diff --git a/pkg/kv/kvpb/api.proto b/pkg/kv/kvpb/api.proto
index 95c00da51300..e80289834272 100644
--- a/pkg/kv/kvpb/api.proto
+++ b/pkg/kv/kvpb/api.proto
@@ -3712,6 +3712,14 @@ service TenantSpanConfig {
   rpc SpanConfigConformance(SpanConfigConformanceRequest) returns (SpanConfigConformanceResponse) {}
 }
 
+// Cluster service offers RPCs for inter-node communication essential for
+// cluster bootstrapping and operation.
+service Cluster {
+  // Join a bootstrapped cluster. If the target node is itself not part of a
+  // bootstrapped cluster, an appropriate error is returned.
+  rpc Join (JoinNodeRequest) returns (JoinNodeResponse) {}
+}
+
 // Batch and RangeFeed service implemented by nodes for KV API requests.
 service Internal {
   rpc Batch (BatchRequest) returns (BatchResponse) {}
diff --git a/pkg/server/init.go b/pkg/server/init.go
index cdd8fe0764f1..c1b84272a3de 100644
--- a/pkg/server/init.go
+++ b/pkg/server/init.go
@@ -466,7 +466,10 @@ func (s *initServer) attemptJoinTo(
 		BinaryVersion: &latestVersion,
 	}
 
-	initClient := kvpb.NewInternalClient(conn)
+	var initClient kvpb.RPCClusterClient
+	if !rpcbase.TODODRPC {
+		initClient = kvpb.NewGRPCInternalClientAdapter(conn)
+	}
 	resp, err := initClient.Join(ctx, req)
 	if err != nil {
 		status, ok := grpcstatus.FromError(errors.UnwrapAll(err))
diff --git a/pkg/server/server.go b/pkg/server/server.go
index 900cb8bb9d20..8f4701172d74 100644
--- a/pkg/server/server.go
+++ b/pkg/server/server.go
@@ -995,6 +995,9 @@ func NewServer(cfg Config, stopper *stop.Stopper) (serverctl.ServerStartupInterf
 	if err := kvpb.DRPCRegisterTenantSpanConfig(drpcServer, node); err != nil {
 		return nil, err
 	}
+	if err := kvpb.DRPCRegisterCluster(drpcServer, node); err != nil {
+		return nil, err
+	}
 	kvserver.RegisterPerReplicaServer(grpcServer.Server, node.perReplicaServer)
 	if err := kvserver.DRPCRegisterPerReplica(drpcServer, node.perReplicaServer); err != nil {
 		return nil, err