After a Flex-Algo is defined by a user based on service requirements, the IGP can use this Flex-Algo to calculate paths that meet the requirements.
You can select one or two devices in the same IGP domain to configure flexible algorithm definitions (FADs). To improve reliability, you are advised to select two devices. A FAD is generally represented by a 3-tuple: Metric-Type, Calc-Type, and Constraints.
Because each user can individually define their Flex-Algos, the same Flex-Algo running on devices in the same IGP domain may have different FADs. To ensure that the path calculated using a specific Flex-Algo is loop-free, one FAD must be preferentially selected and advertised in the domain.
The detailed selection rules are as follows:
In the advertisement domain of FADs, the FAD with the highest priority is preferred.
If the FADs advertised in an IS-IS domain have the same priority, the FAD generated by the device with the largest system ID is preferred.
The system view is displayed.
A Flex-Algo is created, and the Flex-Algo view is displayed.
The priority of the Flex-Algo is configured.
A larger value indicates a higher priority.
The Metric-Type of the Flex-Algo is configured.
After this command is configured, links must have the corresponding metric type. Otherwise, these links will be pruned and cannot participate in IGP path calculation.
The affinity attribute of the Flex-Algo is configured.
A FAD can constrain a path to include or exclude a link with a specific affinity attribute. The following three types of affinity attributes are defined for FADs:
Include-All Admin Group (include-all): A link is included in path calculation only if each link administrative group bit has the same name as the corresponding affinity bit.
The configuration is committed.