Allied Telesis AT-S63 - Manual (Page 69)

AT-S63 Management Software Features Guide
Section I: Basic Operations 69
Master and Member Switches
The activities of the devices of a stack are coordinated by a master switch.
There can be only one master switch, but it can be any unit in a stack. The
master switch is assigned module ID 1, as explained in “Module ID
Numbers” on page 70. This switch maintains the active configuration file,
which contains the parameter settings for all of the switches in the stack.
The stack also has a backup master switch. This unit, which is assigned
module ID 2, maintains a copy of the active configuration file and assumes
the role of the master switch if the current master switch fails or is removed
from the stack.
The other switches of a stack are called member switches.