Added back-pipe for role assertion issues.
diff --git a/core/api/src/main/java/org/onlab/onos/net/device/DeviceProviderService.java b/core/api/src/main/java/org/onlab/onos/net/device/DeviceProviderService.java
index 5401646..7f28374 100644
--- a/core/api/src/main/java/org/onlab/onos/net/device/DeviceProviderService.java
+++ b/core/api/src/main/java/org/onlab/onos/net/device/DeviceProviderService.java
@@ -1,6 +1,7 @@
 package org.onlab.onos.net.device;
 
 import org.onlab.onos.net.DeviceId;
+import org.onlab.onos.net.MastershipRole;
 import org.onlab.onos.net.provider.ProviderService;
 
 import java.util.List;
@@ -45,4 +46,13 @@
      */
     void portStatusChanged(DeviceId deviceId, PortDescription portDescription);
 
+    /**
+     * Notifies the core about the providers inability to assert the specified
+     * mastership role on the device.
+     *
+     * @param deviceId identity of the device
+     * @param role mastership role being asserted
+     */
+    void unableToAssertRole(DeviceId deviceId, MastershipRole role);
+
 }
diff --git a/core/net/src/main/java/org/onlab/onos/net/device/impl/DeviceManager.java b/core/net/src/main/java/org/onlab/onos/net/device/impl/DeviceManager.java
index 2f61925..9b6c83a 100644
--- a/core/net/src/main/java/org/onlab/onos/net/device/impl/DeviceManager.java
+++ b/core/net/src/main/java/org/onlab/onos/net/device/impl/DeviceManager.java
@@ -224,6 +224,11 @@
                 post(event);
             }
         }
+
+        @Override
+        public void unableToAssertRole(DeviceId deviceId, MastershipRole role) {
+            // FIXME: implement response to this notification
+        }
     }
 
     // Posts the specified event to the local event dispatcher.