A method of a network device identifies multi-homed prefixes in an intermediate system-intermediate system (IS-IS) area or IS-IS domain during shortest path first (SPF) computation for use in a loop free alternate (LFA) computation. The method and network device select a next node in a shortest path tree (SPT) and determine a set of prefixes associated with the selected node in the SPT. A next prefix from the set of prefixes of the selected node is selected and a check is made whether the selected prefix exists in the local RIB associated with another node of a same level, then the selected prefix is marked as a multi-homed prefix in the local RIB. A check is made whether all prefixes associated with the selected node are processed and whether all nodes in the SPT have been processed, before downloading the local RIB to a global RIB.