Deploying Cisco Catalyst 3850 Switch Stackwise-480 Nsf And Sso - Cisco Catalyst 3850 Deployment Manual

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The Cisco Catalyst 3850 Switches support a wide range of Layer 2, Layer 3, and wireless stateful capabilities to

provide nonstop network communication. In real time, the Cisco IOS XE Software running on the active switch

synchronizes its protocol state machines, software forwarding tables, and system configuration to the Cisco IOS

XE Software instance running on the standby switch. The other primary core services hosted by Cisco IOS XE

Software are the integrated applications, such as the wireless control module (WCM). In Cisco StackWise-480

mode, the WCM is operational on the active Cisco Catalyst 3850 Switch that communicates with the locally

attached Cisco wireless access points (WAPs), wireless clients, and distributed mobility peers to build a roaming

network domain. The WCM on the standby switch is in hot-standby state as a Cisco IOS XE Software process. In

real time, the active WCM performs the stateful synchronization of wireless protocols and control and provisioning

of wireless access points (CAPWAP) tunnel information with the standby switch. If the active switch fails, the

standby switch becomes the wireless controller by resynchronizing with the Cisco WAPs and mobility peers.

In the initial software release, the Cisco Catalyst 3850 Switch supports CAPWAP tunnels and Dynamic Transport

Layer Security (DTLS), but not high availability for wireless clients. During a switchover, the new active WCM

flushes the last-known wireless client and rebuilds the database and forwarding tables. As a result, the wireless

client must restart communication with new wireless controller, using the same initial steps (such as 802.1X

authentication, Dynamic Host Configuration Protocol [DHCP] request, and so on) to reconnect to the network.

Deploying Cisco Catalyst 3850 Switch StackWise-480 NSF and SSO

To maximize availability, the SSO capability is enabled by default when Cisco Catalyst 3850 Switches are

deployed in Cisco StackWise-480 mode. No user configuration is required to enable SSO capability on a Cisco

Catalyst 3850 Switch stack. You can verify that SSO is configured and operational by using the show redundancy

state command. This is sample output showing SSO redundancy in a Cisco StackWise-480-based network design:

In stacking mode, the Cisco Catalyst 3850 active switch automatically performs SSO protocol synchronization with

the standby switch. By default, the nonstop forwarding (NSF) subsystem in all the switches in a Cisco Catalyst

3850 Switch stack operates in NSF helper mode and supports nonstop data forwarding and graceful recovery

during active to standby (Layer 3) switchover. Implementing NSF capability allows the remaining Cisco Catalyst

3850 Switches in the stack to continue forwarding data while the new active switch gracefully recovers the protocol

state machines. To enable the graceful restart capability for supported protocols, you must manually enable

graceful-restart capability under a routing instance. This sample configuration shows how to enable NSF capability

for Enhanced Interior Gateway Routing Protocol (EIGRP):

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