With the advent of virtualization technologies, networks and routing for those networks can now be simulated using commodity hardware rather than actual routers. For example, virtualization technologies such as those provided by VMWare, XEN, or User-Mode Linux can be adapted to allow a single physical computing machine to be shared among multiple virtual networks by providing each virtual network user with one or more virtual machines hosted by the single physical computing machine, with each such virtual machine being a software simulation acting as a distinct logical computing system that provides users with the illusion that they are the sole operators and administrators of a given hardware computing resource. In addition, routing can be accomplished through software, providing additional routing flexibility to the virtual network in comparison with traditional routing. As a result, in some implementations, supplemental information other than packet information can be used to determine network routing.