Administration: Stack Management
Stack Changes
Cisco 350, 350X and 550X Series Managed Switches, Firmware Release 2.4, ver 0.4 124
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Connecting a New Unit
When a unit is inserted into the stack, a stack topology change is triggered. The unit ID is 
assigned (in case of auto numbering), and the unit is configured by the master.
One of the following cases can occur when connecting a new unit to an existing stack:
• No duplicate unit IDs exist.
- Units with user-defined IDs retain their unit ID.
- Units with automatically-assigned IDs retain their unit ID.
- Factory default units receive unit IDs automatically, beginning from the lowest 
available ID. 
• One or more duplicate unit IDs exist. Auto numbering resolves conflicts and assigns 
unit IDs. In case of manual numbering, only one unit retains its unit ID and the other(s) 
are shutdown.
• The number of units in the stack exceeds the maximum number of units allowed. The 
new units that joined the stack are shut down, and a SYSLOG message is generated 
and appears on the master unit.
The following shows an example of auto numbering when a master-enabled unit joins the 
stack. There are two units with unit ID = 1. The master selection process selects the best unit to 
be the master unit. The best unit is the unit with the higher uptime in segments of 10 minutes. 
The other unit is made the backup.
Auto-numbered Master-enabled Unit