An SR policy consists of a set of one or more candidate paths. Each candidate path may be described by an SR policy route, that may be a static SR policy that is configured under the config>router>segment-routing>sr-policies context, or a dynamic route imported by BGP. The router checks the consistency of the following BFD and protection parameters across all of the SR policy routes for a specified SR policy.
{Maintenance-policy existence}
bfd-enable
bfd-template <name>
mode {linear | ecmp-protected}
revert-timer <timer-value>
Maintenance-policy existence covers the case where the existing programmed route is an SR policy with no maintenance policy, and the new route has a maintenance policy, and vice-versa.
Consistency is enforced across all of the static SR policy candidate paths and dynamic SR policy routes that make up a segment routing policy. Since SR policy routes or paths are imported sequentially and cannot be considered together, inconsistencies are handled as follows:
First policy route imported/configured:
Check: valid set of parameters
Action: If OK, program in data path and activate
Second policy route imported/configured:
Check: valid set of parameters, consistency with existing activated policy route
Action If OK, program in data path and activate, else hold in CPM but do not program
Third policy route imported/configured:
Check: valid set of parameters, consistency with existing activated policy route (s)
Action If OK, program in data path and activate, else hold in CPM but do not program
Inconsistent policy routes (paths) are only programmed if their parameters are valid and any programmed routes for that SR policy are deleted.
By using the same maintenance policy for all of the SR policy's routes, inconsistencies between the BFD and protection parameters of SR policy routes belonging to a specified SR policy can be avoided.