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Adding a New Switch to an Existing EX2300, EX3400, or EX4300 Virtual Chassis


You can use this procedure to:

  • Add an EX2300 switch to an existing EX2300 Virtual Chassis.


    Starting with Junos OS Release 18.4R1, you can combine any models of EX2300 switches, including EX2300 multigigabit models, into the same EX2300 Virtual Chassis using this procedure. In releases prior to Junos OS Release 18.4R1, EX2300 multigigabit switches cannot be combined with any other models of EX2300 switches in the same Virtual Chassis.

  • Add an EX3400 switch to an existing EX3400 Virtual Chassis.

  • Add an EX4300 switch to an existing non-mixed EX4300 Virtual Chassis. For example:

    • Add an EX4300 multigigabit model (EX4300-48MP) switch to a Virtual Chassis consisting of all EX4300 multigigabit model switches.

    • Add any other type of EX4300 switch to a Virtual Chassis that contains only EX4300 switches and no EX4300 multigigabit model switches.

  • Add an EX4300 switch to a mixed EX4300 Virtual Chassis that consists of a supported combination of EX4300 multigigabit model switches and any other EX4300 switches.


You cannot use this procedure to add an EX4300 multigigabit model (EX4300-48MP) switch to an existing EX4300 Virtual Chassis that consists only of other non-multigigabit EX4300 model switches. EX4300 multigigabit model switches must be in the primary and backup Routing Engine roles in an EX4300 Virtual Chassis that contains both types of switches. As a result, in that case, you should first create a new multigigabit EX4300 Virtual Chassis with multigigabit EX4300 switches in the primary and backup roles, and then merge the other non-multigigabit EX4300 model switches from the original non-mixed Virtual Chassis into a new mixed-mode EX4300 Virtual Chassis.

To add an EX4300 switch to any other type of Virtual Chassis, see the following other references for adding member switches to a mixed Virtual Chassis with EX4600 or QFX Series switches, or adding an EX4300 switch (excluding multigigabit models) as a leaf node to a Virtual Chassis Fabric (VCF):


To join an existing Virtual Chassis, new member switches must be running the same version of Junos OS that is running on the Virtual Chassis primary. If you have configured the automatic software update feature in an existing Virtual Chassis, the primary switch updates newly added members with the correct software version automatically, if necessary. Otherwise, you must manually install the correct software version. See Understanding Automatic Software Update on Virtual Chassis Member Switches.

Before you begin, be sure you have:

  • Confirmed that the new switch is supported as a member of the Virtual Chassis and in the role in which you want to add it. See Understanding EX Series Virtual Chassis and Understanding Virtual Chassis Components for details on the different EX Series switches, switch combinations, and switch roles that are supported or recommended in a Virtual Chassis.

  • Mounted the new switch in a rack.

  • Determined which ports you will use as Virtual Chassis ports on the new switch, and the member ports in the existing Virtual Chassis to which you will interconnect the new switch.

    See Virtual Chassis Port Options for the ports that can be used as VCPs on switches that support Virtual Chassis.

  • If you are expanding a preprovisioned configuration:

    • Made a note of the serial number (the number is on the back of the switch). You will need to edit the Virtual Chassis configuration to include the serial number of the new member switch.


      Serial number values are case-sensitive.

    • Edited the existing Virtual Chassis configuration to include the serial number of the new member switch. The parameters specified in the primary Virtual Chassis configuration file are applied to the new switch after it has been interconnected to an existing member switch.

    • (If you are using the autoprovisioning feature to add a member switch to an existing preprovisioned Virtual Chassis) Confirmed that the member ports in the Virtual Chassis to which you will interconnect the new switch are not already configured as VCPs. One condition for automatic VCP conversion is that the ports on both sides of the new link must not already be configured as VCPs. See Automatic Virtual Chassis Port (VCP) Conversion for details on the requirements and conditions under which this feature will be invoked.

  • (Optional) Configured Ethernet interfaces on different member switches into the same LAG. For example, see Example: Configuring Aggregated Ethernet High-Speed Uplinks Between an EX4200 Virtual Chassis Access Switch and an EX4200 Virtual Chassis Distribution Switch.

    An active member switch might temporarily go down before coming back up as part of this procedure. Having traffic load-balanced across member switches using a LAG helps alleviate traffic loss during this procedure.

  • (Optional) Considered deleting the no-split-detection configuration item if you are expanding a two-member Virtual Chassis with this option configured. The split detection and merge feature is recommended for Virtual Chassis configurations with more than two members, and is enabled by default when a Virtual Chassis is initially set up.

To add a new member switch to an existing Virtual Chassis configuration:

  1. If the new member switch has been previously configured, revert that switch’s configuration to the factory defaults before interconnecting it into the Virtual Chassis. See Reverting to the Default Factory Configuration for the EX Series Switch.
  2. (Required for a mixed EX4300 Virtual Chassis only) A mixed EX4300 Virtual Chassis contains a combination of EX4300 multigigabit model (EX4300-48MP) switches and other EX4300 switches.

    If you are adding a new switch in this case, set the new switch into mixed mode, and reboot the switch for the mode change to take effect as follows:

    • If the new switch is an EX4300 multigigabit model (EX4300-48MP) switch:

      user@device> request virtual-chassis mode mixed reboot

    • If the new switch is any other EX4300 model switch, you must also configure the switch with a special port mode by including the ieee-clause-82 option when you set mixed mode. This port mode enables VCPs on the EX4300 switch to communicate with VCPs on multigigabit model member switches:

      user@device> request virtual-chassis mode ieee-clause-82 mixed reboot

    If adding this switch to the Virtual Chassis converts a non-mixed EX4300 Virtual Chassis into a mixed EX4300 Virtual Chassis, log into the Virtual Chassis and set all the existing member switches into mixed mode as well, and reboot the Virtual Chassis to complete the configuration:

    user@vc-master> request virtual-chassis mode mixed reboot all-members

    For example, if you have an EX4300 Virtual Chassis consisting of all EX4300 multigigabit model member switches, that is a non-mixed EX4300 Virtual Chassis. If you add an EX4300 switch that isn’t a multigigabit model to that Virtual Chassis, you must change the mode to mixed on all existing members when you add the new switch.

    Wait for the reboot operation to complete on any affected switches in this step before moving to the next step.

  3. Power off the new switch, and interconnect the unpowered new switch to one member of the existing Virtual Chassis configuration using a supported VCP.

    Connect only one VCP on the unpowered new switch to a VCP on a member switch in the existing Virtual Chassis at this point in the procedure.

  4. Power on the new switch.
  5. Set the interconnecting interface as a Virtual Chassis Port (VCP), if needed:

    user@switch> request virtual-chassis vc-port set pic-slot 1 port port-number

    You do not need to perform this step in the following cases:

    • You are using dedicated VCPs, which do not need to be configured. EX4300 multigigabit model (EX4300-48MP) switches have dedicated VCPs on the rear panel, which are the only VCP port options on those switches.

    • You do not typically need to perform this step with QSFP+ ports on EX3400 and EX4300 switches that are not multigigabit models. All QSFP+ ports on these switches are configured as VCPs by default. However, you might use the request virtual-chassis vc-port command to set a QSFP+ port back into a VCP if the QSFP+ port had previously been reconfigured as a network port.

    • If you have the right conditions to use the autoprovisioning feature, after the new switch is provisioned and cabled into the Virtual Chassis, the interconnecting links automatically convert into VCP links. You do not need to manually set the ports on either side of the links as VCPs.

  6. Confirm that the new member switch is now included within the Virtual Chassis configuration by entering the show virtual-chassis command. The new member switch should be listed in the output and the Status is Prsnt.
  7. Cable the next port into the Virtual Chassis, configuring the ports into VCPs if needed.Caution

    If you immediately cable both VCPs on the new switch into the existing Virtual Chassis at the same time, a member switch that was already part of the Virtual Chassis might become nonoperational for several seconds. Network traffic to this switch is dropped during the downtime.

    The member switch will return to the normal operational state with no user intervention, and normal operation of the Virtual Chassis will resume after this downtime.