Figure 14: Example of a Partitioned Data Stack with a Failover Condition
Power-On Sequence for Switch Stacks
Consider these guidelines before you power on the switches in a stack:
• The sequence in which the switches are first powered on might affect the switch that becomes the stack
master.
• There are two ways to elect an active switch:
• If you want a particular switch to become the active switch, configure it with the highest priority.
Among switches with same priority, the switch with the lowest MAC address becomes the active
switch.
• If you want a particular switch to become the active switch, power on that switch first. This switch
remains the active switch until a reelection is required. After 2 minutes, power on the other switches
in the stack. If you have no preference as to which switch becomes the active switch, power on all
the switches in the stack within 1 minute. These switches participate in the active switch election.
Switches powered on after 2 minutes do not participate in the election.
• Power off a switch before you add it to or remove it from an existing switch stack. If changes are made
to the stack without powering down the switches, the following results can occur:
• If two operating partial ring stacks are connected together using a stack cable, a stack merge can
take place. This situation reloads the whole stack (all switches in the stack).
• If some switches in the stack are completely separated from the stack, a stack split can occur.
• A stack split can occur on a full ring stack if:
• More than one running switch is removed without powering down.
• More than one stack cable is removed without powering down.
• A stack split can occur in a partial ring stack if:
• A switch is removed without powering down.
Cisco Catalyst 9200 Series Switches Hardware Installation Guide
37
Installing the Switch
Power-On Sequence for Switch Stacks
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