diff --git a/src/vnet/l2/l2_learn.h b/src/vnet/l2/l2_learn.h
index 0d95de0..000ab59 100644
--- a/src/vnet/l2/l2_learn.h
+++ b/src/vnet/l2/l2_learn.h
@@ -34,6 +34,10 @@
   /* maximum number of dynamically learned mac entries */
   u32 global_learn_limit;
 
+  /* client waiting for L2 MAC events for learned and aged MACs */
+  u32 client_pid;
+  u32 client_index;
+
   /* Next nodes for each feature */
   u32 feat_next_node_index[32];
 
@@ -42,6 +46,7 @@
   vnet_main_t *vnet_main;
 } l2learn_main_t;
 
+#define L2LEARN_DEFAULT_LIMIT (L2FIB_NUM_BUCKETS * 16)
 
 l2learn_main_t l2learn_main;