Which of the following statements regarding BGP Fast Reroute is FALSE?

Question

Options

• ABGP Fast Reroute is triggered by IGP events.
• BThe backup path is pre-computed and installed in the FIB.
• CBGP Fast Reroute is independent of number of affected prefixes.
• DBGP Fast Reroute uses the optimal path to the destination.

• A
  6% (2)
• B
  3% (1)
• D
  90% (28)

Explanation

Option D is false because BGP Fast Reroute deliberately uses a pre-computed backup (alternate) path, not the optimal path - the optimal path is already the active primary route. The backup path may be suboptimal by design; what matters is that it's ready to forward traffic immediately upon failure without waiting for control-plane reconvergence.

Why the distractors are true (and thus not the answer):

• A is true: BGP FRR is triggered by IGP events (e.g., link-down detection via BFD or IGP updates), which signal the need to activate the pre-installed backup.
• B is true: The core mechanism of BGP FRR is pre-computing the backup path and installing it in the FIB before a failure, enabling forwarding-plane-speed switchover.
• C is true: Because paths are pre-installed, switchover time is constant regardless of how many prefixes are affected - this scalability is a primary advantage over traditional BGP convergence.

Memory tip: Think of BGP FRR as a pre-packed detour, not a GPS reroute. It's ready in the FIB waiting to be used - fast, but not necessarily the scenic optimal route.

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