diff --git a/neutron_tempest_plugin/api/test_port_forwarding_negative.py b/neutron_tempest_plugin/api/test_port_forwarding_negative.py
new file mode 100644
index 0000000..76dd6ee
--- /dev/null
+++ b/neutron_tempest_plugin/api/test_port_forwarding_negative.py
@@ -0,0 +1,83 @@
+# Copyright 2020 OpenStack Foundation
+# All Rights Reserved.
+#
+#    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 tempest.lib.common.utils import data_utils
+from tempest.lib import decorators
+from tempest.lib import exceptions
+
+from neutron_tempest_plugin.api import base
+from neutron_tempest_plugin import config
+
+CONF = config.CONF
+
+
+class PortForwardingNegativeTestJSON(base.BaseNetworkTest):
+    required_extensions = ['router', 'floating-ip-port-forwarding']
+
+    @classmethod
+    def resource_setup(cls):
+        super(PortForwardingNegativeTestJSON, cls).resource_setup()
+        cls.ext_net_id = CONF.network.public_network_id
+
+        # Create network, subnet, router and add interface
+        cls.network = cls.create_network()
+        cls.subnet = cls.create_subnet(cls.network)
+        cls.router = cls.create_router(data_utils.rand_name('router'),
+                                       external_network_id=cls.ext_net_id)
+        cls.create_router_interface(cls.router['id'], cls.subnet['id'])
+
+    @decorators.attr(type='negative')
+    @decorators.idempotent_id('63c0d406-99d5-11ea-bb37-0242ac130002')
+    def test_mapping_same_fip_and_external_port_to_different_dest(self):
+        port1 = self.create_port(self.network)
+        port2 = self.create_port(self.network)
+        fip_for_pf = self.create_floatingip()
+
+        self.create_port_forwarding(
+            fip_for_pf['id'],
+            internal_port_id=port1['id'],
+            internal_ip_address=port1['fixed_ips'][0]['ip_address'],
+            internal_port=1111, external_port=2222,
+            protocol="tcp")
+
+        self.assertRaises(
+            exceptions.BadRequest,
+            self.create_port_forwarding,
+            fip_for_pf['id'],
+            internal_port_id=port2['id'],
+            internal_ip_address=port2['fixed_ips'][0]['ip_address'],
+            internal_port=3333, external_port=2222,
+            protocol="tcp")
+
+    @decorators.attr(type='negative')
+    @decorators.idempotent_id('0c229a4c-9f28-11ea-bb37-0242ac130002')
+    def test_mapping_different_external_ports_to_the_same_destination(self):
+        port = self.create_port(self.network)
+        fip_for_pf = self.create_floatingip()
+
+        self.create_port_forwarding(
+            fip_for_pf['id'],
+            internal_port_id=port['id'],
+            internal_ip_address=port['fixed_ips'][0]['ip_address'],
+            internal_port=1111, external_port=3333,
+            protocol="tcp")
+
+        self.assertRaises(
+            exceptions.BadRequest,
+            self.create_port_forwarding,
+            fip_for_pf['id'],
+            internal_port_id=port['id'],
+            internal_ip_address=port['fixed_ips'][0]['ip_address'],
+            internal_port=1111, external_port=5555,
+            protocol="tcp")