diff --git a/core/api/src/main/java/org/onlab/onos/cluster/InstanceId.java b/core/api/src/main/java/org/onlab/onos/cluster/InstanceId.java
new file mode 100644
index 0000000..7292a85
--- /dev/null
+++ b/core/api/src/main/java/org/onlab/onos/cluster/InstanceId.java
@@ -0,0 +1,7 @@
+package org.onlab.onos.cluster;
+
+/**
+ * Controller cluster identity.
+ */
+public interface InstanceId {
+}