This disclosure describes techniques relating to assigning unique segment identifiers (SIDs) in a segment routing network. In one example, this disclosure describes a method that includes receiving, by a computing system and from a node on a network, a request to allocate a segment identifier for use in a segment routing network; allocating, by the computing system and from a block of addresses, an assigned segment identifier; responding to the request by outputting, by the computing system and over the network to the node, information about the assigned segment identifier; and maintaining the assigned segment identifier.