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Chapter 2:
SFE2000/SFE2000P Gigabit Ethernet Switch Reference Guide
Chapter
2
We recommend that when combining two stacks, you reset the switches in one stack to factory default
mode and then add the switches as described in “Adding Units to a Running Stack” in the “Building
Automatically-Configured Stacks” section.
• If one of the merged stacks had neither a Stack Master unit nor a Backup Master unit, then units
belonging to this group are inserted into the stack as described in “Replacing a Failed Member
Stack Unit in an Operational Stack.” The Master either connects the running units to the stack
using the current Unit ID numbers or renumbers them.
Understanding Stacking Cable Failure
If the stacking connection cables fail and cause a stack split, the scenario described in “Merging Two
Stacks” applies. This occurs only if the stack uses a chain topology. Single stacking cable failure will not
cause a stack split if a ring topology is used.
Inserting Too Many Units into a Stack
If you try to insert too many units into a stack, when all units (existing and newly inserted) are powered
on at the same time, the following occurs:
1. A Stack Master is elected following the Master Discovery and Master Election processes.
2. All other units are shut down.
When a running group of units is added to an existing stack and each one of the stack groups has an
elected Stack Master, and the total of existing units and inserted units exceeds the maximum allowed
number of units (8) in a stack:
• The Master Detection and Master Election processes determine the Stack Master out of one of
the two combined stacking groups.
• When switches are added to a running stack, the Unit ID Allocation and Duplicate ID conflict
resolution processes detect an error if too many switches are present in the stack, and no changes
are made to units that originally belonged to the group managed by the newly-elected Stack
Master. The original switches retain their ID assignments and configurations. The units that
originally belonged to the group managed by the Stack Master that lost its “mastership” are shut
down.
NOTE: Any time two stacks are combined into one stack,
there is no way to maintain the configuration for both sets of
switches. All dynamic information of the units that belong
to the portion of the stack that was not re-elected to be the
Stack Master is relearned.
NOTE: Occasionally, due to a race condition during the
boot process, some of the units might be connected and join
the stack.