diff --git a/core/api/src/main/java/org/onosproject/core/DefaultGroupId.java b/core/api/src/main/java/org/onosproject/core/DefaultGroupId.java
index 7467c3c..3f95559 100644
--- a/core/api/src/main/java/org/onosproject/core/DefaultGroupId.java
+++ b/core/api/src/main/java/org/onosproject/core/DefaultGroupId.java
@@ -61,7 +61,7 @@
     @Override
     public String toString() {
         return MoreObjects.toStringHelper(this)
-                .add("id", id)
+                .add("id", "0x" + Integer.toHexString(id))
                 .toString();
     }
 }
diff --git a/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java b/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java
index e1a71fc..3e2335b 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/instructions/Instructions.java
@@ -576,7 +576,7 @@
 
         @Override
         public String toString() {
-            return type().toString() + SEPARATOR + Integer.toHexString(groupId.id());
+            return type().toString() + SEPARATOR + "0x" + Integer.toHexString(groupId.id());
         }
 
         @Override
diff --git a/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java b/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java
index e4173b3..42ef9dd 100644
--- a/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java
+++ b/core/api/src/main/java/org/onosproject/net/group/GroupOperation.java
@@ -31,6 +31,7 @@
     private final GroupId groupId;
     private final GroupDescription.Type groupType;
     private final GroupBuckets buckets;
+    private final GroupMsgErrorCode failureCode;
 
     public enum Type {
         /**
@@ -48,6 +49,28 @@
     }
 
     /**
+     * Possible error codes for a failure of a group operation.
+     *
+     */
+    public enum GroupMsgErrorCode {
+        GROUP_EXISTS,
+        INVALID_GROUP,
+        WEIGHT_UNSUPPORTED,
+        OUT_OF_GROUPS,
+        OUT_OF_BUCKETS,
+        CHAINING_UNSUPPORTED,
+        WATCH_UNSUPPORTED,
+        LOOP,
+        UNKNOWN_GROUP,
+        CHAINED_GROUP,
+        BAD_TYPE,
+        BAD_COMMAND,
+        BAD_BUCKET,
+        BAD_WATCH,
+        EPERM;
+    }
+
+    /**
      * Group operation constructor with the parameters.
      *
      * @param opType group operation type
@@ -63,6 +86,23 @@
         this.groupId = checkNotNull(groupId);
         this.groupType = checkNotNull(groupType);
         this.buckets = buckets;
+        this.failureCode = null;
+    }
+
+    /**
+     * Group operation copy-constructor with additional field to set failure code.
+     * Typically used by provider to return information to the core about
+     * the failure reason for a group operation.
+     *
+     * @param groupOp the original group operation
+     * @param failureCode failure code for a failed group operation
+     */
+    private GroupOperation(GroupOperation groupOp, GroupMsgErrorCode failureCode) {
+        this.opType = groupOp.opType;
+        this.groupId = groupOp.groupId;
+        this.groupType = groupOp.groupType;
+        this.buckets = groupOp.buckets;
+        this.failureCode = failureCode;
     }
 
     /**
@@ -109,6 +149,12 @@
 
     }
 
+    public static GroupOperation createFailedGroupOperation(GroupOperation groupOperation,
+                                                            GroupMsgErrorCode failureCode) {
+        checkNotNull(groupOperation);
+        return new GroupOperation(groupOperation, failureCode);
+    }
+
     /**
      * Returns group operation type.
      *
@@ -145,6 +191,15 @@
         return this.buckets;
     }
 
+    /**
+     * Returns the failure code representing the failure of a group operation.
+     *
+     * @return error code for failure of group operation
+     */
+    public GroupMsgErrorCode failureCode() {
+        return failureCode;
+    }
+
     @Override
     /*
      * The deviceId, type and buckets are used for hash.
diff --git a/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java b/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java
index 64b7c87..250dfb9 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java
@@ -88,7 +88,8 @@
 import static org.slf4j.LoggerFactory.getLogger;
 
 /**
- * Manages inventory of group entries using trivial in-memory implementation.
+ * Manages inventory of group entries using distributed group stores from the
+ * storage service.
  */
 @Component(immediate = true)
 @Service
@@ -450,16 +451,18 @@
             matchingExtraneousGroup = getMatchingExtraneousGroupbyId(
                                 groupDesc.deviceId(), groupDesc.givenGroupId());
             if (matchingExtraneousGroup != null) {
-                log.debug("storeGroupDescriptionInternal: Matching extraneous group found in Device {} for group id {}",
+                log.debug("storeGroupDescriptionInternal: Matching extraneous group "
+                        + "found in Device {} for group id 0x{}",
                           groupDesc.deviceId(),
-                          groupDesc.givenGroupId());
+                          Integer.toHexString(groupDesc.givenGroupId()));
                 //Check if the group buckets matches with user provided buckets
                 if (matchingExtraneousGroup.buckets().equals(groupDesc.buckets())) {
                     //Group is already existing with the same buckets and Id
                     // Create a group entry object
-                    log.debug("storeGroupDescriptionInternal: Buckets also matching in Device {} for group id {}",
+                    log.debug("storeGroupDescriptionInternal: Buckets also matching "
+                            + "in Device {} for group id 0x{}",
                               groupDesc.deviceId(),
-                              groupDesc.givenGroupId());
+                              Integer.toHexString(groupDesc.givenGroupId()));
                     StoredGroupEntry group = new DefaultGroup(
                               matchingExtraneousGroup.id(), groupDesc);
                     // Insert the newly created group entry into key and id maps
@@ -476,10 +479,27 @@
                 } else {
                     //Group buckets are not matching. Update group
                     //with user provided buckets.
-                    //TODO
-                    log.debug("storeGroupDescriptionInternal: Buckets are not matching in Device {} for group id {}",
+                    log.debug("storeGroupDescriptionInternal: Buckets are not "
+                            + "matching in Device {} for group id 0x{}",
                               groupDesc.deviceId(),
-                              groupDesc.givenGroupId());
+                              Integer.toHexString(groupDesc.givenGroupId()));
+                    StoredGroupEntry modifiedGroup = new DefaultGroup(
+                               matchingExtraneousGroup.id(), groupDesc);
+                    modifiedGroup.setState(GroupState.PENDING_UPDATE);
+                    getGroupStoreKeyMap().
+                        put(new GroupStoreKeyMapKey(groupDesc.deviceId(),
+                                                groupDesc.appCookie()), modifiedGroup);
+                    // Ensure it also inserted into group id based table to
+                    // avoid any chances of duplication in group id generation
+                    getGroupIdTable(groupDesc.deviceId()).
+                        put(matchingExtraneousGroup.id(), modifiedGroup);
+                    removeExtraneousGroupEntry(matchingExtraneousGroup);
+                    log.debug("storeGroupDescriptionInternal: Triggering Group "
+                            + "UPDATE request for {} in device {}",
+                              matchingExtraneousGroup.id(),
+                              groupDesc.deviceId());
+                    notifyDelegate(new GroupEvent(Type.GROUP_UPDATE_REQUESTED, modifiedGroup));
+                    return;
                 }
             }
         } else {
@@ -754,7 +774,7 @@
         GroupEvent event = null;
 
         if (existing != null) {
-            log.debug("addOrUpdateGroupEntry: updating group entry {} in device {}",
+            log.trace("addOrUpdateGroupEntry: updating group entry {} in device {}",
                     group.id(),
                     group.deviceId());
             synchronized (existing) {
@@ -779,7 +799,7 @@
                 existing.setBytes(group.bytes());
                 if ((existing.state() == GroupState.PENDING_ADD) ||
                     (existing.state() == GroupState.PENDING_ADD_RETRY)) {
-                    log.debug("addOrUpdateGroupEntry: group entry {} in device {} moving from {} to ADDED",
+                    log.trace("addOrUpdateGroupEntry: group entry {} in device {} moving from {} to ADDED",
                             existing.id(),
                             existing.deviceId(),
                             existing.state());
@@ -787,7 +807,7 @@
                     existing.setIsGroupStateAddedFirstTime(true);
                     event = new GroupEvent(Type.GROUP_ADDED, existing);
                 } else {
-                    log.debug("addOrUpdateGroupEntry: group entry {} in device {} moving from {} to ADDED",
+                    log.trace("addOrUpdateGroupEntry: group entry {} in device {} moving from {} to ADDED",
                             existing.id(),
                             existing.deviceId(),
                             GroupState.PENDING_UPDATE);
@@ -911,18 +931,19 @@
         }
 
         log.warn("groupOperationFailed: group operation {} failed"
-                + "for group {} in device {}",
+                + "for group {} in device {} with code {}",
                 operation.opType(),
                 existing.id(),
-                existing.deviceId());
+                existing.deviceId(),
+                operation.failureCode());
+        if (operation.failureCode() == GroupOperation.GroupMsgErrorCode.GROUP_EXISTS) {
+            log.warn("Current extraneous groups in device:{} are: {}",
+                     deviceId,
+                     getExtraneousGroups(deviceId));
+        }
         switch (operation.opType()) {
             case ADD:
                 if (existing.state() == GroupState.PENDING_ADD) {
-                    //TODO: Need to add support for passing the group
-                    //operation failure reason from group provider.
-                    //If the error type is anything other than GROUP_EXISTS,
-                    //then the GROUP_ADD_FAILED event should be raised even
-                    //in PENDING_ADD_RETRY state also.
                     notifyDelegate(new GroupEvent(Type.GROUP_ADD_FAILED, existing));
                     log.warn("groupOperationFailed: cleaningup "
                             + "group {} from store in device {}....",
@@ -1220,13 +1241,13 @@
         for (Group group : extraneousStoredEntries) {
             // there are groups in the extraneous store that
             // aren't in the switch
-            log.debug("Group AUDIT: clearing extransoeus group {} from store for device {}",
+            log.debug("Group AUDIT: clearing extraneous group {} from store for device {}",
                     group.id(), deviceId);
             removeExtraneousGroupEntry(group);
         }
 
         if (!deviceInitialAuditStatus) {
-            log.debug("Group AUDIT: Setting device {} initial AUDIT completed",
+            log.info("Group AUDIT: Setting device {} initial AUDIT completed",
                       deviceId);
             deviceInitialAuditCompleted(deviceId, true);
         }
@@ -1266,7 +1287,7 @@
     }
 
     private void extraneousGroup(Group group) {
-        log.debug("Group {} is on device {} but not in store.",
+        log.trace("Group {} is on device {} but not in store.",
                   group, group.deviceId());
         addOrUpdateExtraneousGroupEntry(group);
     }
diff --git a/drivers/default/src/main/java/org/onosproject/driver/pipeline/OFDPA2GroupHandler.java b/drivers/default/src/main/java/org/onosproject/driver/pipeline/OFDPA2GroupHandler.java
index 56433cf..7a42d93 100644
--- a/drivers/default/src/main/java/org/onosproject/driver/pipeline/OFDPA2GroupHandler.java
+++ b/drivers/default/src/main/java/org/onosproject/driver/pipeline/OFDPA2GroupHandler.java
@@ -556,7 +556,8 @@
         }
 
         // assemble info for l2 flood group
-        Integer l2floodgroupId = L2_FLOOD_TYPE | (vlanId.toShort() << 16) | nextObj.id();
+        // since there can be only one flood group for a vlan, its index is always the same - 0
+        Integer l2floodgroupId = L2_FLOOD_TYPE | (vlanId.toShort() << 16);
         int l2floodgk = L2_FLOOD_TYPE | nextObj.id() << 12;
         final GroupKey l2floodgroupkey = new DefaultGroupKey(OFDPA2Pipeline.appKryo.serialize(l2floodgk));
         // collection of group buckets pointing to all the l2 interface groups
@@ -1007,7 +1008,7 @@
         if (gceSet != null) {
             for (GroupChainElem gce : gceSet) {
                 log.info("Group service {} group key {} in device {}. "
-                                + "Processing next group in group chain with group id {}",
+                                + "Processing next group in group chain with group id 0x{}",
                         (added) ? "ADDED" : "processed",
                         key, deviceId,
                         Integer.toHexString(gce.groupDescription.givenGroupId()));
@@ -1020,7 +1021,7 @@
                 pendingNextObjectives.invalidate(key);
                 nextGrpList.forEach(nextGrp -> {
                     log.info("Group service {} group key {} in device:{}. "
-                                    + "Done implementing next objective: {} <<-->> gid:{}",
+                                    + "Done implementing next objective: {} <<-->> gid:0x{}",
                             (added) ? "ADDED" : "processed",
                             key, deviceId, nextGrp.nextObjective().id(),
                             Integer.toHexString(groupService.getGroup(deviceId, key)
@@ -1116,7 +1117,6 @@
             this.nextObj = nextObj;
         }
 
-        @SuppressWarnings("unused")
         public List<Deque<GroupKey>> groupKey() {
             return gkeys;
         }
diff --git a/providers/openflow/group/src/main/java/org/onosproject/provider/of/group/impl/OpenFlowGroupProvider.java b/providers/openflow/group/src/main/java/org/onosproject/provider/of/group/impl/OpenFlowGroupProvider.java
index 2801f12..162c89d 100644
--- a/providers/openflow/group/src/main/java/org/onosproject/provider/of/group/impl/OpenFlowGroupProvider.java
+++ b/providers/openflow/group/src/main/java/org/onosproject/provider/of/group/impl/OpenFlowGroupProvider.java
@@ -37,6 +37,7 @@
 import org.onosproject.net.group.GroupBuckets;
 import org.onosproject.net.group.GroupDescription;
 import org.onosproject.net.group.GroupOperation;
+import org.onosproject.net.group.GroupOperation.GroupMsgErrorCode;
 import org.onosproject.net.group.GroupOperations;
 import org.onosproject.net.group.GroupProvider;
 import org.onosproject.net.group.GroupProviderRegistry;
@@ -56,6 +57,7 @@
 import org.projectfloodlight.openflow.protocol.OFGroupDescStatsEntry;
 import org.projectfloodlight.openflow.protocol.OFGroupDescStatsReply;
 import org.projectfloodlight.openflow.protocol.OFGroupMod;
+import org.projectfloodlight.openflow.protocol.OFGroupModFailedCode;
 import org.projectfloodlight.openflow.protocol.OFGroupStatsEntry;
 import org.projectfloodlight.openflow.protocol.OFGroupStatsReply;
 import org.projectfloodlight.openflow.protocol.OFGroupType;
@@ -64,6 +66,7 @@
 import org.projectfloodlight.openflow.protocol.OFStatsReply;
 import org.projectfloodlight.openflow.protocol.OFStatsType;
 import org.projectfloodlight.openflow.protocol.OFVersion;
+import org.projectfloodlight.openflow.protocol.errormsg.OFGroupModFailedErrorMsg;
 import org.slf4j.Logger;
 
 import com.google.common.collect.Maps;
@@ -135,7 +138,6 @@
 
     @Override
     public void performGroupOperation(DeviceId deviceId, GroupOperations groupOps) {
-        Map<OFGroupMod, OpenFlowSwitch> mods = Maps.newIdentityHashMap();
         final Dpid dpid = Dpid.dpid(deviceId.uri());
         OpenFlowSwitch sw = controller.getSwitch(dpid);
         for (GroupOperation groupOperation: groupOps.operations()) {
@@ -329,11 +331,17 @@
                                     pendingGroupOperations.get(pendingGroupId);
                             DeviceId deviceId = DeviceId.deviceId(Dpid.uri(dpid));
                             if (operation != null) {
+                                OFGroupModFailedCode code =
+                                        ((OFGroupModFailedErrorMsg) errorMsg).getCode();
+                                GroupMsgErrorCode failureCode =
+                                        GroupMsgErrorCode.values()[(code.ordinal())];
+                                GroupOperation failedOperation = GroupOperation
+                                        .createFailedGroupOperation(operation, failureCode);
                                 providerService.groupOperationFailed(deviceId,
-                                        operation);
+                                        failedOperation);
                                 pendingGroupOperations.remove(pendingGroupId);
                                 pendingXidMaps.remove(pendingGroupId);
-                                log.warn("Received an group mod error {}", msg);
+                                log.warn("Received a group mod error {}", msg);
                             } else {
                                 log.error("Cannot find pending group operation with group ID: {}",
                                         pendingGroupId);