Understanding How the Master in a Virtual Chassis Configuration Is Elected
All switches that are interconnected in a Virtual Chassis configuration are member switches of that Virtual Chassis. Each Virtual Chassis configuration has one member that functions as the master and controls the Virtual Chassis configuration.
When a Virtual Chassis configuration boots, the JUNOS software for EX-series switches automatically runs a master election algorithm to determine which member switch takes the role of master.
The algorithm that the software uses to determine the master is as follows:
- Choose the member with the highest user-configured mastership priority (255 is the highest possible value).
- Choose the member that was master the last time the Virtual Chassis configuration booted.
- Choose the member that has been included in the Virtual Chassis configuration for the longest period of time. (For this to be a deciding factor, there has to be a minimum time lapse of one minute between the power-ons of the individual interconnected member switches.)
- Choose the member with the lowest MAC address.
The variations among switch models, such as whether the switch has 48 or 24 ports, do not impact the master election algorithm. To ensure that a specific member is elected as the master:
- Power on only the switch that you want to configure as master of the Virtual Chassis configuration.
- Configure the mastership priority of that member to have the highest possible value (255).
- Continue to configure other members through the master member, as desired.
- Power on the other members.