The LFA SPF policy consists of applying a route next hop policy template to a set of prefixes.
The user first creates a route next hop policy template under the global router context.
CLI syntax
config>router>route-next-hop-policy>template template-nameA policy template can be used in both IS-IS and OSPF to apply the specific criteria described in the next sub-sections to prefixes protected by LFA. Each instance of IS-IS or OSPF can apply the same policy template to one or more prefix lists and to one or more interfaces.
The commands within the route next hop policy use the begin-commit-abort model introduced with BFD templates. The following are the steps to create and modify the template.
To create a template, the user enters the name of the new template directly under route-next-hop-policy context.
To delete a template which is not in use, the user enters the no form for the template name under the route-next-hop-policy context.
The user enters the editing mode by executing the begin command under route-next-hop-policy context. The user can then edit and change any number of route next hop policy templates. However, the parameter value can still be stored temporarily in the template module until the commit is executed under the route-next-hop-policy context. Any temporary parameter changes are lost if the user enters the abort command before the commit command.
The user is allowed to create or delete a template instantly when in the editing mode without the need to enter the commit command. Furthermore, the abort command if entered has no effect on the prior deletion or creation of a template.
After the commit command is issued, IS-IS or OSPF re-evaluates the templates and if there are any net changes, it schedules a new LFA SPF to re-compute the LFA next hop for the prefixes associated with these templates.