diff --git a/neutron_lib/api/validators.py b/neutron_lib/api/validators.py
index b8f5c6b55..c6f1ad8de 100644
--- a/neutron_lib/api/validators.py
+++ b/neutron_lib/api/validators.py
@@ -540,6 +540,22 @@ def validate_ip_address_or_none(data, valid_values=None):
         return validate_ip_address(data, valid_values)
 
 
+def validate_ip_or_subnet_or_none(data, valid_values=None):
+    """Validate data is an IP address, a valid IP subnet string, or None.
+
+    :param data: The data to validate.
+    :param valid_values: Not used!
+    :return: None if data is None or a valid IP address or a valid IP subnet,
+    otherwise a human readable message indicating why the data is neither an
+    IP address nor IP subnet.
+    """
+    msg_ip = validate_ip_address_or_none(data)
+    msg_subnet = validate_subnet_or_none(data)
+    if msg_ip is not None and msg_subnet is not None:
+        return _("'%(data)s' is neither a valid IP address, nor "
+                 "is it a valid IP subnet") % {'data': data}
+
+
 def validate_subnet(data, valid_values=None):
     """Validate data is an IP network subnet string.
 
@@ -888,6 +904,7 @@ validators = {'type:dict': validate_dict,
               'type:hostroutes': validate_hostroutes,
               'type:ip_address': validate_ip_address,
               'type:ip_address_or_none': validate_ip_address_or_none,
+              'type:ip_or_subnet_or_none': validate_ip_or_subnet_or_none,
               'type:ip_pools': validate_ip_pools,
               'type:mac_address': validate_mac_address,
               'type:mac_address_or_none': validate_mac_address_or_none,
diff --git a/neutron_lib/tests/unit/api/test_validators.py b/neutron_lib/tests/unit/api/test_validators.py
index 5dbf7e963..d92f45a4e 100644
--- a/neutron_lib/tests/unit/api/test_validators.py
+++ b/neutron_lib/tests/unit/api/test_validators.py
@@ -1026,3 +1026,50 @@ class TestAttributeValidation(base.BaseTestCase):
             {'port_id': '11111111-ffff-ffff-ffff-000000000000'},
         ]
         self.assertIsNone(validators.validate_subports(body))
+
+
+class TestValidateIPSubnetNone(base.BaseTestCase):
+
+    def test_validate_none(self):
+        self.assertIsNone(validators.validate_ip_or_subnet_or_none(None))
+
+    def test_validate_ipv4(self):
+        testdata = "172.0.0.1"
+        self.assertIsNone(validators.validate_ip_or_subnet_or_none(testdata))
+
+    def test_validate_ipv4_subnet(self):
+        testdata = "172.0.0.1/24"
+        self.assertIsNone(validators.validate_ip_or_subnet_or_none(testdata))
+
+    def test_validate_ipv6(self):
+        testdata = "2001:0db8:0a0b:12f0:0000:0000:0000:0001"
+        self.assertIsNone(validators.validate_ip_or_subnet_or_none(testdata))
+
+    def test_validate_ipv6_subnet(self):
+        testdata = "::1/128"
+        self.assertIsNone(validators.validate_ip_or_subnet_or_none(testdata))
+
+    def test_validate_ipv4_invalid(self):
+        testdata = "300.0.0.1"
+        self.assertEqual(("'300.0.0.1' is neither a valid IP address, nor is "
+                          "it a valid IP subnet"),
+                         validators.validate_ip_or_subnet_or_none(testdata))
+
+    def test_validate_ipv4_subnet_invalid(self):
+        testdata = "172.0.0.1/45"
+        self.assertEqual(("'172.0.0.1/45' is neither a valid IP address, nor "
+                          "is it a valid IP subnet"),
+                         validators.validate_ip_or_subnet_or_none(testdata))
+
+    def test_validate_ipv6_invalid(self):
+        testdata = "xxxx:0db8:0a0b:12f0:0000:0000:0000:0001"
+        self.assertEqual(("'xxxx:0db8:0a0b:12f0:0000:0000:0000:0001' is "
+                          "neither a valid IP address, nor is it a valid IP "
+                          "subnet"),
+                         validators.validate_ip_or_subnet_or_none(testdata))
+
+    def test_validate_ipv6_subnet_invalid(self):
+        testdata = "::1/2048"
+        self.assertEqual(("'::1/2048' is neither a valid IP address, nor is "
+                          "it a valid IP subnet"),
+                         validators.validate_ip_or_subnet_or_none(testdata))
diff --git a/releasenotes/notes/validator_ip_or_subnet_or_none-0175f906a9113954.yaml b/releasenotes/notes/validator_ip_or_subnet_or_none-0175f906a9113954.yaml
new file mode 100644
index 000000000..8a7506f37
--- /dev/null
+++ b/releasenotes/notes/validator_ip_or_subnet_or_none-0175f906a9113954.yaml
@@ -0,0 +1,3 @@
+---
+features:
+  - Added validator validate_ip_or_subnet_or_none