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Managing Stacking
Stacking Failover Topology
Page 73
Notes
• If two members are discovered with the same Unit ID the stack continues to function, however only
the unit with the older join time joins the stack. A message is sent to the user, notifying that a unit failed
to join the stack.
Removing and Replacing Stacking Members
Stacking member 1 and Stacking member 2 are Stacking Master enabled units. Unit 1 and Unit 2 are either desig-
nated as Master Unit or Secondary Master Unit. The Stacking Master assignment is performed during the configu-
ration process. One Master enabled stack member is elected Master, and the other Master enabled stack member
is elected Secondary Master, according to the following decision process:
• If only one Stacking Master enabled unit is present, it is elected Master.
• If two Stacking Masters enabled stacking members are present, and one has been manually configured as
the Stacking Master, the manually configured member is elected Stacking Master.
• If two Master enabled units are present and neither has been manually configured as the Stacking Master, the
one with the longer up-time is elected Stacking Master.
• If the two Master enabled stacking members are the same age, Unit 1 is elected Stacking Master.
Notes
• Two stacking member are considered the same age if they were inserted within the same ten minute
interval.
For example, Stack member 2 is inserted in the first minute of a ten-minute cycle, and Stack member 1 is inserted
in fifth minute of the same cycle, the units are considered the same age. If there are two Master enabled units that
are the same age, then Unit 1 is elected master.
The Stacking Master and the Secondary Master maintain a Warm Standby. The Warm Standby ensures that the
Secondary Master takes over for the Stacking Master if a failover occurs. This guarantees that the stack continues
to operate normally.
During the Warm Standby, the Master and the Secondary Master are synchronized with the static configuration
only. When the Stacking Master is configured, the Stacking Master must synchronize the Stacking Secondary
Master. The Dynamic configuration is not saved, for example, dynamically learned MAC addresses are not saved.
Each port in the stack has a specific Unit ID, port type, and port number, which is part of both the configuration
commands and the configuration files. Configuration files are managed only from the device Stacking Master,
including:
• Saving to the FLASH
• Uploading Configuration files to an external TFTP Server
• Downloading Configuration files from an external TFTP Server
Whenever a reboot occurs, topology discovery is performed, and the master learns all units in the stack. Unit IDs
are saved in the unit and are learned through topology discovery. If a unit attempts to boot without a selected Mas-
ter, and the unit is not operating in stand-alone mode, the unit does not boot.
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