diff --git a/neutron/plugins/ml2/plugin.py b/neutron/plugins/ml2/plugin.py
index 6ef4d107c7..422cbff86e 100644
--- a/neutron/plugins/ml2/plugin.py
+++ b/neutron/plugins/ml2/plugin.py
@@ -580,9 +580,15 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
                 # to prevent deadlock waiting to acquire a DB lock
                 # held by another thread in the same process, leading
                 # to 'lock wait timeout' errors.
+                #
+                # Process L3 first, since, depending on the L3 plugin, it may
+                # involve locking the db-access semaphore, sending RPC
+                # notifications, and/or calling delete_port on this plugin.
+                # Additionally, a rollback may not be enough to undo the
+                # deletion of a floating IP with certain L3 backends.
+                self._process_l3_delete(context, id)
                 with contextlib.nested(lockutils.lock('db-access'),
                                        session.begin(subtransactions=True)):
-                    self._process_l3_delete(context, id)
                     # Get ports to auto-delete.
                     ports = (session.query(models_v2.Port).
                              enable_eagerloads(False).
diff --git a/neutron/tests/unit/ml2/test_ml2_plugin.py b/neutron/tests/unit/ml2/test_ml2_plugin.py
index be987827c1..5cb6df44bc 100644
--- a/neutron/tests/unit/ml2/test_ml2_plugin.py
+++ b/neutron/tests/unit/ml2/test_ml2_plugin.py
@@ -24,6 +24,7 @@ from neutron.common import exceptions as exc
 from neutron.common import utils
 from neutron import context
 from neutron.db import db_base_plugin_v2 as base_plugin
+from neutron.extensions import external_net as external_net
 from neutron.extensions import multiprovidernet as mpnet
 from neutron.extensions import portbindings
 from neutron.extensions import providernet as pnet
@@ -147,6 +148,22 @@ class TestMl2PortsV2(test_plugin.TestPortsV2, Ml2PluginV2TestCase):
                 mock.call(_("The port '%s' was deleted"), 'invalid-uuid')
             ])
 
+    def test_l3_cleanup_on_net_delete(self):
+        l3plugin = manager.NeutronManager.get_service_plugins().get(
+            service_constants.L3_ROUTER_NAT)
+        kwargs = {'arg_list': (external_net.EXTERNAL,),
+                  external_net.EXTERNAL: True}
+        with self.network(**kwargs) as n:
+            with self.subnet(network=n, cidr='200.0.0.0/22'):
+                l3plugin.create_floatingip(
+                    context.get_admin_context(),
+                    {'floatingip': {'floating_network_id': n['network']['id'],
+                                    'tenant_id': n['network']['tenant_id']}}
+                )
+        self._delete('networks', n['network']['id'])
+        flips = l3plugin.get_floatingips(context.get_admin_context())
+        self.assertFalse(flips)
+
     def test_delete_port_no_notify_in_disassociate_floatingips(self):
         ctx = context.get_admin_context()
         plugin = manager.NeutronManager.get_plugin()