rtual cluster created
in the Envoy configuration when <code>global.outboundTrafficPolicy.mode</code> is set to
<code>REGISTRY_ONLY</code>. In this mode, all traffic to external service is blocked unless
<a href=/v1.21/docs/reference/config/networking/service-entry/>service entries</a>
are explicitly added for each service. To implement this, the default virtual
outbound listener at <code>0.0.0.0:15001</code> which uses
<a href=https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/upstream/service_