Google Cloud details GKE ClusterNetworkPolicy three-tier model in LLM isolation test

[Google Cloud] Google Cloud described its experiment with ClusterNetworkPolicy (CNP) in Google Kubernetes Engine (GKE), saying standard Network Policies limit policy application to the namespace level while CNP lets administrators apply granular networking policies across an entire cluster and scale security and governance policies. According to Google Cloud, CNP follows a three-tier precedence flow: an admin tier at top precedence, where cluster administrators enforce mandatory security rules that cannot be bypassed, such as blocking metadata access; a network policy tier in the middle, for namespace-scoped policies managed by application teams to control ingress and egress for their microservices; and a baseline tier at bottom precedence, where administrators set fallback defaults such as a default-deny posture across namespaces. The Codelab experiment aims to restrict traffic to the LLM namespace, allow only authorized clients and prevent cluster-wide access to the metadata API except for DNS port 53. It uses a custom VPC with Cloud NAT, a GKE Standard cluster running GKE Dataplane V2, a TPU v5e node pool in a 2x2 topology, and Gemma 4 served with vLLM on port 8000, with three namespaces: gemma-llm, client-ns and untrusted-tenant.