This article provides information about the general non-provisioned configuration for EX/QFX devices

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

• Power on only the switch that you want to function as the primary Routing Engine.
• Configure the highest possible primary-role priority value (255) for the member that you want to function as the primary Routing Engine:

[edit virtual-chassis]
user@switch# set member 0 mastership-priority 255

• 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:

[edit virtual-chassis]
user@switch# set member 1 mastership-priority 255

• Configure not-split-detection on a 2 members VC:

[edit virtual-chassis]
user@switch# set no-split-detection

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.

• 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.
• To configure uplink ports as VCPs to interconnect the member switches (Run on each switch)

user@switch> request virtual-chassis vc-port set pic-slot 1 port 0
user@switch> request virtual-chassis vc-port set pic-slot 1 port 1

NOTE: if the switch is having dedicated VCPs it doesn't require any VC port configuration