Power-On Sequence For Switch Data Stacks - Cisco Catalyst 3850 Hardware Installation Manual

Chapter 2 Switch Installation
Figure 2-5
Figure
does not have redundant connections. In
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 2-5
Figure 2-6

Power-On Sequence for Switch Data Stacks

Consider these guidelines before you power on the switches in a stack:
•
•
If changes are made to the stack without powering down the switches, the following results can occur:
•
OL-26779-02
and Figure 2-6 show data stacks of Catalyst 3850 switches with failover conditions. In
2-5, the StackWise cable is bad in link 2. Therefore, this stack provides only half bandwidth and
Example of a Data Stack with a Failover Condition
1
3
Example of a Partitioned Data Stack with a Failover Condition
1
2
The sequence in which the switches are first powered on might affect the switch that becomes the
active switch and the standby switch.
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.
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).
Figure 2-6, link 2 is bad. Therefore, this stack partitions into
2
Catalyst 3850 Switch Hardware Installation Guide
Data Stack Cabling Configurations
2-7