A method and apparatus routes packets through a network. A network node has outgoing links each associated with at least one link ID. At least one of the links is associated with link IDs. A received packet includes a state variable and routing information which encodes a set of link IDs associated with respective links forming a path through the network. The encoding forms a probabilistic data structure used to test whether a link ID is a member of the set of link IDs. For each of the plurality of outgoing links, the data structure is tested for membership of the link's associated link ID.