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Configuring Primary Role of a Virtual Chassis

Note:

  • This topic applies to all QFX Virtual Chassis and all EX Series Virtual Chassis except EX8200 Virtual Chassis.

  • If the Virtual Chassis is being managed through Juniper Mist, see the following topic for instructions to reassign member roles: Reassign the Virtual Chassis Member Roles.

A Virtual Chassis configuration has two Routing Engines—one is the switch in the primary Routing Engine role and the other is the switch in the backup Routing Engine role. The remaining members operate in the linecard role. You can designate the role (primary, backup, or linecard) that a member switch performs within any Virtual Chassis whether or not you are using a preprovisioned configuration. For details on which switches in a mixed Virtual Chassis we recommend or require you to configure into the primary or backup Routing Engine role, see Understanding Mixed EX Series and QFX Series Virtual Chassis.

Note:

We recommend that you always use commit synchronize rather than commit to save configuration changes for a Virtual Chassis to ensure that the changes are saved on both Routing Engines.

Configuring Primary Role Using a Preprovisioned Configuration File

To configure primary role using a preprovisioned configuration:

  1. Note the serial numbers of the switches that you want to function as the primary and backup Routing Engines.
    Note:

    Serial number values are case-sensitive.

  2. Power on only the switch that you want to function as the primary Routing Engine.
  3. Edit the configuration to specify the preprovisioned configuration mode:
  4. Specify the serial numbers of the member switches that you want to function as primary and backup, specifying their role as routing-engine:
    Note:

    You cannot directly modify the primary-role priority value when you configure a member switch in a preprovisioned Virtual Chassis. The Virtual Chassis generates the primary-role priority values automatically. The values depend on the role you assign to the member switches in the configuration file. The default primary-role priority on any switch is 128. When you configure the primary and backup Routing Engine members, the primary-role priority changes to 129 on those members. According to the primary-role election algorithm, the member that you powered on first gets priority and becomes the primary. See Understanding How the Primary in a Virtual Chassis Is Elected. You can configure only two members with the routing-engine role.

  5. Specify the serial numbers of any other member switches you are including in the Virtual Chassis configuration. You can also explicitly configure their role as line-card.

Configuring Primary Role Using a Configuration File That Is Not Preprovisioned

To configure primary role of the Virtual Chassis through a configuration that is not preprovisioned:

  1. Power on only the switch that you want to function as the primary Routing Engine.
  2. Configure the highest possible primary-role priority value (255) for the member that you want to function as the primary Routing Engine:
  3. Configure the same primary-role priority value (continue to edit the Virtual Chassis configuration on the primary) for the member that you want to be the backup Routing Engine:
    Note:

    You should assign the same (highest) primary-role priority value to both the primary and backup Routing Engine members for reliable graceful Routing Engine switchover (GRES) operation. This and the other primary-role election considerations also help keep primary role from switching back and forth rapidly between the two members under failover conditions.

  4. Use the default primary-role priority value (128) for the remaining member switches or configure the primary-role priority to a value that is lower than the value specified for members acting in the primary and backup Routing Engine roles.

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