Power-On Sequence For Switch Stacks - Cisco Catalyst 9300 Series Hardware Installation Manual

Power-On Sequence for Switch Stacks

Figure 23: 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
• There are two ways to elect an active switch:
• If two operating partial ring stacks are connected together using a stack cable, a stack merge can take
• 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:
• A stack split can occur in a partial ring stack if:
• In a split stack, depending on where the active and standby switches are located, either two stacks might
Cisco Catalyst 9300 Series Switches Hardware Installation Guide
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master.
• 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.
If changes are made to the stack without powering down the switches, the following results can occur:
place. This situation reloads the whole stack (all switches in the stack).
• More than one running switch is removed without powering down.
• More than one stack cable is removed without powering down.
• A switch is removed without powering down.
• A stack cable is removed without powering down.
be formed (with the standby taking over as the new active switch in the newly formed stack) or all the
members in the newly formed stack might reload.
Installing a Switch