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

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
26
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