An apparatus searches for one or more first routes coupling starting and ending point nodes in a communication network including an asymmetry node, based on topology information indicating a connection relationship between nodes on the communication network. The apparatus determines, for each of the one or more first routes, whether or not signals are transmittable between the starting and ending point nodes under path restriction imposed on the asymmetry node, based on asymmetry-node information indicating the path restriction imposed on the asymmetry node. The apparatus determines a second route that has a minimum sum of link costs among one or more third routes for which it is determined that signals are transmittable between the starting and ending point nodes under the path restriction imposed on the asymmetry node, based on cost information storing a link cost of a link connecting each pair of adjacent nodes on the communication network.