Question

What information is maintained in the CEF adjacency table?

Answer 1

The CEF (Cisco Express Forwarding) adjacency table maintains information about the next-hop router's Layer 2 (L2) addresses for each prefix in the CEF forwarding table.

In other words, the adjacency table is a mapping table that associates the L2 address of the next-hop router with the destination prefix in the CEF forwarding table. When a packet needs to be forwarded to a destination address, the router looks up the prefix in the CEF table and then checks the adjacency table to determine the L2 address of the next-hop router for that prefix.

The adjacency table is important for optimizing packet forwarding performance, as it enables the router to quickly identify the L2 address of the next-hop router without needing to perform additional L2 address resolution procedures such as ARP (Address Resolution Protocol) for each packet.