diff --git a/demo/tun/main.go b/demo/tun/main.go
new file mode 100644
index 0000000..a3adfe2
--- /dev/null
+++ b/demo/tun/main.go
@@ -0,0 +1,198 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"os"
+
+	"github.com/songgao/water"
+	"github.com/urfave/cli/v2"
+	"github.com/vishvananda/netlink"
+	"golang.org/x/net/ipv4"
+)
+
+const (
+	PORT         = 8000
+	ADDR         = "10.67.0.254"
+	SIP          = "10.69.0.254/24"
+	MAX_PKT_SIZE = 4096
+)
+
+var EP map[string]net.Conn
+var idx = 1
+
+func init() {
+	EP = make(map[string]net.Conn)
+}
+
+func handleConn(conn net.Conn, iface *water.Interface) {
+	EP[fmt.Sprintf("10.69.0.%d", idx)] = conn
+	idx += 1
+
+	go func() {
+		for {
+			buf := make([]byte, MAX_PKT_SIZE)
+			n, err := iface.Read(buf)
+			if err != nil {
+				fmt.Println(err)
+				continue
+			}
+
+			h, err := ipv4.ParseHeader(buf[:n])
+			if err != nil {
+				fmt.Println(err)
+				continue
+			}
+			dst := h.Dst.String()
+			fmt.Printf("iface dst %s\n", dst)
+			p, ok := EP[dst]
+			if !ok {
+				fmt.Printf("pkt from server dst %s no route\n", dst)
+				continue
+			}
+
+			_, err = p.Write(buf[:n])
+			if err != nil {
+				fmt.Println(err)
+				continue
+			}
+		}
+	}()
+
+	for {
+		buf := make([]byte, MAX_PKT_SIZE)
+		n, err := conn.Read(buf)
+		if err != nil {
+			fmt.Println(err)
+			continue
+		}
+
+		h, err := ipv4.ParseHeader(buf[:n])
+		if err != nil {
+			fmt.Println(err)
+			continue
+		}
+		dst := h.Dst.String()
+		fmt.Printf("conn dst %s\n", dst)
+
+		p, ok := EP[dst]
+		if !ok {
+			fmt.Printf("pkt from client dst %s send to loacal", dst)
+			_, err = iface.Write(buf[:n])
+			if err != nil {
+				fmt.Println(err)
+				continue
+			}
+		} else {
+			_, err = p.Write(buf[:n])
+			if err != nil {
+				fmt.Println(err)
+				continue
+			}
+		}
+	}
+}
+
+func setupTun(addr string) (*water.Interface, error) {
+	tname := "tun0"
+	config := water.Config{
+		DeviceType: water.TUN,
+	}
+	config.Name = tname
+
+	iface, err := water.New(config)
+	if err != nil {
+		return nil, err
+	}
+
+	link, err := netlink.LinkByName(tname)
+	if err != nil {
+		return nil, err
+	}
+
+	a, err := netlink.ParseAddr(addr)
+	if err != nil {
+		return nil, err
+	}
+
+	err = netlink.AddrAdd(link, a)
+	if err != nil {
+		return nil, err
+	}
+
+	err = netlink.LinkSetUp(link)
+	if err != nil {
+		return nil, err
+	}
+
+	return iface, nil
+}
+
+func sRun(cCtx *cli.Context) error {
+	ln, err := net.Listen("tcp4", fmt.Sprintf(":%d", PORT))
+	if err != nil {
+		return err
+	}
+	fmt.Println("server listen on port 8000")
+
+	iface, err := setupTun(SIP)
+	if err != nil {
+		return err
+	}
+	fmt.Printf("create tun %s\n", iface.Name())
+
+	for {
+		conn, err := ln.Accept()
+		if err != nil {
+			return err
+		}
+
+		go handleConn(conn, iface)
+	}
+}
+
+func cRun(cCtx *cli.Context) error {
+	conn, err := net.Dial("tcp", fmt.Sprintf("%s:%d", ADDR, PORT))
+	if err != nil {
+		return err
+	}
+	fmt.Println("client dial 8000")
+
+	iface, err := setupTun(cCtx.String("addr"))
+	if err != nil {
+		return err
+	}
+
+	for {
+		go io.Copy(iface, conn)
+		io.Copy(conn, iface)
+	}
+}
+
+func main() {
+	app := &cli.App{
+		Commands: []*cli.Command{
+			{
+				Name:   "server",
+				Action: sRun,
+			},
+			{
+				Name:   "client",
+				Action: cRun,
+				Flags: []cli.Flag{
+					&cli.StringFlag{
+						Name:     "addr",
+						Aliases:  []string{"a"},
+						Required: true,
+					},
+				},
+			},
+		},
+	}
+
+	if err := app.Run(os.Args); err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+}
diff --git a/go.mod b/go.mod
index db61da2..552cdcc 100644
--- a/go.mod
+++ b/go.mod
@@ -12,6 +12,7 @@ require (
 	github.com/songgao/water v0.0.0-20200317203138-2b4b6d7c09d8
 	github.com/urfave/cli/v2 v2.27.1
 	github.com/vishvananda/netlink v1.1.0
+	golang.org/x/net v0.10.0
 	golang.org/x/sync v0.7.0
 	golang.org/x/sys v0.19.0
 	golang.org/x/term v0.19.0
@@ -41,7 +42,6 @@ require (
 	github.com/xrash/smetrics v0.0.0-20201216005158-039620a65673 // indirect
 	golang.org/x/arch v0.3.0 // indirect
 	golang.org/x/crypto v0.9.0 // indirect
-	golang.org/x/net v0.10.0 // indirect
 	golang.org/x/text v0.9.0 // indirect
 	google.golang.org/protobuf v1.30.0 // indirect
 )