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Chapter 2:
SFE2000/SFE2000P Gigabit Ethernet Switch Reference Guide
Chapter
2
Merging Two Stacks
To merge two working stacks and create one stack, first decide if you will merge the stacks while the
incoming units are powered off during insertion, or if both stacks will be running when merged.
If the incoming units are powered off, follow the procedures described in “Building a New Stack” in the
“Building Automatically-Configured Stacks” or “Building Manually-Configured Stacks” sections.
Repeat the process for each unit inserted into the stack.
If both stacks to be merged are running (for example, you are connecting the stacking cables of two
stacks), the following occurs:
• If each of the joined stacks has a Stack Master unit, both Stack Master units perform the Master
Discovery process and participate in the Master Election process. One of the Stack Master units
is selected as the Stack Master unit for the merged stack. The criteria for choosing the Stack
Master are as follows:
– Force Master: If Force Master is enabled, the unit that is configured as the forced unit is
selected as the Stack Master.
– System Up Time: Up time is measured by quantities of 10-minute intervals. If the number of
10 minute intervals is higher for one of the units, this unit is selected as the Stack Master.
– Lowest Unit ID: If both units have the same up time (measured in intervals of 10 minutes),
the unit with the lowest unit ID is selected as the Stack Master.
– Lowest MAC: If both Master unit ID numbers are equal, the unit with the Lower MAC
address is chosen as the Stack Master.
The Stack Master unit that loses its “mastership” in the Master Election process is renumbered if the unit
ID was dynamically allocated. The new Stack Master allocates it a new number and configures it as a
stack member or a Backup Master. It will be shut down if the unit ID was manually allocated. We
recommend that the administrator configure the unit to receive an auto-assigned Unit ID before
reconnecting it to the stack.
When two stacks are combined, all of the configuration information for one of the stacks is lost. Only the
surviving Stack Master (after the discovery and election processes are complete) maintains its
configuration information.
NOTE: There will never be two units with the same Unit
ID at the end of the merge.