What is the result when an active route processor fails that combines NSF with SSO?

Question

Options

• AAn NSF-capable device immediately updates the standby route processor RIB without
• BThe standby route processor immediately takes control and forwards packets along known
• CAn NSF-aware device immediately updates the standby route processor RIB without churning
• DThe standby route processor temporarily forwards packets until route convergence is

• A
  6% (2)
• B
  87% (27)
• C
  3% (1)
• D
  3% (1)

Explanation

NSF + SSO Failover Behavior

When NSF (Non-Stop Forwarding) is combined with SSO (Stateful Switchover), the standby route processor has been continuously synchronized with the active processor's state, so upon failure it immediately assumes control and continues forwarding packets along already-known routes - with no interruption to traffic flow. This is the core purpose of combining these two technologies: SSO ensures seamless stateful handoff, while NSF maintains forwarding continuity during routing protocol reconvergence.

• Option A is incorrect because it's an NSF-capable device (the failing router itself) that maintains forwarding - not a device that "immediately updates the standby RIB." The phrasing is also incomplete and misleading about the role of NSF-capable neighbors.
• Option C is incorrect because it confuses the role of NSF-aware neighbors (which are third-party devices that assist reconvergence) with what actually happens during the switchover itself.
• Option D is incorrect because it implies temporary, degraded forwarding until convergence, which describes basic NSF without SSO - SSO eliminates that gap by pre-synchronizing state.

Memory Tip: Think of SSO as the "warm handoff" and NSF as "keeping the traffic moving." Together = instant takeover, no packet loss - like a relay race where the baton is already in the next runner's hand before the switch.

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