Lenovo Flex System Fabric CN4093, Application Manual

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© Copyright Lenovo 2017 Chapter 13: Stacking
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Stack Membership
A stack contains up to eight switches, interconnected by a stack LAG in a local ring
topology (see Figure 25 on page 242 ). With this topology, only a single stack link
failure is allowed.
An operational stack must contain one Master and one or more Members, as
follows:
 Master
One switch controls the operation of the stack and is called the Master. The
Master provides a single point to manage the stack. A stack must have one and
only one Master. The firmware image, configuration information, and run ‐ time
data are maintained by the Master and pushed to each switch in the stack as
necessary.
 Member
Member switches provide additional port capacity to the stack. Members
receive configuration changes, run ‐ time information, and software updates
from the Master.
 Backup
One member switch can be designated as a Backup to the Master. The Backup
takes over control of the stack if the Master fails. Configuration information and
run ‐ time data are synchronized with the Master.
The Master Switch
An operational stack can have only one active Master at any given time. In a
normal stack configuration, one switch is configured as a Master and all others are
configured as Members.
When adding new switches to an existing stack, the administrator must explicitly
configure each new switch for its intended role as a Master (only when replacing a
previous Master) or as a Member. All stack configuration procedures in this
chapter depict proper role specification.
However, there are scenarios when the two stacks (each having a Master switch)
are interconnected through stacking links. When this occurs, one Master switch
will automatically be chosen as the active Master for the entire stack. The selection
process is designed to promote stable, predictable stack operation and minimize
stack reboots and other disruptions.