350-401 Question #1032: Real Exam Question with Answer & Explanation

Question

What is one difference between the RIB and the FIB?

Options

• AThe RIB keeps all routing information received from peers, and the FIB keeps the minimum
• BThe RIB works at the data plane, and the FIB works at the control plane.
• CThe FIB contains routing prefixes, and the RIB contains the Layer 2 and Layer 3 information
• DThe RIB is known as the CEF table, and the FIB is known as the routing table.

Explanation

The Routing Information Base (RIB) stores all routing intelligence, while the Forwarding Information Base (FIB) contains only the best routes optimized for efficient packet forwarding.

Common mistakes.

• B. The RIB works at the control plane, gathering routing information, while the FIB works at the data plane, performing high-speed packet forwarding.
• C. The RIB contains routing prefixes and associated metrics, while the FIB contains the best routing prefixes along with pre-calculated Layer 2 rewrite information, not just Layer 2 and Layer 3 information in general.
• D. The RIB is typically known as the routing table, and the FIB is known as the CEF table (or forwarding table), not the other way around.

Concept tested. RIB vs. FIB distinction

Reference. https://www.cisco.com/c/en/us/support/docs/ip/express-forwarding/109012-cef-overview.html

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