diff --git a/api-ref/source/v2/networks.inc b/api-ref/source/v2/networks.inc
index 1c8b1d8aa..c3d02a601 100644
--- a/api-ref/source/v2/networks.inc
+++ b/api-ref/source/v2/networks.inc
@@ -40,6 +40,13 @@ The ``external-net`` extension adds the ``router:external`` attribute to
 networks. This boolean attribute indicates the network has an external
 routing facility that's not managed by the networking service.
 
+FloatingIP autodelete internal
+==============================
+
+The ``floatingip-autodelete-internal`` shim extension signals that the
+update of a network's ``router:external`` attribute from ``true`` to
+``false`` autodeletes the unused Floating IPs of that network.
+
 L2 adjacency extension
 ======================
 
diff --git a/api-ref/source/v2/parameters.yaml b/api-ref/source/v2/parameters.yaml
index 4af2e386a..805ed7792 100644
--- a/api-ref/source/v2/parameters.yaml
+++ b/api-ref/source/v2/parameters.yaml
@@ -5437,7 +5437,9 @@ router-subnet_ids:
 router:external:
   description: |
     Indicates whether the network has an external routing facility that's not
-    managed by the networking service.
+    managed by the networking service. If the network is updated from external
+    to internal the unused floating IPs of this network are automatically
+    deleted when extension ``floatingip-autodelete-internal`` is present.
   in: body
   required: true
   type: boolean
diff --git a/neutron_lib/api/definitions/__init__.py b/neutron_lib/api/definitions/__init__.py
index 167282494..4296ece5c 100644
--- a/neutron_lib/api/definitions/__init__.py
+++ b/neutron_lib/api/definitions/__init__.py
@@ -43,6 +43,7 @@ from neutron_lib.api.definitions import firewall_v2
 from neutron_lib.api.definitions import firewallrouterinsertion
 from neutron_lib.api.definitions import flavors
 from neutron_lib.api.definitions import floating_ip_port_forwarding
+from neutron_lib.api.definitions import floatingip_autodelete_internal
 from neutron_lib.api.definitions import floatingip_pools
 from neutron_lib.api.definitions import flowclassifier
 from neutron_lib.api.definitions import ip_allocation
@@ -140,6 +141,7 @@ _ALL_API_DEFINITIONS = {
     fip_port_details,
     flavors,
     floating_ip_port_forwarding,
+    floatingip_autodelete_internal,
     floatingip_pools,
     ip_allocation,
     ip_substring_port_filtering,
diff --git a/neutron_lib/api/definitions/base.py b/neutron_lib/api/definitions/base.py
index 2413aa99f..c530b150a 100644
--- a/neutron_lib/api/definitions/base.py
+++ b/neutron_lib/api/definitions/base.py
@@ -99,6 +99,7 @@ KNOWN_EXTENSIONS = (
     'fip-port-details',
     'flavors',
     'floating-ip-port-forwarding',
+    'floatingip-autodelete-internal',
     'floatingip-pools',
     'ip-substring-filtering',
     'l3-ha',
diff --git a/neutron_lib/api/definitions/floatingip_autodelete_internal.py b/neutron_lib/api/definitions/floatingip_autodelete_internal.py
new file mode 100644
index 000000000..91d70d7b9
--- /dev/null
+++ b/neutron_lib/api/definitions/floatingip_autodelete_internal.py
@@ -0,0 +1,30 @@
+# Copyright 2019 Ericsson
+#
+# 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.
+
+from neutron_lib.api.definitions import l3
+
+
+ALIAS = 'floatingip-autodelete-internal'
+IS_SHIM_EXTENSION = True
+IS_STANDARD_ATTR_EXTENSION = False
+NAME = 'Autodelete floating IPs of internal networks'
+DESCRIPTION = 'Autodelete unused floating IPs' \
+              ' of networks being turned to router:external=False'
+UPDATED_TIMESTAMP = '2019-01-24T00:00:00-00:00'
+RESOURCE_ATTRIBUTE_MAP = {}
+SUB_RESOURCE_ATTRIBUTE_MAP = {}
+ACTION_MAP = {}
+REQUIRED_EXTENSIONS = [l3.ALIAS]
+OPTIONAL_EXTENSIONS = []
+ACTION_STATUS = {}
diff --git a/neutron_lib/tests/unit/api/definitions/test_floatingip_autodelete_internal.py b/neutron_lib/tests/unit/api/definitions/test_floatingip_autodelete_internal.py
new file mode 100644
index 000000000..de82a1214
--- /dev/null
+++ b/neutron_lib/tests/unit/api/definitions/test_floatingip_autodelete_internal.py
@@ -0,0 +1,20 @@
+# Copyright 2019 Ericsson
+#
+# 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.
+
+from neutron_lib.api.definitions import floatingip_autodelete_internal
+from neutron_lib.tests.unit.api.definitions import base
+
+
+class FloatingIPAutodeleteInternalTestCase(base.DefinitionBaseTestCase):
+    extension_module = floatingip_autodelete_internal
diff --git a/releasenotes/notes/floatingip-autodelete-internal-f08675d8d64d34c6.yaml b/releasenotes/notes/floatingip-autodelete-internal-f08675d8d64d34c6.yaml
new file mode 100644
index 000000000..52d8f1ec4
--- /dev/null
+++ b/releasenotes/notes/floatingip-autodelete-internal-f08675d8d64d34c6.yaml
@@ -0,0 +1,4 @@
+---
+features:
+  - |
+    New shim API extension: ``floatingip-autodelete-internal``.