diff --git a/neutron/db/ipam_pluggable_backend.py b/neutron/db/ipam_pluggable_backend.py
index 533b335019c..cf787b24717 100644
--- a/neutron/db/ipam_pluggable_backend.py
+++ b/neutron/db/ipam_pluggable_backend.py
@@ -530,6 +530,22 @@ class IpamPluggableBackend(ipam_backend_mixin.IpamBackendMixin):
             ipam_driver = driver.Pool.get_instance(None, context)
             factory = ipam_driver.get_address_request_factory()
             for port in ports:
+                # Find candidate subnets based on host_id and existing
+                # fixed_ips. This will filter subnets on other segments. Only
+                # allocate if this subnet is a valid candidate.
+                p = self._make_port_dict(port)
+                fixed_configured = (p['fixed_ips'] is not
+                                    constants.ATTR_NOT_SPECIFIED)
+                subnet_candidates = obj_subnet.Subnet.find_candidate_subnets(
+                    context,
+                    network_id,
+                    p.get(portbindings.HOST_ID),
+                    p.get('device_owner'),
+                    fixed_configured,
+                    p.get('fixed_ips'))
+                if subnet['id'] not in [s['id'] for s in subnet_candidates]:
+                    continue
+
                 ip = {'subnet_id': subnet['id'],
                       'subnet_cidr': subnet['cidr'],
                       'eui64_address': True,
diff --git a/neutron/tests/unit/extensions/test_segment.py b/neutron/tests/unit/extensions/test_segment.py
index 08c31f4ab8a..328d520bb1f 100644
--- a/neutron/tests/unit/extensions/test_segment.py
+++ b/neutron/tests/unit/extensions/test_segment.py
@@ -1719,6 +1719,78 @@ class TestSegmentAwareIpam(SegmentAwareIpamTestCase):
         self.assertNotIn(subnet_b0['subnet']['id'], res_subnet_ids)
         self.assertNotIn(subnet_b1['subnet']['id'], res_subnet_ids)
 
+    def test_slaac_segment_aware_add_subnet(self):
+        (network, segment_a, segment_b, subnet_a0, subnet_a1, subnet_b0,
+         subnet_b1) = self._create_net_two_segments_four_slaac_subnets()
+
+        # Create a port with no IP address (since there is no subnet)
+        port_deferred = self._create_deferred_ip_port(network)
+        self._validate_deferred_ip_allocation(port_deferred['port']['id'])
+
+        # Create two ports, port_a with subnet_a0 in fixed_ips and port_b
+        # with subnet_b0 in fixed_ips
+        port_a = self._create_port_and_show(
+            network, fixed_ips=[{'subnet_id': subnet_a0['subnet']['id']}])
+        port_b = self._create_port_and_show(
+            network, fixed_ips=[{'subnet_id': subnet_b0['subnet']['id']}])
+        self._validate_immediate_ip_allocation(port_a['port']['id'])
+        self._validate_immediate_ip_allocation(port_b['port']['id'])
+        self.assertEqual(2, len(port_a['port']['fixed_ips']))
+        self.assertEqual(2, len(port_b['port']['fixed_ips']))
+
+        # Add another subnet on segment_a
+        subnet_a2 = self._create_test_slaac_subnet_with_segment(
+            network, segment_a, '2001:db8:a:2::/64')
+        # The port with deferred allocation should not have an allocation
+        req = self.new_show_request('ports', port_deferred['port']['id'])
+        res = req.get_response(self.api)
+        port_deferred = self.deserialize(self.fmt, res)
+        self._validate_deferred_ip_allocation(port_deferred['port']['id'])
+        self.assertEqual(0, len(port_deferred['port']['fixed_ips']))
+        # port_a should get an allocation on the new subnet.
+        # port_b does not get an allocation.
+        req = self.new_show_request('ports', port_a['port']['id'])
+        res = req.get_response(self.api)
+        port_a = self.deserialize(self.fmt, res)
+        req = self.new_show_request('ports', port_b['port']['id'])
+        res = req.get_response(self.api)
+        port_b = self.deserialize(self.fmt, res)
+        self.assertEqual(3, len(port_a['port']['fixed_ips']))
+        self.assertEqual(2, len(port_b['port']['fixed_ips']))
+        port_a_snet_ids = [f['subnet_id'] for f in port_a['port']['fixed_ips']]
+        self.assertIn(subnet_a2['subnet']['id'], port_a_snet_ids)
+
+    def test_slaac_segment_aware_delete_subnet(self):
+        (network, segment_a, segment_b, subnet_a0, subnet_a1, subnet_b0,
+         subnet_b1) = self._create_net_two_segments_four_slaac_subnets()
+
+        # Create two ports, port_a with subnet_a0 in fixed_ips and port_b
+        # with subnet_b0 in fixed_ips
+        port_a = self._create_port_and_show(
+            network, fixed_ips=[{'subnet_id': subnet_a0['subnet']['id']}])
+        port_b = self._create_port_and_show(
+            network, fixed_ips=[{'subnet_id': subnet_b0['subnet']['id']}])
+        self._validate_immediate_ip_allocation(port_a['port']['id'])
+        self._validate_immediate_ip_allocation(port_b['port']['id'])
+        self.assertEqual(2, len(port_a['port']['fixed_ips']))
+        self.assertEqual(2, len(port_b['port']['fixed_ips']))
+
+        # Delete subnet_b1 on segment_b, port_a should keep it's allocations
+        # on the new subnet. Allocation for deleted subnet removed on port_b.
+        req = self.new_delete_request('subnets', subnet_b1['subnet']['id'])
+        res = req.get_response(self.api)
+        self.assertEqual(webob.exc.HTTPNoContent.code, res.status_int)
+        req = self.new_show_request('ports', port_a['port']['id'])
+        res = req.get_response(self.api)
+        port_a = self.deserialize(self.fmt, res)
+        req = self.new_show_request('ports', port_b['port']['id'])
+        res = req.get_response(self.api)
+        port_b = self.deserialize(self.fmt, res)
+        self.assertEqual(2, len(port_a['port']['fixed_ips']))
+        self.assertEqual(1, len(port_b['port']['fixed_ips']))
+        port_b_snet_ids = [f['subnet_id'] for f in port_b['port']['fixed_ips']]
+        self.assertNotIn(subnet_b1['subnet']['id'], port_b_snet_ids)
+
 
 class TestSegmentAwareIpamML2(TestSegmentAwareIpam):