Last Updated on August 1, 2021 by Admin 2
Which protocol is used to maintain the contents of the Cisco Express Forwarding (CEF) adjacency table?
The CEF adjacency table is maintained as each adjacent node is discovered. Link header entries are created and stored in the adjacency table as the information is learned through the ARP protocol.
Cisco Express Forwarding (CEF) is a Layer 3 switching technology based on information contained in the Forwarding Information Base (FIB) and the adjacency table.
The FIB is conceptually equivalent to a routing table in that it contains information used in the packet forwarding decision. The adjacency table contains information about the adjacent route processors. The adjacency table contains the MAC information for the next-hop addresses for all FIB entries. A device is considered adjacent if it is reachable over a single Layer 2 connection. It is stored in DRAM.
The Layer 3 processor engine builds the FIB and adjacency tables in software. That information is distributed from the control-plane hardware to the data-plane hardware Application Specific Integrated Circuits (ASICs) at the port or line card. This enhances the Layer 3 forwarding operation by moving it from the software-based engine to the ASICs. Of course, there are exception packets that are still software-processed, such as non-conforming protocols and datalink encapsulations.
Reverse ARP (RARP) is used an obsolete networking protocol used by a host computer to obtain its Internet Protocol (IPv4) address when it has available its link-layer address, such as an Ethernet address. It has been replaced with DHCP. It is not used maintain the contents of the Cisco Express Forwarding (CEF) adjacency table
INverse ARP (INARP) is used by Frame relay connection to dynamically learn the DLCI associated with a connection. It is not used maintain the contents of the Cisco Express Forwarding (CEF) adjacency table
PING is a diagnostic tool used to test connectivity. It is not used maintain the contents of the Cisco Express Forwarding (CEF) adjacency table.
Layer 2 Technologies
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