Splitting A Stack; The Stack Master And Backup Master Units Remain In A Group; The Stack Master Or The Backup Master Unit Remains In A Group - Cisco SGE2000 Reference Manual

Chapter
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SGE2000/SGE2000P Gigabit Ethernet Switch Reference Guide
3. The Stack Master performs unit and port configuration for the incoming unit.
• Any configuration information that is relevant to the number assigned to the incoming unit is
applied by the Stack Master. For example, if the incoming unit is assigned the same Unit ID of
the unit it replaced, then when possible, it receives the same configuration as the failed unit.
• If the incoming unit is identical to the replaced unit, the entire configuration of the replaced unit
is applied to the incoming unit and the stack returns to the state it was in before unit failure.

Splitting a Stack

A working stack can be split into two groups, either by failure of a stacking link connecting two units in
the stack, or by a failed unit in a chain topology that causes disconnection between two units in the stack.
In this case, each group is considered as an independent running stack configuration. For each group,
there are three scenarios.

The Stack Master and Backup Master Units Remain in a Group

In this scenario, the Stack Master routes around the missing units. The Master Discovery, Master
Election and Unit ID Allocation & Duplicate Unit ID Conflict Resolution processes occur with the
following results:
• Any configuration information contained in the Stack Master that is relevant to the units which
remained in the split group remains unchanged.
• Topology information (the information for each unit on how to send traffic to any other unit in the
stack) managed by the Stack Master includes only units that are reachable (connected) following the
split.
• The split stack continues to work as it previously did, but with fewer units.
• No unit ID changes are performed in each of the split stacks.
• The Stack Master notifies the system administrator of the removed units and ports that belong to
the unreachable units by sending SYSLOG messages and SNMP traps. They are reported as "not
present."

The Stack Master or the Backup Master Unit Remains in a Group

If the Stack Master unit remains in the group, the scenario described in "Replacing a Failed Member
Stack Unit in an Operational Stack" applies. If the Backup Master unit remains in the group, the scenario
described in "Replacing a Failed Stack Master Unit in an Operational Stack" applies.
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NOTE: If the stack is split in two groups, one with the
Stack Master and one with the Backup Master, both groups
will function.
Chapter 2: Managing Device Information
Stack Troubleshooting and Maintenance