OW_ANY</code>). The default option for this
setting (as of Istio 1.3) is to allow all external service access. This
option can be configured via <a href=/v1.21/docs/reference/config/istio.mesh.v1alpha1/#MeshConfig-OutboundTrafficPolicy-Mode>mesh configuration</a>.</p><p>This is where the BlackHole and Passthrough clusters are used.</p><h2 id=what-are-blackhole-and-passthrough-clusters>What are BlackHole and Passthrough clusters?</h2><ul><li><p><strong>BlackHoleCluster</strong> - The BlackHoleCluster is a vi