istio.io/content/help/faq/security/check-policy.md

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How can I check whether mutual TLS is enabled for a service?	11

The istioctl tool provides an option for this purpose. You can do:

{{< text bash >}} $ istioctl authn tls-check httpbin.default.svc.cluster.local HOST:PORT STATUS SERVER CLIENT AUTHN POLICY DESTINATION RULE httpbin.default.svc.cluster.local:8000 OK mTLS mTLS default/ default/default {{< /text >}}

Refer to Verify mutual TLS configuration for more information.