diff --git a/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/util/VtnConfig.java b/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/util/VtnConfig.java
index 5d70230..5ac0466 100644
--- a/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/util/VtnConfig.java
+++ b/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/util/VtnConfig.java
@@ -113,6 +113,7 @@
      * Gets ports in the controller device.
      *
      * @param handler DriverHandler
+     * @return set of port numbers
      */
     public static Set<PortNumber> getPortNumbers(DriverHandler handler) {
         BridgeConfig bridgeConfig = handler.behaviour(BridgeConfig.class);