Cisco Catalyst 3850 Deployment Manual page 30

The Cisco IOS XE Software high-availability framework is enabled by default on Cisco Catalyst 3850 Switches
when they are deployed in StackWise-480 mode. The newly provisioned Cisco Catalyst 3850 Switch automatically
discovers and dynamically joins the stack ring. The Cisco StackWise-480 technology features system-level N:1
high availability. Adding switches to and removing switches from a stack do not affect the active and hot standby
roles already in effect in the stack.
To enable stateful switchover (SSO) resiliency in Cisco StackWise-480 mode, you must configure each switch with
the same Cisco IOS XE Software version and license. Figure 7 illustrates system roles and operation of Cisco
StackWise-480 when you add Cisco Catalyst 3850 Switches to a stack.
Figure 7. Plug-and-Play Cisco Catalyst 3850 Switch System Role Designation
The unique high-availability architecture in the Cisco StackWise-480 design enables distributed network services,
such as flexible NetFlow, quality of service (QoS), and more, as well as providing system-level redundancy for all
stack-member switches. During a complete stack reload, all switches participate in an election process to
determine assignment of the active and standby roles. Several criteria, including switch priority and MAC
addresses, are compared to elect the active and standby switches in the stack.
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