diff --git a/filter_plugins/unbound_revdns.py b/filter_plugins/unbound_revdns.py
new file mode 100644
index 0000000..a45e08e
--- /dev/null
+++ b/filter_plugins/unbound_revdns.py
@@ -0,0 +1,48 @@
+#!/usr/bin/env python
+
+# Copyright 2017-present Open Networking Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# unbound_revdns - ansible filter - ipv4 address or cidr and generates a
+# reverse DNS string suitable for use with unbound, which requires them in a
+# slightly unusual format when a RFC1918 address is used with a local-zone
+# definition:
+# https://www.unbound.net/documentation/unbound.conf.html
+# https://www.claudiokuenzler.com/blog/699/unbound-dns-not-serving-reverse-lookup-for-internal-addresses-rfc1918
+
+import netaddr
+
+
+class FilterModule(object):
+
+    def filters(self):
+        return {
+            'unbound_revdns': self.unbound_revdns,
+            }
+
+    def unbound_revdns(self, var):
+        (o1, o2, o3, o4) = netaddr.IPNetwork(var).network.words
+
+        revdns = "%d.%d.%d.%d.in-addr.arpa." % (o4, o3, o2, o1)
+
+        if (o2 == 0 or o1 == 10):
+            revdns = "%d.in-addr.arpa." % (o1)
+        elif (o3 == 0
+                or (o1 == 172 and o2 >= 16 and o2 <= 31)
+                or (o1 == 192 and o2 == 168)):
+            revdns = "%d.%d.in-addr.arpa." % (o2, o1)
+        elif(o4 == 0):
+            revdns = "%d.%d.%d.in-addr.arpa." % (o3, o2, o1)
+
+        return revdns