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Routing & Switching · Intermediate

Forwarding Information Base (FIB)

The data-plane table, derived from the RIB, used to forward packets at high speed.

Definition

The FIB mirrors the best routes in the RIB with fully resolved next hops, avoiding recursive lookups during forwarding. Changes in the RIB are pushed to the FIB, and on hardware routers the FIB is programmed into line-card ASICs. Junos calls this the forwarding table on the Packet Forwarding Engine.

Example

show route forwarding-table on Junos displays the FIB.

Exam tip

Forwarding uses the FIB, not the RIB; the FIB has resolved next hops while the RIB may have recursive ones.

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