Managing Device Information
Managing Stacking
Cisco Small Business SFE/SGE Managed Switches Administration Guide 13
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• Master Election. Master Election takes place automatically to select the
Master unit. If there are two or more units in the stack, then a Backup unit is
also automatically selected.
• Topology Discovery. The stack Master unit carries out a process called
topology discovery to learn which units are present in the stack, the order in
which they are connected and the Unit ID that each unit reports itself as
owning. The Master unit then examines the reported Unit IDs and notes any
violations of the Unit ID Validity Rules. These include units reporting
duplicate Unit IDs and units in factory default (Unit ID=0) mode. Topology
discovery also takes place any time a change in the stack topology occurs,
such as removing or adding a unit to the stack.
• Unit ID Conflict Resolution. The Master unit attempts to resolve conflicts
among two or more units contending for the same Unit ID. After applying the
rules for Unit ID Conflict Resolution, one unit retains its Unit ID. The other
contending units are either shut down or reset to Unit ID=0 by the Master
unit.
• Automatic Unit ID Assignment. The Master unit applies automatic
numbering to units with Unit ID=0. These units include new factory units,
units reset to factory default mode by the system administrator pressing the
reset button on the switch or units automatically reset to Unit ID=0 by the
Master unit during Unit ID Conflict Resolution.
• Unit and Port Configuration. At this point, the stack has a valid topology. The
Master unit now configures all member units and their ports according to
the configuration file stored in the Master unit. The Stack Initialization is
complete and the stack enters normal operational mode. Configuration files
are changed only through explicit user configuration. Configuration files are
not automatically modified when:
- Units are Added
- Units are Removed
- Units are reassigned Unit IDs
- Units toggle between Stacking Mode and stand-alone Mode
Each time the system reboots, the Startup Configuration file in the Master
unit is used to configure the stack. If a stack member is removed from the
stack, and then replaced with a unit with the same Unit ID, the stack
member is configured with the original device configuration. Only ports that
are physically present are displayed in the web screens, and can be
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