Mapping discovery for virtual network

A network interface that provides, to a user, access to a virtual network, comprising:

• a physical network interface arranged to receive data packets from the user to be sent across the virtual network, the data packets comprising a destination address in an address space of the virtual network;
• an address mapper arranged to determine from the destination address a forwarding address where the forwarding address is an address in an address space of a forwarding network, the address in the address space of the forwarding network identifying a remote interface in a plurality of remote interfaces, the remote interfaces spanning multiple network segments and being coupled by multipoint tunneling through the forwarding networks;
• and,
• a configuration part arranged to automatically configure the address mapper by sending from the network interface a discovery request for a given virtual network address over the forwarding network, to prompt a response with an indication of a corresponding forwarding address, and to use the indication in such a response to configure the address mapper, wherein the discovery request is encapsulated in a multicast packet that includes a virtual network address and wherein a virtual net daemon tunnels the multicast packet to peer daemons on remote network segments.