H12-821_V1.0 · Question #1120
A forwarding information database (FIB) can directly guide packet forwarding on a router.
The correct answer is A. TRUE. A FIB is a pre-computed lookup table derived from the routing table (RIB) that maps destination prefixes directly to next-hop interfaces and MAC addresses - giving routers everything needed to forward a packet without any additional computation. Because the FIB is already…
Question
Options
- ATRUE
- BFALSE
How the community answered
(62 responses)- A81% (50)
- B19% (12)
Explanation
A FIB is a pre-computed lookup table derived from the routing table (RIB) that maps destination prefixes directly to next-hop interfaces and MAC addresses - giving routers everything needed to forward a packet without any additional computation. Because the FIB is already resolved and optimized for hardware-speed lookup (often implemented in TCAM/ASICs), it directly drives the packet forwarding plane, making A (TRUE) correct. Option B is wrong because it confuses the FIB with the RIB (Routing Information Base); the RIB holds routing protocol data and requires further processing before forwarding can occur, but the FIB skips that step entirely.
Memory tip: Think of the FIB as a phone book - the router already looked up the number (next hop), so when a packet arrives it just dials immediately. The RIB is the raw directory you had to search to build that phone book.
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