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Chapter 2: Virtual Chassis Stacking
Master and Member Switches
Selection of the
Master Switch
48
The stack has one master switch. The functions of the master switch
include:
Coordinating and monitoring stack operations.
Verifying 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.
Verifying 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.
Verifying that the stacking transceivers that connect the switches
together are cabled correctly.
The other switches are called member switches. There can be up to three
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 devices compare the following numbers to choose the master switch
when the stack is reset or powered on:
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 the Stack" on page 101.
After the stack is established and operating, you may, if you choose,
change the priority settings on the individual units and so control which
switch will be the master switch after subsequent power cycles and resets.
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