ew-deployment-model/single-cluster-external-Istiod.svg alt="Istio mesh in a single cluster with Istiod outside"></a></div><figcaption>Single cluster Istio mesh with Istiod in an external control plane cluster</figcaption></figure><p>Mesh admins can expand the service mesh to multiple clusters, which are managed by the same Istiod running in the external cluster. None of the mesh clusters are <span class=term data-title="Primary Cluster" data-body='<p>A primary cluster is a <a href="/docs/reference/glossary/