protected Name getReverseZoneName(Configuration conf) {
    Name name = null;
    String zoneSubnet = getZoneSubnet(conf);
    if (zoneSubnet == null) {
      LOG.warn("Zone subnet is not configured.  Reverse lookups disabled");
    } else {
      // is there a netmask
      String mask = conf.get(KEY_DNS_ZONE_MASK);
      if (mask != null) {
        // get the range of IPs
        SubnetUtils utils = new SubnetUtils(zoneSubnet, mask);
        name = getReverseZoneName(utils, zoneSubnet);
      } else {
        name = getReverseZoneName(zoneSubnet);
      }
    }
    return name;
  }
@Test
  public void testReverseZoneNames() throws Exception {
    Configuration conf = new Configuration();
    conf.set(KEY_DNS_ZONE_SUBNET, "172.26.32.0");
    conf.set(KEY_DNS_ZONE_MASK, "255.255.224.0");

    Name name = getRegistryDNS().getReverseZoneName(conf);
    assertEquals("wrong name", "26.172.in-addr.arpa.", name.toString());
  }