Selecting backup LFA for IS-IS routing protocol

The default loop-free alternate (LFA) selection algorithm or criteria can be overridden with an LFA policy. These policies are configured for each destination (IPv4 and IPv6) and a primary next-hop interface. These backup policies enforce LFA selection based on admin-group, srlg, neighbor, neighbor-tag, bandwidth, protection-type, and metric attributes of the backup path. During backup shortest-path-first (SPF) computation, each attribute (both node and link) of the backup path, stored per backup-next hop, is accumulated by IGP. For the routes created internally by IGP, the attribute set of every backup path is evaluated against the policy configured per destination per prefix primary next-hop interface. The first or the best backup path is selected and installed as the backup next-hop in the routing table. To configure the backup selection policy, include the backup-selection configuration statement at the [edit routing-options] hierarchy level. The show backup-selection command displays the configured policies for a given interface and destination. The display can be filtered against a particular destination, prefix, interface, or logical systems.