ternal service is blocked unless
<a href=/v1.8/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_discovery#original-destination>original destination</a>
is setup as a TCP Proxy with the BlackHoleCluster as the static cluster.
The configuration for the BlackHoleCluster 