Question

A service provider is deploying SR-MPLS with Flexible Algorithm to create a low-latency forwarding plane. The network architect defines Flex-Algo 128 on the controller and configures a subset of routers to participate. During validation, a downstream router that was NOT configured to participate in Flex-Algo 128 is dropping traffic destined to a Prefix-SID advertised for algorithm 128. What is the most likely reason for this behavior?

Accepted Answer

Routers that do not participate in a Flex-Algo do not install forwarding entries for prefixes advertised in that algorithm, so they cannot forward algorithm-specific traffic

Answer

Flex-Algo requires all routers in the IGP domain to share the same SRGB, and a mismatch is silently dropping the labeled packets

Answer

The non-participating router needs an explicit static route for the Flex-Algo 128 Prefix-SID before it will forward the traffic

Answer

Flex-Algo 128 must be redistributed into BGP for the non-participating router to learn the algorithm-specific path