Loop-Free Alternate (LFA) and remote LFA

A Loop-Free Alternate (LFA) is a concept that is used in various technologies, including OSPF, other routing protocols, as well as in MPLS. An LFA is a node other than the primary neighbor, or the primary next hop for a particular route. It is a backup of sorts. Traffic is immediately directed towards the LFA after a network failure. The LFA will receive traffic and will continue to forward it without any knowledge of a failure. LFAs always use a directly connected next hop.

Remote LFAs are LFAs that are not directly connected to the router in question. To achieve this, a tunnel is created from the router in question to the remote LFA node to "simulate" the next-hop nature of a neighbor.

For more information, see:

Protocols with LFA support

Links:

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_pi/configuration/xe-3s/iri-xe-3s-book/iri-ip-lfa-frr.html#GUID-2053F6E5-2855-4F0D-BCDB-62502549CCB0

https://networklessons.com/cisco/ccie-routing-switching-written/ospf-remote-loop-free-alternate-lfa-fast-reroute-frr