Lenovo Flex System Fabric CN4093, Application Manual

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© Copyright Lenovo 2017 Chapter 13: Stacking
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Merging Independent Stacks
If switches from different stacks are linked together in a stack topology without
first reconfiguring their roles as recommended, it is possible that more than one
switch in the stack might be configured as a Master.
Since up to 16 units can be attached to a stack, a merge between two 8 unit stack
can be performed. The user will then have to choose which units will remain in the
final stack and which will be eliminated, since only 8 of them can forward
networking traffic, the rest having the data links disabled.
Note:
Do not merge hybrid stacks if the total number of CN4093 switches exceeds
two units.
Although all switches which are configured for stacking and joined by stacking
links are recognized as potential stack participants by any operational Master
switches, they are not brought into operation within the stack until explicitly
assigned (or “bound”) to a specific Master switch.
Consider two independent stacks, Stack A and Stack B, which are merged into one
stacking topology. The stacks will behave independently until the switches in
Stack B are bound to Master A (or vice versa). In this example, once the Stack B
switches are bound to Master A, Master A will automatically reconfigure them to
operate as Stack A Members, regardless of their original status within Stack B.
However, for purposes of future Backup selection, reconfigured Masters retain
their identity as configured Masters, even though they otherwise act as Members.
In case the configured Master goes down and the Backup takes over as the new
Master, these reconfigured Masters become the new Backup. When the original
configured Master of the stack boots up again, it acts as a Member. This is one way
to have multiple backups in a stack.