Administration: Stack Management
Master Selection Process
Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version) 65
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The following shows a case where one of the duplicate units is renumbered. The
one with the lower MAC retains its unit ID (see Master Selection Process for a
description of this process).
Duplication Between Two Units With Auto Number Unit ID
NOTE If a new stack has more than the maximum number of units (8), all extra units are shut
down.
Master Selection Process
The master unit is selected from the master-enabled units (1 or 2). The factors in
selecting the master unit are taken into account in the following priority:
•Force Master—If Force Master is activated on a unit, it is selected.
•System Up Time—The master-enabled units exchange up-time, which is
measured in segments of 10 minutes. The unit with the higher number of
segments is selected. If both units have the same number of time segments,
and the unit ID of one of the units was set manually while the other unit’s unit
ID was set automatically, the unit with the manually-defined unit ID is
selected; otherwise the unit with the lowest unit ID is selected. If both units
IDs are the same, the unit with the lowest MAC address is chosen. Note:
The up time of the backup unit is retained when it is selected as master in
the switch failover process.
•Unit ID—f both units have the same number of time segments, the unit with
the lowest unit ID is selected.