SRv6 Flex-Algo Route Import

SRv6 Flex-Algo route import allows you to use a route-policy for Flex-Algo mapping. Currently, this applies to two scenarios: IS-IS inter-process route import and BGP route import to IS-IS.

IS-IS Inter-process Route Import

As shown in Figure 1, when an IPv6 route of another IS-IS process is imported to an IS-IS process, if the route carries a Flex-Algo, it can be mapped to a new Flex-Algo. If no mapping is configured, the import node checks whether the process has the corresponding FAD. If not, the import node does not advertise the SRv6 Locator TLV in the process.

Figure 1 SRv6 Flex-Algo route import across IS-IS processes

BGP Route Import to IS-IS

As shown in Figure 2, when an IPv6 route of a BGP process is imported to an IS-IS process, if the route is generated based on the IPv6 Prefix Reachability TLV, it can be converted into the Flex-Algo-based SRv6 Locator TLV and flooded in the IS-IS process. After the original algorithm is mapped to the Flex-Algo in the IS-IS process, the SRv6 Locator TLV is advertised, and Prefix Reachability TLV 236/237 is not advertised. If Prefix Reachability TLV 236/237 is advertised, Prefix Reachability TLV 236/237 is preferentially selected when there are two route sources with the same prefix. As a result, the route generated after mapping to the Flex-Algo cannot be preferentially selected.

Figure 2 Importing an IPv6 route of a BGP process to an IS-IS process