Allied Telesis AT-SBx81CFC960 - Manual (Page 280)

Chapter 14: VCStack Plus Overview
280 Section III: Building a Stack with VCStack Plus
optional. If you choose not to set the value, the controller cards use their
MAC addresses to select the active master controller card for the stack.
The process for selecting the active master controller card is different if the
two switches are reset or power on one after the other. Here, the controller
card that initializes its management software first becomes the active
master controller card for the stack.
Once the active controller card is selected, it remains the active card
unless it fails or is removed from its chassis, at which point another
controller card becomes the active controller card for the stack.