ip正则表达式验证

function isIp(arg_ip){        var exp=/^(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])$/;        var reg = arg_ip.match(exp);        if(reg==null)        {            return false;        }        return true;    }