Master And Member Switches; Selection Of The Master Switch - Allied Telesis AT-SB*908 GEN2 Installation Manual

Master and Member Switches

Selection of the
Master Switch
A stack has a master switch. The main functions of a master switch are
listed here:
 Coordinate and monitor stack operations.
 Verify that the switches are using the same version of
management software. It automatically downloads its management
software over the stacking cables to switches with different
software versions.

Verify that the switches have different ID numbers. It automatically
assigns new ID numbers to resolve situations where two or more
switches have the same ID number.

Verify that the stacking transceivers that connect the switches
together are cabled correctly.
The other switches are called member switches. There can be up to seven
member switches in addition to the master switch. A member switch can
automatically transition to the master role if the current master switch is
removed from the stack or powered off. This ensures continued operations
of the stack even if the master switch stops operating.
The switches of the stack designate the master switch during the
initialization process that they perform whenever they are powered on or
reset. They base the selection of the master switch on the following
parameters:
 Stack priority numbers
 MAC addresses
The stack priority number is an adjustable value of 0 to 255, where the
lower the number, the higher the priority. Typically, the switch with the
lowest priority number (highest priority) becomes the master switch of a
stack. The default priority value is 128.
If the switches have the same priority values, the selection of the master
switch is based on their MAC addresses. As with the priority value, the
lower the MAC address, the higher the priority. The switch with the lowest
MAC address becomes the master switch.
If you power on the stack for the first time without adjusting the priority
values, the master switch is selected based on the MAC addresses if the
units are powered on simultaneously. If you power on the switches one at
a time, the master switch is the first switch to be powered on. This is
explained in Chapter 8, "Powering On and Verifying the Stack" on page
167.
AT-SBx908 GEN2 Installation Guide for Virtual Chassis Stacking
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