Source routing techniques include sending data across several networks, while limiting source routing overhead. For example, the source routing techniques may use a first address format to route data to nodes along a routing path that are within a first network where a source node is located, and use a second address format to route the data to a node along the routing path that is within a second, different network. The node in the second network may similarly route the data through the second network using the first address format for nodes within the second network and, if needed, route the data to a node within a third network using the second address format. This may be repeated for any number of networks to reach a destination.