Refer to the exhibit. A network engineer must optimize link failures on the OSPF routing domain. The solution must follow RFC 5286, and downtime must be no more than 50 ms. All known subnets on R1 mus

Question

Exhibit

Options

• AConfigure ip ospf frr per-prefix candidate enable high under the interface configuration
• BConfigure frr per-prefix enable priority high under the global OSPF configuration.
• CConfigure ip ospf fast-reroute per-prefix candidate enable under the interface configuration.
• DConfigure fast-reroute per-prefix enable prefix-priority low under the global OSPF configuration.

• A
  2% (1)
• B
  14% (6)
• C
  9% (4)
• D
  75% (33)

Explanation

RFC 5286 defines Loop-Free Alternates (LFA) for IP Fast Reroute, which pre-computes backup next-hops to achieve sub-50ms convergence on link failure without waiting for SPF reconvergence. In Cisco IOS XE, OSPF LFA (fast-reroute) is configured in two parts: (1) globally under the OSPF process to enable the feature and define which prefixes to protect, and (2) per-interface to mark candidate interfaces for backup path computation. The command 'fast-reroute per-prefix enable prefix-priority low' under the OSPF process enables protection for ALL prefixes, including those marked as low priority. Since the requirement states that ALL known subnets on R1 must be protected, using 'prefix-priority low' ensures no prefixes are excluded. Option A uses incorrect syntax ('ip ospf frr'). Option B omits the required prefix-priority designation. Option C uses correct interface-level syntax but the interface command alone without the global configuration is insufficient to enable the feature.

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