diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index ed1a3371707a..bc7c9eade679 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -955,11 +955,11 @@ class ComputeManager(manager.Manager):
             LOG.debug(e, instance=instance)
         except exception.VirtualInterfacePlugException:
             # NOTE(mriedem): If we get here, it could be because the vif_type
-            # in the cache is "binding_failed". The only way to fix that is to
-            # try and bind the ports again, which would be expensive here on
-            # host startup. We could add a check to _heal_instance_info_cache
-            # to handle this, but probably only if the instance task_state is
-            # None.
+            # in the cache is "binding_failed" or "unbound". The only way to
+            # fix this is to try and bind the ports again, which would be
+            # expensive here on host startup. We could add a check to
+            # _heal_instance_info_cache to handle this, but probably only if
+            # the instance task_state is None.
             LOG.exception(_LE(
                 'Virtual interface plugging failed for instance. '
                 'The port binding:host_id may need to be manually '
diff --git a/nova/network/os_vif_util.py b/nova/network/os_vif_util.py
index 2b0e536a2fdc..8f6c79247c07 100644
--- a/nova/network/os_vif_util.py
+++ b/nova/network/os_vif_util.py
@@ -411,6 +411,18 @@ def _nova_to_osvif_vif_binding_failed(vif):
     raise NotImplementedError()
 
 
+# VIF_TYPE_UNBOUND = 'unbound'
+def _nova_to_osvif_vif_unbound(vif):
+    """Special handler for the "unbound" vif type.
+
+    The "unbound" vif type indicates a port has not been hooked up to backend
+    network driver (OVS, linux bridge, ...). We raise NotImplementedError to
+    indicate to the caller that we cannot handle this type of vif rather than
+    the generic "Unsupported VIF type" error in nova_to_osvif_vif.
+    """
+    raise NotImplementedError()
+
+
 def nova_to_osvif_vif(vif):
     """Convert a Nova VIF model to an os-vif object
 
diff --git a/nova/tests/unit/network/test_os_vif_util.py b/nova/tests/unit/network/test_os_vif_util.py
index 2abef4a26744..a2dc63a54376 100644
--- a/nova/tests/unit/network/test_os_vif_util.py
+++ b/nova/tests/unit/network/test_os_vif_util.py
@@ -828,3 +828,14 @@ class OSVIFUtilTestCase(test.NoDBTestCase):
                 label="Demo Net",
                 subnets=[]),)
         self.assertIsNone(os_vif_util.nova_to_osvif_vif(vif))
+
+    def test_nova_to_osvif_vif_unbound(self):
+        vif = model.VIF(
+            id="dc065497-3c8d-4f44-8fb4-e1d33c16a536",
+            type="unbound",
+            address="22:52:25:62:e2:aa",
+            network=model.Network(
+                id="b82c1929-051e-481d-8110-4669916c7915",
+                label="Demo Net",
+                subnets=[]),)
+        self.assertIsNone(os_vif_util.nova_to_osvif_vif(vif))