diff --git a/neutron/objects/plugins/ml2/base.py b/neutron/objects/plugins/ml2/base.py
index 8046811b63c..12dc3f44eca 100644
--- a/neutron/objects/plugins/ml2/base.py
+++ b/neutron/objects/plugins/ml2/base.py
@@ -55,6 +55,15 @@ class SegmentAllocation(metaclass=abc.ABCMeta):
                 query = query.order_by(rand_func())
             return query.first()
 
+    @classmethod
+    def get_all_unallocated_segments(cls, context, **filters):
+        with cls.db_context_reader(context):
+            columns = set(dict(cls.db_model.__table__.columns))
+            model_filters = {k: filters[k]
+                             for k in columns & set(filters.keys())}
+            return context.session.query(cls.db_model).filter_by(
+                allocated=False, **model_filters).all()
+
     @classmethod
     def allocate(cls, context, **segment):
         with cls.db_context_writer(context):
diff --git a/neutron/plugins/ml2/drivers/helpers.py b/neutron/plugins/ml2/drivers/helpers.py
index 276665f8e1b..e35615e0018 100644
--- a/neutron/plugins/ml2/drivers/helpers.py
+++ b/neutron/plugins/ml2/drivers/helpers.py
@@ -156,6 +156,22 @@ class SegmentTypeDriver(BaseTypeDriver):
             raise db_exc.RetryRequest(
                 exceptions.NoNetworkFoundInMaximumAllowedAttempts())
 
+        # NOTE(ralonsoh): this debug message is added to debug LP#2086602.
+        # Once fixed, it won't be needed. This debug message should not be
+        # released.
+        LOG.debug('Partial segment allocation fail:')
+        LOG.debug('  - Filters: %s', filters)
+        LOG.debug('  - Non allocated segments:')
+        for non_allocated_segment in (
+                self.segmentation_obj.get_all_unallocated_segments(context,
+                    **filters)):
+            LOG.debug('    - %s', non_allocated_segment)
+        if directory.get_plugin(plugin_constants.NETWORK_SEGMENT_RANGE):
+            LOG.debug('  - Network segment ranges:')
+            for srange in ns_range.NetworkSegmentRange.get_objects(
+                    context.elevated()):
+                LOG.debug('    - %s', srange)
+
     @db_api.retry_db_errors
     def _delete_expired_default_network_segment_ranges(self):
         ctx = context.get_admin_context()