EIGRP LFA FRR
EIGRP Loop-Free Alternate (LFA) Fast Reroute (FRR) is a feature that allows EIGRP to switch to a backup path in less than 50 ms. Fast reroute means we switch to another next hop, Loop-free alternate is an alternative path in the network that is loop-free.
There are two different methods to calculate LFAs:
EIGRP supports LFA FRR since IOS 15.2(4)S or IOS XE 3.7S.
Here is an overview of other routing protocols that support LFA: