Istio creates unique listeners for every
port/protocol combination of platform services which gets hit instead of the
virtual listener if the request is made to an external service on the same port.
In that case, the route configuration of every virtual route in Envoy is augmented to
add the BlackHoleCluster like this:</p><pre><code class=language-json data-expandlinks=true data-repo=istio>{
  &#34;name&#34;: &#34;block_all&#34;,
  &#34;domains&#34;: [
    &#34;*&#34;
  ],
  &#34;routes&#34;: [
    {
      