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Setting an Uplink Port on an EX Series or QFX Series Switch as a Virtual Chassis Port

Use the procedures described in this topic to set up Virtual Chassis ports (VCPs) to connect two switches together in an EX Series or a QFX Series Virtual Chassis.

Switches that can be members of a Virtual Chassis might have:

  • Dedicated VCPs—Ports you can use only as VCPs.

  • Default-configured VCPs—Ports that are already configured into VCPs with the default factory configuration. On some switches these ports can alternatively be converted back into and used as uplink or network ports.

  • Uplink or network ports that are also supported as VCPs—Ports you can configure into VCPs and convert back into uplink or network ports as needed.

If you don’t have or are not using dedicated or default-configured VCPs, you need to convert supported ports into VCPs to interconnect Virtual Chassis members. When a switch has uplink or network ports that can be converted into VCPs, you can use some ports as VCPs and others as network ports or uplinks to other devices in trunk mode. When you set a port as a VCP, you can’t use it for any other purpose.


You don't use the procedures in this topic to set the VCPs on EX4400 switches. EX4400 switches have ports that operate as VCPs by default, and no other ports on the switch can be used as VCPs. If you change the operational mode of the default VCPs to network port mode to use them as network ports instead of as VCPs, to subsequently use the switch in a Virtual Chassis, you must disable network port mode to return those ports to their default VCP mode. To change the default VCPs to network port mode, use the request virtual-chassis mode network-port <reboot> command. To disable network port mode to convert the ports back into VCPs, use the request virtual-chassis mode network-port disable <reboot> command. (When you enable or disable network port mode, you must reboot the switch for the change to take effect.)

You can set ports as VCPs on a standalone switch before interconnecting any links into a Virtual Chassis, or set them after interconnecting one link on the switch into an existing Virtual Chassis. Either way, after the VCP is connected into the Virtual Chassis, the primary switch uses the link to detect the switch and complete the process of adding it as a member.


Most Virtual Chassis also support autoprovisioning, which means that under certain conditions, when you interconnect a member switch into an existing Virtual Chassis, ports that are supported as VCPs will convert automatically into VCPs when you cable the link. This is an easy way to add member switches to a Virtual Chassis without needing to explicitly configure VCPs, but it only works if the ports on both sides of the link are not already configured as VCPs. If you want to use autoprovisioning, you might need to delete VCP settings (whether default-configured or those you previously set explicitly) on either or both sides of the links you are using to interconnect the new member switch. See Automatic Virtual Chassis Port (VCP) Conversion for details.

See Virtual Chassis Port Options for a list of supported VCP ports on each type of switch. For complete details about where a switch has dedicated VCPs, default-configured VCPs, or ports that can be configured as VCPs, and what transceivers and cables are supported to use for VCP connections on that switch, see the hardware documentation for the switch. In general, even if a port is supported as a VCP, you can’t use it as a VCP if it’s channelized.

When to Configure VCPs

You typically configure a port as a Virtual Chassis Port (VCP) for one of the following reasons:

  • You are configuring a Virtual Chassis composed of switches that support Virtual Chassis but do not have default-configured VCPs or dedicated VCPs.

  • You are using default-configured VCPs or dedicated VCPs to interconnect members in a Virtual Chassis, and want to add redundant VCP links between members using additional ports that can be configured into VCPs.

  • You want to interconnect two switches into a Virtual Chassis that have dedicated VCPs but are located in different wiring closets or sites, and the switches are farther apart than the maximum length of a dedicated VCP cable.

  • You previously changed a default-configured VCP to use it as a network or uplink port, and now you want to use it as a VCP again.

We recommend that you have two uplink VCP connections within each wiring closet for redundancy. VCPs automatically bundle into a Link Aggregation Group (LAG) when two or more ports operating at the same speed are configured into VCPs between the same two member switches. See Understanding Virtual Chassis Port Link Aggregation for details.


If you set a port as a VCP to create a redundant link with a dedicated VCP connection on EX4200, EX4500, or EX4550 switches, to avoid traffic looping within the Virtual Chassis, you must reboot the Virtual Chassis after configuring the port conversion and cabling the VCP link. See Troubleshooting an EX Series Virtual Chassis for more information.

Prepare Virtual Chassis Member Switches Before Converting VCPs

Before converting a port into a VCP and interconnecting the switch into a Virtual Chassis:

  1. Verify which ports can be used as VCPs in your particular configuration. See Virtual Chassis Port Options for a summary of the VCP options on switches that support Virtual Chassis, and the hardware documentation for each type of switch for complete details about the ports and installed transceivers that can be used as VCPs.
  2. If you are configuring an uplink module port as a VCP, if needed, install the uplink module in the member switches that you want to interconnect.
  3. Log into the switch that is or will be the primary of the Virtual Chassis.

    Do not power on the other switches at this point.

  4. (EX Series switches only) Run EZSetup on the switch that you are configuring to be the primary member switch. Make sure the hostname and other identification, time zone, and network properties are set up on the primary. See Connecting and Configuring an EX Series Switch (CLI Procedure) for details. The parameters you specify for the primary apply to the entire Virtual Chassis, including all the member switches that you interconnect later.
  5. If you want to configure and manage the Virtual Chassis remotely, specify the VME global management interface. You can configure the VME global management interface when you are setting up the primary or you can do it after completing the other configuration steps for the Virtual Chassis. See Configuring the Virtual Management Ethernet Interface for Global Management of an EX Series Virtual Chassis (CLI Procedure).
  6. Configure primary role of the Virtual Chassis using either a nonprovisioned or preprovisioned configuration. See Configuring Primary Role of a Virtual Chassis for details.

A Virtual Chassis has two Routing Engines, one in the primary role and the other in the backup role. Therefore, we recommend that you always use commit synchronize rather than simply commit to save configuration changes made for a Virtual Chassis. This ensures that the configuration changes are saved in both Routing Engines.

Before you begin to interconnect new Virtual Chassis members across long distances, such as between wiring closets:

  • Prepare the existing Virtual Chassis for interconnecting with a potential member switch that is beyond the reach of a dedicated Virtual Chassis cable by setting at least one uplink VCP on an existing member of the Virtual Chassis.

  • Prepare the potential member switch for interconnecting with the existing Virtual Chassis by setting at least one uplink VCP on the standalone switch.