Unit Id Assignment; Duplicate Unit Ids - Cisco SF500-24 Administration Manual

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Unit ID Assignment

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• Splitting the stack
• Inserting other slave units to the stack, for instance because the units were
previously disconnected from the stack due to a failure. This can happen in
a chain topology if a unit in the middle of the stack fails.
During topology discovery, each unit in a stack exchanges packets, which contain
topology information.
After the topology discovery process is completed, each unit contains the stack
mapping information of all units in the stack.
After topology discovery is completed, each unit in a stack is assigned a unique
unit ID.
The unit ID is set in the System Mode and Stack Management page in one of the
following ways:
• Automatically (Auto)—The Unit ID is assigned by the topology discovery
process. This is the default setting.
• Manually—The unit ID is manually set to an integer from 1-8. In addition,
manual numbering includes the following options:
- 1 - Force Master—Forces unit 1 to be the master.
- 2 - Force Master—Forces unit 2 to be the master.

Duplicate Unit IDs

If you assign the same unit ID to two separate units, only one of them can join the
stack with that unit ID.
If auto numbering has been selected, the duplicate unit is assigned a new unit
number. If auto numbering was not selected, the duplicate unit is shut down.
The following examples show where unit ID duplication might occur.
The following shows a case where two units were manually assigned the same
unit ID. Unit 1 does not join the stack and is shut down. It did not win the master
selection process between the master-enabled units (1 or 2).
Cisco 500 Series Stackable Managed Switch Administration Guide Release 1.3
Administration: Stack Management
Unit ID Assignment