diff --git a/neutron/db/db_base_plugin_common.py b/neutron/db/db_base_plugin_common.py
index 2ea013d22ce..cdcd347aa12 100644
--- a/neutron/db/db_base_plugin_common.py
+++ b/neutron/db/db_base_plugin_common.py
@@ -107,6 +107,12 @@ class DbBasePluginCommon(common_db_mixin.CommonDbMixin):
             subnet_id=subnet_id
         )
         context.session.add(allocated)
+        # NOTE(kevinbenton): We add this to the session info so the sqlalchemy
+        # object isn't immediately garbage collected. Otherwise when the
+        # fixed_ips relationship is referenced a new persistent object will be
+        # added to the session that will interfere with retry operations.
+        # See bug 1556178 for details.
+        context.session.info.setdefault('allocated_ips', []).append(allocated)
 
     def _make_subnet_dict(self, subnet, fields=None, context=None):
         res = {'id': subnet['id'],
diff --git a/neutron/db/models_v2.py b/neutron/db/models_v2.py
index 51a483c0084..dc909b13afa 100644
--- a/neutron/db/models_v2.py
+++ b/neutron/db/models_v2.py
@@ -119,7 +119,8 @@ class Port(model_base.BASEV2, HasId, HasTenant):
     network_id = sa.Column(sa.String(36), sa.ForeignKey("networks.id"),
                            nullable=False)
     fixed_ips = orm.relationship(IPAllocation, backref='port', lazy='joined',
-                                 passive_deletes='all')
+                                 cascade='all, delete-orphan')
+
     mac_address = sa.Column(sa.String(32), nullable=False)
     admin_state_up = sa.Column(sa.Boolean(), nullable=False)
     status = sa.Column(sa.String(16), nullable=False)