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[EX] The sequence of master election process in VC environment EX-series switch



Article ID: KB10921 KB Last Updated: 05 Mar 2017Version: 6.0
All switches that are interconnected as a virtual chassis are member switches of that virtual chassis. Each virtual chassis has one member that functions as the master and controls the virtual chassis.

When a virtual chassis boots, the JUNOS for EX-series software 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:
  1. Choose the member with the highest user-configured mastership priority (255 is highest possible value).
  2. Choose the member that was master the last time the virtual chassis booted.
  3. Choose the member that has been included in the virtual chassis 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 powering on the interconnected member switches.)
  4. Choose the member with the lowest MAC address.
The model, such as whether there are 48 or 24 ports, does not impact the master election algorithm. To ensure that a specific member is elected as the master, you should explicitly configure the mastership–priority of that member to have the highest possible value (255).
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