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Routing & Switching · Advanced

Adjacency Table

The CEF table holding Layer 2 rewrite information for each next hop, built from ARP and other resolution protocols.

Definition

Each FIB entry points to an adjacency containing the prebuilt Layer 2 header for the next hop. Special adjacencies include glean (needs ARP), punt (send to CPU), drop, discard and null. Incomplete adjacencies cause traffic to be punted until ARP resolves.

Example

show adjacency detail

Exam tip

A 'glean' adjacency means the next hop is on a connected subnet but its MAC is not yet resolved.

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