diff --git a/scripts/link.sh b/scripts/link.sh
new file mode 100755
index 0000000..d87464b
--- /dev/null
+++ b/scripts/link.sh
@@ -0,0 +1,40 @@
+#! /bin/bash
+controller=`hostname`
+switches=`ifconfig -a | grep sw |grep -v eth | awk '{print $1}'`
+
+function host2ip (){
+   ip=`grep $1 /etc/hosts |grep -v "ip6"|  awk '{print $1}'`
+   echo $ip
+}
+
+# link.sh 00:00:00:00:ba:5e:ba:11 1 up
+
+if [ $# != 3 ];then
+ echo "usage: $0 <dpid> <port> <up|down>"
+fi
+
+src_dpid="dpid:"`echo $1 | sed s'/://g'`
+src_port=$2
+cmd=$3
+
+for s in $switches; do
+    dpid=`sudo ovs-ofctl  show  $s |grep dpid | awk '{print $4}'`
+    if [  "x$dpid" == "x$src_dpid" ]; then
+        intfs=`sudo ovs-ofctl show $s |grep addr | awk '{print $1}' | sed 's/.*(//g' | sed 's/):$//g'`
+	intf_list=()
+	for i in $intfs; do
+	  intf_list+=($i)
+        done
+	intf=${intf_list[$src_port]}
+        if [ x$cmd == "xup" ]; then
+	    echo "sudo ifconfig ${intf}  up"
+	    sudo ifconfig ${intf}  up
+        elif [ x$cmd == "xdown" ]; then
+	    echo "sudo ifconfig ${intf}  down"
+	    sudo ifconfig ${intf}  down
+        else
+	    echo "sudo ifconfig ${intf}"
+	    sudo ifconfig ${intf} 
+        fi
+    fi
+done