350-401 Question #1352: Real Exam Question with Answer & Explanation

Question

Which feature works with SSO to continue forwarding packets after a route processor failure until the control plane recovers?

Options

• ANSF
• BRSVP
• CHSRP
• DECMP

Explanation

NSF (Non-Stop Forwarding) works hand-in-hand with SSO (Stateful Switchover) to allow a router to continue forwarding data plane traffic even after a route processor (RP) failure, while the control plane rebuilds its routing tables - this combination is often called NSF/SSO. Without NSF, a failover event would cause a routing protocol reconvergence that drops traffic; NSF prevents this by signaling neighboring routers to continue forwarding packets along known paths during the recovery window.

Why the distractors are wrong:

• RSVP is a resource reservation protocol used for QoS and MPLS traffic engineering - it has no role in maintaining forwarding during RP failures.
• HSRP (Hot Standby Router Protocol) provides gateway redundancy between multiple physical routers, not within a single router's dual-RP chassis.
• ECMP (Equal-Cost Multi-Path) is a load-balancing technique that distributes traffic across multiple equal-cost paths - it is unrelated to RP failover continuity.

Memory Tip: Think of NSF = "Never Stop Forwarding" - it partners with SSO to keep packets moving even when the brain (RP) of the router needs to recover. If SSO is the switchover, NSF is the safety net that keeps traffic alive during that switchover.

No community discussion yet for this question.