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You are tasked to install Cilium and enable transparent encryption in a cluster in which the following conditions applies:
Internal cluster traffic is IPv6-only
The current cluster is running on 5001 nodes
The cluster is planned to connect to another cluster which has 5001 nodes through Cluster Mesh
What are your recommendations regarding transparent encryption?
A is a supported recommendation: Cilium's WireGuard implementation provides transparent encryption between Cilium-managed endpoints, works with Cluster Mesh, and distributes node public keys to remote clusters through clustermesh-apiserver. All participating clusters must enable WireGuard, and inter-cluster firewalls must permit UDP port 51871. IPv6-only pod traffic does not inherently disqualify WireGuard.
However, this question is no longer uniquely answerable from current Cilium documentation. Current IPsec documentation supports IPv6 pod-to-pod connectivity and sets its cluster or Cluster Mesh limit at more than 65,535 nodes. The described mesh contains 10,002 nodes, so option B is also technically supportable under the stated facts. The older distinction apparently assumed by the supplied key is no longer sufficient to exclude IPsec.
Options C and D are definitively false. Ten thousand and two nodes remain below the documented IPsec ceiling, and transparent encryption is not restricted to IPv4. WireGuard may still be selected for its automatic per-node key-pair distribution and simpler Cluster Mesh integration, but workload performance, kernel support, firewall rules, key-management requirements, and operational testing should inform a production recommendation.
Official references
WireGuard Transparent Encryption, IPsec Transparent Encryption
Study Guide topic: Transparent-encryption selection, IPv6, Cluster Mesh, and scaling limits.