js正则表达式证验IP

js正则表达式验证IP
function IP2V() {
var ip = "192.68.23.6.36" ;
var re =  /^((1?\d?\d|(2([0-4]\d|5[0-5])))\.){3}(1?\d?\d|(2([0-4]\d|5[0-5])))$/
alert("ip:" + re.test(ip));

}