diff --git a/raft/log.go b/raft/log.go
index 3c5266629..d69536a7c 100644
--- a/raft/log.go
+++ b/raft/log.go
@@ -1,6 +1,12 @@
 package raft
 
+const (
+	normal int = iota
+	config
+)
+
 type Entry struct {
+	Type int
 	Term int
 	Data []byte
 }
diff --git a/raft/node.go b/raft/node.go
index 674ca1c55..f9e62ca6d 100644
--- a/raft/node.go
+++ b/raft/node.go
@@ -33,7 +33,7 @@ func New(addr int, peer []int, heartbeat, election tick) *Node {
 
 // Propose asynchronously proposes data be applied to the underlying state machine.
 func (n *Node) Propose(data []byte) {
-	m := Message{Type: msgProp, Data: data}
+	m := Message{Type: msgProp, Entries: []Entry{{Data: data}}}
 	n.Step(m)
 }
 
diff --git a/raft/raft.go b/raft/raft.go
index 30651c4bc..4278eca5b 100644
--- a/raft/raft.go
+++ b/raft/raft.go
@@ -63,7 +63,6 @@ type Message struct {
 	PrevTerm int
 	Entries  []Entry
 	Commit   int
-	Data     []byte
 }
 
 type index struct {
@@ -103,6 +102,9 @@ type stateMachine struct {
 
 	// the leader addr
 	lead int
+
+	// pending reconfiguration
+	pendingConf bool
 }
 
 func newStateMachine(addr int, peer []int) *stateMachine {
@@ -254,9 +256,23 @@ func (sm *stateMachine) Step(m Message) {
 		sm.bcastAppend()
 		return
 	case msgProp:
+		if len(m.Entries) != 1 {
+			panic("unexpected length(entries) of a msgProp")
+		}
+
 		switch sm.lead {
 		case sm.addr:
-			sm.log.append(sm.log.lastIndex(), Entry{Term: sm.term, Data: m.Data})
+			e := m.Entries[0]
+			if e.Type == config {
+				if sm.pendingConf {
+					// todo: deny
+					return
+				}
+				sm.pendingConf = true
+			}
+			e.Term = sm.term
+
+			sm.log.append(sm.log.lastIndex(), e)
 			sm.ins[sm.addr].update(sm.log.lastIndex())
 			sm.maybeCommit()
 			sm.bcastAppend()
diff --git a/raft/raft_test.go b/raft/raft_test.go
index 2e3b2dc78..a77f69fd2 100644
--- a/raft/raft_test.go
+++ b/raft/raft_test.go
@@ -45,16 +45,17 @@ func TestLogReplication(t *testing.T) {
 		{
 			newNetwork(nil, nil, nil),
 			[]Message{
-				{To: 0, Type: msgProp, Data: []byte("somedata")},
+				{To: 0, Type: msgProp, Entries: []Entry{{Data: []byte("somedata")}}},
 			},
 			1,
 		},
 		{
 			newNetwork(nil, nil, nil),
 			[]Message{
-				{To: 0, Type: msgProp, Data: []byte("somedata")},
+
+				{To: 0, Type: msgProp, Entries: []Entry{{Data: []byte("somedata")}}},
 				{To: 1, Type: msgHup},
-				{To: 1, Type: msgProp, Data: []byte("somedata")},
+				{To: 1, Type: msgProp, Entries: []Entry{{Data: []byte("somedata")}}},
 			},
 			2,
 		},
@@ -82,8 +83,8 @@ func TestLogReplication(t *testing.T) {
 				}
 			}
 			for k, m := range props {
-				if !bytes.Equal(ents[k].Data, m.Data) {
-					t.Errorf("#%d.%d: data = %d, want %d", i, j, ents[k].Data, m.Data)
+				if !bytes.Equal(ents[k].Data, m.Entries[0].Data) {
+					t.Errorf("#%d.%d: data = %d, want %d", i, j, ents[k].Data, m.Entries[0].Data)
 				}
 			}
 		}
@@ -93,8 +94,8 @@ func TestLogReplication(t *testing.T) {
 func TestSingleNodeCommit(t *testing.T) {
 	tt := newNetwork(nil)
 	tt.send(Message{To: 0, Type: msgHup})
-	tt.send(Message{To: 0, Type: msgProp, Data: []byte("some data")})
-	tt.send(Message{To: 0, Type: msgProp, Data: []byte("some data")})
+	tt.send(Message{To: 0, Type: msgProp, Entries: []Entry{{Data: []byte("some data")}}})
+	tt.send(Message{To: 0, Type: msgProp, Entries: []Entry{{Data: []byte("some data")}}})
 
 	sm := tt.peers[0].(*stateMachine)
 	if sm.log.committed != 2 {
@@ -111,8 +112,8 @@ func TestCannotCommitWithoutNewTermEntry(t *testing.T) {
 	tt.cut(0, 3)
 	tt.cut(0, 4)
 
-	tt.send(Message{To: 0, Type: msgProp, Data: []byte("some data")})
-	tt.send(Message{To: 0, Type: msgProp, Data: []byte("some data")})
+	tt.send(Message{To: 0, Type: msgProp, Entries: []Entry{{Data: []byte("some data")}}})
+	tt.send(Message{To: 0, Type: msgProp, Entries: []Entry{{Data: []byte("some data")}}})
 
 	sm := tt.peers[0].(*stateMachine)
 	if sm.log.committed != 0 {
@@ -135,7 +136,7 @@ func TestCannotCommitWithoutNewTermEntry(t *testing.T) {
 
 	// after append a entry from the current term, all entries
 	// should be committed
-	tt.send(Message{To: 1, Type: msgProp, Data: []byte("some data")})
+	tt.send(Message{To: 1, Type: msgProp, Entries: []Entry{{Data: []byte("some data")}}})
 	if sm.log.committed != 3 {
 		t.Errorf("committed = %d, want %d", sm.log.committed, 3)
 	}
@@ -197,7 +198,7 @@ func TestCandidateConcede(t *testing.T) {
 
 	data := []byte("force follower")
 	// send a proposal to 2 to flush out a msgApp to 0
-	tt.send(Message{To: 2, Type: msgProp, Data: data})
+	tt.send(Message{To: 2, Type: msgProp, Entries: []Entry{{Data: data}}})
 
 	a := tt.peers[0].(*stateMachine)
 	if g := a.state; g != stateFollower {
@@ -284,7 +285,7 @@ func TestProposal(t *testing.T) {
 
 		// promote 0 the leader
 		send(Message{To: 0, Type: msgHup})
-		send(Message{To: 0, Type: msgProp, Data: data})
+		send(Message{To: 0, Type: msgProp, Entries: []Entry{{Data: data}}})
 
 		wantLog := newLog()
 		if tt.success {
@@ -320,7 +321,7 @@ func TestProposalByProxy(t *testing.T) {
 		tt.send(Message{To: 0, Type: msgHup})
 
 		// propose via follower
-		tt.send(Message{To: 1, Type: msgProp, Data: []byte("somedata")})
+		tt.send(Message{To: 1, Type: msgProp, Entries: []Entry{{Data: []byte("somedata")}}})
 
 		wantLog := &log{ents: []Entry{{}, {Term: 1, Data: data}}, committed: 1}
 		base := ltoa(wantLog)
@@ -491,6 +492,29 @@ func TestStateTransition(t *testing.T) {
 	}
 }
 
+func TestConf(t *testing.T) {
+	sm := newStateMachine(0, []int{0})
+	sm.becomeCandidate()
+	sm.becomeLeader()
+
+	sm.Step(Message{Type: msgProp, Entries: []Entry{{Type: config}}})
+	if sm.log.lastIndex() != 1 {
+		t.Errorf("lastindex = %d, want %d", sm.log.lastIndex(), 1)
+	}
+	if !sm.pendingConf {
+		t.Errorf("pendingConf = %v, want %v", sm.pendingConf, true)
+	}
+	if sm.log.ents[1].Type != config {
+		t.Errorf("type = %d, want %d", sm.log.ents[1].Type, config)
+	}
+
+	// deny the second configuration change request if there is a pending one
+	sm.Step(Message{Type: msgProp, Entries: []Entry{{Type: config}}})
+	if sm.log.lastIndex() != 1 {
+		t.Errorf("lastindex = %d, want %d", sm.log.lastIndex(), 1)
+	}
+}
+
 func TestAllServerStepdown(t *testing.T) {
 	tests := []stateType{stateFollower, stateCandidate, stateLeader}