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
index 7292a85..14f1eda 100644
--- a/core/api/src/main/java/org/onlab/onos/cluster/InstanceId.java
+++ b/core/api/src/main/java/org/onlab/onos/cluster/InstanceId.java
@@ -1,7 +1,50 @@
 package org.onlab.onos.cluster;
 
+import java.util.Objects;
+
+import static com.google.common.base.MoreObjects.toStringHelper;
+
 /**
  * Controller cluster identity.
  */
-public interface InstanceId {
+public class InstanceId {
+
+    private final String id;
+
+    // Default constructor for serialization
+    protected InstanceId() {
+        id = null;
+    }
+
+    /**
+     * Creates a new cluster instance identifier from the specified string.
+     *
+     * @param id string identifier
+     */
+    public InstanceId(String id) {
+        this.id = id;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj instanceof InstanceId) {
+            final InstanceId other = (InstanceId) obj;
+            return Objects.equals(this.id, other.id);
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        return toStringHelper(this).add("id", id).toString();
+    }
+
 }