diff --git a/xds/internal/client/rds_test.go b/xds/internal/client/rds_test.go
index 10745e9e97d..33bcc2ad13f 100644
--- a/xds/internal/client/rds_test.go
+++ b/xds/internal/client/rds_test.go
@@ -1077,6 +1077,96 @@ func (s) TestRoutesProtoToSlice(t *testing.T) {
 			},
 			wantErr: true,
 		},
+		{
+			name: "totalWeight is nil in weighted clusters action",
+			routes: []*v3routepb.Route{
+				{
+					Match: &v3routepb.RouteMatch{
+						PathSpecifier: &v3routepb.RouteMatch_Prefix{Prefix: "/a/"},
+					},
+					Action: &v3routepb.Route_Route{
+						Route: &v3routepb.RouteAction{
+							ClusterSpecifier: &v3routepb.RouteAction_WeightedClusters{
+								WeightedClusters: &v3routepb.WeightedCluster{
+									Clusters: []*v3routepb.WeightedCluster_ClusterWeight{
+										{Name: "B", Weight: &wrapperspb.UInt32Value{Value: 20}},
+										{Name: "A", Weight: &wrapperspb.UInt32Value{Value: 30}},
+									},
+								}}}},
+				},
+			},
+			wantErr: true,
+		},
+		{
+			name: "The sum of all weighted clusters is not equal totalWeight",
+			routes: []*v3routepb.Route{
+				{
+					Match: &v3routepb.RouteMatch{
+						PathSpecifier: &v3routepb.RouteMatch_Prefix{Prefix: "/a/"},
+					},
+					Action: &v3routepb.Route_Route{
+						Route: &v3routepb.RouteAction{
+							ClusterSpecifier: &v3routepb.RouteAction_WeightedClusters{
+								WeightedClusters: &v3routepb.WeightedCluster{
+									Clusters: []*v3routepb.WeightedCluster_ClusterWeight{
+										{Name: "B", Weight: &wrapperspb.UInt32Value{Value: 50}},
+										{Name: "A", Weight: &wrapperspb.UInt32Value{Value: 20}},
+									},
+									TotalWeight: &wrapperspb.UInt32Value{Value: 100},
+								}}}},
+				},
+			},
+			wantErr: true,
+		},
+		{
+			name: "default totalWeight is 100 in weighted clusters action",
+			routes: []*v3routepb.Route{
+				{
+					Match: &v3routepb.RouteMatch{
+						PathSpecifier: &v3routepb.RouteMatch_Prefix{Prefix: "/a/"},
+					},
+					Action: &v3routepb.Route_Route{
+						Route: &v3routepb.RouteAction{
+							ClusterSpecifier: &v3routepb.RouteAction_WeightedClusters{
+								WeightedClusters: &v3routepb.WeightedCluster{
+									Clusters: []*v3routepb.WeightedCluster_ClusterWeight{
+										{Name: "B", Weight: &wrapperspb.UInt32Value{Value: 60}},
+										{Name: "A", Weight: &wrapperspb.UInt32Value{Value: 40}},
+									},
+								}}}},
+				},
+			},
+			wantRoutes: []*Route{{
+				Prefix:           newStringP("/a/"),
+				WeightedClusters: map[string]WeightedCluster{"A": {Weight: 40}, "B": {Weight: 60}},
+			}},
+			wantErr: false,
+		},
+		{
+			name: "default totalWeight is 100 in weighted clusters action",
+			routes: []*v3routepb.Route{
+				{
+					Match: &v3routepb.RouteMatch{
+						PathSpecifier: &v3routepb.RouteMatch_Prefix{Prefix: "/a/"},
+					},
+					Action: &v3routepb.Route_Route{
+						Route: &v3routepb.RouteAction{
+							ClusterSpecifier: &v3routepb.RouteAction_WeightedClusters{
+								WeightedClusters: &v3routepb.WeightedCluster{
+									Clusters: []*v3routepb.WeightedCluster_ClusterWeight{
+										{Name: "B", Weight: &wrapperspb.UInt32Value{Value: 30}},
+										{Name: "A", Weight: &wrapperspb.UInt32Value{Value: 20}},
+									},
+									TotalWeight: &wrapperspb.UInt32Value{Value: 50},
+								}}}},
+				},
+			},
+			wantRoutes: []*Route{{
+				Prefix:           newStringP("/a/"),
+				WeightedClusters: map[string]WeightedCluster{"A": {Weight: 20}, "B": {Weight: 30}},
+			}},
+			wantErr: false,
+		},
 		{
 			name:       "with custom HTTP filter config",
 			routes:     goodRouteWithFilterConfigs(map[string]*anypb.Any{"foo": customFilterConfig}),
diff --git a/xds/internal/client/xds.go b/xds/internal/client/xds.go
index 65287a485a8..b9522411323 100644
--- a/xds/internal/client/xds.go
+++ b/xds/internal/client/xds.go
@@ -522,8 +522,14 @@ func routesProtoToSlice(routes []*v3routepb.Route, logger *grpclog.PrefixLogger,
 				route.WeightedClusters[c.GetName()] = wc
 				totalWeight += w
 			}
-			if totalWeight != wcs.GetTotalWeight().GetValue() {
-				return nil, fmt.Errorf("route %+v, action %+v, weights of clusters do not add up to total total weight, got: %v, want %v", r, a, wcs.GetTotalWeight().GetValue(), totalWeight)
+			// envoy xds doc
+			// default TotalWeight https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/route/v3/route_components.proto.html#envoy-v3-api-field-config-route-v3-weightedcluster-total-weight
+			wantTotalWeight := uint32(100)
+			if tw := wcs.GetTotalWeight(); tw != nil {
+				wantTotalWeight = tw.GetValue()
+			}
+			if totalWeight != wantTotalWeight {
+				return nil, fmt.Errorf("route %+v, action %+v, weights of clusters do not add up to total total weight, got: %v, expected total weight from response: %v", r, a, totalWeight, wantTotalWeight)
 			}
 			if totalWeight == 0 {
 				return nil, fmt.Errorf("route %+v, action %+v, has no valid cluster in WeightedCluster action", r, a)