from the <code>ALLOW_ANY</code> mode to the <code>REGISTRY_ONLY</code> mode.</p><div><aside class="callout tip"><div class=type><svg class="large-icon"><use xlink:href="/v1.2/img/icons.svg#callout-tip"/></svg></div><div class=content>You can add controlled access to services that are already accessible in <code>ALLOW_ANY</code> mode.
This way, you can start using Istio features on some external services without blocking any others.
Once you&rsquo;ve configured all of your services, you can then switch the m