IS-IS Policy Based Loop Free Alternate(LFA) routes

Support for IS-IS loop-free alternate (LFA) routes essentially adds IP fast-reroute capability for IS-IS. The device precomputes multiple loop-free backup routes for all IS-IS routes. These backup routes are preinstalled in the Packet Forwarding Engine, which performs a local repair and implements the backup path when the link for a primary next hop for a particular route is no longer available. The selection of the LFA is done randomly by selecting any matching LFA to progress to the given destination. This does not ensure best backup coverage available for the network. To choose the best LFA, you can configure network-wide backup selection policies for each destination (IPv4 and IPv6) and a primary next-hop interface. These policies are evaluated based on admin-group, srlg, bandwidth, protection-type, metric, and neighbor information.