At the data link layer, a FIB is most notably used to facilitate Ethernet bridging based on MAC addresses.
Other data-link-layer technologies using FIBs include Frame Relay, Asynchronous Transfer Mode (ATM) and Multiprotocol Label Switching (MPLS).
Without a functional FIB, all frames received by a network switch would be echoed back out to all other ports, much like an Ethernet hub.
These tables may be configured statically, or they can be distributed by the Private Network-to-Network Interface (PNNI) protocol.
FIBs are optimized for fast lookup of destination addresses and can improve performance of forwarding compared to using the routing information base (RIB) directly.
[1] FIBs can also play a role in an Internet best current practice (BCP) of ingress filtering.
[citation needed] While the IETF document BCP 38 on ingress filtering[2] does not specify a method of implementing source address filtering, some router vendors have implemented a mechanism that employs reverse-path forwarding lookups in the router's tables to perform this check.
For the routers near the edge of the Internet, packet filters can provide a simpler and more effective solution than methods that employ routing information lookup, though this approach can be challenging when managing routers that are reconfigured often.
[4][failed verification] Specific router implementations may, when a destination address or other FIB criterion is matched, specify another action to be done before forwarding (e.g., accounting or encryption), or apply an access control list that may cause the packet to be dropped.