350-401 Question #764: Real Exam Question with Answer & Explanation

Question

When using BFD in a network design, which consideration must be made?

Options

• ABFD is used with first hop routing protocols to provide subsecond convergence.
• BBFD is more CPU-intensive than using reduced hold timers with routing protocols.
• CBFD is used with dynamic routing protocols to provide subsecond convergence.
• DBFD is used with NSF and graceful to provide subsecond convergence.

Explanation

BFD is primarily used to integrate with dynamic routing protocols to provide sub-second failure detection, enabling rapid network convergence.

Common mistakes.

• A. While BFD can integrate with First Hop Redundancy Protocols (FHRPs), its most significant and widespread application for overall network convergence is with dynamic routing protocols, making this choice too narrow.
• B. BFD is designed to be very lightweight and is generally less CPU-intensive than reducing native routing protocol hello and hold timers to excessively low values for fast detection.
• D. BFD's function is rapid failure detection, whereas Nonstop Forwarding (NSF) and Graceful Restart are mechanisms that allow a router to continue forwarding data during control plane restarts, serving a different purpose.

Concept tested. BFD benefits and integration with routing protocols

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bfd/configuration/xe-16/ird-bfd-xe-16-book/ird-bfd-overview.html

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