Jenkins master slave url problem

Hi, I have an issue with this tutorial:

following the instruction I was stuck trying to connect the slave to the master. I have only a sigle node, so i thought I’ll not have problem using the environment variable JENKINS_MASTER: http://jenkins:8080. But the slave is trying and trying without any good result.

So I try the following:

curl --user jenkins http://jenkins:8080/plugin/swarm/slaveInfo

with this result:

<!DOCTYPE html>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="icon" href="/assets/images/logos/favicon.ico">
    <!-- 1.1.14 -->
    <meta name="description" content="">
    <meta name="viewport" content="width=570">
    <base href="/" />
    <link rel="stylesheet" href="/assets/vendor-4c8809d1ad53f671fcc119c842733a88.css">
    <link id="theme" rel="stylesheet">
    <script src="/assets/vendor-ebfa7dda04b9f2b654291bf27e70bf22.js"></script>
    <script src="/assets/ui-399966b411601a514e01ca71c9068e2e.js"></script>
    <div id="ember-basic-dropdown-wormhole"></div>

it’s spected somthing like:

if I change the internal URL provided by rancher DNS “http://jenkins:8080” for the actual Host URL i get the correct response.

So, what is the problem with the rancher URL?