High Availability Switching Practice Questions

Answers and explanations appear when you work through the set above.

1. In Cisco IOS XE Stateful Switchover (SSO) configuration, what is the status of the secondary Route Processor (RP) while the primary RP is operational?

   • Active/active, sharing the control plane load
   • Standby hot, with state synchronized
   • Cold standby, booting only after a failover occurs
   • Disabled until an administrator activates it from the CLI

2. What is the standard virtual MAC address format generated by HSRP Version 1 for group number 10 (0x0A)?

   • 0000.0c07.ac0a
   • 0000.0c9f.f00a
   • 0007.b400.000a
   • 0100.5e00.000a

3. How do High Availability Nonstop Forwarding (NSF) and Stateful Switchover (SSO) work together on a modular Cisco switch during an active Route Processor failover?

   • SSO keeps protocol state tables synchronized, while NSF reloads the forwarding ASICs on every line card to clear stale entries.
   • SSO keeps hardware state synchronized so links stay up, while NSF lets neighbors keep routing adjacencies during recovery.
   • NSF reboots all line cards to clear stale entries, while SSO is responsible only for keeping IPsec session state.
   • SSO cannot work without BGP Graceful Restart, whereas NSF operates only on Layer 2 spanning-tree adjacencies.

4. Which supervisor redundancy mode synchronizes state to minimize forwarding disruption during a supervisor switchover?

   • Route Processor Redundancy (RPR)
   • RPR-Plus
   • Stateful Switchover (SSO)
   • Hot Standby Router Protocol (HSRP)

5. In Cisco StackWise Virtual (SV), how are control plane operations handled across the dual-switch deployment?

   • Both switches run their own independent control plane protocols in an active/active arrangement with two management IPs.
   • One switch runs the control plane as active and the other is hot standby, so the pair acts as one logical device.
   • The control plane is offloaded to an external Cisco Catalyst Center appliance that programs both switches remotely.
   • Only Layer 2 switching is supported across the pair, so routing must stay on a separate upstream router.

6. What trigger causes a Cisco StackWise primary switch failover to transition the standby stack member to the active role?

   • A high-priority syslog message arrives from a downstream neighbor switch
   • A link flap is detected on an untagged access port of the active switch
   • The active switch fails, reloads, or is removed from the stack
   • A new member with a lower priority value is added to the running stack

7. What total stacking bandwidth capacity is provided by Cisco StackWise-480 technology on Catalyst 3850/9300 series switches?

   • 480 Gbps
   • 160 Gbps
   • 80 Gbps
   • 960 Gbps

8. Which command verifies the current SSO redundancy state of the active and standby supervisors on a modular Catalyst switch?

   • show redundancy
   • show spanning-tree summary
   • show standby brief
   • show etherchannel summary

9. In a Cisco StackWise Virtual topology, what is the purpose of the Dual-Active Detection (DAD) link separate from the StackWise Virtual Link (SVL)?

   • It carries all production data traffic between the two chassis whenever the SVL interconnect becomes congested.
   • It gives the pair a separate path to detect an SVL failure while both are up, preventing a split-brain dual-active state.
   • It supplies redundant power between the two chassis so that one unit can keep the other one running during a PSU outage.
   • It synchronizes the NTP clock and the configuration between the two switches so their logs line up correctly.

10. What does NSF Graceful Restart accomplish specifically for a routing protocol such as OSPF during a supervisor switchover on an SSO-enabled switch?

    • Neighbors keep the adjacency and forward on the last known routes while the new active supervisor rebuilds OSPF.
    • OSPF is disabled entirely on the switch until the switchover completes and the new supervisor has fully booted.
    • Every OSPF neighbor is forced to reset its adjacency at once so the new supervisor can rebuild a clean database.
    • OSPF hellos are permanently replaced with BFD packets so that the neighbors never notice the supervisor change.

11. Which HSRP feature allows a router that was previously active, after recovering from a failure, to automatically reclaim the active role from a lower-priority router that took over during the outage?

    • Preempt
    • Tracking
    • Authentication
    • Virtual MAC assignment

12. In a dual-supervisor SSO switch, why does a switchover between supervisors typically not cause the connected line cards or their interfaces to reset?

    • SSO syncs FIB and adjacency state to the standby beforehand, so line cards keep forwarding from programmed tables.
    • Line cards run their own operating system that is unrelated to the supervisor and never needs any state from it.
    • Every interface is administratively shut down before a switchover and brought back up only after it completes.
    • SSO disables all Layer 2 forwarding during normal operation, so there is no hardware state left to lose at failover.

13. Which redundancy mode provides less forwarding continuity than SSO because it does not synchronize dynamic state (such as Layer 2/Layer 3 forwarding tables) between the active and standby supervisor?

    • Route Processor Redundancy (RPR)
    • Stateful Switchover (SSO) mode
    • Cisco StackWise Virtual (SVL)
    • Nonstop Forwarding (NSF) with SSO

14. What is the significance of HSRP's virtual IP address remaining constant during an active router failover to the standby router?

    • Hosts keep the same gateway IP and ARP entry, because the new active router answers with the same virtual MAC.
    • Every end host must be reconfigured with a new default gateway address after the failover has completed.
    • The virtual IP changes to the standby router's own physical interface address, and hosts re-ARP for it.
    • All DHCP leases on the segment are invalidated, so hosts must request new addresses after every single failover.

15. In Cisco StackWise Virtual, what happens when Dual-Active Detection confirms a genuine dual-active (split-brain) condition?

    • Both switches keep forwarding as active at the same time, and no further action is taken by either one
    • One switch enters recovery mode and shuts its interfaces except SVL, DAD, and excluded ports
    • The recovery switch reboots into ROMMON and stays there until an administrator reloads it manually
    • The pair automatically converts itself into an HSRP pair, with one switch acting as the standby router

16. Why is Bidirectional Forwarding Detection (BFD) often paired with NSF-aware routing protocols on high-availability switches instead of relying solely on the routing protocol's own hello/dead timers?

    • BFD detects neighbor loss in milliseconds, much faster than hello/dead timers, and can work alongside NSF.
    • BFD replaces the routing protocol entirely, so OSPF and EIGRP no longer need to form adjacencies at all.
    • BFD operates only on wireless backhaul links, so it is used to protect the access points rather than uplinks.
    • BFD automatically disables NSF whenever it is configured, which is why it prevents slow graceful restarts.

17. How do Stateful Switchover (SSO) and Nonstop Forwarding (NSF) collaborate on a dual-supervisor Cisco Catalyst switch during an active supervisor failure?

    • SSO keeps control plane state in sync, while NSF lets neighbors keep adjacencies and routes.
    • SSO encrypts Layer 2 frames, while NSF manages power distribution across PoE switch ports.
    • SSO forces a complete reboot of all line cards, while NSF rebuilds the RIB from scratch using BGP updates.
    • SSO operates exclusively on WAN Edge devices, while NSF is restricted to lightweight access points.