@Override
  public void tombstone(NetworkEntity network) throws ExternalException {
    List<Vm> vmsOnNetwork = vmBackend.filterByNetwork(network.getId());
    if (!vmsOnNetwork.isEmpty()) {
      logger.info("There are {} VMs still on network {}", vmsOnNetwork.size(), network.getId());
      return;
    }

    xenonClient.delete(
        NetworkServiceFactory.SELF_LINK + "/" + network.getId(), new NetworkService.State());
    tombstoneBackend.create(Subnet.KIND, network.getId());
    logger.info("network {} tombstoned", network.getId());
  }