How does the SRv6 IS-IS Flexible Algorithm function on the data plane?

Question

Options

• AIt applies path computation algorithms to learn the topology and compute a pair of disjoint LSPs.
• BIt uses the TE metric in its path calculations to optimize the cumulative TE metric.
• CIt automatically delivers traffic to the destination over an engineered path computed by the IGP.
• DIt uses the IGP metric in its path calculations to optimize reachability.

• A
  3% (2)
• B
  6% (4)
• C
  75% (48)
• D
  16% (10)

Explanation

C is correct because SRv6 Flexible Algorithm operates on the data plane by encoding the algorithm ID directly into SRv6 SIDs, allowing routers to automatically forward packets along the IGP-computed engineered path - no explicit signaling protocol (like RSVP-TE) is needed. The intelligence lives in the control plane (IS-IS computes the topology-aware path), and the data plane simply executes it.

Why the distractors are wrong:

• A is wrong because computing disjoint LSP pairs describes RSVP-TE control plane behavior, and "LSPs" are an MPLS concept - not SRv6.
• B is wrong because while Flex-Algo can optionally use TE metrics, that describes one possible control plane configuration, not the data plane function; also, it isn't limited to TE metric.
• D describes standard IS-IS SPF behavior (optimize reachability via IGP metric) - that's the default algorithm, not what makes Flex-Algo distinctive, and again refers to path calculation, not data plane forwarding.

Memory tip: Think of Flex-Algo's data plane role as "follow the SID, trust the IGP" - the algorithm is baked into the SRv6 SID, so the data plane automatically steers traffic without any explicit tunnel signaling, which is the whole SR philosophy applied to engineered paths.

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