A flexible-algorithm routing method comprises: receiving, by a first router, a route advertisement including a base node label, for a second router, associated with a segment routing path without flexible-algorithm, wherein the second router participates in a flexible-algorithm; deducing, by the first router and from the base node label, a node label, for the second router, associated with a segment routing path with the flexible-algorithm; and constructing, by the first router, a label stack including the node label for the second router to steer a packet to the second router via the segment routing path with the flexible-algorithm.