As the network administrator of a company checks the FIB of the router. What fields does the FIB contain? (Multiple choice)

Question

Options

• ATimeStamp
• BInterface
• CDestination/Mask
• DCost

• A
  74% (29)
• B
  8% (3)
• C
  5% (2)
• D
  13% (5)

Explanation

There appears to be an error in the provided answer key, and following it would teach you incorrect networking fundamentals. Let me clarify what the FIB actually contains.

The Forwarding Information Base (FIB) is a data structure derived from the routing table that routers use for fast packet forwarding decisions. Its standard fields are Destination/Mask (C) and Interface (B) - along with next-hop address. Destination/Mask identifies the network prefix a packet must match, and the outgoing Interface tells the router where to physically forward that packet. These two are the core FIB entries present in virtually every implementation (Cisco, Huawei, Juniper, etc.).

Cost (D) is a distractor because cost/metric belongs to the Routing Information Base (RIB), not the FIB. The FIB is already pre-computed for forwarding; it doesn't need to re-evaluate path cost.

TimeStamp (A) is not a standard FIB field - timestamps appear in routing protocol adjacency tables or log entries, not in the forwarding table itself.

Memory tip: Think of FIB as "Direction + Interface" - where to send it (Destination/Mask) and which door to use (Interface). If your exam key says only A is correct, the key likely contains an error - the accepted correct answers should be B and C.

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