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Routing & Switching · Intermediate

Cisco Express Forwarding (CEF)

Cisco's default topology-based switching mechanism using a precomputed FIB and adjacency table for fast forwarding.

Definition

CEF builds the Forwarding Information Base from the RIB and the adjacency table from ARP or other Layer 2 resolution, so packets are forwarded without per-packet route lookups by the CPU. It supports per-destination (default) and per-packet load sharing and is required for MPLS. On hardware platforms CEF tables are programmed into ASIC TCAM.

Example

show ip cef 10.1.1.0 detail

Exam tip

CEF has replaced process switching and fast switching; per-destination load sharing is the default.

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