How do the RIB and FIB differ in function?
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Correct answer: The FIB is populated based on RIB content..
Why this is the answer
The Forwarding Information Base (FIB) is populated directly from the Routing Information Base (RIB). The RIB contains all learned routes and their associated metrics, while the FIB is an optimized subset of the RIB specifically designed for fast packet forwarding. The router's control plane manages the RIB, making routing decisions, and then populates the FIB, which the data plane uses for efficient lookup and forwarding. The RIB is not a mirror image of the FIB; rather, the FIB is derived from the RIB. IP source prefix-based switching decisions are made using the FIB, not the RIB. While the RIB stores all IP routing information, the FIB is a specialized table for forwarding, not a comprehensive storage of all routing data.
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