Techniques are provided for optimizing multicast routing in a network. At a router device, a message is sent to one or more physical devices. The message is configured to solicit a response indicating a network assignment for each of the physical devices. A response message is received from each of the physical devices. The response message comprises network assignment information for each of the physical devices. For each of the physical devices, the network assignment information is translated into a segment identifier. The segment identifier is distributed to other router devices in the network.