1. A virtual machine manager, the virtual machine manager being arranged to host one or more virtual machines, the virtual machines forming part of a segmented virtual network, the virtual machine manager being arranged to receive outgoing messages from the virtual machines, at least a given one of the outgoing messages having a part allocated for an intermediate destination address representing an intermediate node in a local segment of the segmented virtual network, the intermediate node being suitable for passing the given outgoing message on towards a destination node in another of the segments, the virtual machine manager having a router for determining a new intermediate destination address outside the local segment, and for routing the given outgoing message according to the new intermediate destination address.