1. A method, comprising: advertising, into a global computer network, from a particular field area router (FAR) in a local computer network having a plurality of FARs, a common subnet prefix assigned to the local computer network, wherein each of the plurality of FARs of the local computer network is configured to accept any traffic destined to the local computer network; building a tunnel overlay among the plurality of FARs of the local computer network; receiving a packet at the particular FAR destined to a particular device in the local computer network; and in response to the particular FAR not having a host route to the particular device, selecting a specific FAR of the plurality of FARs to forward the packet to on the tunnel overlay based on the specific FAR having the host route to the particular device and forwarding the packet on the tunnel overlay to the selected FAR.