func setNetworkInterface(prefix, network, subnet string) *compute.NetworkInterface {
	var netif = new(compute.NetworkInterface)
	netif.AccessConfigs = []*compute.AccessConfig{
		&compute.AccessConfig{
			Type: "ONE_TO_ONE_NAT",
			Name: "External NAT",
		},
	}
	netif.Network = prefix + "/global/networks/" + network
	if subnet != "" {
		netif.Subnetwork = "regions/us-east1/subnetworks/" + subnet
	}

	return netif

}