through the user interfaces.

This example describes how to configure a mixed EX4200 and EX4500 Virtual Chassis using a preprovisioned configuration file:


This example uses the following hardware and software components:

  • Junos OS Release 11.1 or later for EX Series switches


    You must use Junos OS Release 11.4 or later if you are including three or more EX4500 switches in an EX4500 Virtual Chassis or a mixed EX4200 and EX4500 Virtual Chassis.

  • Two EX4500 switches, each with a Virtual Chassis module

  • Two EX4200 switches

Before you create the preprovisioned configuration of the Virtual Chassis and interconnect the members across the wiring closets, be sure you have:

  1. Made a list of the serial numbers of all the switches to be connected as a Virtual Chassis configuration.

  2. Noted the desired role (routing-engine or line-card) for each switch.

  3. Ensured that the same version of Junos OS is running on all current or prospective member switches.

Overview and Topology

A preprovisioned configuration file links the serial number of each switch in the Virtual Chassis configuration to a specified member ID and role. The serial number must be specified in the configuration file for the member to be recognized as part of the Virtual Chassis configuration.

You designate additional members, which are not eligible for election as primary, as having the line-card role in the preprovisioned configuration file.

In this example, two EX4500 switches (SWA-0 and SWA-1) are in the routing-engine role and interconnected to two EX4200 switches (SWA-2 and SWA-3) in the linecard role using dedicated Virtual Chassis ports (VCPs).

SWA-0 will be the primary of the Virtual Chassis configuration. This example shows how to create a preprovisioned configuration file on SWA-0 for all member switches that will be interconnected in the Virtual Chassis configuration. The preprovisioned configuration file includes member IDs for all member switches.

SWA-1 will be the backup of the Virtual Chassis configuration. Both SWA-0 and SWA-1 are specified in the preprovisioned configuration file with the role of routing-engine. All other members are specified with the role of line-card.

After all member switches are interconnected with their dedicated VCPs, you can simply power on the switches after saving and committing the preprovisioned configuration file. The primary detects the connection of the members through the dedicated VCPs and applies the parameters specified in the preprovisioned configuration file.


You can use interfaces on SFP, SFP+, and XFP uplink modules as VCPs. When an uplink module port or SFP network port is set as a VCP, it cannot be used for any other purpose.

We will bring up the Virtual Chassis configuration in stages. First, we power on SWA-0 (without powering on any other switches) and create the preprovisioned configuration file. Then we power on the remaining switches.


The topology for this example consists of:

  • Two EX4500 switches (SWA-0 and SWA-1)

  • Two EX4200 switches (SWA-2 and SWA-3)

Table 1 shows the Virtual Chassis configuration settings for a preprovisioned Virtual Chassis.

Table 1: Components of a Preprovisioned Mixed EX4200 and EX4500 Virtual Chassis
Switch Serial number Member ID Role Hardware





EX4500 switch with a Virtual Chassis module





EX4500 switch with a Virtual Chassis module





EX4200 switch





EX4200 switch


To configure the Virtual Chassis across multiple wiring closets using a preprovisioned configuration, perform this task:


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


Step-by-Step Procedure

To create a preprovisioned configuration for the Virtual Chassis:

  1. Power on the EX4500 switch (SWA-0)in the primary role..

  2. Set the PIC mode to Virtual Chassis mode on SWA-0:

  3. Set the Virtual Chassis mode to mixed:

  4. Reboot the switch.

  5. After the switch reboots, specify the preprovisioned configuration mode:

  6. Specify all members to be included in the Virtual Chassis configuration, listing each switch's serial number with the desired member ID and the desired role:

  7. Power on the remaining switches.

  8. Set the Virtual Chassis mode to mixed on the remaining switches:

  9. Reboot the switches.

  10. When the reboot completes, physically cable the switches together using the dedicated VCPs.


Display the results of the configuration on SWA-0:


To confirm that the configuration is working properly, perform these tasks:

Verifying the Member IDs and Roles of the Member Switches


Verify that the member IDs and roles are all set as expected.


Display the members of the Virtual Chassis configuration:


The output shows that all members listed in the preprovisioned configuration file are connected to the Virtual Chassis configuration. It confirms that SWA-0 (member 0) is functioning as the primary of the Virtual Chassis configuration. The other switch configured with the routing-engine role (SWA-1) is functioning as the backup. The Neighbor List displays the interconnections of the member VCPs.


To troubleshoot a preprovisioned Virtual Chassis configuration that is interconnected across wiring closets, perform these tasks:

Troubleshooting Nonoperational VCPs


A VCP shows a status of down.


Check the cable to make sure that it is properly and securely connected to the ports.