Allied Telesis AT-S63 - Manual (Page 37)

AT-S63 Stack Command Line Interface User’s Guide
Section I: Basic Operations 37
The switches should be numbered starting with ID number 1. The switch
assigned ID number 1 will be the master switch of the stack. Any switch
can be the master switch, but it should be either the top or bottom switch in
the rack to make it easy to identify. Additionally, the switches do not have
to be numbered in the same order as their arrangement in the rack in
relation to the master switch, but they will be easier to identify if their
numbers and their order in the rack match.
Dynamic Module
ID Numbers
Dynamic module ID numbers are automatically assigned by the
management software to the switches during the discovery process of the
stack, and are based on the MAC addresses of the units. The switch with
the lowest MAC address is assigned module ID 1 and automatically
becomes the master switch. The switch with the second lowest address is
assigned module ID 2, and so on.
Dynamic module ID numbers can be problematic for stacks of more than
two switches for several reasons. First, the order of the ID number
assignments might not match the physical arrangement of the devices in
the rack. Although the switches in a stack do not have to be sequentially
numbered in the equipment rack, identifying the units will be easier if the
order of the units in the rack and their numbers reflect each other. For
example, a stack of five switches assigned dynamic module ID numbers
might be numbered from top to bottom in the rack as follows: 2, 4, 1, 3, 5.
Such a sequence could lead to mistakes when you enter the configuration
commands.
Another drawback to this approach is that the number assignments could
be significantly impacted by the addition or removal of a switch, which, in
turn, could alter the configurations of the switches. As explained
previously, the configuration commands in the active configuration file on
the master switch identify the switches by their module ID numbers.
Consequently, any change to the number assignments can result in a
change to a switch’s parameter settings.
For instance, introducing into a stack a new switch whose MAC address is
lower than the MAC address of an existing switch will change the module
ID assignments of one or more of the devices. A cascade effect could
result in which the new switch takes on the configuration of a preexisting
switch since it has a lower MAC address, while the displaced switch takes
on another configuration, and so on.
Furthermore, if a new switch’s MAC address is the lowest in the stack, it
becomes the new master switch. This could result in the entire stack losing
its configuration, because the new master switch is unlikely to have the
same stack configuration file as the previous master switch.
It should also be noted that a backup master switch is not supported in a
stack with dynamic module ID numbers. That feature is reserved for stacks
with static ID numbers.