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

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Power-On Sequence for Switch Stacks

In this figure, link 2 is bad. Therefore, this stack partitions into two stacks, and the top and bottom switches

become the active switch in the stack. If the bottom switch is a member (not active or standby switch), it

reloads.

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

• 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:

Cisco Catalyst 9300 Series Switches Hardware Installation Guide

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.

Switch Installation

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