In one embodiment, a device determines a set of sources and used destinations for traffic in a computer network, where nodes of the network are configured to send all traffic to the used destinations through a root node of the computer network according to a directed acyclic graph (DAG). The device may then also determine a set of capable nodes as common ancestors to source-destination pairs that provide a more optimal path between the source-destination pairs than traversing the root node, and instructs the set of capable nodes to store downward routes to forward traffic for one or more of the used destinations according to the stored downward route rather than through the root node.