This feature modifies the LFA next-hop selection algorithm. The SRLG and admin-group criteria are applied before running the LFA next-hop selection algorithm. Links that do not include one or more of the admin-groups in the include-group statements and links that belong to admin-groups that have been explicitly excluded using the exclude-group statement, and the links which belong to the SRLGs used by the primary next-hop of a prefix are first pruned. The pruning applies only to IP next hops.
Only IP next hops (specified using the command nh-type ip) are supported on 7210 SAS and are considered for LFA selection.
The following is the modified LFA selection algorithm which is applied to prefixes resolving to a primary next-hop which uses a specific route next-hop policy template:
Prune the IP LFA next-hops that use the following links:
links which do not include one or more of the admin-groups in the include-group statements in the route next-hop policy template
links which belong to admin-groups which have been explicitly excluded using the exclude-group statement in the route next-hop policy template
links which belong to the SRLGs used by the primary next-hop of a prefix
Continue with the set indicated in the nh-type value in the route next-hop policy template if not empty; otherwise continue with the other set.
Within IP next-hop set:
Prefer LFA next-hops which do not go over the Pseudo-Node (PN) used by the primary next-hop.
Within selected subset prefer the node-protect type or the link-protect type according to the value of the protection-type option in the route next-hop policy template.
Within the selected subset, select the best admin-groups according to the preference specified in the value of the include-group option in the route next-hop policy template.
Within selected subset, select lowest total cost of a prefix.
If same total cost, select lowest router-id.
If same router-id, select lowest interface-index.